Stenopodidae comprises about 28 species in tropical and subtropical waters around the world, but only two of them in the South Atlantic Ocean (SAO)—Stenopus scutellatus and S. hispidus. Larvae of S. scutellatus were never registered in SAO and those of S. hispidus remain poorly researched. The present study fully describes first to seventh zoea of S. hispidus collected in the plankton of SAO, adjacent to Brazil. In addition, eight larvae of S. scutellatus and two larvae of non-identified Stenopodidea from the same area were also described.

The present work reports the existence of parasitic castration induced by the bopyrid isopod Argeiopsis inhacae parasitizing the branchial chamber of female Stenopus hispidus. Parasitized and unparasitized females of S. hispidus displayed similar intermoult periods (14 ± 2 d) and exhibited similar mating behaviours. However, despite exhibiting typical mating behaviour, parasitized females were never able to produce any egg clutch when paired with unparasitized males; neither displayed the typical ‘dorsal bright green spot’ evidencing the presence of large vitellogenic oocytes. The idea that bopyrid infections generally lead to the ‘reproductive death’ of the decapod host is reinforced and the apparent existence of a heavily sex-biased infection towards females in S. hispidus may just be a consequence of the still limited number of surveyed specimens.