TEMPERATURE AND EMBRYONIC-DEVELOPMENT IN RELATION TO SPAWNING AND FIELD OCCURRENCE OF LARVAE OF 3 ANTARCTIC ECHINODERMS

The effects of temperature on development and viability were measured at 14 levels between -2 degrees C and + 3 degrees C on embryos of two asteroids (Odontaster validus and Odontaster meridionalis) and an echi noid (Sterechinus neumayeri) from Signy Island, Antarctica. Developmen t rates were 2 to 10 times slower than those for temperate or tropical echinoderms, with times to hatching up to 240 h. Development rates fo r the two asteroids differed by 1.15 x, and rates for both species app roximately doubled over the experimental temperature range. In O. vali dus, embryo viability was independent of temperature, but in O. meridi onalis viability declined with increasing temperature. Development rat es for S. neumayeri were little affected by temperature above +0.2 deg rees C, but declined rapidly at lower temperatures. Conversely, the nu mber of nonviable eggs was low and constant below +1.7 degrees C, but rose rapidly at higher temperatures. A window of optimal temperature, between +0.2 degrees C and +1.7 degrees C, has therefore been proposed for development time and embryo viability in this population of S. ne umayeri. Spawning trials and field observations of larvae indicated th at the time of gamete release and periods of larval development in S. neumayeri coincided with austral summer sea temperatures in the same w indow. Embryos of O. meridionalis and O. validus are released in winte r, when temperatures are constantly below -1.6 degrees C. Comparison o f the different strategies suggests that larval food supply and predat ion during planktonic phases are not the dominant ecological factors f or these species.