Meeting Abstract
P1.41 Monday, Jan. 4 Heterochrony in Development During Extended Incubation in California Grunion MARTIN, K.L.M.**; MORAVEK, C.L.; Pepperdine Univ., Malibu, CA; Pepperdine Univ., Malibu, CA kmartin@pepperdine.edu
Embryos of California Grunion Leuresthes tenuis, a beach-spawning marine fish, are hatching competent within two weeks post fertilization, but do not hatch until triggered by environmental cues. Oviposition occurs out of water at the highest semilunar tides, and embryos develop terrestrially, buried under damp sand. When waves of the subsequent semilunar tide wash the embryos out, they hatch immediately and begin larval development. Embryonic development to hatching competence occurs in a sequence similar to other Atheriniform fishes, and hatchlings are at an advanced stage prepared for free swimming and feeding. Subsequent larval development resembles that of other Atheriniformes. If the waves fail to reach the shore height of the buried embryos, they do not hatch but continue to incubate for up to 35 days post fertilization. During this time the embryos are metabolically active and behaviorally alert. They may be triggered to hatch by agitation in seawater at any time, and they hatch within seconds. Whenever hatching occurs, larval life begins. However, when hatching is delayed for L. tenuis beyond the time of hatching competence, development dramatically slows. The embryo does not develop in the same way as a hatchling of the same chronological age. The delayed embryo appears to arrest most aspects of development at the stage of hatching competence, including organogenesis and fin development. Careful examination reveals continued development and growth only in the melanophores, the saggital otoliths, and the teeth when embryonic incubation is extended. Thus it is possible to obtain L. tenuis siblings of the same chronological age but very different stages of development, depending on hatching date. Funding provided by NOAA, National Marine Fisheries Service, California Coastal Commission, and National Geographic Society.
