Cookie cutter shark

7/14/2016

This week, we will talk about the cookie cutter shark (Isistius brasiliensis). Swimming worldwide in warm waters near islands, this "cigar" (a nickname) searches for prey in the deep (2.3 miles or 3.7 km); they migrate at night to the surface to continue feeding, too.

What makes these animals even cooler? They take on animals many times their size! Anything from edible fish (i.e. sharks) and mammals (i.e. whales and dolphins) to non-edible submarines (i.e. the rubber part of the sonar dome has gotten so badly bit, it caused an oil leak and the submarine had to surface).

So, how do they do it? They latch onto their prey with their bear-trap teeth and then spin their bodies to take out that iconic cookie-shaped chunk of flesh out of whatever poor sucker they got. Don't worry, these bites are usually not fatal to large animals. If you don't think that's the coolest thing ever, get out. Literally, exit the web browser because these animals are about to get even cooler: they glow in the dark, too.

Like many deep-sea critters, these sharks have bioluminescence to help with camouflage. This bioluminescence pattern is actually broken up, so it looks either like small, tasty treats (which lures big fish to the shark and then chomp) or light filtering down from above and uninteresting to predators (they are known to swim in schools to achieve this). Win-win situation.

This shark has the best Halloween costume of all: a parasite. #Finfact: The cookie cutter shark is the only parasitic shark! The scientific term is, "facultative ectoparasite." I mean, doesn't that sound like a great idea? Kiddos, you still have a chance to go get this raving costume idea!

Another neat fact: Like other sharks, they shed their teeth... but unlike other sharks, they don't replace single teeth but entire rows at one time! (Melissa note #4195: I'm imagining dentures for a cookie cutter shark and the picture in my head is way more amusing than it should be.)

Sadly, not a lot is known about the cookie cutter shark and the IUCN has listed the cookie cutter shark under Least Concern (LC).

ever heard of this teeny shark?

glossary

Bioluminescence: The production and emission of light by a living organism.
IUCN: International Union for Conservation of Nature.