OMANA, E.C.; SHUSTER, S.M; Northern Arizona University: PARADELLA DIANAE (CRUSTACEA: ISOPODA) IN THE NORTHERN GULF OF CALIFORNIA: ECOLOGY AND REPRODUCTIVE BIOLOGY

Paradella dianae is a sexually dimorphic and protogynous sphaeromatid isopod that is widely distributed due to international shipping. Although common residents of intertidal communities, little is known about its biology. We are the first to document P. dianae in the northern Gulf of California, where it inhabits empty tests of the barnacle Tetraclita squamosa. We examined P. dianae collected from T. squamosa tests on a rocky reef near Puerto Pe�asco, Sonora, Mexico over many years. We found that P. dianae form social aggregations within the barnacle tests consisting of males, females and juveniles. We identified three male morphologies in this population and distinguish each using morphological and gametic characteristics. Females are iteroparous and undergo ten distinct stages in a tripartite reproductive molt cycle. Females also possess seminal receptacles and are capable of sperm storage, a condition thought to be rare in sphaeromatid isopods. A proportion of females in this population undergo protogynous sex change. Based upon our experiments, sex change does not appear to be socially mediated. These findings reveal the mating system of Paradella dianae in the northern Gulf of California to be extremely complex. Further study of this system may provide insight into the evolution of sex determination, mating systems and sexual dimorphism in the isopod Crustacea.