dr. Dan 



By Renee Wolcott Shannon • Photos by Scott 



T 



I he estuary is like a giant organism," 

 says Dan Rittschof. "You find crabs in its 

 armpit. It smells different in different 

 places." 



Colleagues and students at Duke 

 University Marine Laboratory know to 

 expect such offbeat and provocative 

 comments from Rittschof, a zoology 

 professor who has taught at the lab since 

 1982. Fellow researchers call him "a 

 creative scientist" and "a guy with ideas 

 going off like popcorn." Students call him 

 "Dr. Dan," praise his teaching and leave 

 friendly messages taped to his office door. 



In person, Rittschof s energy is 

 palpable. He is a compact, wiry man with 

 permanently tanned skin and an unruly 

 beard. He walks fast, laughs often, shows 

 off his research projects with enthusiasm 

 and a flair for drama. "I can make crabs 

 puke and teach you how to catch flounder 

 with your bare hands," he boasts, and he's 

 not kidding. 



His research focuses on the biochem- 

 istry and physiology of animal behavior. 

 "I'm curious about what makes animals do 

 things," he says. In the past, he's asked 

 how hermit crabs locate new shells, why 

 fish prefer certain foods, and how barnacle 

 larvae know where to settle — and he's 

 found answers in bio-active molecules and 

 chemical sensory systems. Given the right 

 mix of molecules, he can make a fish eat 

 gravel. 



Several years ago, North Carolina Sea 

 Grant funded a project in which Rittschof 

 collaborated with fellow Duke scientist 

 Celia Bonaventura to develop a nutritious, 

 palatable food for larval fish. The lack of 

 such a food has traditionally posed a 

 problem for aquaculturists. 



Even adult fish do not select and 

 "taste" food the way we do, with our 

 tongues. Instead, fish have epibranchial 



organs that sense the chemical makeup of 

 food. "A fish sucks something into its 

 mouth and stuffs it into the epibranchial 

 organ," says Rittschof. "If it tastes good, 

 the fish swallows it. If it doesn't, it spits it 

 out." Preferred foods share certain 

 chemical traits — complex combinations 

 of molecules that fish find "tasty." 



Fish food used in aquaculture is often 

 based on cereal, which lacks the flavor 

 molecules that fish prefer. "Cereal doesn't 

 taste like a hamburger," Rittschof says. 

 "Vegetarians know that." The researchers' 

 first hurdle was to find a flavoring that 

 adult fish preferred — and they found that 

 soup stock was a favorite with a wide 

 range of fish, including salmon, trout, 

 flounder and bass. 



The second hurdle was to convince 

 larval fish to eat a processed food. Fish are 

 visual predators who expect their food to 

 move, and baby fish usually eat micro- 

 scopic creatures like rotifers or brine 

 shrimp. Even adult fish must be trained to 

 accept fish pellets as food, and no one was 

 sure that baby fish could learn to recognize 

 motionless fish flakes as something edible. 



In Rittschof and Bonaventura' s 

 experiment, they fed baby flounder 

 through pipettes — first with brine shrimp 

 and later with manufactured liposomes full 

 of the nutrients they needed. The lipids in 

 the liposomes' walls prevented the food 

 from dissolving in water. And the 

 researchers found that the larval fish would 

 eat the processed food. 



"Baby flounder are very smart," 

 Rittschof says. "They'll sit at the end of the 

 pipette and wait for food." He remembers 

 this more than anything else about the 

 experiment, though his findings led to the 

 large-scale production of flavored fish food 

 and the development of chemically 

 attractive fishing lures. 



D. Taylor 



His appreciation for the miniscule 

 flounder, and for the way they adapt to 

 their environment, reflects his boundless 

 curiosity about animals, their habitats and 

 the surprises they offer. This curiosity 

 makes him a perfect match for Duke 

 Marine Lab, which is situated in Beaufort 

 amid estuaries and barrier islands and 

 which celebrates the importance of a sense 

 of place. 



"Dan embodies one of the primary 

 principles of the lab, which is that it is a 

 field station," says Mike Orbach, director 

 of the marine lab. "People can get out and 

 get dirty, literally, and see nature in all its 

 cycles." Orbach says Rittschof is one of the 

 most active faculty members, as far as 

 getting students involved with field 

 research. "He's a denizen of Carteret 

 County waters — he knows where 

 everything is all the time." 



One reason for this knowledge is that 

 Rittschof spends day and night at the 

 marine lab, exposing students to the natural 

 world that surrounds Pivers Island. He 

 leads countless field trips. He keeps his 

 laboratory and office open for student 

 projects, and students have used his printer 

 to spool off reams of research papers. 



Rittschof serves as mentor and guide 

 for many undergraduates' independent 

 study projects. "I don't recognize disciplin- 

 ary boundaries," he says. "I'll follow a 

 problem across any line. ... I've worked on 

 almost all the common animals around 

 here." 



Continued 



at right: duke researcher 

 dan Rittschof proudly displays 

 one of the tagged flounder 

 he tracks in the esturay. 



18 AUTUMN 1999 



