Selachi: the Sharks


I have a confession to make. I have a bit of a love affair with sharks.

They’re amazing! And eerily astounding. Sharks are ancient creatures. The first sharks date back to the Ordovician period, about 420 MILLION years ago. That’s even before land vertebrates and some plants were around. Sharks went through a few hundred millennia of evolution, but about 100 million years ago (that’s the Lower Cretaceous, when dinosaurs showed up), the shark population hit a general body plan that stuck and haven’t really changed since. Basically evolution looked at them and decided that yup, got it right there.

Let’s ogle a little more closely at sharks. I mean, besides the deadly grace of a shark gliding silently through the water, these guys have pretty awe-inspiring construction. Take, for example, their ampullae of Lorenzini – electromagnetic field detectors around the shark’s “face” that are used for sensing the fields produced by prey – by every living thing, actually, including you and I. Putting it more poetically, without even seeing you, sharks can sense your existence.

And that’s just one organ. Sharks, like all fish, also have a lateral line used to detect vibrations and movements of the water. Of course there’s sharks’ famous sense of smell, too. Sharks can smell up to one part per million of blood in sea water. Put a different way, that’s one drop of blood in a million drops of water. What’s more, sharks can smell that drop from hundreds of meters away.

Going poetic again, not only can sharks sense your existence, they can also sense your distress.

And it’s a shark’s job, as author Diane Duane puts it, to find distress and end it.

Noble, really, when you think about it. Considering that sharks, unlike humans, aren’t gratuitous about it. They’re apex predators, yes, but unlike their counterpart at the top of land’s food chain – humans – they aren’t apex wasters too.

Too bad we’re slaughtering them.

Up next – how to turn the tides on threats to the ocean.


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