That's A Moray Monday: Or Meta-Moray Monday

A couple of weeks ago I did a quick round-up of the Moray eels showcased thus far in my weekly Moray Monday feature. In lieu of featuring a new species this week, I thought I'd step back a bit and see the forest for the trees. I realize I jumped into Moray Monday's without first providing a suitable moray primer. So excuse me while I get all meta on you and spend some time talking about morays in general.

In case you haven't been paying attention, Moray eels are large cosmopolitan eels of the family Muraenidae. There are approximately 200 species in 15 genera. The typical length of a moray is 1.5 m (5 ft), with the largest being the Slender Giant moray, Strophidon sathete, at up to 4 m (13 ft).

As members of a vertebrate group--teleost fish--renowned for morphological extravagance, morays have a particularly economical body plan. The dorsal fin of the moray extends from just behind the head, along the back and joins seamlessly with the caudal and anal fins. Most species lack pectoral and pelvic fins, adding to their snake-like appearance. Their eyes are rather small; morays rely on their highly developed sense of smell, lying in wait to ambush prey.

The body of the moray is often patterned to assist in camouflage. Interestingly, camouflage coloration and patterns can also being present inside the mouth. Their jaws are wide, with a snout that protrudes forward. They possess large teeth, well adapted to tear flesh as opposed to holding or chewing.

Discovered only last year and featured here on MBSL&S, Moray eels have a second set of jaws in their throat called pharyngeal jaws, which also possess teeth. When feeding, morays launch these jaws into the oral cavity, where they grasp struggling prey and transport it into the throat and down to the rest of the digestive system. Moray eels are the only known type of animal that uses pharyngeal jaws to actively capture and restrain prey.

Morays secrete a protective mucus over their smooth scaleless skin which contains a toxin in some species. Morays have much thicker skin and high densities of goblet cells in the epidermis that allows mucus to be produced at a higher rate than in other eel species. This allows sand granules to adhere to the sides of their burrows in sand-dwelling morays, making the walls of the burrow more permanent. Their small circular gills, located on the flanks far posterior to the mouth, require the moray to maintain a gape in order to facilitate respiration.

Morays are carnivorous and feed primarily on other fish, cephalopods, mollusks, and crustaceans. Groupers, other morays, and barracudas are among their few predators. There is a commercial fishery for several species, but some have been known to cause ciguatera fish poisoning. While some species of moray will actively hunt along the reef face or in sea grass beds and tide pools, most morays hide in crevices in the reefs and are typical ambush predators, waiting until their prey is close enough for capture.

The moray species most familiar to the general public tend to be circum-tropical, frequenting tropical and subtropical coral reefs to depths of 150 m, where they spend most of their time concealed inside crevices and alcoves. However the Global Biodiversity Information Facility Network has compiled a map of Muraenidae distribution that indicates observation of moray individuals in pretty chilly waters. I was myself surprised to see morays in the same lattitudes as Greenland and Antarctica.

In the December 2006 issue of PLoS Biology, a team of biologists announced the discovery of interspecies cooperative hunting involving morays. The biologists, who were engaged in a study of Red Sea cleaner fish (fish that enter the mouths of other fish to rid them of parasites), discovered that a species of reef-associated grouper, the roving coral grouper (Plectropomus pessuliferus), often recruited morays to aid them while hunting for food. This is the first discovery of cooperation between fish in general.

Morays have received a bad rap as being vicious or ill-tempered. In fact, morays are reclusive and so called "attacks" on humans are often self-defense responses to being disturbed or pestered, or accidental bites that result from wild individuals that have been habituated to human presence (mistakenly labeled "tame morays") through the practice of fish feeding. When bites do occur, morays can inflict a nasty wound. Though not poisonous, their backward-pointing teeth are often covered with bacteria which may infect the wound.