Lalat Buah ( Bactrocera sp.)

Salah satu hama penting tanaman hortikultura yang saat ini menjadi isu nasional juga menjadi faktor pembatas perdagangan (trade barrier). Adalah lalat buah. Komoditas ekspor suatu negara dapat ditolak oleh negara lain dengan alasan terdapatnya lalat buah.
Jenis Lalat Buah di IndonesiaLalat buah yang banyak terdapat di Indonesia adalah dari genus Bactrocera dan salah satu jenis yang sangat penting dan ganas adalah Bactrocera dorsalis Hendel complex. B. dorsalis Hendel complex merupakan lalat buah yang bersifat polifag, mempunyai sekitar 26 jenis inang seperti belimbing, jambu biji, tomat, cabai merah, melon, apel, nangka kuning, mangga, dan jambu air.
Selain merusak buah-buahan seperti jatuhnya buah muda yang terserang, serangan hama ini juga menyebabkan buah menjadi busuk dan dihinggapi belatung lalat buah juga merupakan vektor bakteri Escherichia coli, penyebab penyakit pada manusia sehingga dapat dijadikan alasan untuk menghambat perdagangan. Untuk mencegah masuknya spesies baru lalat buah ke Indonesia, pemerintah mengeluarkan Permentan No.37/ KPTS/HK. 060/172006 yang menetapkan hanya tujuh pintu masuk buah segar ke Indonesia, yaitu Batu Ampar, Batam; Ngurah Rai, Bali; Makassar; Belawan, Medan; Tj. Priok, Jakarta; Tj. Perak, Surabaya, dan Cengkareng, Jakarta.
Intensitas serangan lalat buah di beberapa daerah di Jawa Timur dan Bali menunjukkan variasi yang cukup besar, berkisar antara 6,4-70% Intensitas serangan lalat buah pada mangga berkisar antara 14,8-23%. Namun tidak jarang kerusakan yang diakibatkan lalat buah, khususnya pada belimbing dan jambu biji, dapat mencapai 100% .
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Gejala

Pada buah yang terserang biasanya terdapat lubang kecil di bagian tengah kulitnya. Serangan lalat buah ditemukan terutama pada buah yang hampir masak. Gejala awal ditandai dengan noda/titik bekas tusukan ovipositor (alat peletak telur) lalat betina saat meletakkan telur ke dalam buah. Selanjutnya karena aktivitas hama di dalam buah, noda tersebut berkembang menjadi meluas. Larva makan daging buah sehingga menyebabkan buah busuk sebelum masak. Apabila dibelah pada daging buah terdapat belatung-belatung kecil dengan ukuran antara 4-10 mm yang biasanya meloncat apabila tersentuh. Kerugian yang disebabkan oleh hama ini mencapai 30-60%. Kerusakan yang ditimbulkan oleh larvanya akan menyebabkan gugurnya buah sebelum mencapai kematangan yang diinginkan.
Bioekologi

Dalam siklus hidupnya lalat buah mempunyai 4 stadium hidup yaitu telur, larva, pupa dan dewasa. Lalat buah betina memasukkan telur kedalam kulit buah jeruk atau di dalam luka atau cacat buah secara berkelompok. Lalat buah betina bertelur sekitar 15 butir. Telur berwarna putih transparan berbentuk bulat panjang dengan salah satu ujungnya runcing. Larva lalat buah hidup dan berkembang di dalam daging buah selama 6-9 hari. Larva mengorek daging buah sambil mengeluarkan enzim perusak atau pencerna yang berfungsi melunakkan daging buah sehingga mudah diisap dan dicerna. Enzim tersebut diketahui yang mempercepat pembusukan, selain bakteri pembusuk yang mempercepat aktivitas pembusukan buah. Jika aktivitas pembusukan sudah mencapai tahap lanjut, buah akan jatuh ke tanah, bersamaan dengan masaknya buah, larva lalat buah siap memasuki tahap pupa, larva masuk dalam tanah dan menjadi pupa. Pupa berwarna kecoklatan berbentuk oval dengan panjang 5 mm. Lalat dewasa berwarna merah kecoklatan, dada berwarna gelap dengan 2 garis kuning membujur dan pada bagian perut terdapat garis melintang. Lalat betina ujung perutnya lebih runcing dibandingkan lalat jantan. Siklus hidup dari telur menjadi dewasa berlangsung selama 16 hari. Fase kritis tanaman yaitu pada saat tanaman mulai berbuah terutama pada saat buah menjelang masak. Lalat buah yang mempunyai ukuran tubuh relatif kecil dan siklus hidup yang pendek peka terhadap lingkungan yang kurang baik. Suhu optimal untuk perkembangan lalat buah ? 26?C, sedangkan kelembaban relatif sekitar 70%. Kelembaban tanah sangat berpengaruh terhadap perkembangan pupa. Kelembaban tanah yang sesuai untuk stadia pupa adalah 0-9%. Cahaya mempunyai pengaruh langsung terhadap perkembangan lalat buah. Lalat buah betina akan meletakkan telur lebih cepat dalam kondisi yang terang, sebaliknya pupa lalat buah tidak akan menetas apabila terkena sinar. Lalat buah paling banyak menyerang pada pamelo (Citrus grandis) dan sedikit yang menyerang jeruk manis (C. sinensis) maupun keprok (C. reticulata). Pada pamelo diidentifikasi sebagai B. carambolae dan B. papayae. Pada pamelo serangan lalat buah kadang-kadang bersamaan dengan serangan penggerek buah Citripestis sagitiferella, sehingga agak sulit membedakan serangga tersebut. Hama ini banyak ditemukan di sentra-sentra produksi jeruk seperti di Sumatera Utara dan Jawa Timur.

Pengendalian Lalat Buah

Di Hawaii, pengendalian lalat buah memadukan beberapa teknik pengendalian, di antaranya dengan atraktan dalam perangkap, yang dapat menekan penggunaan pestisida kimia sintetis hingga 75-95%. Beberapa teknik pengendalian telah banyak dikembangkan, di antaranya penggunaan GA (Gibberellic Acid), yaitu membuat penampilan buah-buahan tidak matang, sehingga lalat buah enggan meletakkan telur pada buah. Selain itu, pelepasan serangga mandul, khususnya jantan mandul, telah dikembangkan pula dan memberikan hasil yang memuaskan. Teknik lain yang sudah berhasil dikembangkan di Australia adalah foliage baiting (penggunaan umpan beracun), coversprayng (penyemprotan tanaman beserta buahnya dengan insektisida), dan trapping (perangkap dengan atraktan di dalamnya), selain menjaga sanitasi kebun (Broghton etal., 2004).
Pengendalian dengan Atraktan (Zat Pemikat)

Penggunaan atraktan metil eugenol merupakan cara pengendalian yang ramah lingkungan dan telah terbukti efektif. Atraktan dapat digunakan untuk mengendalikan hama lalat buah dalam tiga cara, yaitu: (a) mendeteksi atau memonitor populasi lalat buah, (b) menarik lalat buah untuk kemudian dibunuh dengan perangkap, dan (c) mengacaukan lalat buah dalam perkawinan, berkumpul, dan cara makan.

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Climate Change Makes Migrations Longer For Birds

A team of scientists, led by Durham University, have published findings that show that the marathon flights undertaken by birds to spring breeding grounds in Europe, are going to turn into even more epic journeys; the length of some migrations could increase by as much as 250 miles.

The research team looked at the current migration patterns of European Sylvia warblers, a group of birds that are common residents and visitors to Europe, like the Blackcap. Published in the Journal of Biogeography, the scientists demonstrate evidence of potential breeding ranges shifting northwards in the future, while the wintering ranges remain stationary for many species.

The team used simulation models to see how climate change might affect warblers and found that climate change will have significant impacts, particularly on the projected migration distances for some of the long distance fliers.

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Some 500 million birds are estimated to migrate to Europe and Asia from Africa; birds as small as 9 grams undertake the annual migration of 1,000s of miles between the two continents to find food and suitable climate. Birds have to put on a large amount of weight as fat before migrating long distances; they even shrink the size of some of their internal organs to become more fuel efficient. Some species must double their weight to have enough energy to undertake the huge journeys. The first of these migrants are now starting to reappear once again in the UK countryside.
Team leader, Dr Stephen Willis of Durham University, said birds face an increasing fight to survive: “Most warblers come here in spring and summer time to take advantage of the surplus of insects, and leave for warmer climes in the autumn. From 2071 to 2100, nine out of the 17 species we looked at are projected to face longer migrations, particularly birds that cross the Sahara desert.
“Our findings show that marathon migrations for some birds are set to become even longer journeys. This is bad news for birds like the Whitethroat, a common farmland bird. The added distance is a considerable threat.”
Co-author of the research paper, Professor Rhys Green of Cambridge University and RSPB said: "These tiny birds make amazing journeys, pushing themselves to the limits of endurance. Anything that makes those journeys longer or more dependent on rare and vulnerable pit-stop habitats used for refuelling on migration could mean the difference between life and death.”
In terms of EU policy, the predicted effects of climate change on birds indicate a need for an appraisal of the designation of protected areas for migrant species, including key areas used for stopovers on long-distance migrations. The protection of bird species within the European Union is covered by legal directives that require member states to designate and protect Special Areas of Conservation (SACs) for habitats and Special Protection Areas (SPAs), the latter specifically designated to protect birds.
The research predicts that some species that fly long distances (on average 2,800 miles to 3,700 miles), are likely to face significantly longer flights, up to 250 miles longer, and shorter distance fliers may face journeys of up to 125 miles longer. Some birds cross the Mediterranean Sea and the Sahara in one go, whilst others pause to refuel in North Africa before crossing the desert. Night flying when the temperature is cooler is a technique that is also used by some of the long distance fliers.
Northern parts of the species’ ranges are expected to become of increasing importance and in some cases, species of northern populations are already thought to be exhibiting increases. Some birds might also be able to find new short distance routes. One common migrant, the Blackcap has already started spending winters in the UK.
Professor Rhys Green said: "These findings come as many people in the UK are enjoying the sights and sounds of their favourite birds returning after a winter in Africa. The challenges are large if we are to continue to see and hear these harbingers of the spring in anything like the numbers we are used to witnessing.
"We have already seen evidence that birds' ranges are moving north to track suitable climate conditions in the way predicted by past modelling. This latest research suggests they will face an increase in the length of an already arduous journey.”
Assuming increases in the fuel requirements for longer migrations can be physiologically accommodated by birds, they are likely to require more time for feeding prior to migration and/or additional stopovers to feed.
Nathalie Doswald, a student on the Durham team, said: “The projected distances for migrations would require long and short distance fliers to increase their fuel loads by 9 per cent and 5 per cent of lean body mass respectively. The predicted future temperature changes and the associated changes in habitat could have serious consequences for many species.”
Dr Willis said: “Some species may be able to adapt and change, for example by adopting shorter migration routes, if they can find enough food at the right time. Bird migrations are incredible feats of stamina and endurance but, as temperatures rise and habitats change, birds will face their biggest challenge since the Pleistocene era.”
Average migration distances – now and (in brackets) predicted for the future.
The four species with the largest predicted migration increases:
Subalpine Warbler – 1,615 miles (1,895-2,081miles) - Southern Europe to sub-Saharan Africa
Orphean Warbler – 1,679 miles (1,926-2,019 miles) - Southern Europe to sub-Saharan Africa
Barred Warbler – 2982 miles (3480-3,573 miles) - Central Europe to sub-Saharan Africa
Whitethroat – 3,417 miles (3,541-3,759 miles) – All Europe to sub-Saharan Africa
This research was funded by the Natural Environment Research Council and the RSPB.

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All Octopuses Are Venomous: Could Lead To Drug Discovery

Once thought to be only the realm of the blue-ringed octopus, researchers have now shown that all octopuses and cuttlefish, and some squid are venomous. The work indicates that they all share a common, ancient venomous ancestor and highlights new avenues for drug discovery.

Conducted by scientists from the University of Melbourne, University of Brussels and Museum Victoria, the study was published in the Journal of Molecular Evolution.
Dr Bryan Fry from the Department of Biochemistry at the Bio21 Institute, University of Melbourne said that while the blue-ringed octopus species remain the only group that aredangerous to humans, the other species have been quietly using their venom for predation, such as paralysing a clam into opening its shell.

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“Venoms are toxic proteins with specialised functions such as paralysing the nervous system” he said.
“We hope that by understanding the structure and mode of action of venom proteins we can benefit drug design for a range of conditions such as pain management, allergies and cancer.”
While many creatures have been examined as a basis for drug development, cephalopods (octopuses, cuttlefish and squid) remain an untapped resource and their venom may represent a unique class of compounds.
Dr Fry obtained tissue samples from cephalopods ranging from Hong Kong, the Coral Sea, the Great Barrier Reef and Antarctica.
The team then analysed the genes for venom production from the different species and found that a venomous ancestor produced one set of venom proteins, but over time additional proteins were added to the chemical arsenal.
The origin of these genes also sheds light on the fundamentals of evolution, presenting a prime example of convergent evolution where species independently develop similar traits.
The team will now work on understanding why very different types of venomous animals seem to consistently settle on the similar venom protein composition, and which physical or chemical properties make them predisposed to be useful as toxin.
“Not only will this allow us to understand how these animals have assembled their arsenals, but it will also allow us to better exploit them in the development of new drugs from venoms,” said Dr Fry.
“It does not seem a coincidence that some of the same protein types have been recruited for use as toxins across the animal kingdom.”

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New Orangutan Population Found in Indonesia

Conservationists discovered a new population of orangutans in a remote, mountainous corner of Indonesia — perhaps as many as 2,000 — giving a rare boost to one of the world's most endangered great apes.
A team surveying forests nestled between jagged, limestone cliffs on the eastern edge of Borneo island counted 219 orangutan nests, indicating a "substantial" number of the animals, said Erik Meijaard, a senior ecologist at the U.S.-based The Nature Conservancy.
"We can't say for sure how many," he said, but even the most cautious estimate would indicate "several hundred at least, maybe 1,000 or 2,000 even."

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The team also encountered an adult male, which angrily threw branches as they tried to take photos, and a mother and child.
There are an estimated 50,000 to 60,000 orangutans left in the wild, 90 percent of them in Indonesia and the rest in neighboring Malaysia.
The countries are the world's top producers of palm oil, used in food, cosmetics and to meet growing demands for "clean-burning" fuels in the U.S. and Europe. Rain forests, where the solitary animals spend almost all of their time, have been clear-cut and burned at alarming rates to make way for lucrative palm oil plantations.

The steep topography, poor soil and general inaccessibility of the rugged limestone mountains appear to have shielded the area from development, at least for now, said Meijaard. Its trees include those highly sought after for commercial timber.
Birute Mary Galdikas, a Canadian scientist who has spent nearly four decades studying orangutans in the wild, said most of the remaining populations are small and scattered, which make them especially vulnerable to extinction.
"So yes, finding a population that science did not know about is significant, especially one of this size," she said, noting that those found on the eastern part of the island represent a rare subspecies, the black Borneon orangutan, or Pongo pygmaeus morio.
The 700-square mile (2,500-square kilometer) jungle escaped the massive fires that devastated almost all of the surrounding forests in the late 1990s. The blazes were set by plantation owners and small-scale farmers and exacerbated by the El Nino droughts.
Nardiyono, who headed The Nature Conservancy's weeklong survey in December, said "it could be the density is very high because after the fires, the orangutans all flocked to one small area."
It was unusual to come face-to-face with even one of the elusive creatures in the wild and to encounter three was extraordinary, he said, adding that before this expedition, he had seen just five in as many years.
Conservationists say the most immediate next step will be working with local authorities to protect the area and others that fall outside of national parks. A previously undiscovered population of several hundred also was found recently on Sumatra island, home to around 7,000.
"That we are still finding new populations indicates that we still have a chance to save this animal," said Paul Hartman, who heads the U.S.-funded Orangutan Conservation Service Program, adding it's not all "gloom and doom."
Noviar Andayani, head of the Indonesian Primate Association and Orangutan Forum, said the new discoveries point to how much work still needs to be done to come up with accurate population assessments, considered vital to determining a species' vulnerability to extinction.
"There are many areas that still have not been surveyed," she said, adding that 18 private conservation groups have just started work on an in-depth census based on interviews with people who spend time in the forests.
They include villagers and those working on plantations or within logging concessions.
"We hope this will help fill in a few more gaps," said Andayani, adding that preliminary tests in areas where populations are known indicate that the new interview-based technique could provide a clearer picture than nest tallies.
"Right now the information and data we have about orangutans is still pretty rudimentary," she said.
Some experts say at the current rate of habitat destruction, the animals could be wiped out within the next two decades.

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Scientists Milk Animals For Malaria Vaccine

In their quest to mass-produce an effective malaria vaccine, scientists might one day replace expensive manufacturing facilities with a goat. In a study reported December 18 in the Proceedings of the National Academy of Sciences online, researchers developed mice that could secrete an experimental malaria vaccine into their milk. When the purified candidate vaccine was injected into monkeys, it protected four out of five animals from a lethal dose of the malaria parasite. If the process can be scaled up to larger animals such as goats -- and early experiments indicate it can -- livestock might prove to be inexpensive, high-yield malaria vaccine factories. “A vaccine must not only be effective, it must be cheap to manufacture if it is to be used in those countries hit hardest by malaria,” says lead author Anthony Stowers, Ph.D., a malaria researcher at the National Institute of Allergy and Infectious Diseases (NIAID). “Using transgenic animals to achieve both ends is an exciting possibility. If it works, a herd of several goats could conceivably produce enough vaccine for all of Africa.”

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Transgenic animals are so named because they contain a gene, called a transgene, from another individual or organism. For years transgenic animals, particularly mice, have been used to help scientists understand how genes work and interact with one another. More recently, researchers have introduced genes encoding specific proteins into animals to produce large quantities of those proteins for medical use. Dr. Stowers and his colleagues investigated whether transgenic animals could produce proteins for use in malaria vaccines.
Dr. Stowers and Louis Miller, M.D., chief of NIAID’s Laboratory of Parasitic Diseases and the director of its Malaria Vaccine Development Unit, joined other investigators from NIAID and Genzyme Transgenics Corporation, Framingham, Mass., to produce two transgenic mouse strains. Each strain carried a form of the gene for a surface protein from the deadliest malaria parasite, Plasmodium falciparum. The researchers designed the transgenes to be switched on by the cells that line the mammary glands, such that the resulting proteins would be secreted into the animals’ milk.
Both mouse strains produced large quantities of the desired vaccine protein, which was used to vaccinate monkeys against malaria. Only one of the five immunized animals contracted the disease. By comparison, six out of seven unvaccinated animals had to be treated for virulent malaria.
The high yield of the protein and its ability to stimulate protective immunity in mice offers promising evidence that the technique could also be used in goats or even cows. The researchers had anticipated future studies in goats by designing the transgenes’ on/off switch using regulatory elements from goat DNA. Preliminary experiments, which have not yet been published, suggest the procedure works well in the larger animals. That possibility offers a far more practical option for large-scale vaccine production.
Anthony S. Fauci, M.D., who as NIAID director guides an extensive research program on global infectious diseases, believes this approach is promising. “Malaria causes untold suffering in the poorest regions of the world, so we cannot restrict our focus simply to finding a vaccine that works,” he says. “Rather, we must look for innovative strategies that will bring effective vaccines to regions where economic conditions preclude the use of costly alternatives. Transgenic animals could be one way to accomplish that goal.”
The study involved many researchers from the two participating institutions. Among these, Drs. Li-How Chen and Harry Meade directed the studies conducted at Genzyme Transgenics. B. Fenton Hall, M.D., from NIAID’s Parasitology and International Programs Branch, also helped initiate the project and played an active role in its development.
NIAID is a component of the National Institutes of Health (NIH). NIAID supports basic and applied research to prevent, diagnose, and treat infectious and immune-mediated illnesses, including HIV/AIDS and other sexually transmitted diseases, tuberculosis, malaria, autoimmune disorders, asthma and allergies.

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Chimps beat college students in memory test

When chimpanzees and university students went head-to-head in a short-term memory test, the chimps scored higher. The study was led by a Kyoto, Japan scientist who has studied the cognitive abilities of primates for 30 years.
In a recent study a Japanese researcher used short-term memory tests to compare the cognitive abilities between chimps and college students. The chimps won. Tetsuro Matsuzawa, director of the Primate Research Institute at Japan’s Kyoto University, has been studying chimpanzees and chimpanzee communities for 30 years.
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In his official bio at the university he compares the genomic difference between humans as comparable to the difference between horses and zebras and suggests humans are “98.77% chimpanzee.” He has long made the case that humans and chimpanzees are close genetic relatives and that they should co-exist peacefully.

To demonstrate their cognitive strengths, Matsuzawa taught three chimps, ages one through five, to recognize numbers one through nine. The test involved random flashing numbers on a touch screen computer. After a fraction of a second, the numbers were masked by white squares. The chimps were able to remember the location of up to eight of the numbers, and touch the spot where they had appeared in the correct order. But the college undergrads who volunteered for the study could only accurately recall the location of up to five numbers.

Matsuzawa opposes the use of primates in biomedical research and helped launch SAGA (Support for African/Asian Great Apes) in 1998. SAGA promotes conservation of chimpanzee, gorilla and orangutan natural habitats and supports non-invasive scientific inquiry.

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Why Lizards Shed Their Tail

Aegean wall lizardCredit: Johannes Foufopoulos

Did you know that some lizards have the ability to quickly shed their tail when under attack from a predator? Researchers had assumed that predator-prey relationships were a key factor in determining this ability in lizards. A deeper look however has given insight into why some lizards have this ability while others don't. The answer lies in the type of predator, specifically those that kill their prey with venom.
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In a study of lizards in Greece and the Aegean islands, researchers noticed that lizards with the quick tail-shedding ability were located in areas that were also populated by vipers. This ability is advantageous. If the lizard is bitten on its tail, it can shed the tail before the deadly venom is able to reach any vital organs. The lizard can then regrow its tail over time. Lizards that are located in areas where venomous snakes are not around do not have this same ability to quickly shed their tails.

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Defense Mechanisms

Defense mechanisms are very important to all animal life. Animals must eat to survive. With predators always on the lookout for a meal, prey must constantly avoid being eaten. Any adaptation the prey uses adds to the chances of survival for the species. Some adaptations are defense mechanisms which can give the prey an advantage against enemies.

Leopard camouflaged in the grass.U.S. Fish and Wildlife Service/Gary Stolz

Defense Mechanisms

There are several ways animals avoid falling prey to a predator. One way is very direct and comes naturally. Imagine you are a rabbit and you have just noticed a fox preparing to attack. What would be your initial response? Right, you'd run. Animals can use speed as a very effective means of escaping predators. Remember, you can't eat what you can't catch!

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Another defense mechanism is camouflage or protective coloration. One form, cryptic coloration, allows the animal to blend in with its environment to avoid being detected. It is important to note that predators also use cryptic coloration to avoid detection by unsuspecting prey.

Trickery can also be used as a formidable defense. False features that appear to be enormous eyes or appendages can serve to dissuade potential predators. Mimicking an animal that is dangerous to a predator is another effective means of avoiding being eaten.

Physical or chemical combat are other types of defense mechanisms. Some animals' physical features make them a very undesirable meal. Porcupines, for example, make it very difficult for predators with their extremely sharp quills. Similarly, predators would have a tough time trying to get to a turtle through its protective shell.

Chemical features can be just as effective. We all know the hazards of scaring a skunk! The chemicals released result in a not so pleasant aroma that an attacker will never forget. The dart frog also uses chemicals (poisons secreted from its skin) to deter attackers. Any animals that eat these small frogs are likely to get very sick or die.

Predator-Prey Relationship

To sum it all up, the predator-prey relationship is important to maintaining balance among different animal species. Adaptations that are beneficial to prey, such as chemical and physical defenses, ensure that the species will survive. At the same time, predators must undergo certain adaptive changes to make finding and capturing prey less difficult.

Without predators, certain species of prey would drive other species to extinction through competition. Without prey, there would be no predators. Thus, this relationship is vital to the existence of life as we know it.

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Ribosomes

In Journey into the Cell, we looked at the structure of the two major types of cells: prokaryotic and eukaryotic cells. Now we turn our attention to the protein assemblers of a eukaryotic cell, the ribosomes.

Ribosomes are organelles that consist of RNA an proteins. They are responsible for assembling the proteins of the cell. Depending on the protein production level of a particular cell, ribosomes may number in the millions.

Distinguishing Characteristics:

Ribosomes are typically composed of two subunits: a large subunit and a small subunit. Ribosomal subunits are synthesized by the nucleolus. These two units join together when the ribosome attaches to messenger RNA to produce a protein in the cytoplasm.

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Location in the Cell:

There are two places that ribosomes usually exist in the cell: suspended in the cytosol and bound to the endoplasmic reticulum. These ribosomes are called free ribosomes and bound ribosomes respectively. In both cases, the ribosomes usually form aggregates called polysomes.

Free ribosomes usually make proteins that will function in the cytosol, while bound ribosomes usually make proteins that are exported or included in the cell's membranes. Interestingly enough, free ribosomes and bound ribosomes are interchangeable and the cell can change their numbers according to metabolic needs.

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Reproduction in Animals: Sexual Reproduction

Individual organisms come and go, but, to a certain extent, organisms "transcend" time through reproducing offspring.

Now let's take a look at sexual reproduction.

Human Ovum(Egg) and SpermCopyright Dennis Kunkel

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Sexual Reproduction

In sexual reproduction, two individuals produce offspring that have genetic characteristics from both parents. Sexual reproduction introduces new gene combinations in a population.

Gametes

In animals, sexual reproduction encompasses the fusion of two distinct gametes to form a zygote. Gametes are produced by a type of cell division called meiosis.

The gametes are haploid (containing only one set of chromosomes) while the zygote is diploid (containing two sets of chromosomes).

In most cases, the male gamete, called the spermatozoan, is relatively motile and usually has a flagellum. On the other hand, the female gamete, called the ovum, is nonmotile and relatively large in comparison to the male gamete.

Types of Fertilization

There are two mechanisms by which fertilization can take place.

The first is external (the eggs are fertilized outside of the body); the second is internal (the eggs are fertilized within the female reproductive tract).

Patterns and Cycles

Reproduction is not a continuous activity and is subject to certain patterns and cycles. Oftentimes these patterns and cycles may be linked to environmental conditions which allow organisms to reproduce effectively.

For example, many animals have estrous cycles that occur during certain parts of the year so that offspring can typically be born under favorable conditions.

Likewise, these cycles and patterns can be controlled by hormonal cues as well as other seasonal cues like rainfall.

All of these cycles and patterns allow organisms to manage the relative expenditure of energy for reproduction and maximize the chances of survival for the resulting offspring.

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Endangered Species

What are Endangered Species?

Rare, endangered, or threatened plants and animals are elements of our natural heritage that are declining rapidly or are on the verge of vanishing. They are plants and animals that exist in small numbers that may be lost forever if we do not take quick action to stop their decline. If we cherish these species, like we do other rare and beautiful objects, these living organisms become treasures of the highest magnitude.

Why Preserve Endangered Plants and Animals?

Preservation of plants and animals is important, not only because many of these species are beautiful, or can provide economic benefits for us in the future, but because they already provide us many valuable services. These organisms clean air, regulate our weather and water conditions, provide control for crop pests and diseases, and offer a vast genetic "library" from which we can withdraw many useful items.
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Extinction of a species could potentially mean the loss of a cure for cancer, a new antibiotic drug, or a disease-resistant strain of wheat. Each living plant or animal may have values yet undiscovered. Scientists estimate there are thirty to forty million species on earth. Many of these species are represented by dozens of genetically distinct populations. We know very little about most species; less than two million are even described. Oftentimes, we do not even know when a plant or animal becomes extinct. Game animals and a few insects are watched and studied. Other species need attention too. Perhaps in them may be found a cure for the common cold or a new organism that will prevent millions of dollars of loss to farmers in their constant fight against crop diseases.

There are many examples of a species' value to society. An antibiotic was discovered in the soils of the threatened New Jersey Pine Barrens Natural Area. A species of perennial corn was found in Mexico; it is resistant to several diseases of corn. An insect was discovered that when frightened produces an excellent insect-repelling chemical.

Why Have Species Become Endangered?

• Habitat Loss

Loss of habitat or the "native home" of a plant or animal is usually the most important cause of endangerment. Nearly all plants and animals require food, water, and shelter to survive, just as humans do. Humans are highly adaptable, however, and can produce or gather a wide variety of foods, store water, and create their own shelter from raw material or carry it on their backs in the form of clothing or tents. Other organisms cannot.

Some plants and animals are highly specialized in their habitat requirements. A specialized animal in North Dakota is the piping plover, a small shorebird which nests only on bare sand or gravel on islands of rivers or shorelines of alkali lakes. Such animals are much more likely to become endangered through habitat loss than a generalist like the mourning dove, which nests successfully on the ground or in trees in the country or city.

Some animals are dependent on more than one habitat type and need a variety of habitats near each other to survive. For example, many waterfowl depend on upland habitats for nest sites, and nearby wetlands for food supplies for themselves and their broods.

It must be emphasized that habitat does not have to be completely eliminated to lose its usefulness to an organism. For example, the removal of dead trees from a forest may leave the forest relatively intact, but eliminate certain woodpeckers that depend on dead trees for nest cavities.

The most serious habitat loss totally changes the habitat and renders it unfit for most of its original resident organisms. In some areas, the greatest changes come from plowing native grasslands, draining wetlands, and constructing flood-control reservoirs.

• Exploitation

Direct exploitation of many animals and some plants took place before conservation laws were enacted. In some places, exploitation was usually for human food or furs. Some animals, such as Audubon's sheep, were hunted to extinction. Others such as the grizzly bear, maintain remnant populations elsewhere.

• Disturbance

The frequent presence of man and his machines may cause some animals to abandon an area, even if the habitat is not harmed. Some large raptors, like the golden eagle, fall into this category. Disturbance during the critical nesting period is especially harmful. Disturbance combined with exploitation is even worse.

What Are The Solutions?

Habitat protection is the key to protecting our rare, threatened, and endangered species. A species cannot survive without a home. Our first priority in protecting a species is to ensure its habitat remains intact.

Habitat protection can be done in a variety of ways. Before we can protect a plant's or animal's habitat, we need to know where this habitat is found. The first step, then is to identify where these vanishing species are found. This is being accomplished today by state and federal agencies and conservation organizations.

Second to identification is planning for protection and management. How can the species and its habitat be best protected, and once protected, how can we make sure the species continues healthy in its protected home? Each species and habitat is different and must be planned on a case-by-case basis. A few protection and management efforts have proven effective for several species, however.

Legislation was passed to protect the most endangered species in the United States. These special species cannot be destroyed nor can their habitat be eliminated. They are marked in the endangered species list by an *. Several federal and state agencies are beginning to manage threatened and endangered species on public lands. Recognition of private landowners who have voluntarily agreed to protect rare plants and animals is underway. All these efforts need to continue and be expanded to keep our natural heritage alive.

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The African House Snake

Red phase House Snake from Botswana

hatching albino "Zululand" House Snakes

hatchling "Zululand" House Snakes

red phase male

cinnamon phase female about to swallow a mouse

L. inornatus

Lamprophis aurorae

L. fuliginosus

L. aurorae

Striped House Snake

Albino House Snake

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normal and albino "Zululand" House Snakes

juvenile brown phase African House Snake

juvenile green phase African House Snake

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Insect Biology and Ecology

Insects are the dominant life-form on earth. Millions may exist in a single acre of land. About one million species have been described, and there may be as many as ten times that many yet to be identified. Of all creatures on earth, insects are the main consumers of plants. They also play a major role in the breakdown of plant and animal material and constitute a major food source for many other animals.

Insects are extraordinarily adaptable creatures, having evolved to live successfully in most environments on earth, including deserts and the Antarctic. The only place where insects are not commonly found is the oceans. If they are not physically equipped to live in a stressful environment, insects have adopted behaviors to avoid such stresses. Insects possess an amazing diversity in size, form, and behavior.

It is believed that insects are so successful because they have a protective shell or exoskeleton, they are small, and they can fly. Their small size and ability to fly permits escape from enemies and dispersal to new environments. Because they are small they require only small amounts of food and can exist in very small niches or spaces. In addition, insects can produce large numbers of offspring relatively quickly. Insect populations also possess considerable genetic diversity and a great potential for adaptation to different or changing environments. This makes them an especially formidable pest of crops, able to adapt to new plant varieties as they are developed or rapidly becoming resistant to insecticides.

Insects are directly beneficial to humans by producing honey, silk, wax, and other products. Indirectly, they are important as pollinators of crops, natural enemies of pests, scavengers, and food for other creatures. At the same time, insects are major pests of humans and domesticated animals because they destroy crops and vector diseases. In reality, less than one percent of insect species are pests, and only a few hundred of these are consistently a problem. In the context of agriculture, an insect is a pest if its presence or damage results in an economically important loss.

The adage "know your enemy" is especially appropriate when it comes to insect pests. The more we know about their biology and behavior, including their natural enemies, the more likely we will be able to manage them effectively.



Left: Hippodamia glacialis, a predator of aphids. J.Ogrodnick
Center: Cotesia congregata, a parasitoid of caterpillars. K.Kester
Right: The larvae of Sphenoptera jugoslavica feed on the roots of the plant pest diffuse knapweed. R.Richard
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Insect Anatomy

Insects and closely related organisms have a lightweight, but strong exterior skeleton (exoskeleton) or integument. Their muscles and organs are on the inside. This multi-layered exoskeleton protects the insect from the environment and natural enemies. The exoskeleton also has many sense organs for detecting light, pressure, sound, temperature, wind, and odor. Sense organs may be located almost anywhere on the insect body, not just on the head.

Insects have three body regions: head, thorax, and abdomen. The head functions mainly for food and sensory intake and information processing. Insect mouthparts have evolved for chewing (beetles, caterpillars), piercing-sucking (aphids, bugs), sponging (flies), siphoning (moths), rasping-sucking (thrips), cutting-sponging (biting flies), and chewing-lapping (wasps). The thorax provides structural support for the legs (three pairs) and, if present, for one or two pairs of wings. The legs may be adapted for running, grasping, digging, or swimming. The abdomen functions in digestion and reproduction.

The internal anatomy of insects is characterized by an open circulatory system, a multitude of breathing tubes, and a three-chambered digestive system. With the exception of a heart and an aorta, there are few blood vessels; insect blood simply flows around inside the body cavity. Air enters the insect through a few openings (spiracles) in the exoskeleton, and makes its way to all areas of need by way of branching tubes, which permeate the body. The insect digestive system is long and tube-like, often divided into three sections, each with a different function. The insect nervous system transports and processes information received from the sense organs (sight, smell, taste, hearing, and touch). The brain, located in the head, processes information, but some information is also processed at nerve centers elsewhere in the body.

Knowledge about the structure and function of the insect exoskeleton has proven critical in developing insecticide formulations that are able to penetrate this multi-layered protective covering. Studies of insect communication have led to the discovery of chemical compounds used by insects to locate each other or host plants, and many of these have now been identified and produced synthetically. For example, pheromones are very specific compounds released by insects to attract others of the same species, such as for mating. Synthetic pheromones are now widely used to bait insect traps for detecting the presence of a pest, to determine its abundance, or for control. Control may involve the use of many traps to "trap out" the pest or the pheromones can be dispersed throughout the crop to "confuse" insects, making it more difficult for them to find a mate.

As simple as it may seem, knowing what type of mouthparts an insect has can be very important in deciding on a management tactic. For example, insects with chewing mouthparts can be selectively controlled by some insecticides that are applied directly to plant surfaces and are only effective if ingested; contact alone will not result in death of the insect. Consequently, natural enemies that feed on other insects, but not the crop plant, will not be harmed.

Since insects obtain oxygen through their spiracles, plugging these openings causes death. That is how insecticidal oils control insects. Components of the microbial insecticide Bacillus thuringiensis enter the digestive system and break down the gut lining. Knowledge of the nervous system of insects has led to the development of several types of insecticides designed to disrupt normal nerve function. Some of these are effective simply by contacting the insect.

Insect Reproduction

Most species of insects have males and females that mate and reproduce sexually. In some cases, males are rare or present only at certain times of the year. In the absence of males, females of some species may still reproduce. This is common, particularly among aphids. In many species of wasps, unfertilized eggs become males while fertilized eggs become females. In a few species, females produce only females.

A single embryo typically develops within each egg, except in the case of polyembryony, where hundreds of embryos may develop per egg. Insects may reproduce by laying eggs or, in some species, the eggs may hatch within the female which shortly thereafter deposits young. In another strategy common to aphids, the eggs hatch within the female and the immatures remain within the female for some time before birth.

Insect Growth and Development (Metamorphosis)

Insects typically pass through four distinct life stages: egg, larva or nymph, pupa, and adult. Eggs are laid singly or in masses, in or on plant tissue or another insect. The embryo within the egg develops, and eventually a larva or nymph emerges from the egg. There are generally several larval or nymphal stages (instars), each progressively larger and requiring a molt, or shed of the outer skin, between each stage. Most weight gain (sometimes > 90%) occurs during the last one or two instars. In general, neither eggs, pupae, nor adults grow in size; all growth occurs during the larval or nymphal stages.

The two types of metamorphosis typical of insect pests and natural enemies are gradual (egg > nymph > adult) and complete (egg > larva > pupa > adult). In gradual metamorphosis, the nymphal stages resemble the adult except that they lack wings and the nymphs may be colored differently than the adults. Nymphs and adults usually occupy similar habitats and have similar hosts. Gradual metamorphosis is typical of true bugs and grasshoppers; complete metamorphosis is typical of beetles, flies, moths, and wasps. The immatures of these latter species do not resemble the adults, may occupy different habitats, and feed on different hosts. Some moth and wasp larvae weave a silken shell (cocoon) to protect the pupal stage; in flies, the last larval skin becomes a puparium that protects the pupal stage.

Insects are cold-blooded, so that the rate at which they develop is mostly dependent on the temperature of their environment. Cooler temperatures result in slowed growth; higher temperatures speed up the growth process. If a season is hot, more generations may occur than during a cool season.

A better understanding of how insects grow and develop has contributed greatly to their management. For example, knowledge of the hormonal control of insect metamorphosis led to the development of a new class of insecticides called insect growth regulators (IGR). The insect growth regulators are very selective in the insects they affect. Based on information about insect growth rates relative to temperature, computer models can be used to predict when insects will be most abundant during the growing season and, consequently, when crops are most at risk.

Insect Classification and Identification

It is necessary to classify insects so that we can organize what we know about them and determine their relationships with other insects. For example, all members of a particular species will feed on similar foods, have similar developmental characteristics, and exist in similar environments. Most often, insect species are classified based on similarities in appearance (morphology). The flies, for example, can be distinguished and classified separately from all other winged insects because they have only one pair of wings. The hierarchy used to classify the diamondback moth, a worldwide pest of crucifers, is as follows:

• Phylum - Arthropoda
• Class - Insecta
• Order - Lepidoptera
• Family - Plutellidae
• Genus - Plutella
• species - Plutella xylostella

This universal method is used to prevent confusion among geographic regions of the world. Consequently, Plutella xylostella refers to the same insect species in the United States as it does in Asia or anywhere else in the world. Common names, however, can vary from one location to another.

Insect Ecology

Ecology is the study of the interrelationships between organisms and their environment. An insect's environment may be described by physical factors such as temperature, wind, humidity, light, and biological factors such as other members of the species, food sources, natural enemies, and competitors (organisms using the same space or food source). An understanding or at least an appreciation of these physical and biological (ecological) factors and how they relate to insect diversity, activity (timing of insect appearance or phenology), and abundance is critical for successful pest management.

Some insect species have a single generation per season (univoltine), while others may have several (multivoltine). The striped cucumber beetle, for example, overwinters as an adult, emerges in the spring, and lays eggs near the roots of young cucurbit plants. The eggs hatch, producing larvae that emerge as adults later in the summer. These adults overwinter to start the cycle again the next year. In contrast, egg parasitoids like Trichogramma overwinter as immatures within the egg of their host. During the summer they may have several generations.
Insects adapt to many types of environmental conditions during their seasonal cycle. To survive the harsh winters, cucumber beetles enter a dormant state. While in this dormant state, metabolic activity is minimal and no reproduction or growth occurs. Dormancy can also occur at other times of the year when conditions may be stressful for the insect.

It is often better to consider insects as populations rather than individuals, especially within the context of an agroecosystem. Populations have attributes such as density (number per unit area), age distribution (proportion in each life stage), and birth and death rates. Understanding the attributes of a pest population is important for good management. Knowing the age distribution of a pest population may indicate the potential for crop damage. For example, if most of the striped cucumber beetles are immatures, direct damage to the above ground portions of the plant is unlikely. Similarly, if the density of a pest is known and can be related to the potential for damage, an action may be required to protect the crop. Information about death rates due to natural enemies can be very important. Natural enemies do nothing but reduce pest populations and understanding and quantifying their impact is important to effective pest management. This is all the more reason to conserve their numbers.

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The Defense Methods of Spiders

In the world, there is one type of creature that most people are afraid of, Spiders. Ever since I was younger, I have always enjoyed keeping and watching spiders. If more people would study spiders, they would find out there is lots about spiders that is very interesting. There are species of spiders that are prey - specific prey - catching. The types of species are known as araneophagic salticids. Another thing about spiders that people don't realize is that spider have defense maginisms to protect them from predators, such as, flicking their hairs off their abdomen. Reproduction for spiders can be very dangerous and challenging for the male. When males are ready to mate, they have to be careful so that they don't either get cannibalized or chased either by the female or another male.

Spiders have prey preference

All spiders are predators and have prey - catching behaviors which are different. In spiders, there are two different types of predators. One is the stenophagous and the other is euryphagous. The stenophagous predators behavior may or may not be specialized being prey - specific prey - catching. The euryphagous predators behavior is not as specialized as what their diet is. This type of predator may be specialized in prey - catching but not specialized in their diet. There is two types of jumping spiders which have stenophagous behavior, one is ant - eating species and the other is spider - eating species. Both have certain ways they catch their prey. When the ant - eating species catch their prey they must be careful so that they don't get killed in the process. An ant is an insect which most species of spiders will not choose for prey. The spider - eating species uses the web of the prey to catch their prey. First thing for them to do is to get on the web without making the web move, instead of walking across the whole web to catch the prey they stay in one place and jiggle the web so the prey thinks it is prey for them. The species of spiders that use their prey's web to catch them are known as araneophagic salticids which are Brettus adonis, Brettus cingulatus, and Gelotia lanka from Sri Lanka; Cyrba algerina from Southern Europe; Cyrba ocellata from Australia, Kenya, Sri Lanka, and thailand; and five species of Portia which are P. africana and P. schultzi from Kenya, P. albimana from Sri Lanka, P. labiata from Malaysia and Sri Lanka and P. fimbriata from Australia, Malaysia, and Sri Lanka. These types of spiders also catches prey which are outside of the webs, then invades another spiders web which it uses aggressive mimicry and catches the resident spider and takes insects and resident spider eggs also.
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One species of spiders uses a cryptic stalking motion to catch the salticids. This spider is in Queensland, Australia known as Portia fimbriata. When P. fimbriata moves in a web, it moves very slowly and when detected it is too late for the salticid to escape. Salticids have secondary eyes which are good movement detectors and if it sees the P. fimbriata it moves around a lot to figure out what is behind it. If this happens, the P. fimbriata totally stands still until the salticid turns away again. P. fimbriata may have to be concerned with the size and type of prey to eat because a salticid which is large maybe able to either injure or kill the P. fimbriata. The size of the meal is more important to females then males. Females are normally bigger then males and have a greater need for large food and are more ready to take a risk getting their prey.

There were tests done on the feeding habits of the P. fimbriata. In the tests, the female P. fimbriata ate web building spiders and salticids more often then eating insects, but they preferred to eat salticids over web building spiders. There was a test done to see if the P. fimbriata female would take a web building spider over an insect. Most of them would drop the insect and take the web building spider. Another test done was to find if the P. fimbriata female would take an insect over an salticid. The P. fimbriata female would drop the insect for the salticid. Another test done was with size of prey they would eat. Sizes were very small, small, and large web building and salticids. The P. fimbriata females ate small species more often then very small species. Also they ate large species more often then small species. With males they resembled females by attacking spiders first more often then attacking insects. With both male and female P. fimbriata, they ate salticids more often then web building spiders. Males ate small spiders more often then very small spiders like female, but males are different in eating small spiders more often then large spiders. In all tests done with insects, the P. fimbriata also took spiders over insects. Portia is a genus of salticids which studied in nature feed mostly on web building spiders. The behavior of Portia salticids are prey - specific prey - catching against web building spiders. These types of predators have an unusual diet and evolved prey - specific prey - catching behavior for certain types of prey. Species of spiders that eat prey which can be dangerous to them have prey - specific prey - catching behavior and have distinctive preferences for unusual and dangerous prey. Studying males in nature, they often feed on the same types of web building spiders as females do and also use same behaviors as females, prey - specific prey - catching. Both male and female P. fimbriata prefer web building spiders over insects but often prey on cursorial salticids. They both use cryptic stalking to catch the cursorial salticids. When catching prey, females are more effective then males. When P. fimbriata catches prey it first touches the prey with its forelegs, and slowly moves over the prey and bites it. Most all species of Portia studied seldom leaps on any kind of prey.

Defense Behaviors

There are species of spiders that use their urticating hair on their dorsum of the abdomens for defense. When they use hair for defense, they release their hairs by using their hind legs. Then they rub their abdomen with their hind legs and the hairs fly off their abdomen and hit what they are protecting them selves from. The main species of spiders that use this defense are the Mygalomorph. These hairs are found in different places on different spiders. The hairs on the genus Ephebopus are found on a distinctive pad on the distal prolateral surface of the pedipalpal femur. One genus of Mygalomorph which has hairs on the abdomen has never been recorded with hair flicking, this is the genus Aviculariinae. According to the Bertani and Marques 1995/1996 article, the mechanism which releases the hairs are still not known very well. Aviculariinae have five species which they insert urticating hairs by direct contact with the predator, reported by Bertani and Marques. There were tests done on certain spiders, these were Avicularia avicularia, Avicularia walckenaeri, Avicularia sp., Pachistopelma rufonigrum, Theraphosinae, Acanthoscurria atrox, Vitalius sorocabae, Lasiodora klugi, Grammostola actaeon, and Theraphosa blondi. These species were studied in the Laboratorio de Artropodos of the Instituto Butantan, Sao Paulo. To test this defense behavior in the laboratory, they were touched with forceps or tip of a finger which caused them to respond. All tests were recorded to study the defense method in greater detail. The main species that showed the hair flicking defense was the Theraphosinae spiders. To flick their hairs, they lifted either one or both hind legs on the dorsum of the abdomen and kicked the hair off them. With the Aviculariinae species, they have well developed claw tufts at ends of legs to help them hold on to the object and directed their abdomen toward the object. The Aviculariinae turned its abdomen toward the object and rubbed it against the object. After hairs hit the skin, they penetrate into the skin slowly and embeds completely after one to two days. This species would only use the rubbing method for defense if they were in their silk webs but if out of the web, they would take a flight and run across the cage floor or climb the walls. Theraphosicae have many spines on their legs which help to comb the hairs to flick them off the abdomen. Theraphosicae are the only group that can flick and shed their hairs. Many hairs still remain attached while others are combed off the abdomen. The Aviculariinae do not have spines on their legs like the Theraphosidae, but a few have apical spines. There is a difference in size and types of hairs between Theraphosidae and Aviculariinae. The Theraphosidae have type I, type III, and type IV. Type I hairs are 0.2 to 0.6 mm in length, type III hairs are 0.3 to 1.2 mm in length , and type IV hairs are 0.06 to 0.2 mm in length. Most of the hair are thin, short, and flow by air. Aviculariinae spiders have two types of hair, type II and type V. Type II are only found in the abdomen of the genera Avicularia, Pachistopelma, and Iridopelma. Type II are 0.5 mm in length which are longer than the other hairs. They are also stout and have many small, scale-like barbs. When this type are scraped off the spider, they do not get carried by air but fall to the ground instead. The penetrating tip of the hair in type II are directed downwards which in type I, type III, and type IV are directed upward. The type II hairs are only released when the abdomen of the spider is touched and the penetrating tip rises up to come in contact with the object that touched it. The next type of hair are type V which are short and stout, with many barbs and are easily blown thru the air. The types of hair have different structures and release in different ways. These urticating hairs are the same size as cactus thorns and when they touch the skin, you can't see them but sure can fill them.

Reproduction in Spiders

Female spiders can have multiple mating. Males have to be concerned about this because they have to make sure that their sperm fertilizes the eggs and not by another male. To prevent this from happening, the male has to ejaculate lots of sperm and prevent the female from attracting other males. To stop the female from attracting other males, males can physically repell them by placing obstructions over her genital opening, or by transferring chemical compounds that induce refractory period which female will not be sexually receptive anymore. There is a period where mate guarding is used until onset of refractory period begins. Male spiders using mechanisms that enable the female to mate with other males have been reported by Austad 1984, Christenson et al. 1985, Suter 1990, Watson 1991, Dodson and Beck 1993, Eberhard et al. 1993, Masumoto 1993, Uhl 1993, and Prenteret al. 1994. Watson 1986 found a species of spider that used a sex attracting pheromone that destroyed the web of the female, which was the male Linyphia litigiosa. Another type of male spider studied by Masumoto 1993, used a copulatory plug during mating which inhibits the transfer of sperm by other male spiders, this species are known as the Agelena limbata. Many male species stay around the female after mating to repell off other males. Andrade 1996 found that male redback spiders sexually cannibalize to reduce the proportion of eggs that were fertilized by subsequently mating.

Many females after mating go into the refractory period and are not sexually receptive to other males that are around her, this is common in most insects also. This type of period has not totally been widely documented for spiders. The multiple mating by females are more likely to be in gregarious spiders then solitary spiders. More males are attracted by female gregarious because of the aggregation which males can move easily among these females. A gregarious spider which form aggregation of orb webs share structural threads like other females, this spider is known as Gasteracantha minax which is the Australian jewel spider. A female G. minax spiders can be surrounded by several courting males which wait at edge of her web for her to react for mating. Without leaving the aggregation, the males can count several females. Before mating, court male G. minax locates the female web and constructs a mating thread from the vegetation of the edge of the female web. Then the male goes halfway up the thread with his first and second pair of legs. The female eventually moves out onto the thread toward the male. The male and female touches legs before the male grabs her tightly and clasps her ventral surface of her abdomen with his legs. The male then places one of his palps adjacent to the females epigyne, inserts his embolus, and transfers sperm. Then they take less then a minute interval which the female returns to central hub while male is still attached. Eventually male leaps away from female by the thread attached to the web. The male then courts the female a second time and inserts the embolus from his other palp. For more details on the mating and courtship behavior among these spiders refer to Mascord 1970 and Robinson and Robinson 1980. Different species of orb weaving maybe different in sexual dimorphism. In some species, females maybe larger in the order of magnitude then males. Usually females are at least one and a half times bigger in size then males and court of a mating thread is less pronounced in different species. During mating the female G. minax are three times the weight size of the male G. minax which is surprising for the courtship behavior. Elgar and Bathgate did some experiments to investigate the way male G. minax reduce the females to remate. To do this Elgar and Bathgate introduced males at different times during the courtship and mating sequence. They also did another experiment study on the influence of male-male competition and sexual cannibalism on sexual dimorphism.

The amount of G. minax spiders were counted in late December 1992 and early January 1993 on the coastal salt marsh fringe of Port Philip Bay at Williamstown, Victoria. Then Elgar and Bathgate counted the number of males and females on solitary or aggregated webs that were bisected by the transect lines. They also collected immature males and females from this group. Elgar and Bathgate put the immature males and females in individual containers in the laboratory for them to mature. These spiders were feed bush flies known as Lucilia cuprina. The mature females were weighed on an electronic balance and transferred into a enclosed perspex mating frame with the measurements of 70 x 50 x 10 cm.Within a few days, the females built a complete orb web. Most females used in the study weighed 38.3 mg. The males were weighed on the days that they were used for mating. The average weight was 13.7 mg for males. For Elgar and Bathgate to test the relationship between female receptivity and male mate-guarding behavior then introduced the males either while mating was going on or the following day after mating. One test was to add one male only to a virgin female and he was either removed after successfully doing both pedipalp insertions or left in mating frame overnight with the female. The next test was to release one male into the mating frame with a virgin female then releasing the second male in the same mating frame either during first or second pedipalp insertion of the first male or male released into the mating frame with solitary female the next day after mating occured. These types of testing were done to see what happens with courtship, copulation, and aggressive behavior of males and females at different times of mating. When putting males in with females, they were put on the base of the mating frame which then the males would find the female orb webs themselves by walking up the side of the frame. Elgar and Bathgate would record the time the male got to the orb web. Copulation was initiated and ended when female would chase the male and the males would chase the rival males. For Elgar and Bathgate to tell what male was whom, they would either tell by size or natural markings.

The results of Elgar and Bathgates experiments, the adult and immature G. minax female spiders per aggregation at Williamstown was 3.1 and for male adult G. minax per aggregation was 1.6. There were nine females and four males that were the largest aggregation. Between number of females and number of males there were positve correlation found within aggregations. When Elgar and Bathgate did these experiments, they found out it was hard to estimate the number of adult males per female for each aggregation because they could not always tell which females the males congregated. The mean of adult males per solitary females were 1.45. The solitary females had at least one male and one of these females had three males on the periphery of her web. It took about 20.2 minutes for the male G. minax to locate the orb web of the female G. minax and then the female would capture and cannibalize the male before he could embrace her, this happened in three of thirty trials. The males that were cannibalized by females did not have a different weight from those males that avoided being cannibalized. The females that were cannibalistic did not have a weight difference from females that were noncannibalistic. There was also no differences in behavior in the males that were either cannibalized or noncannibalized. Elgar and Bathgate defined the duration of copulation as the time when the male first embraced the female to when he leapt away from her. The duration copulation had a positive correlation with that of the second compulation when female encountered a single male. The duration of either first or second copulation was not significantly correlated with either male or female size. There were also no difference in duration of first copulation with either virgin females or mated females with mating males.

Studing in the field, males that were already on the female orb web would pluck or pull silk threads to get rid of intruding males. These aggressive interactions would work when one male would retreat and go to the edge of the orb web. This also happenend in the laboratory when other males were introduced to the orb web. In the lab, the males that were already there would chase the other males off the web. The time between first and second copulation was 22.7 minutes when there was no other males in the web. When other males were present, the time was shorter. The duration of the second copulation was influenced when other males were present. When no other males were present, the duration of the second copulation were longer then the first copulation but if another male was present, it was not much different.

Female G. minax would mate several times if she was not mated the day before. For male to mate with a female after she mated before, the courtship must be within an hour after previous mating. Females would chase the males off more frequently if they were mated a day before compared to within the hour. Males reacted to other males more often it they would be in the web the same time they were copulating then if the male entered the web the following day. The male left overnight with the female would move off the orb web by the next morning. When male spiders mate, there are things they have to be careful so that they don't get cannbalized by the female or chased off by either another male or the female. For spiders to survive, they must have different methods to defend themselves. Spiders all are very defensive when it comes to catching prey, protecting themselves from predators, and when they are ready to reproduce.

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Common marmoset (Callithrix jacchus)

SOCIAL ORGANIZATION AND BEHAVIOR

Though they have been studied in captive settings since the 1960s, the social structure of wild common marmosets is less well known than other reproductive and behavioral characteristics (Digby 1995; Ferrari & Digby 1996). Long thought to be monogamous, evidence from recent field studies shows that they have a social structure that revolves around a stable, extended family unit with a few dominant breeding individuals and flexible mating behavior (Digby & Barreto 1993; Digby 1995; Ferrari & Digby 1996; Sussman 2000). Groups of common marmosets range in size from three to 15 animals, but usually have about nine members (Stevenson & Rylands 1988; Ferrari & Lopes Ferrari 1989). Within the group, three generations are often encompassed including one or two breeding females with one breeding male and related adults (possibly parents or siblings) and the breeding pairs' offspring (Ferrari & Digby 1996). Using genetic evidence to tease apart the relationships within a group of common marmosets, it has been demonstrated that females within a group are closely related (as close as mother/daughter or sisters) while breeding males are distantly related, and probably immigrated from another group. When males are closely related to breeding females, they do not breed with them (Nievergelt et al. 2000). Unlike many other primate species, emigration does not occur during adolescence in common marmosets. Instead, they remain in their group until they are adults and then the males leave the group to find breeding females. Emigration by adults is balanced by recruitment through births, keeping the group size relatively stable over time, though very little is known about when and why adult common marmosets leave their groups (Ferrari & Digby 1996). Group stability is compromised in the wild because the death of a breeding adult will cause a group to break up and separate into new groups (Lazaro-Perea 2001).
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Social status within the group is linked to breeding status, and while the breeding pair is usually codominant, if there is more than one breeding female, one of the breeding females is dominant over the other. For nonbreeding individuals, the dominance hierarchy is age-graded and sex is not a factor (Digby 1995). Dominant individuals displace others at feeding sites and exhibit a variety of postures, vocalizations, and behaviors that include open-mouth threats, nips, cuffs, lunges, grabs, ear-tuft flicks, genital presenting, chasing, and biting (Abbott 1984; Digby 1995). They are the center of social life in the group and subordinate animals favor being in proximity with dominant individuals and groom them preferentially (Digby 1995).

Photo: Ludwig Miller

One of the defining social behaviors of common marmosets is their system of cooperative breeding and infant care (Digby & Barreto 1993; Digby 1995; Sussman 2000). The breeding adults in the group depend on the cooperation of their adult siblings and offspring to care for their new infants to ensure their survival. This requires behavioral and physiological reproductive suppression of adult and developing females and behavioral reproductive suppression of adult and developing males in the group by the breeding pair, a phenomenon that has been well studied among captive common marmosets (Saltzman et al. 1997; Baker et al. 1999). In response to a dominant, unrelated, female, submissive common marmosets become anovulatory while her daughters may continue to cycle (Ziegler &de Sousa 2002). Rather than dispersing, finding a breeding partner, and forming a new group, subordinate marmosets that are sexually mature and could otherwise mate stay within the family unit. This strategy may be beneficial under certain ecological conditions. For example, where marmosets live in extremely high population densities, dispersal may not be possible because of lack of available territory and hostile encounters with other marmoset groups in the area or high chance of predation if ranging solitarily (Dietz 2004). Staying within the group, at least for a while, to help raise their nieces and nephews or siblings may be the best choice to maximize fitness. Because these helpers are likely related to the dominant female, it is within their interest to ensure the survival of her offspring because they are also related to them and the survival of the infants increases the related caregiver's inclusive fitness (Saltzman et al. 1997).

REPRODUCTION

Sexual behavior and reproductive parameters are often skewed in captivity compared to natural conditions and as such, data from laboratory settings often must be substantiated by observations and tests from wild animals. The common marmoset is no exception, though recently there have been advances in hormonal monitoring techniques resulting in data from wild common marmosets (Albuquerque et al. 2001).

Photo: Gustl Anzenberger

The mating patterns of wild common marmosets are exceptionally complex and vary over time. While monogamy was long thought to be rule among common marmosets because of captive studies, there have been observations of polygyny, polyandry, and monogamy in the wild (Digby 1995; Nievergelt et al. 2000). Field data support that most mating is monogamous and when two females are pregnant within a group, it is because the subordinate female, the daughter of the dominant female, mated with a male from a neighboring group. The non-dominant female is not fully reproductively suppressed, but her pregnancy does not result in viable offspring (Digby 1999; Nievergelt et al. 2000; Arruda et al. 2005). Even though the subordinate females lose their infants, this pattern of mating with extra-group males may be a strategy to identify potential future mates. This is supported because subordinate females that mated successfully but did not produce viable offspring emigrated from their natal groups shortly after and joined another group, assuming a breeding position (Arruda et al. 2005).

Menarche occurs between nine and 14 months of age but common marmosets do not menstruate nor are there any external signs of ovulation. The ovarian cycle lasts between 24 and 30 days, but averages 28 days (Hearn 1982; Kendrick & Dixson 1983). In captivity, in the presence of a dominant female, unrelated young female marmosets generally will not ovulate and though they are sexually mature, they do not cycle and are unable to breed, but the dominant female's daughters do exhibit ovarian cyclicity even if they do not mate (Abbott 1984; Ziegler &Sousa 2002). Under natural conditions, the presence of two breeding females has been observed, but the females are always closely related, either mother and daughter or sisters (Digby & Barreto 1993; Nievergelt et al. 2000; Arruda et al. 2005). For females, the mechanism by which this occurs is both behavioral and physiological but variations in reproductive suppression are not well understood. That is, it is unclear why in most but not all circumstances only one female breeds while in other instances there are two breeding females (Saltzman et al. 1997). One factor that contributes to the suppression of ovulation in subordinate female common marmosets is the presence of a related male. In laboratory studies, young adult females do not ovulate or exhibit sexual behavior in the presence of their fathers, probably a defense against inbreeding, but if the biological father is replaced by another adult male, within a few weeks ovulation occurs coupled with sexual solicitations and an increase in aggressive behavior towards their mothers (Abbott 1984; Saltzman et al. 1997). One explanation for this is daughters are trying to displace their mothers as the dominant breeding female in their group and have more opportunities to mate and increase their overall fitness.

Once the social conditions are suitable for a female to begin breeding, common marmosets reproduce consistently over the remainder of their adult lives. Females solicit mating by tongue-flicking displays directed at males. Common marmosets mate throughout their ovarian cycle but the majority of mating occurs in a three- to four-day window on either side of ovulation (Kendrick & Dixson 1983). Gestation lasts about five months (143 to 153 days) and soon after parturition (within 10 days), female marmosets begin to cycle again and shortly thereafter become pregnant (Lunn & McNeilly 1982; Sussman 2000). The interbirth interval exhibited by common marmosets is five months and they give birth twice each year (Stevenson & Rylands 1988). Common marmosets exhibit a high degree of birth seasonality in the wild and have two birth peaks during the year; during September, October, and November as well as April, May, and June (Stevenson & Rylands 1988). One of the major factors thought to influence this strict seasonality is rainfall, which directly affects food availability (Di Bitetti & Janson 2000). Common marmosets give birth at the end of the dry season and at the end of the rainy season to maximize food availability. Because nursing is so energetically costly, females need to minimize the nutritional stress they experience by rearing their infants during periods of relative food abundance (Di Betetti & Janson 2000). Additionally, the pattern of habitual twinning among common marmosets means nursing and rearing infants is even more energetically taxing. Common marmosets do not always give birth to twins; they also have single births and triplets. The reproductive patterns of common marmosets would not be possible if there were not special adaptations to infant rearing and parental care.

PARENTAL CARE

Group support for developing infants is necessary among common marmosets. Twins are often 20 to 27% of the mother's total body weight; this is the equivalent of a 135-pound woman giving birth to two 16-pound babies. A female would not be able to care for infants alone because of the high demands of pregnancy and lactation as well as the mechanical difficulties of carrying two heavy infants, therefore all age-sex classes contribute to infant survival and development among common marmosets (Stevenson & Rylands 1988; Rothe et al. 1993; Tardif et al. 1993; Kinzey 1997). As discussed previously, compliance with cooperative rearing is probably linked to kin selection and fitness. The non-reproductive helpers in the group are probably related to the infants because they are related to the breeding female. It is within their interest to ensure the survival of her offspring because this increases the helper's inclusive fitness (Rothe et al. 1993; Saltzman et al. 1997). Studies on captive marmosets indicate that survival rate increases as number of non-reproductive helpers increases, up to a point. The highest survival rate of infants (95.7%) is found in groups of 10 common marmosets (the breeding pair and eight helpers) (Rothe et al. 1993). Interestingly, the average group size in the wild is about nine members.

Photo: Gustl Anzenberger

From birth, common marmosets have a very strong cling reflex and do not voluntarily leave their carrier's back for the first two weeks of life. They are very active starting in the second week, crawling on their carrier's back and investigating their surroundings (Stevenson & Rylands 1988). Immediately after birth, the breeding male and presumptive father of the infants begins to carry the twins and caregiving by offered by the father, mother, or other members of the group (Yamamoto 1993). Over the following weeks, time off the backs of carriers gradually increases and the infants develop locomotory behaviors and coordination and begin to exhibit play behavior (Stevenson & Rylands 1988). By about three months of age, the infants are almost completely weaned and are capable of self-feeding, though they do not gnaw their own holes to feed on gum but rather lick the holes created by older individuals (Stevenson & Rylands 1988). The infancy stage lasts until about five months of age and is followed by the juvenile period, which lasts between five and 10 months (Stevenson & Rylands 1988; Yamamoto 1993). By five months, common marmoset juveniles are 75% of their adult weight. Interaction with other group members besides parents is emphasized and play becomes rougher as future status is worked out. During the juvenile period, another set of infants is usually born and carrying and play with infants also characterizes this period of development (Yamamato 1993). Between nine and 14 months, the sub-adult stage begins, characterized by the full repertoire of adult behaviors as well as puberty. By 15 months, common marmosets have reached their adult weight and are capable of reproduction but do not reproduce until social conditions are adequate (Yamamato 1993).

COMMUNICATION

Like all primates, vocal and visual communication is important to common marmosets. Facial expressions and vocalizations convey information about social status, emotional state, and intent to other individuals (Stevenson & Rylands 1988). Because of their small size and the natural habitats they are found in, visual signals are important in close-range communication while vocal communication is more important over longer distances (Jones 1997). Some expressive facial and postural positions include the "partial open mouth stare," "frown," and "slit-stare" which are used to signify alarm, aggression, and submission. When common marmosets flatten their ear-tufts close to their heads in "tuft-flatten" position, this signifies submission, fear, and sometimes curiosity of new objects (Stevenson & Rylands 1988).

Photo: Ludwig Miller

Common marmosets use vocal signals in a variety of situations including in response to unexpected movements and in threatening situations (Jones 1997). Alarm calls in response to sudden movement include "staccatos," which are a series of short ascending calls, and "tsiks," that are brief descending calls given either alone or in a series. Alarm calls are brief, high-pitched vocalizations that elicit fleeing behavior from other group members and are given in response to threatening situations (Lazaro-Perea 2001). There are some calls that are generally used and which lack obvious contextual connection including "phee" and "trill" calls (Jones 1997). "Phee" calls have high sound intensity and sound like very loud, high pitched whistles. They are usually given in a series of one to five notes that last about two seconds each. They are important for long-range vocal contact and play a role in mate attraction, maintenance of group cohesion, territorial defense, and location of lost group members (Jones 1997). "Trill" calls are also generic vocalizations, but sound much different from "phees." They have lower pitch and have cyclic frequency fluctuations that give them a distinctive vibrato sound. These calls are given by all animals of any age, sex, and status and their main purpose probably is to monitor group members by identifying and locating their position in low visibility areas (Jones 1997).

Unlike the apes and Old World monkeys, smell is very important to New World monkeys. They have a specialized organ in their nasal cavity called the vomeronasal organ that allows them to process chemical signals in a focused manner and discern information about other animals (Evans 2003). Because of the presence of this "second nose," scents are very important tools of communication in New World monkeys, and common marmosets convey information by marking objects with secretions from specialized scent glands on their chests and around their anus and genitals (Lazaro-Perea et al. 1999). The main information conveyed by scent-marking includes demarcating home range and resources within that range, signifying social status, and advertising reproductive status (Stevenson & Rylands 1988; Lazaro-Perea et al. 1999; Ziegler et al. 2005).

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