Effect of microalgal food on the sex reversal of Hippolyte inermis (Crustacea: Decapoda)

The effect of diatoms of the genus Cocconeis on the sex reversal of the shrimp Hippolyte inermis Leach was examined in the laboratory. Randomised experiments were carried out to investigate the functional response of shrimps to various diets. The benthic diatom Cocconeis neothumensis was offered, alternatively, during the larval phase and during the postlarval phase, and the results obtained with shrimps produced by individual females were compared. Results demonstrated that diets based on green alga Enteromorpha sp. or dry commercial food did not influence the normal protandric development, as most shrimps at sexual maturation were males. Conversely, diets containing C. neothumensis did influence the protandric development, as most shrimps at sexual maturation were females and the sex ratio was significantly different from that obtained with diets not containing C. neothumensis. These results provide an explanation of the patterns observed in the field, and are in accordance with the seasonal abundances of diatoms in the leaf stratum of Posidonia oceanica.