Intersexuality in a natural population of the terrestrial isopod Porcellio scaber

Intersex phenotypes are rarely observed in natural isopod populations and their expression is typically associated with infection ofWolbachia, a reproductive parasite that manipulates arthropod reproduction. During an intensive sampling effort of a natural population of the isopodPorcellio scaber, an adult individual was isolated that expressed both male and female traits. The intersex individual exhibited clearly developed external male genitalia and carried multiple eggs in its brood pouch. NoWolbachiainfection could be identified in this individual, a result that needs to be approached with caution due to suboptimal DNA preservation for diagnostic PCR assays.Wolbachiawere, however, detected in two adult females of the same population, and appear closely related to isolates that infect other terrestrial isopod species. This is the first demonstration that intersex phenotypes can arise under natural conditions inP. scaber.