Thermal tolerances of embryos and planktotrophic larvae of Archaeopneustes hystrix (A. Agassiz) (Spatangoidea) and Stylocidaris lineata (Mortensen) (Cidaroidea), bathyal echinoids from the Bahamian Slope

Abstract

Thermal tolerances of early embryos and echinopluteus larvae were studied for two common bathyal echinoids, Archaeopneustes hystrix (A. Agassiz) and Stylocidaris lineata Mortensen. Both species have adult distributions centered at a depth of 550 m on the slopes of the Bahamian Islands, though A. hystrix extends to a shallower depth than S. lineata. Early embryos incubated at 4 temperatures in laboratory incubators developed at the same rates as embryos transplanted by submersible to depths having comparable temperatures. Embryos of both species could tolerate temperatures as high as 25°C. Stylocidaris lineata retained this ability during 2-arm and 4-arm echinopluteus stages, but larvae of A. hystrix died at temperatures above 20°C. The lower depth limits of both species and the upper limit of A. hystrix corresponded closely to the thermal tolerances of larvae. Larvae of S. lineata could potentially migrate to the euphotic zone to feed, but larvae of A. hystrix probably must disperse and feed at greater depths.