While many of us were on vacation in July, marine biologists from SpeSeas were hard at work peering at eelpouts, squat lobsters, and carnivorous sponges. Hosted aboard the Schmidt Ocean Institute’s ship Falkor, the research group completed the most comprehensive deep-sea survey ever around the islands of Trinidad and Tobago, discovering 20 potential new species.
Read more: “Behold, Crawzilla, the Not-Quite-Biggest Crayfish Ever Caught”
Along the way, though, they got a whole new look at previously recorded species as well. Case in point: An ROV cruising about 1,259 meters below the sea surface secured footage of a black swallower fish that had just consumed prey many times its body size. The species (Chiasmodon niger) grows to only about 4 to 8 inches long, yet pursues fish as much as four times its length and 10 times its mass. It can eat such fish whole by dislocating its jaw and distending its stomach like a balloon, leaving it looking like a snake that’s eaten a rabbit.
The black swallower wasn’t physically captured by the ROV, so the exact contents of its stomach can’t be diagnosed. “If only we had a CT scanner at sea,” lead author Diva Amon lamented in a press release. “The mystery of what this little guy had for lunch may never be solved."
Still, with few exceptions, past sightings have only been of dead black swallowers, like the one caught in 2007 by a fisherman in Grand Cayman that had eaten a huge snake mackerel. (Black swallowers are difficult to spot alive because they spend most of their time way down in the twilight zone.) If the diminutive predator gets too ambitious, it can’t digest the prey before decomposition starts, releasing gases that force the pair to the surface, where they both die. The Woods Hole Oceanographic Institution compares the feeding behavior of the black swallower to a hot-dog eating contest.
It’s an apt comparison as the black swallower filmed by the ROV was trying to swim with an extremely distended belly on which the skin had stretched so much that it was transparent, a window into the fish’s internal organs.
Talk about gorging yourself until you might burst. 
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Lead Image: ROV SuBastian/Schmidt Ocean Institute
