Cracking the secrets of crabs

And they're off! Is it a horse race? Nope. It's a blue crab race.

Every year at Coast Day, Charles Epifanio, professor of marine biology-biochemistry, holds crab races for the enjoyment of the general public. It's just one of the many ways in which he shares his research and seeks to help others understand it.

Although Epifanio has been tagged with the nickname "the crab guy," he conducts research on all types of marine larvae--the early life stages of fish, shellfish and other marine organisms. More specifically, he is interested in the biology of marine larvae, how larvae interact with their environment and the resulting transport of these tiny organisms from place to place in the ocean. However, as it turns out, crab larvae are really good "white rats" for this kind of work, he says, and so he readily admits that the nickname fits.

"And, besides, crabs are cool," Epifanio says.

One of his long-term research efforts is a project involving the dispersal and recruitment of Atlantic blue crab larvae (Callinectes sapidus), which is being done in close collaboration with Richard Garvine, Maxwell P. and Mildred H. Harrington Professor of Marine Studies. A distinctive aspect of the project is satellite tracking of larvae in Delaware Bay and mathematical modeling of their transport by wind, waves and currents.

Epifanio says he considers this research to be the signature achievement of his group. "It is a true multidisciplinary effort, involving biological and physical oceanography," he says.

The results of this work are providing new insights into the role that natural forces, as opposed to commercial and sport harvesting, play in controlling the population of the Atlantic blue crab in the Delaware Bay. Variations in such physical factors as wind and river discharge may explain as much as 50 percent of the difference in landings from year to year, Epifanio says. He and his team now are developing predictive models that will help resource managers take these physical factors into account.

Epifanio's research on larval transport has led to work at greater depths--of the ocean, that is. In a recent study funded by the National Science Foundation, Epifanio and his colleagues investigated the dispersal of larvae of the vent crab Bythograea thermydron from one hydrothermal vent site to another in the Pacific Ocean. These vents are found on the ocean floor more than a mile below the surface. Even as the vents spew hot water, laden with toxic chemicals, at temperatures of up to 350 degrees Centigrade, they support a wide variety of marine organisms.

During the journey from the vents to a research ship at the surface of the ocean, most vent organisms die of depressurization or temperature shock. By contrast, the crab larvae not only can survive the two-hour ascent but also can be kept alive for several months, according to findings by Epifanio, graduate student Gina Perovich and associate scientist Ana I. Dittel. As a result of those findings, the research team was able to study the development of the various stages of the larvae.

"We found that the larval forms have a normal external eye structure, but their retina is 'tuned' to the wavelengths of the light they might encounter in the water column above the vents," Epifanio says. "The adult crabs, on the other hand, have no external eye structure and were believed to be blind."

Based on this unusual discovery, the research team expanded to include Robert N. Jinks at Franklin and Marshall College in Lancaster, Pa., and Thomas W. Cronin at the University of Maryland in Baltimore County, who specialize in the physiology of eyes. The team found that upon metamorphosis to an adult, the external eye structure of the vent crab is lost. This leaves a naked retina, which is extremely sensitive to the faint light produced by chemical and physical processes at the vents.

"These naked retinas are about 7 million times more sensitive to light than are larval eyes with all of their external structure," Epifanio says. "Thus, the juveniles and adults are well adapted to sensing the very dim light produced by the vents and to determining the general direction from which that light is coming. This undoubtedly helps the crabs orient to different vent fields."

In addition to his research success, Epifanio has been honored for the attention he gives his students. The principal adviser for a total of 53 graduate students and a committee member for more than 100 others during his years at UD, Epifanio received the University's new Outstanding Graduate Advising and Mentor Award last year.

"I'll always remember that he took a chance with me as a master's student," says M. Brandon Jones, a current doctoral student under Epifanio's guidance. "He saw qualities in me that I knew were there, but had never used because I had never been challenged."

Cecily Natunewicz, an assistant professor at the U.S. Naval Academy, who received both her master's and doctoral degrees under the guidance of Epifanio, says she first met him as a summer intern in his lab in 1994.

"Although I was only an undergraduate, Dr. Epifanio easily integrated me into his lab team and challenged me to design and execute my own independent research project," she says.

A member of the UD faculty since 1971, Epifanio has served as associate dean of the College and director of the Marine Biology­Biochemistry Program. In 1992, he was instrumental in initiating the Hugh R. Sharp Campus public tour program, which has attracted more than 10,000 visitors.

--Kari Gulbrandsen