EVIDENCE FOR WOLBACHIA SPP IN THE ESTUARINE ISOPOD SPHAEROMA-RUGICAUDA (CRUSTACEA) - A LIKELY CYTOPLASMIC SEX-RATIO DISTORTER

This paper describes the first evidence for endocytobiotic Wolbachia-r elated bacteria in an estuarine crustacean, the isopod Sphaeroma rugic auda. Four populations were studied (one from Calvados [France] and th ree from East Anglia [UK]), in which females and intersexes from femal e-biased progenies were infected. No bacteria were found in males rega rdless of their origin, or in the females from most progenies having 1 :1 sex ratios. These characteristics are very similar to those of the cytoplasmic sex determination in the terrestrial isopod Armadillidium vulgare. In this species, Wolbachia overrides genetic sex determinatio n, feminizes genetic males and induces the production of highly female -biased broods by infected mothers.