Meeting Abstract

S8.2  Thursday, Jan. 6  Taking the plunge: How do California grunion embryos respond so quickly to sudden changes in the environment? Physiology of the response to hatching triggers for a teleost fish MARTIN, Karen L*; BAILEY, Karen J; MORAVEK, Cassadie L; CARLSON, Kjirsten A; Pepperdine University; Pepperdine University; Pepperdine University; Pepperdine University kmartin@pepperdine.edu

The California grunion Leuresthes tenuis, a marine silverside fish, spawns in the high intertidal zone of wave swept sandy beaches on the California coast. During oviposition at spring tides, clutches are buried in damp sand at a tidal height so that incubation occurs above the water line. Hatching of the terrestrial eggs is prevented until triggered in response to an environmental cue, agitation in seawater. In nature this happens as the tides rise during the following lunar cycle, and high waves wash the egg-encased embryos out to sea. Embryos attain hatching competence after a set period of time, but do not hatch unless and until the trigger is presented. Embryonic life can continue for a variable duration after hatching competence. Hatching can be triggered artificially at any time once the embryo is hatching competent. When the trigger is presented by agitating the egg-encased embryos in sea water, hatching occurs rapidly, within a few seconds. Hatching requires changes in the chorion as well as muscular activity by the embryo to break free. A variety of experiments to examine the mechanisms underlying this unusual form of environmentally cued hatching are discussed in the context of interactions between the organism and the hatching medium to include behavioral, biochemical, morphological, physiological, and mechanical components. L. tenuis shares some hatching physiology with more typical teleosts and has some unique features related to environmentally cued hatching.