Regeneration of swimming antennae after partial amputation in long- and short-lived Daphnia

Abstract Regeneration, the ability of an animal to restart a developmental process and thus rebuild itself following injury or loss, is generally thought to be inversely related to aging, the progressive decline of organismal functions and fitness that occurs as adults get older. We sought to test whether recently evolved differences of aging in the crustacean Daphnia were accompanied by evolutionary divergence of regenerative ability. Using the short-lived D. pulex and the long-lived D. pulicaria , we conducted an assessment of regenerative ability in which we amputated part of the swimming antenna and observed subsequent regeneration. In four clones isolated from independent populations (two of each taxon), we found substantial regeneration of both the setae and the ramus of the swimming antenna. However, our data did not support our prediction that the long-lived D. pulicaria would have greater regenerative ability than D. pulex. In fact, we found that for both measures of regeneration, D. pulex was significantly better than D. pulicaria . We discuss possible reasons for this outcome, and describe how Daphnia may be a useful invertebrate model for understanding regeneration and aging.