Meeting Abstract

75.4  Friday, Jan. 7  Does extended incubation affect morphology and feeding ability of larval California grunion, Leuresthes tenuis? CARRILLO, A.*; ALMASARWEH, F.A.; DICKSON, K.A.; California State University Fullerton; California State University Fullerton; California State University Fullerton

The California grunion, Leuresthes tenuis, has the ability to extend embryonic incubation beyond hatching competency. Normal incubation occurs when embryos are triggered to hatch at 8-14 days post-fertilization (dpf) by wave action from the spring high tide that follows fertilization. If that does not occur, embryos can extend incubation and hatch during a subsequent spring high tide. We investigated effects of extended incubation (28 dpf) on morphology and feeding activity in grunion larvae. We tested the hypotheses that 28-dpf larvae would have more developed skeletal structures in the jaws and caudal fin, and greater feeding rates, than 10-dpf larvae (normal incubation). Eggs that were collected from six females were fertilized, incubated at 20°C, and stimulated to hatch at 10 and 28 dpf. Feeding rates of 10-dpf and 28-dpf larvae were measured based on the change in rotifer density over a 4-h period. From each batch of eggs, 30 larvae were cleared and stained at both 10 and 28 dph to observe skeletal structures. The number and lengths of the skeletal elements in the caudal fin were measured and the number of dentary and pharyngeal teeth were counted. In all batches studied, the 28-dpf larvae had significantly more dentary and pharyngeal teeth, and more and larger precursors of the hypural skeletal elements, than the 10-dpf larvae. The 28-dpf larvae also had significantly greater feeding rates. Thus, extended incubation in L. tenuis results in larvae that have more developed skeletal structures and consume rotifers at greater rates, which may improve larval survival. [This study was partially supported by grants from CSUF and the Southern California Academy of Sciences.]