Effects of salinity on larval tolerance and early developmental rates of four species of echinoderms

Abstract

Larval tolerances and developmental rates of four species and one hybrid cross of echinoderms were determined as a function of salinity. Fertilization and development of Strongylocentrotus droebachiensis (O.F. Muller, 1776), Strongylocentrotus purpuratus (Stimpson, 1857), Strongylocentrotus pallidus (G.O. Sars, 1871), and Pisaster ochraceus (Brandt, 1835) larvae were observed. A hybrid was created by fertilizing eggs of S. droebachiensis with sperm from S. pallidus. Fertilized eggs were placed in filtered, natural seawater (30‰ S) diluted to 30, 27.5, 25, 22.5, and 20‰ S and cleavage and larval development were observed over 32 days. Developmental rates differed among salinity treatments within each species. For each species, embryos and larvae at lower salinities (20, 22.5, and 25‰ S) tended to develop more slowly than those at higher salinities (27.5 and 30‰ S). Pisaster ochraceus and S. droebachiensis larvae survived all salinity treatments throughout the experimental period. The hybrid larvae exhibited salinity tolerances and developmental rates intermediate between values reported for the more stenohaline larvae of S. pallidus and those for the more euryhaline larvae of S. droebachiensis. The interaction of a secondary stressor (food availability) with salinity was examined; algal concentration did not influence the survival, developmental rate, or length of P. ochraceus or S. droebachiensis larvae.