Wednesday 13 November 2013

Tentacled Snake

Image: Josh More
Erpeton tentaculatum
A snake... TENTACLED?! Does it scurry across the floor like a scaly centipede on dozens of tentacle-legs? Does it grab hold of prey and squeeze the life out of it with dozens of tentacle-arms? Does it repeatedly inject venom by the gallon with dozens of hypodermic tentacle-fangs?

Or does it mostly sit quietly with a couple of innocuous tentacles sticking out of its snout like a huge handlebar moustache?

Image: Smithsonian's National Zoo
We humans don't have much to fear from this little snake. They reach only 60 or 90 cm (2 or 3 feet) long and they're very slim and trim. Their fangs are small and positioned at the back of their mouth, which is hardly ideal for biting anything bigger than themselves.

If you're a small fish, however...

Image: Kenneth C. Catania
Meet thy moustachioed doom.

Tentacled Snakes are entirely aquatic. They need to surface in order to breathe, but they spend all their time in murky lakes and slow-moving rivers in Thailand, Cambodia and Vietnam. They even give birth to live young so they don't have to climb up onto land to lay their eggs like sea turtles do.

Image: Josh More
They hold themselves in a very particular position as they wait for a chance to ambush prey. Their tail end delves into the plants and assorted debris of the lake sediment and anchors them in place. Meanwhile, the rest of the body is held rigid and lurches up like stray tree branch before curling into a J-shape. It all looks much like a gentleman's umbrella stuck in the mud.

And then, with shocking speed, it eats a fish. "That's no umbrella", say bemused eye-witnesses. The poor fish probably doesn't have a chance to say anything before it's snatched up, bitten by those fangs at the back of the umbrella's snake's mouth and swallowed whole.

Video: Nicky Nancke

It all happens so quickly that we only recently discovered what actually happens!

The Tentacled Snake doesn't just mindlessly lunge at the fish with incredible speed. Instead, it deviously makes use of the fish's own thoughtless reactions to ensure it swims right where the snake wants it to. It's like the Foot-eating Monster tapping you under the knee with a little hammer so that you unthinkingly plunge your foot right into his waiting jaws.

The reflex in question is called the C-start, and it's controlled by a pair of neurons called the Mauthner cells which are present in the brains of virtually all fish and amphibians.

Image: Kenneth C. Catania
When a fish feels motion on one side of its body - the kind of motion which may indicate an umbrella suddenly coming to life and lunging for the kill, for example - the fish immediately turns its head to the other direction. This is the C-shape of the C-start. The next step is to quickly swim in that direction, away from the disturbance. These Mauthner cells are extremely fast, and it can be less than one tenth of a second between the fish sensing disturbance in the water and its muscles working to propel it away from danger.

There isn't even time for the fish to gasp in surprise. So what's a a snake to do against this incredible escape reflex?

The answer, is that it doesn't move its head... not at first, anyway. In its J-shaped position, it waits until a fish wanders into the space between its body and head. Then it flicks that part of its body, sending a ripple at the fish. The fish is alarmed, it reacts, it makes to swim away from this terrible danger and ends up diving straight into the jaws of the Tentacled Snake.

It's a cruel and devilishly intelligent strategy, befitting of one who wears a handlebar moustache. Which reminds me, what is that thing for, anyway?

Image: Josh More
Turns out the tentacles are sensitive to the movement of fish, which is very useful in the dingy, sluggish waters the Tentacled Snake calls home.

Me, I'm pretty sure they're main use is to be twirled villainously when they tie lady-fish to train tracks for no discernible reason.


Anonymous said...

This is a fantastic blog you have. Very enlightening and also very funny. Keep up the good work.

Joseph JG said...

Thanks, Craig!

TexWisGirl said...

pretty funky! don't really care for that 'stache, though! :)

Joseph JG said...

It's very dastardly!

Esther said...

Celebrating movember all year long!

Joseph JG said...