Honolulu Star-Advertiser © Susan Scott
April 5, 2010
What did the Hawaiian moray eel say to the African moray eel?
Hawaii residents might venture a guess after reading a study to be published this month in the online edition of the Journal of Heredity. In it, researchers report that at least two species of Hawaii’s morays are genetically related to the same two species in South Africa and Panama.
This is incredible given that during their entire lives, moray eels rarely move more than a few hundred feet from their home territories. How, then, do these fish manage to range from the Hawaiian Islands through Indonesia and across the Indian Ocean to Africa?
By producing offspring that would make ancient Polynesian voyagers proud.
An immature moray eel is called a leptocephalus, Latin for “small head.” This larval form of eel looks more like a leaf than a fish, narrow at both ends and wide in the middle. A close examination, though, reveals two eyes and a mouth at one end. (Picture at australianmuseum.net.au/image/Eel-leptocephali.)
Don’t count on seeing these youngsters while snorkeling or diving. Although they can grow to several inches long, these babies are transparent except for their dark eyes.
Leptocephali body walls are only a few cells thick. Still, some of these see-through moray offspring live at sea for a year or more, surviving on the waste products and cast-off molts of other drifting animals as they move along.
Even with such a long life span, though, making it across two-thirds of the planet is still pretty unlikely. Through DNA studies, the researchers learned that it took tens of thousands to millions of years for the two moray species to make it to those distant waters and establish stable populations.
The two eel species studied were the yellow margin moray, or puhi paka, and the undulated moray, or puhi lau milo. Using lobster traps, fish traps and spears, the research team from Washington University in St. Louis and the University of Hawaii collected 289 of these eels from 29 sites, sustaining only two injuries, one to a hand and one to a foot.
This is a noteworthy achievement, since these two morays, growing to 3.5 feet and 4 feet long respectively, are known for their aggressive natures. In one published account, a biologist watched his pet yellow margin moray eat his pet scorpion fish tail first. When the scorpion fish’s head proved to be too big to swallow, the eel scraped it across the tank’s bottom until the head fell off.
Some divers hand-feed and stroke yellow margin morays, and occasionally bear the scars to prove it. Few try this, however, with undulated morays. While photographing an undulated moray, an experienced Hawaii researcher reported that the eel lunged out of its hole to bite his camera housing.
Of the 150 or so species of moray eels that range throughout the Indo-Pacific, 42 are found in Hawaii. Given the morays’ hardy and long-lived larvae, this is understandable.
What is not clear is, given this ability to travel long distances, how so many morays evolved into different species, and why the undulated and yellow margin morays stayed the same.
But that’s the nature of research biology: Answer one question and others crop up, some serious, some not. When I read this study, it occurred to me that if a Hawaiian moray met a moray from the Indian Ocean, it would probably say, “You live in Africa? You know my cousin?”