How would he describe the Pacific hagfish? "Disgusting, in short," says Chris Glover, a biologist at the University of Canterbury in New Zealand, who studies the gray, eel-like creatures. Eptatretus stoutii live on the seafloor, usually between 300 and 700 feet deep, and they feed primarily on the sunken corpses of marine animals like whales.
Since such prizes don’t rain down every day, and since the fish have to compete with other organisms for those carcasses that do sink, they’ve found several ways to make the most of any chance to chow down. For starters, says Glover, they coat potential prey with "just copious, copious quantities of the stickiest, gooiest slime imaginable," so that only the hagfish will want to eat it. (Juvenile humans have been known to apply a similar strategy -- licking every M&M in the bag -- to avoid sharing with their own species.) The slime also works to defend against fishy predators, clogging attackers’ gills and suffocating them if they get too close.
Glover and colleagues recently discovered another way hagfish are both incredibly efficient and incredibly unsavory eaters. Noticing their proclivity for burrowing into the decaying carcasses to dine on them -- and realizing that a "soup of nutrients" like proteins and carbohydrates was likely forming inside the rotting animals -- they ran tests on hagfish skin. Turns out the scavengers were absorbing nutrients across the entire surface of their bodies while at the same time munching with their mouths.
While their permeability allows hagfish to maximize the nutrition they get from each meal, it comes with certain disadvantages. For instance, decaying animals produce toxins that the hagfish may be forced to absorb. And because hagfish enjoy no real barrier between themselves and their surroundings, their range may be severely limited: Moving to saltier waters, for example, would likely increase the salinity of their very tissue.
Still, E. stoutii appear pretty accomplished when it comes to survival. Scientists believe the earliest hagfish originated more than 500 million years ago, and they consider them to be "proto-vertebrates" -- invertebrates with many similarities to vertebrates, which may represent the transition from one to the other. Studying how their skin works as a sort of gut, Glover says, could eventually help illuminate how digestive systems developed, and why it might be useful to have them "inside the body as opposed to all over it."
True, Glover says, hagfish won’t win any beauty contests, but that doesn’t mean they don’t deserve a second glance. "They’re kind of scary-looking and they’re kind of intimidating," he says, "but they’re fairly extraordinary animals."