Post Some Educational Trivia!

Some jellyfish have eyes.

Box jellyfish have a pair of peepers that they use to navigate. This raises interesting questions about cognition; jellyfish don't have brains, so how can they see and process visual information?

We don't actually know the answer to that question but we do know they're weirdly cute.

 

Hey let's do more marine wildlife stuff.

This not so cute fella is a bigfin squid:



They live in the very deepest depths of the ocean, way down in the hadal zone more than 6 km under the surface. Adult specimens have only been observed a handful of times. We don't know what they eat. We don't know why their tentacles are bent that way. We don't know what they do for fun, other than float around and look creepy. We estimate that they might be up to 12 meters long but even that we're not completely sure of because the only evidence we have is a couple of grainy bits of footage.

There's some weird and wild stuff down there, and a lot more questions than answers.

 

This, on the other hand, is a Greenland shark:



They also live in the deep ocean, though not quite as deep as our bigfin friend, ranging down to around 1200 meters. Greenland sharks have possibly the slowest metabolism of any vertebrate in the world, which means they do everything slowly. This is because they're cold blooded, and they live in very cold waters where a balmy summer day might get up to around 7 degrees celsius.

Greenland sharks are an example of a phenomenon called deep sea gigantism. In plain terms, creatures that live deep in the ocean tend to get really big. Greenland sharks, for their part, can grow to be over 6 meters long and have been estimated to weigh 1000kg or more. The leading theory is that this is an advantage due to the square-cube law; the bigger a critter gets, the less surface area it has as a ratio to its overall mass, meaning it's better at retaining heat. This is good if you're not capable of generating heat on your own and live somewhere very cold. Regardless, greenland sharks have evolved to do everything very slowly as a means of preserving energy. How slowly? Well, they can live to be over 500 years old so they got time. We're not 100% sure but biologists have estimated that gestation can take up to 18 years, so even giving birth is slow AF. Once born they swim around at an average speed of about 30 cm/s, or roughly 1 km/h. They grow at a rate of roughly 1 cm per year, and can take 150 years to reach sexual maturity.

Interestingly, we know that Greenland sharks are predators, though we have no particular idea how they actually catch anything. Scientists have hypothesized that they might just swim around and wait to bump into a prey animal that's sick, injured, sleeping, or dying. Moving as slow as they do they are very quiet predators and can catch anything by surprise if it's keeping still. If they do actively hunt, they most likely hunt by smell. Why? Because they're almost totally blind. While blindness isn't uncommon in deep sea critters, the greenland shark has a particularly nausea-inducing reason for this; their eyes are often parasitized by a small crustacean called a Ommatokoita that does irreparable damage to the cornea. I'm including an image below but you've been warned, it's pretty gross.

 

Another example of deep sea gigantism is the giant isopod:



This specimen is being cradled like a baby by someone who probably isn't entirely mentally healthy; this is clear by the fact that they are willingly touching a 30 cm long bug.

Aside from their size, there's actually not too much interesting about these fellas. They're deep sea scavengers, often feeding on carrion though they're perfectly happy to munch on sea cucumbers or really anything else they can get their mandibles on. They're really just much bigger versions of their terrestrial cousins, who are sometimes known as wood lice, pill bugs, or roly polys. They'll even roll up into a ball as a defence mechanism.

I did fib a bit earlier when I called this fellow a bug. Isopods are actually crustaceans, meaning they're more closely related to crabs and lobsters than insects and arachnids; though all of the above are examples of arthropods, so perhaps they're all bugs? In any case, they allegedly taste like lobster. If you're brave, next time you encounter a roly poly in your back yard you can find out for yourself!