Study of perkinsosis in the grooved carpet shell clam Ruditapes decussatus in Galicia (NW Spain). III. The effects of Perkinsus olseni infection on clam reproduction

Abstract

This study evaluated the effects of the protistan parasite Perkinsus olseni on the reproduction of the grooved carpet shell clam Ruditapes decussatus from Ria de Arousa, Galicia (NW Spain). Clams collected during a one-year period were processed by histology, and their histological sections were examined for gonadal stage, volume fraction of the gonadal components, and infection by P. olseni. R. decussatus had an annual cycle with four gonadal periods: rest (November–January), gametogenesis (February–March), ripeness (April–August) and reabsorption (September–October). The effects of the disease on the gonadal cycle occurred mainly during the gametogenesis and ripeness periods. P. olseni inhibited the gonadal development during the gametogenesis months, delaying the process until the ripeness period, and reduced the percentage of ripe individuals during the ripeness months. The inflammatory reaction caused by P. olseni infection affected the volume fraction (VF) of the gonadal components by increasing the VF occupied by hemocytes, and so reducing the VF of gametes, intrafollicular empty space, follicular walls, and connective tissue. However, no significant effect of infection on gonadal index, fecundity or spawning efficiency was obtained. Therefore, infected R. decussatus may recover from the delay of late gametogenesis, produce gametes and spawn without affecting spawning efficiency or fecundity.