In Vivo Observations of Larval Brooding in the Chilean Oyster, Ostrea chilensis Philippi, 1845

The Chilean oyster Ostrea chilensis broods its larvae within the mantle cavity. In vivo observations, made with an endoscope, have demonstrated that the female does not undergo gill modification before or during the brooding process. The veliger larvae move freely, have no physical connections with the tissues of the mother, and are often seen as an aggregation ("swarm") around the labial palps. The larvae show a distinct circulation pattern inside the mantle cavity of the mother. Sporadic but strong pallial currents eject larvae from the swarm and transport them between the demibranchs to the posterior region, from which some return anteriorly in the basal ciliated tracts of the gills, and others on the marginal ciliated grooves. Larvae frequently move from the basal to the marginal groove of a demibranch via the ordinary filaments, although they occasionally travel in the opposite direction, moving along the principal filaments from the marginal groove to the basal tract. The circulation of the larvae in the mantle cavity may serve to irrigate them, thereby facilitating gas exchange and suspension-feeding. The veligers are not lecithotrophic, but readily remove and ingest particles suspended in the mantle cavity. The impact on the nutrition of the mother is not yet known, although the presence of particles in the food grooves and tracts and the transfer of material to the palps suggest that the feeding mechanism functions normally during brooding.