Sea snakes have some of the most potent venoms of any snake, but most of the 60 or so species are docile, rare, or sparing with their venom. The beaked sea snake (Enhydrina schistosa) is an exception. It lives throughout Asia and Australasia, has a reputation for being aggressive, and swims in estuaries and lagoons where it often gets entangled in fishing nets. Unwary fishermen get injected with venom that’s more potent than a cobra’s or a rattlesnake’s. It’s perhaps unsurprising that this one species accounts for the vast majority of injuries and deaths from sea snake bites.
But this deadliest of sea snakes has a secret: it’s actually two sea snakes.
By analysing the beaked sea snake’s genes, Kanishka Ukuwela from the University of Adelaide has shown that the Asian individuals belong to a completely different branch of the sea snake family tree than the Australian ones. They are two species, which have evolved to look so identical that until now, everyone thought they were the same. They’re a fantastic new example of convergent evolution, when different species turn up at life’s party wearing the same clothes.
The black mamba has a fearful reputation, and it’s easy to see why. It can move at around 12.5 miles (20 kilometres) per hour, making it one of the world’s fastest snakes, if not the fastest. Its body can reach 4.5 metres in length, and it can lift a third of that off the ground. That would give you an almost eye-level view of the disturbingly black mouth from which it gets its name. And inside that mouth, two short fangs deliver one of the most potent and fast-acting venoms of any land snake.
Combined with its reputation for aggression (at least when cornered) and you’ve got a big, intimidating, deadly, ornery serpent that can probably outrun you. It’s not the most obvious place to go looking for painkillers.
But among the cocktail of chemicals in the black mamba’s venom, Sylvie Diochot and Anne Baron from the CNRS have found a new class of molecules that can relieve pain as effectively as morphine, and without any toxic side effects. They’ve named them mambalgins.
It turns out that if you unleash giant snakes into a place that didn’t previously have giant snakes, the other local animals don’t fare so well. That seems obvious, but you might be surprised at just how badly those other animals fare.
Since 2000, Burmese pythons have been staging an increasingly successful invasion of Florida. No one knows exactly how they got there. They normally live in south-east Asia and were probably carried over by exotic wildlife traders. Once in America, they could have escaped from pet stores or shipping warehouses. Alternatively, overambitious pet owners could have released when they got too large for comfort. Either way, they seem to be thriving.
With an average length of 12 feet (4 metres), the pythons are formidable predators. They suffocate their prey with powerful coils, and they target a wide variety of mammals and birds. The endangered Key Largo woodrat and wood stork are on their menu. So are American alligators (remember this oft-emailed photo?). Conservationists are trying to halt the spread of the giant snakes, out of concern that their booming numbers could spell trouble for local wildlife.
Michael Dorcas from Davidson College thinks they are right to be concerned. In the first systematic assessment of the pythons’ impact, Dorcas has found that many of Florida’s mammals have plummeted in numbers in places where the snakes now live.
To fans of cheesy pop music, the beat of someone else’s heart is a symbol of romantic connection. To a boa constrictor, those beats are simply a sign that it hasn’t finished killing yet.
A constricting snake like a boa or a python kills its prey by suffocation. It uses the momentum of its strike to throw coils around its victim’s body. Then, it squeezes. Every time the prey exhales, the snake squeezes a little more tightly. Soon, the victim can breathe no more.
We’ve known this for centuries but amazingly, no one has worked out how the snakes can tell when to stop constricting. Scott Boback from Dickinson College has the answer. Through its thick coils, a boa can sense the tiny heartbeats of its prey. When the heart stops, the snake starts to relax.
When Thomas Headland first met the world’s longest snake, he was on the way to the toilet. He was living in the Philippine rainforest with a group of hunter-gatherers called the Agta. On the walk to the outhouse behind his hut, he stumbled across a reticulated python curled up on the trail. “The hairs on the back of my neck stood up and I shouted for help,” he recalls. At his cries, six to seven Agta jumped up from the surrounding bushes… and started laughing. Their new American neighbour had fallen for the old previously-killed-python-on-the-path gag. “I didn’t know what jokers these people were at the time,” says Headland.
Giant snakes frequently attack people in fantasy and science-fiction stories, but such attacks are not merely the stuff of fiction. Through his extensive work with the Agta, Headland has found that a quarter of all the men have been attacked by pythons.
Everyone has felt pain, and many experience it daily. But for such a universal sensation, it is still a mysterious one. We are only starting to understand the molecules that produce a painful sensation. Nature, however, is well ahead of us. Many animals are armed with chemicals that hijack the nervous systems of their targets, producing feelings of intense pain. They are unknowing neuroscientists, and by studying their weapons, we can better understand how pain manifests in our bodies.
Take the Texas coral snake. This brightly coloured serpent, clad in warning hues of red, black and yellow, usually shies away from confrontation. When it’s threatened, it defends itself with venom that can cause excruciating and unremitting pain.
In comic books, many superheroes have gained extraordinary powers after being transfused with the (often modified or irradiated) blood of animals. But, as so often happens, life proves stranger than fiction. At the University of Colorado, Boulder, a group of mice have grown bigger hearts after scientists injected them a chemical cocktail, inspired by the blood of pythons.
When the situation demands it, the muscles of mammal hearts grow larger and pump more vigorously. That’s useful for pregnant women who need to pump for two, toddlers who need to fuel their rapid growth, or athletes who need to power their regularly exercise. But growing hearts can also be bad news if they’re triggered by genetic disorders, high blood pressure or heart attacks. These situations can cause “hypertrophic cardiomyopathy”, where the heart’s thickening walls force it to work harder to pump blood.
To understand how hearts get bigger, Cecilia Riquelme turned to an animal whose heart swells in size every time it eats – the Burmese python. Pythons can swallow extremely large prey like pigs or deer, and they remodel their organs to cope with their meals. Their intestines and liver nearly double in size. As, as Stephen Secor discovered in the 90s, their hearts become 40 percent bigger in just two to three days. For comparison, most mammal hearts only become 10 to 20 percent bigger after months of exercise.
A bird of prey flies through the skies of Europe and spots a snake on the ground below. Travelling at high speed and soaring at great height, it has mere seconds to decide if it should attack. If the snake is harmless, it could end up with a nice meal. If the snake is venomous, it could get a fatal bite. How can the bird tell the difference? The shape of the head provides a clue.
All of the dangerously venomous snakes in Europe are vipers, like the adder or the horned viper. And all of them have a triangular head. The shape is so distinctive that you can easily recognise these snakes from a distance. And some harmless species like the grass snake, smooth snake and viperine snake use that to their advantage. When threatened, they flatten their narrow heads into a triangle, mimicking the shape of their more dangerous cousins.
On Orchid Island, off the coast of Taiwan, green turtles come ashore to lay their eggs. A single female can deposit around a hundred eggs, and the island’s beaches are littered with these clutches. These nests are such a rich source of food that they are worth defending. And that’s exactly what the Taiwanese kukrisnake does. The females treat turtle nests like their own private larder. They guard them, and aggressively ward off rivals with a false head and dagger-like teeth.
Kukrisnakes are named for a special set of teeth. These are shaped like kukris, the curved knives that are the signature weapon of the Nepalese gurkhas. The gurkhas, renowned as brave and fierce warriors, use their kukris to behead their enemies. The kukrisnakes use their weapons merely to slit eggshells, but they can also be used in combat. People who have mishandled these snakes have been left with gushing open wounds for their carelessness.
There are several different kukrisnakes and they’re just a few of the 2,700 or so serpent species alive today. But the Taiwanese kukrisnakes are the only definitively territorial ones of the lot, and even then only the ones on Orchid Island are, and only the females. Despite a few anecdotal reports, no other snake species protects a specific resource over a long period of time. Why makes this specific population of snakes different?
In the novel Dr. No, the titular villain explains to James Bond that he once survived an assassination attempt because his heart was in the wrong place. The good doctor had a condition called situs inversus – his organs were mirror images of their normal versions, found on the opposite side of his body. His heart, being on the right, was unharmed when his would-be murderer stabbed the left side of his chest. Having a mirror-image body can be useful when someone’s out to kill you and while that’s true for criminal masterminds, it also applies to snails.
In Japan, Satsuma snails have shells that mostly coil in the same direction. If you put your finger in the shell’s centre and follow the spiral outwards, you would probably move in a clockwise circle. And Iwasaki’s snail-eating snake knows it.