Changes in Secondary Sexual Characters of Males of Thor Floridanus (Decapoda, Hippolytidae), Infested by Bopyrinella Thorii (Isopoda, Bopyridae)

Abstract

AbstractThis study describes changes in the secondary sexual characters of Thor floridanus Kingsley, 1878 males, caused by the isopod Bopyrinella thorii (Richardson, 1904). Of 380 specimens of T. floridanus examined, the females were more often infested (n = 313) than the males (n = 41), and had a wider size range (0.7-2.85 mm POCL) compared to the males (0.9-2.32 mm POCL); no ovigerous females of T. floridanus were found. In 25 males the appendix masculina was reduced in size, the endopod of the second pleopod was barely ornamented, and the flexor margin of the propod of the third pereiopod was similar to that of the female of the species; all those males were classified as “feminized”. Those individuals were infested mainly by pairs of mature parasites, and 75% of the “primary” males carried cryptoniscus larvae, suggesting that the “feminization” of the males is caused by the parasite, as a result of the sexual development of hosts and parasites.