This is quite the nostalgic post for me, as we’re returning in part to the very first arthropods ever featured on The ArthroBlogger: the beloved mulch lobster (aka roly poly). As much as I’d love to make another post all about mulch lobsters (which could definitely happen someday, we’ll see), today is all about their ocean-dwelling cousin, the giant isopod.
Imagine this: a mulch lobster the size of a beaver, with eyes that will haunt your nightmares, living at the bottom of the ocean. That’s pretty much the gist of a giant isopod.
Besides their good looks, another commonality between giant isopods and tiny mulch-dwelling isopods is their diet. While mulch lobsters eat decaying matter in your garden, giant isopods mostly eat decaying matter that sinks down to the bottom of the ocean (aka marine snow), although they have been known to hunt live prey as well. Giant isopods also enjoy a whale fall, when a dead whale sinks to the ocean floor and becomes a magnificent feast for a variety of saltwater scavengers.
When you have to wait for your food to drift down to you, however, you have to be willing to wait a pretty long time, so the giant isopod’s metabolism is pretty slow. In fact, one captive giant isopod reportedly survived for five years without food – which raises some questions. However, it may not have been the isopod caretakers’ faults that their Godzilla mulch lobster never touched his dinner plate. According to Dee Ann Auten of the Aquarium of the Pacific, giant isopods can be incredibly picky eaters that require careful attention to properly nourish. Even after presenting her isopods with food every day, one of the big crustaceans only ate twice throughout all of 2013.
Thanks to its tough shell and lack of much desirable meat, the giant isopod doesn’t have many predators. Plus, it can curl into a ball like a mulch lobster as well, practically transforming itself into an impenetrable undersea bowling ball. Its large size not only deters smaller predators, but also may help the isopod withstand the pressure of the deep, as it’s been found chilling on the ocean floor more than 7000ft below sea level. Since giant isopods have been measured at lengths of over two feet while their terrestrial cousins barely reach 5/8 of an inch, I figured the nickname “Godzilla mulch lobster” would be more than appropriate for these mega isopods.
The eyes of both giant isopods and cats glow green when illuminated by a flashlight, but the felines definitely have them beat when it comes to quality of vision. Living deep in the ocean means the giant isopod isn’t exposed to a lot of light, so it relies more on its antennae than its eyes to navigate its environment.
While it does spend a lot of time resting to conserve energy, the giant isopod is an excellent swimmer. It even likes to swim upside down! Scientists haven’t quite figured out why Godzilla mulch lobsters behave this way, so I’m going to assume that they just enjoy goofing off. That, or the combination of a dark environment and poor eyesight makes them forget where the floor is from time to time.
While they aren’t nearly as accessible as mulch lobsters, I would love to see a giant isopod someday. Better yet, I’d love to introduce the two armadillo-esque crustaceans to each other. I’ve got to find some tiny scuba tanks so I can take a few mulch lobsters down to meet their colossal cousins.
…Or I could just take them to an aquarium. That might be easier.