Protandric simultaneous hermaphroditism (PSH), in which individuals first reproduce as males and then later in life as simultaneous hermaphrodites, is a novel sexual system described for marine shrimps (genus Lysmata). PSH is considered a 'mixed' sexual system because species featuring it have characteristics of both strict sequential hermaphrodites (i.e., in which individuals reproduce as one sex first and then later life as the opposite) and strict simultaneous hermaphrodites (i.e., in which individuals reproduce as both male and female throughout their life). Recently, various theoretical models explaining the evolution of this 'mixed' sexual system have been proposed. In this study, these models will be tested for the first time using the shrimp Lysmata wurdemanni as a model species. In addition, this study will explore whether or not the social environment (i.e., the number and relative abundance of individuals of the different sexual morphs in a population) affects the proportion of time/resources invested into male and female reproduction by shrimps (i.e., sex allocation). Hypotheses on this 'social mediation of sex allocation' as predicted for strict sequential and strict simultaneous hermaphrodites will be tested. Intellectual Merit: The proportion of resources/time allocated to male and female reproduction in this PSH shrimp may shift according to predictions formulated for both strictly sequential and strictly simultaneous hermaphrodites. If so, this would suggest that strictly sequential hermaphroditism, strict simultaneous hermaphroditism, and PSH are "variations of a single theme" from an evolutionary perspective. Sex allocation theory may be in need of a single comprehensive model predicting the evolution of sequential hermaphroditism, simultaneous hermaphroditism, PSH, and gonochorism, all together. Such a model will be proposed in the present study based on information from experiments on the costs and benefits of the sexual functions in the studied shrimp. Broader impact: Funding of this proposal will enhance the Co-PI's doctoral training and professional development. In addition, this study contemplates the training of undergraduate students. This training and the interaction with graduate students are expected to stimulate the interest of undergraduates in science, and help them to launch their scientific carriers. The PI has a strong record of educating graduate and undergraduate students.
