Reproductive Biology in Shrimp

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A marine shrimp, Lysmata wurdemanni, has a unique reproductive system among decapod crustaceans (shrimps, crabs, lobsters). As in protandric shrimps, most individuals function first as a male and then change to female when they are larger and older. However, unlike other gender-changers, the capacity to produce male gametes and fertilize as a male is retained during the female -phase, i.e., the "females" are simultaneous hermaphrodites. This is a unique system in which to test hypotheses on the proximate and ultimate factors explaining sequential hermaphroditism, not only in Lysmata spp. but also in other protandric shrimps. One set of objectives is to determine why, in terms of reproductive costs and benefits, an individual makes the gender change and why male reproductive function is retained in the female phase. With this species, such costs and benefits can be measured and compared within the same individual. The other important goal of the project is to determine if gender change is environmentally controlled, i.e., mediated by the population and social structure in which an individual occurs.Research on sequential hermaphroditism in fishes has revealed much about the factors involved in its control and evolution. In decapod shrimps, there has been little testing of theory about hermaphroditism. Using Lysmata wurdemanni as a model system, the proposed research will take a crucial first step in testing questions on environmental gender determination in shrimps and on the evolution of unusual hermaphroditic systems in the genus Lysmata. The research will contribute to an explanation of how and why sequential and simultaneous hermaphroditism have evolved in some decapod crustaceans but not in many other closely-related taxa.