Life-history patterns of two southern California Nebalia species (Crustacea: Leptostraca): The failure of form to predict function

Laboratory and held studies on Nebalia hessleri and N. daytoni off the coast of San Diego, Southern California, showed that although morphologically similar, the habitats, behavior, natural history of these two species are surprisingly different. In laboratory experiments, each species avoided the other's habitat (sand and mats of macrophyte detritus), and in the field, transplanted individuals failed to survive in the other species' habitat. N. hessleri, which inhabits subtidal mats of macrophyte detritus, survived and reproduced well in the laboratory, was iteroparous, and a large percentage of adults were male. This species occurred at very high densities in the field: and ate essentially everything offered in the laboratory, with a diet in the field consisting largely of plant detritus and carrion. The other species, N. daytoni, differed in nearly every way, it inhabited organically impoverished sands, survived poorly in the laboratory, was apparently semelparous, and a small percentage of the adult population was male.