Behavioral Cost of Reproduction in a Freshwater Crustacean (Eulimnadia texana)


Stephen C. Weeks, Program in Integrated Bioscience, Department of Biology, The University of Akron, Akron, OH 44325, USA.


It is commonly noted that investments in reproduction, both physiological and behavioral, can trade off with other life-history traits, such as growth and survival. In males, behavioral reproductive activities (e.g., copulations) are associated with weight loss, increased predation risk, reduced future reproductive output, and decreased lifespans. It is uncommon to find species in which increased copulations actually increase survival. Herein, we examine one such species, the androdioecious (males + hermaphrodites) crustacean Eulimnadia texana, in which increased copulations have been associated with increased lifespan. We examined two potential causes of this association: (1) males not copulating actually expend significant energy by searching for mates and (2) males are experiencing shorter lifespan primarily because they are more inbred than hermaphrodites. We found that isolated males did indeed expend more energy than hermaphrodites, consistent with previous studies showing that males swim over twice as much as hermaphrodites when isolated. Additionally, although inbreeding was associated with reduced lifespan, outcrossed males still had shorter lifespans relative to outcrossed hermaphrodites. Thus, isolated males consistently show decreased lifespans relative to isolated hermaphrodites, which is not explainable only on the basis of level of inbreeding. We conclude that the costly searching behavior of these males is the likely underlying cause of this observed difference in lifespan between the sexes, as previously suggested.