BAEZA, J.A.; The University of Lousiana at Lafayette: The evolution of protandric-simultaneous hermaphroditism in the shrimp Lysmata wurdemanni is a consequence of sex-dependent time commitments but not sex-dependent mortality rates.

Protandric simultaneous hermaphroditism (PSH), as recently reported for shrimps in the genus Lysmata, is a novel sexual system in which individuals invariably reproduce as males first (MP individuals) and later in life as simultaneous hermaphrodites (SHP individuals). I test here two recently proposed models (i.e., sex-dependent time commitments and sex-dependent mortality rates) explaining the evolution of PSH in the shrimp L.wurdemanni. Specific predictions/assumptions of each model were evaluated in the laboratory using observational/manipulative experiments. I found no evidence that the sex-dependent mortality model explains PSH in the studied species because mortality suffered by SHPs due to predatory fishes was not greater but similar to that suffered by MPs, in contrast to that predicted by this model. On the other hand, the time SHPs required to replenish their sperm reservoir after mating as males was shorter than the time they required to produce and brood two consecutive eggs clutches. Small SHPs also experienced a heavier mortality rate by fish predators than large SHPs. This sex-dependent reproductive time commitment and size-dependent mortality agree with predictions of the sex-dependent time commitment model that additionally explain the evolution of PSH in L.wurdemanni. This study stresses the necessity of explaining the evolution of strict simultaneous and sequential hermaphroditism, as well as mixed sexual systems such as PSH with a single comprehensive theoretical model.