Species Profile – Giant Isopod
On a recent night sample, there were gasps of both delight and horror when the ship’s fantail lights illuminated one of the samples. I was, unfortunately, already in my bunk and so missed it when they brought up a Bathynomus giganteus, a Giant Isopod. This thing looks like the stuff of horror movies to some, or nature in the extreme to us naturalist types. The Giant Isopod is related to the sow bugs so familiar to us back home (aka pill bugs, roly-poly, and many other common names), but it looks like a mechanical one on steroids. In fact, it doesn’t even look real and it reminds me of something we would sell at the Museum store during our annual BugFest event.
But real it was. Ours was medium-sized, probably 8–10 inches in length and 4–5 inches wide (it might fit in a shoe box, maybe). I have read reports of some monsters reaching over 2 feet in length! A head-on view looks like a heavily armored vehicle in some sci-fi movie. Giant isopods have been found in depths from 200 to over 2000 m. They are believed to feed on dead whales, squid, fish and other material that fall into the depths in addition to devouring slow moving prey such as sea cucumber, sponges, and other creatures found on the deep-sea floor.
Females have a brood pouch, or marsupium, formed by overlapping plates on their underside. The fertilized eggs are huge — up to 0.5 inches — and are believed by some to be the largest eggs of any known marine invertebrate. Young are retained in the brood pouch until they emerge looking like miniatures of the adults (young isopods are known as mancae).
Giant isopods were first discovered in 1879 at a time when there was still debate whether there was life in the deep ocean. I can only imagine what stories must have been told about this seemingly alien creature from the depths back then if it evokes the variety responses I saw on board our ship the next day. And if, in its strange appeal, it garners interest in (and hopefully more awareness and concern for) these deep-sea environments from those that might not otherwise care, then the Giant Isopod is a worthy ambassador.