ABSTRACT: This study evaluates possible parasitic castration induced by a bopyrid isopod of the
genus Parabopyrella, which parasitizes the branchial chamber of the simultaneously hermaphroditic
shrimp Lysmata amboinensis. Parasitized shrimp (PS) carried embryos and produced significantly
fewer larvae (mean ± SD: 363 ± 102; p = 0.002) than formerly parasitized shrimp (FPS) (1297 ± 143)
and unparasitized shrimp (US) paired with other US (1409 ± 102), with PS (1362 ± 234) or with FPS
(1384 ± 157). Starvation trials revealed no significant differences in the quality of larvae produced by
PS, FPS and US paired with other US, PS and FPS. Host embryo production is only quantitatively, not
qualitatively, affected, probably due to nutritional drain and/or endocrine disruption caused by the
parasite. The host male sexual system remains fully functional and ‘reproductive death’ does not
occur. The feminization of pleopods that prevents parasitized males of gonochoric species from successfully
copulating seems to have no effect on L. seticaudata: pleopods are always feminized during
their transition from male to simultaneous hermaphrodite phase, with adults being able to successfully
fertilize broods. Parabopyrella sp. significantly affects the female sexual system of its host, but
does not cause castration, as recorded for L. seticaudata parasitized by the bopyrid isopod Eophryxus
lysmatae (an abdominal parasite).