Oceanography Wednesday: The Mystery of the Moray Eels

This article explains how all the different sciences come together at one point or another.

Take oceanography, for example. If you're a physical oceanographer, you deal with the ocean bed, the composition of the water around the world, the temperature, etc. So you also have to know about geology.

If you're a marine biologist, you study the animals and organisms within the water itself. And so you'd be interested in biology, and species.

Moray Eel Evolution Baffles Scientists; 'Species Don’t Do That'

ST. LOUIS, Missouri -- Joshua Reece became interested in moray eels in 2005 when he was applying to the PhD program at the University of Hawai'i. Instead of taking him on a campus tour, his host, Brian Bowen, PhD, a biologist at the university, took him on a dive. Along the southwest coast of Oahu, Reece looked under a rock ledge and was startled to see five different species of moray eels looking back. When he later captured the eels, he found the same fish species in all of their bellies.

Reece immediately recognized the five eels as a dissertation project on a platter. "How can you have seven species of the same fish eating the same thing and, quite literally, living under the same rock?" he asks. "Species don't do that; if they exploit the same niche they don't diversify, and if they diversify they don't exploit the same niche."

What was up with the eels?

Reece, who is currently a graduate student in biology in Arts & Sciences at Washington University in St. Louis, still doesn't know the answer but having just completed the first phylogeographic survey of the Muraenidae, the family to which the eels belong, he now has a better sense of the problem.

The study, published in the online edition of the Journal of Heredity, was co-authored by Bowen, Allan Larson, PhD, professor of biology at Washington University and Reece's advisor, and two biology undergraduate students at Washington University: Kavita Joshi, now a student at the Washington University School of Medicine, and Vadim Goz, now at Mount Sinai Medical School.

Reece and his colleagues collected two species of eels, the undulated moray (Gymnothorax undulatus) and the yellow-edged moray (G. flavimarginatus) at a dozen different locations across the Indo-Pacific ocean. They were looking for genetic differences that might indicate interruptions in gene flow among populations of the eels either now or in the past.

The Indo-Pacific is a huge expanse of water, covering fully two-thirds of Earth's surface. Yet Reece and his colleagues found both species to be genetically homogeneous across the entire ocean basin.

Their results qualify the morays as the most cosmopolitan of reef fish but only deepens the mystery of how they — and the other 150 species of moray eel in the Indo-Pacific — formed separate species in the first place.