EN
The influence on the gonadosomatic index of the adult Proctoeces lintoni (Digenea), a parasite of the gonads of the key-hole limpet Fissurella limbata (Gastropoda), was analyzed. Parasitic biomass reached as much 34.9% of gonadic weight, with a maximum of 99.4%. The gonadosomatic index computed as: (gonadic weight x total length ⁻¹) x 100, shows significant differences when compared with a corrected gonadosomatic index that excludes the parasitic biomass. Thus, caution must be taken when the gonadosomatic index is considered as a valid parameter in parasitized gonads.