Meeting Abstract
8.8 Sunday, Jan. 4 Instant Fish: Environmentally Triggered Hatching in Beach Spawning California Grunion MARTIN, K.L.**; MCCLURE, M.; BLANK, T.; VANDERGON, T.; RUMBLE, J.; SLEDGE, J.; Pepperdine Univ.; Pepperdine Univ.; Univ. of North Texas; Pepperdine Univ.; Pepperdine Univ.; Pepperdine Univ. kmartin@pepperdine.edu
A coastal marine silverside, the California Grunion Leuresthes tenuis emerges from water to spawn on sandy beaches. During oviposition at lunar high tides, grunion eggs are buried in damp sand in the high intertidal zone. There they will be above the water line for over a week, emerged until the wave wash of a subsequent lunar rising tide reaches them on shore. Oviposition in damp sand is beneficial for clutches of chorion-encased fish embryos, providing high oxygen, suitable temperatures, and protection from desiccation. However this terrestrial incubation habitat is fatal to a delicate hatchling. Thus hatching must occur only when the embryo is submerged in water. The release of the hatchlings from their surrounding membranes into their new aquatic habitat must occur very quickly, within seconds as waves sweep over the oviposition site. However, release must not occur too soon, because hatching under a layer of sand is lethal. The California Grunion has several unique behavioral and physiological adaptations for this dramatic life history switch point. These include the ability to delay hatching for more than double the original incubation period, extremely rapid emergence from the chorion once the process has been initiated, and a unique environmental trigger for initiation of hatching. The environmental trigger provides a means for synchronization of hatching. Hatching is a two-stage process involving action of chorionase and muscular exertion by the embryo to break free of the weakened egg membranes. The physiological and behavioral adaptations for hatching of L. tenuis are characterized through a series of experiments, and compared to other fish and amphibians with aquatic and terrestrial incubation. Supported by NOAA, CA SeaGrant R/CZ195.
