Assessment of gonadal follicle size in the invading bivalve Limnoperna fortunei (Mytilidae).

Limnoperna fortunei is an invasive gonochoristic and byssate freshwater bivalve originary from Southeast Asia. It shows great adaptive-reproductive ability, so knowledge of the gonadal cycle is an important factor for the prevention and control of this bioinvasion. This species is highly damaging to natural and human environments. We analyzed the distribution and maturity state of reproductive follicles in the mantle of both male and females. Male results are not shown but, in general, they followed the same pattern as that of females. Routine histological techniques included serial longitudinal sections and transversal sections in three body regions (anterior, middle and psoterior). Oocytes with conspicuous nucleoli were measured on both types of sections to estimate the maturity stage in the different regions. ANOVA indicates that there were no significant differences in maturity ratio between the studied regions, so that a small number of sections would render precise results to assess maturity.