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Hickeys of Doom



O Hai!


Cookiecutter Sharks - Isistius brasiliensis - are small, 50cm-long, sharks found in warm oceans worldwide, and usually stay in the deeps, although like many deep-sea fish do follow the daily plankton migration up and down. But they're not plankton-feeders, oh no. Their schtick is to wait until a bigger fish, whale, dolphin, long-distance swimmer, or nuclear submarine comes past, and then bite a chunk out of it, almost exactly like an ice cream scoop at work. The resulting wound is deep and circular, and caused much bafflement to the Navy engineers who were trying to figure out what was biting pieces out of their sonar domes, until the connection was made. They're also called cigar sharks, because of their shape and colour, luminous sharks, because they can glow in the dark (possibly to lure larger predators close ) and demon whale-biters, because, well, look at the little bastards.

Video clip below of a dolphin who was unfortunate enough to swim too close



These wounds were once considered the work of invertebrate parasites, by some biologists. That makes me almost glad that it was merely a shark.

Christopher Taylor, the Catalogue of Organisms blogger who led me to the paper linked to above, describes them as 'fascinatingly evil' which is pretty accurate. That ghastly array of teeth is even more remarkable than the more usual shark teeth are, because in order to maintain the perfect flesh-scooping edge, they lose the entire lower row at once and replace them with a new one. Not much else is known about their biology, because they spend most of their time in water a kilometre deep. Something we can all be grateful for.

Comments

q99
Oct. 28th, 2011 07:42 am (UTC)
Pretty interesting critter. Doesn't strike me as *too* evil- better to lose a chunk than to get eaten entirely!

Weird that it'd bump into a human swimmer.
drhoz
Oct. 28th, 2011 09:26 am (UTC)
Apparently it was an island-to-island swim
q99
Oct. 28th, 2011 10:15 am (UTC)
Yea, but that close to the surface too has to be rare.
drhoz
Oct. 28th, 2011 10:54 am (UTC)
not as much as you might think - after all, they come up to the surface at night, when the predators can't spot them as easily

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