Effect of microalgae treated with natural toxins on the nutrition and development of filter-feeding sea-urchin larvae

Filter-feeding larvae of the sea urchin Paracentrotus lividus fed phytoplankton previously exposed to sublethal amounts of toxins were chosen as a model to assess the potential effects of natural toxins on survivorship, development and feeding behaviour. The marine microalga Cricosphaera elongata was incubated with organic extract of the green seaweed Caulerpa taxifolia and then offered to larvae at different stages of development. Sensitivity to the toxin-treated food depended on the larval stage at which exposure began. Larvae reared from first feeding (4-arm stage) with toxin-treated microalgae were most sensitive (25% survival, delay in development and a metamorphosis rate of 32%). A diet begun at the 8-arm stage caused a decrease in survival and abnormal development; however, all the remaining larvae achieved metamorphosis. Certain ontogenic stages were more sensitive than others; in all treatments, mortality rate was highest during the formation of the echinus rudiment. Feeding experiments comparing ingestion of inert and toxin-treated polystyrene microspheres suggested that larvae discriminate against toxin-treated particles. (C) 1999 Elsevier Science Ltd. All rights reserved