You know the good stuff is going to keep rolling in from my research cruise to Mid-Cayman Spreading Center. At the end of JC82, we had the opportunity to join a bolt-on cruise to explore the seabed around Montserrat. During a biological survey of the surrounding abyssal plain, we twice stumbled on a giant deep-sea isopods hanging out on the sea floor, doing their isopod thing. This was my first opportunity to observe a giant deep-sea isopod (Bathynomus giganteus*) alive and in the wild. My previous experiences have been limited to well preserved specimens.
Giant isopod behavior is not something that falls within my expertise. Like Craig McClain at Deep Sea News, I’m fascinated by the evolution of their large body size and how a relatively abundant population of such giants can be supported in the food limited deep benthos. But giant isopods are not common in my study area and what little I know of their behavior comes from the very few videos available, mostly of them scavenging on baited camera traps. So I was pretty surprised when the ROV Isis came across this delightful giant maintaining its burrow.
This isn’t the first time Bathynomus burrowing has been observed; the behavior is actually fairly well documented (at least, well-documented for deep-sea species). But as fascinating as watching a 20+ centimeter-long roly-poly digging it’s hole 800 meters deep on the seafloor near one of the most active volcanoes in the Caribbean is, what we found next was even more amazing:
So yeah, I knew these guys could swim, but I imagined it was an awkward, lobster-like back stroke that didn’t really lend the creature much dignity. Watching this isopod rise from the seafloor and gracefully glide away is in complete contrast to my previously limited opinion of Bathynomous swimming abilities.
*There are 20 different species in the Bathynomus genus, and while these two are probably Bathynomus giganteus, identifying species based off a few minutes of video is imprecise and it is possible that these are a different, closely related species.