fauna

I never miss a chance to reblog pictures of the Rough-scaled Bush Viper (Atheris hisida) from the forests of western Africa. Look at that adorable and highly venomous face :3

(Source: sharkgrime)

IUCN: Almost one in five reptiles struggling to survive

15 Feb. 2013 | International news release

Nineteen percent of the world’s reptiles are estimated to be threatened with extinction, states a paper published today by the Zoological Society of London (ZSL) in conjunction with experts from the IUCN Species Survival Commission (SSC).

The study, printed in the journal of Biological Conservation, is the first of its kind summarising the global conservation status of reptiles. More than 200 world renowned experts assessed the extinction risk of 1,500 randomly selected reptiles from across the globe.

Out of the 19% of reptiles threatened with extinction, 12% classified as Critically Endangered, 41% Endangered and 47% Vulnerable.

“This is a very important step towards assessing the conservation status of reptiles globally,” says Philip Bowles, Coordinator of the Snake and Lizard Red List Authority of the IUCN Species Survival Commission. “The findings sound alarm bells about the state of these species and the growing threats that they face. Tackling the identified threats, which include habitat loss and over-harvesting, are key conservation priorities in order to reverse the declines in these reptiles.”…

(read more: International Union of Concerned Scientists)

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photos:

Kuroiwa’s Ground Gecko (Goniurosaurus kuroiwae) by Hidetoshi Ota; Hump Snout Lizard (Lyriocephalus scutatus) by Ruchira Somaweera; Spiny-flanked Chameleon (Trioceros laterispinis) by Michele Menegon; Amphisbaena fuliginosa by Laurie Vitt; Ahaetulla nasuta by Ruchira Somaweera; Egyptian Saw-scaled Viper (Echis pyramidum) by Michele Menegon

biomedicalephemera:

Ways to Die: Snake Venom

The vast majority of snakes that one encounters in the wild (unless you live in Australia or India) are either non-venomous to humans or want nothing to do with you.

However, should you stumble upon a rattlesnake nest or coral snake hole while texting in the middle of nowhere, there will probably be a combination of different enzymes and polypeptides pumped into your body, via the modified parotid salivary glands (right below the ear in humans) that snakes have evolved over the ages, to disable their prey. Of course, you’re not prey, but you stepped on a snake while texting. It has every reason to envenomate you.

While all snakes have multiple active enzymes in their venom, all snakes dangerous to humans have either neurotoxins or cytotoxins as a significant component in their venom. For the most part, elapids (such as the cobras and mambas) create neurotoxins, while the viperids (such as vipers, adders, and rattlesnakes) create cytotoxins.

Neurotoxins

• Dendrotoxins: Inhibit neurotransmission by blocking the exchange of positive and negative ions across the pre-synaptic neuronal membrane, causing paralysis. Found in some rattlesnakes (such as the Mojave) and mambas.
• Fasciculins: Destroys acetylcholinesterase (AChE) in synaptic clefts of nerves. Without AChE, acetylcholine (ACh) is not broken down, and remains bound to the postsynaptic vesicles of the nerve, leading to constant contraction of the related muscles. This is called tetany or tetanic paralysis. Found only in mambas.
• α-neurotoxins: Very large group of toxins that mimic ACh and bind to post-synaptic vesicles, leading to numbness and paralysis. Found in cobras, kraits, and sea snakes. 

Cytotoxins

• Cardiotoxins: Target muscle cells and cause depolarization. If enough of these components reach the heart, the depolarization can cause irregular heartbeat or spontaneous stopping of the heart. Can cause fasciculations in skeletal muscles. Found in the Naja genus, and in King Cobras. Minor but important component of mamba venom.
• Phospholipases: Proteins that target the phospholipid bilayer of cells, causing cellular rupture. Can cause extreme blistering at site of bite. Relatively uncommon, found in the Japanese Habu.
• Hemotoxins: Burst red blood cells (hemolysis), causing thin blood, internal bleeding, and blood clots due to the massive clotting response. Found to some degree in almost all vipers, as well as some cobras.

Images:
Top: Bungaris fasciatus - Banded Krait. An elapid, and the largest of the kraits. Has neurotoxic venom. [source]
Center Right: Hydrophis robusta [now Hydrophis spiralis] - Yellow Sea-Snake. The longest sea snake, at 3 m (9.8 ft). A member of the Hydrophiinae, separate from other elapids. Though they have some of the most toxic venom in the world, bites are extremely uncommon and often unnoticed. [source]
Center Left: Vipera russellii - Russell’s Viper. A particularly aggressive viperid. Necrosis and amputation following envenomation not uncommon, due to hemolysis and local cell damage. [source]
Bottom: Vipera caudisona [now Crotalus horridus] - Timber Rattlesnake. A venomous viperid endemic to the United States. Primarily hemotoxic venom, very low fatality rate, but very painful bites. [source]

Matilda’s Horned Bush Viper (Atheris matildae)

Discovered in SW Tanzania in 2010, the viper can grow to 65cm. “This particular animal looks fierce and probably is venomous,” said researcher Tim Davenport, a Briton who has lived in Tanzania for 12 years. “However, it is actually a very calm animal and not at all aggressive. I have handled one on a number of occasions.” The Viper was named for Davenport’s 7 tear old daughter.

(photos: Tim Davenport/WCS)

(via: OurAmazingPlanet)