Nanostructures Make Viper Skin Ultra-Black and Stealthy
by Laura Poppick
From even a short distance, this West African Gaboon viper looks just like a pile of dead leaves. New research shows that the highly-camouflaged snake owes its elusiveness to nanostructures in its black scales.
The velvety-black patches on this snake’s back are so dark and absorb so much light, they look like gaps in the snake’s body. This illusion allows the lurkers to dissolve into leaf litter as they wait for prey on the rainforest floor.
To determine what makes these scales appear so black, a team of German scientists examined the snake’s skin under a scanning electron microscope (SEM), and found differences in the nanostructures of dark and pale scales that explain the high contrast, the team reports today in Scientific Reports…
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.”…
Desert Horned Viper (Cerastes cerastes), highly venomous, found in sandy desert areas of North Africa and the Middle East, up to 85 cm (~33 in) in length, egg laying, feed on a wide variety of small mammals and reptiles, tend to move across loos sand by “side winding”.
The element of surprise gives this Rhinoceros Viper (Bitis nasicornis) in Cameroon an edge over prey. Quick-kill venom finishes the job. Vipers provide valuable toxins, including those used in drugs for hypertension and heart disease and to control bleeding during surgery.
In the Kgalagadi Transfrontier National Park, South Africa, photographer Piet Heymans came across the extraordinary sequence photographed below. The photos are taken near Langklaas in the park along a stretch of road where a puddle had formed from rains the night before. The photos show a Cape cobra (Naja nivea) eating a Puff adder (Bitis arietans)…
They are highly venomous and can be found in the rainforests of Central Africa. It is the highly keeled and bristle-like scales that give it an almost feathery appearance thus earning it the common name of Feathered tree viper. While a bite from one of these snakes would be a serious event as no known antivenin exists, because of their remote location they rarely come in contact with humans.
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.
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.
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]
The Rough-scaled Bush Viper (Atheris hispida) is a venomous semi-raboreal snake snake found amongst bushes and reeds in forest habitats in West Africa. They are nocturnal, and feed on a variety of small reptiles, frogs, and small mammals. They may reach a length of up to 73 cm.
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.