Meeting Abstract

60.4  Wednesday, Jan. 6  The Role of Good Genes and Genetic Compatibility in Multiply Mating Horseshoe Crabs JOHNSON, S.L.*; BROCKMANN, H. J.; University of Florida; University of Florida sheriljohnson@ufl.edu

Why do females of so many species mate with several males when the sperm from a single male is often sufficient to fertilize all their eggs? Direct benefits (e.g., nuptial gifts, paternal care) to multiple mating are not expected in externally fertilizing species. These females may gain from mating multiply by insuring fertilization, increasing offspring diversity, improving male quality (‘good genes’) or increasing genetic compatibility. We evaluate the importance of good genes and genetic compatibility in a natural population of the American horseshoe crab, Limulus polyphemus. In this species attached pairs migrate to shore and spawn on high tides; the male fertilizes the female’s eggs externally with free-swimming sperm as the eggs are being laid in the sand. Unattached males are attracted to spawning pairs by visual and chemical cues and become satellites of some (polyandrous) females while ignoring others (monandrous). When present, satellites fertilize a high proportion of the female’s eggs. But, recent research has shown that polyandry is also very costly in this system. We evaluate the importance of good genes and genetic compatibility by conducting a series of in vitro fertilization experiments. Results indicate that attached males of a monandrous and polyandrous females may differ in quality and that partial incompatibilities between males and females may provide a selective advantage to offset the costs of multiple mating. As an ancient and independently evolved arthropod, Limulus provides a unique opportunity to extend our understanding of the evolution of multiple mating.