Fish o' the Day - hagfish

OK, we're really stretching here. Sure, the whole "fish" thing is pretty nebulous. Bony fish - no doubt. Sharks and their kin - sure. Lampreys? Starting to get a little iffy there, but they're aquatic vertebrates with fins so we're probably safe calling them jawless fish. But hagfish? While traditionally they were grouped with the lampreys in the Class Agnatha, they've recently been kicked out of Club Vertebrata based on molecular analyses. But, for our purposes, they're fish.

We're also cheating a little in that hagfish are not a single "fish", but rather a group of some 60 species belonging to 5 genera. The best known are in the genus Myxine, but we know little enough about them that it's not terribly inappropriate to lump them all together.

Hagfish are considered by some to be among the most disgusting animals on the planet. That's a little harsh - I personally think they're pretty fascinating. But, if your primary claim to fame is producing prodigious amounts of slime and eating dead or dying fish from the inside out, you have to expect a little disrespect.

Their eel-like body, averaging perhaps 18 inches in length, is lined with glands that produce enormous amounts of a slimy secretion. Check it out...




They have the lowest blood pressure of any vertebrate (or, ex-vertebrate), and have accessory hearts that help push their blood along its way. They also have a unique ability to throw their body into a knot, an adaptation that they can use to scrape the slime off their body. This neat trick may also help them escape from predators, and perhaps allow them to squirm into and out of the bodies of fish on which they're feeding.

We're just beginning to get a handle on their reproductive biology, but we do know that they produce a surprisingly small number of eggs - ranging from just a couple to thirty or so. The eggs are equipped with hook-like structures and tend to stick together. There's even some indication of egg guarding behavior.

As for feeding, well, there's this...





Hagfish actually feed primarily on polychaete worms burrowing in the sediment in the deep, cold water that they frequent. Presented the opportunity, however, they won't turn down a meal in the form of a dead or dying fish on a long-line, or a sunken whale carcass.

Disgusting? Maybe so. But they're a delicacy in Korea. Of course.