Males in many animal species exhibit discontinuous variationin their reproductive behavior or adult body form. The geneticbasis, if any, for differences among males in such species isunknown. Moreover, the mechanisms maintaining different maletypes in a single population are poorly understood. Paracerceis sculpta is a marine isopod crustacean that exhibits threedistinct adult male types. Dr. Sassaman's research combinestechniques in behavioral ecology and biochemical genetics to (1)identify the hereditary, behavioral and social mechanismsmaintaining the three male types in the population, and (2) todetermine the nature of genetic differences among males. Usingenzymes as genetic markers, Dr. Sassaman will conduct paternityanalyses of young produced in the field. By monitoring changesin success among different males types, Dr. Sassman will measurehow relative male reproductive success varies over time. He willalso conduct specific crosses among lines to determine whether afew or many genes determine male body form. A simple geneticmechanism could itself determine a polymorphism, while a morecomplex mode of inheritance could indicate that male body type issubstantially influenced by local conditions.
