Wednesday, October 24, 2007

Cobra Venom

Among snakes, cobras and coral snakes may be singled out as having a particularly neurotoxic venom; among other animals, the venom of arachnids also falls into the neurotoxic category. The spitting cobra can spray its venom from a distance of about 2.4 (about 8 ft) into the eyes of its victims, causing temporary blindness and great pain. Venom coming in contact with human eyes causes an immediate and severe irritation of the conjunctiva and cornea that, if untreated, may result in permanent blindness. The venom of cobras, a neurotoxin, acts powerfully on the nervous system. With effective serum more available, however, the high death rate from cobra bites in some areas of Asia has decreased. Cobra venom has been used for many years in medical research because it has an enzyme, lecithinase, that dissolves cell walls as well as membranes surrounding viruses.

A common misconception is that baby snake are deadlier than adults. While not proven scientifically, it would seem that an adult cobra can control the the amount of venom delivered, if any, with each bite, depending on the threat it feels. A baby snake has no control over the amount of venom delivered by its bite, thus always giving a full dose. A baby cobra is fully able to defend itself in as little as three hours after entering the world. Cobras are completely immune to the venom produced by their species.

Venom: poison of animal origin, usually restricted to poisons that are administered by biting or stinging and used to capture—and, sometimes, aid in digesting—prey, or for defense. Thus the poisons secreted by the skin of some toads, or accumulated in the bodies of numerous inedible animals, are ordinarily not considered venoms. The most familiar venomous animals are certain snakes and insects and the spiders and other arachnids. Venomous species occur throughout the animal kingdom, however, including the mammals. Some shrews, for example, have venomous saliva, and the platypus bears poison spurs on its hind legs. The severity of a venom's effects depends on several factors, such as its chemical nature, the stinging or biting mechanism involved, the amount of venom delivered, and the size and condition of the victim. For example, all spiders are venomous, but the venoms of most are too weak or minute in quantity to have noticeable effects on humans; in addition, many spiders cannot even puncture human skin. Thus, few of them are poisonous to humans, but their venoms are quite effective on insect prey. Chemically, venoms vary greatly across the animal kingdom and are not readily defined. Snake venoms, for example, are complex mixtures of enzymatic proteins and different toxins. In terms of their effects, however, they may be broadly categorized as hemotoxic (damaging blood vessels and causing hemorrhage) or neurotoxic (paralyzing nerve centers that control respiration and heart action); they may also contain agents that promote or prevent blood clotting. Sometimes a combination of these effects is involved, however, and variations may occur within genera or even within species. The effects of insect stings are usually the result of histamines that produce local irritation and swelling. Serums against various venoms can be produced by injecting animals such as horses with sublethal doses and extracting the immune serum, or antivenin, that the animal body produces. Venoms themselves have occasional medicinal uses; for example, some are used as painkillers in cases of arthritis or cancer, and some serve as coagulants for people with hemophilia.

Note the distinction between venomous and poisonous: venomous refers to a creature that has the ability to secrete or utilize it's venom externally, while poisonous includes creatures that contain a poison substance. Often poisonous creatures are harmless unless eaten. Venomous creatures can often use their poison as a weapon. Cobras are all venomous, yet most are not poisonous, so long as the venom glands are not eaten.

Monday, October 15, 2007

Authorities give clean chit to Whitaker

(Maneka Gandhi had accused Whitaker of exporting king cobra venom Permission for project on conservation of king cobra was withdrawn in April)

BANGALORE: Allegations of extraction and export of the venom of king cobras against noted herpetologist Romulus Whitaker, levelled by the former Union Minister and animal activist Maneka Gandhi, have been proved baseless in the inquiry conducted by the Deputy Conservator of Forests, Shimoga Wildlife Division.

According to reliable sources in the Forest Department, the officials did not find any prima-facie evidence to prove that Mr. Whitaker and his research group extracted venom in the Agumbe research station.

“Venom extraction and storage is a complex procedure that requires certain equipment. During the inquiry, officials did not find anything that could prove this,” the sources said.

Pending inquiry, the department had in April withdrawn permission for an ambitious project by Mr. Whitaker on the conservation of the king cobra in the rainforests of Agumbe in the Western Ghats.

Principal Chief Conservator of Forests (Wildlife) I.B. Srivastava told The Hindu that he had received a report in this regard from the DCF during the last week of August. “After studying the report, I have asked for some clarifications from the DCF, and a final decision on the issue will be taken shortly,” he added.

The report submitted by the DCF, it is learnt, suggests that Mr. Whitaker should be allowed to continue his research after being issued a warning.

Forest Department sources said that Mr. Whittaker and his associates had given live demonstrations of king cobras in a few educational institutions, for which the departmental permission had not been obtained. “He (Mr. Whitaker) has stated that the awareness programmes had been conducted following a request from the Range Forest Officer. But we feel that he should have sought permission from the higher authorities before he conducted those demonstrations,” sources said.

Founder of the Snake Park and Crocodile Bank in Chennai, Mr. Whitaker entered into a memorandum of understanding with the Karnataka Forest Department this year for setting the king cobra telemetry project.

The five-year research project on the largest venomous snake of India was initiated to study the king cobras’ unique nesting behaviour, breeding biology and conservation through telemetric tracking.

Monday, October 8, 2007

Snakes eat poisonous toads and steal their venom

22:00 29 January 2007 news service
Rowan Hooper

Toads on the Japanese island of Ishima seem to be losing their evolutionary battle with snakes. Most snakes, and indeed most other animals, avoid eating toads because of the toxins in their skin. Rhabdophis tigrinus snakes, however, not only tolerate the toxins, they store the chemicals for their own defensive arsenal.

Deborah Hutchinson at Old Dominion University in Norfolk, Virginia, US, and colleagues, found that snakes on Ishima had bufadienolide compounds – toad toxins – in their neck glands, while those snakes living on the toad-free island of Kinkazan had none.

The snakes are unable to synthesise their own toxins, so they can only have derived bufadienolide compounds from their diet. Hutchinson’s team confirmed this by feeding snake hatchlings either a toad-rich or a toad-free diet. Toad-fed snakes accumulated toad-toxins in the nuchal glands on the back of the neck; snakes on a toad-free diet did not.

“Rhabdophis tigrinus is the first species known to use these dietary toxins for its own defence,” says Hutchinson.

Fight or flight
What is more, when attacked, snakes on different islands react differently. On Ishima, snakes stand their ground and rely on the toxins in their nuchal glands to repel the predator. On Kinkazan, the snakes flee.

“Snakes on Kinkazan have evolved to use their nuchal glands in defence less often than other populations of snakes, presumably due to their lack of defensive compounds,” says Hutchinson.

Moreover, baby snakes benefit too. The team showed that snake mothers with high toxin levels pass on the compounds to their offspring. Snake hatchlings thus also enjoy the toad-derived protection.

Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas0610785104)