Logerwell, E. A. Marine Life Research Group, elogerwell@ucsd.edu
Ohman, M. D. Marine Life Research Group, mohman@ucsd.edu

We investigated the interacting effects of copepod body size and the presence of egg masses on the risk of predation. We hypothesized that the predation risk associated with carrying eggs should increase steeply with body size. To test this hypothesis we conducted selection experiments involving three-spined sticklebacks (Gasterosteus aculeatus) and copepods ranging from body mass 0.58 to 740 micro-g C: Oithona similis, Corycaeus anglicus, Pseudocalanus newmani, P. moultoni, Pseudodiaptomus marinus, and Paraeuchaeta elongata. We found that sticklebacks selected ovigerous females of the two smallest-bodied species of copepods (Oithona similis and Corycaeus anglicus). In contrast, fish showed no significant selection for ovigerous females of the remaining, larger-bodied species. Unexpectedly, egg mass position (i.e., in a ventral, dorsal or lateral location on the urosome) appeared to influence predation risk more than did body size, resulting in higher predation risk for the cyclopoid and poecilostomatoid species than for the calanoid species we tested. Although the sticklebacks showed no statistically significant preference for ovigerous females of any of the four calanoid species, for each species the overall proportion of ovigerous females ingested was slightly greater than 0.50. Thus, whether body size influences the susceptibility of egg-brooding calanoid copepods to predation remains an open question.
Day: Thursday, Feb. 4
Time: 10:30 - 10:45am
Location: Hilton of Santa Fe
Code: SS22TH1030H