UNIVERSITY OF CHICAGO MEDICAL CENTER, DAN KITCHENS For decades, researchers and marine fisheries managers have considered the adipose fin—a small protuberance between the dorsal and tail fins—a vestigial organ, a relic of a bygone evolutionary era. But a study published today (March 5) in the Proceedings of the Royal Society B shows that bony versions of these structures have evolved independently and from more than one ancestor, suggesting that the adipose fin could play a subtle, yet vital, as-yet unidentified role in fish.
Adipose fins are small, fleshy and usually not as elaborately structured as other fins. Although some 6,000 species of fish—including trout, catfish, and salmon—have them, relatively few researchers have studied these structures in the last half-century.
In order to understand the relationships between fish with adipose fins and those without them, researchers from the University of Chicago and the University of Kansas built on an existing phylogenetic tree that included more than 200 species, adding fossil record data to determine when and in which species adipose fins arose. Thomas Stewart, a graduate student at Chicago, matched nearly 750 skeletal specimens—pulled from the Field Museum collection in Chicago and the electronic collections of both the California Academy of Sciences and the French Museum of Natural History—to ...
