 Cartilage-Framed Horror
Spring is here, but most of us are in no condition to appreciate the warmer weather with exams looming above us. I am no different, so I wish to speak on an easy topic this week. Sharks enjoy something of an exalted place amongst animals, alongside lions, bears and large, carnivorous dinosaurs - apex predators that inspire awe and fear, universally regarded as “cool,” though not many bother to read up on the intricacies of the shark world. So let us take a closer look at some of the oldest and oddest residents of the oceans. If you wish, you can get on an image search engine and look up pictures as you go, hopefully it will be worth your time (and of course, you may end up reading from people who, unlike me, actually know a great deal about sharks!)
The first shark in line is an ancient one. Helicoprion lived 225 to 280 million years ago, and yet it was already recognizable as a shark. Its name apparently translates to “spiral saw,” and that's a rather accurate description of the animal - its lower jaw was a bizarre, swirling structure full of teeth. It is not very clear how it fed with what essentially was an organic buzzsaw stuck to its mouth. Perhaps the spiral could unfurl and impale nearby fish, or it might have been a specialized structure to break shells of ammonites. Though physically impossible, I like to think that it spun like a chainsaw, cleaving unfortunate prey in a maelstrom of sharp teeth.
Other bizarre, extinct sharks include Edestus, which grew a single line of large teeth that made the animal's mouth look like spiny scissors, and Damocles, named after the male's greatly elongated dorsal fin hanging above his head like the famed sword of Damocles.
When it comes to odd shapes, modern sharks clearly do not shame their ancestors! The cookiecutter shark apparently chose the lamprey's way of life, in that it has a circular mouth full of sharp teeth and their main function is not to kill prey, but to bite big chunks of flesh out of larger animals - seals, whales, large fish, other sharks and so on. Due to this way of feeding, they have also earned the name "demon whale-biters," and indeed many whales bear deep, circular cuts associated with this animal. They are known to try out newer prey (!), such as submarines, and the US Navy apparently had quite some trouble with cookiecutter sharks - the animals frequently attacked the sonar domes of nuclear submarines, effectively destroying the submarine's navigation capabilities!
Another odd modern shark is the goblin shark. Other than its unusually large nose from which it gets its name, the goblin shark appears normal... Until it literally extends its mouth to grab prey. A video of such a bite is a sight to behold, and I highly recommend watching one!
The keen senses of sharks are also famous, especially their sense of smell, though another, “sixth” sense is often overlooked. Sharks have gel-filled pores on their skin, called ampullae of Lorenzini, and their purpose is to detect electromagnetic fields. While more active sharks rely on their sense of smell to detect prey from far away, the ampullae are extremely sensitive and can even detect electrical fields of living animals in close range, allowing the shark to “home in on” buried or hidden prey. The ampullae may also have a role in temperature detection. And being fish, sharks possess a lateral line, allowing the animals to detect movement in surrounding water. So extensive is a shark's sensory arsenal that a blinded shark would probably perform just fine!
On this note I will end this week's column. Good luck to all in your midterms!
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