Effects of temperature on fertilization and early cleavage of some tropical echinoderms,with emphasis on Echinometra mathaei

Select temperatures, above normal, are shown to reduce success of fertilization and normal early cleavage in the laboratory for the echinoderms Acanthaster planci (L.), Culcita novaeguineae Muller and Troschel, Linckia laevigata (L.), Echinometra mathaei (de Blainville), and Diadema savignyi Michelin. The data indicate that cleavage is more sensitive to increased temperature than is fertilization. Upper tolerance limits for early cleavage in most of the species examined is near 34.0°C. The early developmental stages of A. planci were the most sensitive to elevated temperature, and those of E. mathaei, the least sensitive. Further experiments with E. mathaei showed that unfertilized ova were still viable, dividing normally when fertilized after 2 h exposure at 36.0°C. The ova were significantly less viable after 3 h. Early cleavage stages of E. mathaei were resistant to 36.0°C for exposure times of up to 40 min, but were inhibited beyond this period. It is suggested that the ability of E. mathaei to develop normally at 34.0°C (6C° above ambient temperature) and to withstand limited exposure to 36.0°C may account for the wide distribution of this species in habitats which are often subjected to broad temperature fluctuations, such as reef flats.Contribution No. 46 from the University of Guam Marine Laboratory.