This week we will descend to the deep sea to examine a small shark with a sweet-sounding name. Our featured creature this week is the Cookiecutter Shark (Isistius brasiliensis). This semi-parasitic shark used to be known as the cigar shark because of the look and color. At only about 20 inches, Cookiecutters are small with large eyes that help them see their prey in the darkness of the deep sea. Like many deep sea organisms, these sharks have a pattern of photophores along their underside, which contain light producing chemicals. The photophores are arranged on the in such a way that they create “counter Illumination”, a way to camouflage by creating light and shadows.
The name “Cookiecutter Shark” may bring to mind yummy baked goodness, but don’t be fooled! This little shark is called “The Cookiecutter”, not for its baking skills, but for it’s very distinctive bite pattern. They have small pointed teeth in their upper jaw and large triangular teeth that are all connected at the base in their lower jaws. These bottom teeth are essentially a single unit and are lost and replaced all at the same time. Imagine losing all of your bottom teeth at the same time! It is ok though, since like most sharks, Cookiecutters replace their lost teeth with a whole new plate of sizable chompers. They are so big that they are the largest shark teeth in relation to the jaw in existence (in other words, they have seriously big teeth for such a tiny mouth!) The impact of thes teeth is where the “cookiecutter” part comes in. When a Cookiecutter shark bites into its prey, it suctions its lips onto their skin. Once locked in, they perform a little twisting spin move and, because of their unique teeth and jaw construction, they are able to scoop a perfectly round chunk of flesh – the living melon baller. The mark left behind is a very distinctive circular wound, exactly the same every time, just like a cookiecutter.
Cookie cutters use their photophores on their bellies to attract their prey. The counter illumination creates the illusion that the Cookiecutter shark is actually a much smaller prey fish. Once their prey gets close enough, the Cookiecutter goes in for the bite. These sharks often do not kill their targets, because even though their bite can be gruesome, it is rarely damaging to their often considerably larger prey. Even though they are a small shark, Cookiecutters tend to prey on larger animals, even those up to 10x their own size! Cookiecutters are known to eat from a variety of animals including squid, crustaceans, large fish, seals, dophins, sharks, and whales. In fact, scientists have found the tell-tale signs of Cookiecutter bites on fearsome predators like the Great White Shark!
Join us next week for another shark from around the world.
Edited by KC O’Shea