Meeting Abstract

P1.214  Wednesday, Jan. 4  Effects of Variable Environmental Temperatures on Hatching Success and Larval Length and Yolk Area in the California grunion, Leuresthes tenuis VARGAS, F; CARRILLO, A; HULSE, K; HOCKERSMITH, B; DICKSON, K*; California State Univ., Fullerton

California grunion spawn on sandy beaches during spring high tides in March–August. Fertilized eggs incubate in the sand until they are washed out by waves, the trigger for hatching, 10-14 days post-fertilization (dpf). If not washed out, embryos can extend incubation in the sand until a subsequent spring high tide. This study tested the hypotheses that, compared with constant temperature, incubation at the variable temperatures that occur in the sand where grunion eggs are laid results in reduced hatching success and less yolk, but does not affect mean larval length at hatching. Environmental sand temperatures were recorded at Cabrillo Beach, Los Angeles, CA, every 10 min during the 2011 spawning season. Gametes stripped from male and female grunion collected on Cabrillo Beach were mixed in filtered sea water. Three replicate containers of fertilized eggs were placed into each of three environmental chambers, one set at a constant 20&degC, one in which temperature changed hourly to match the mean sand temperatures recorded in April 2011 (range of 11.7-20.0&degC), and one set at 16.3&degC, the average of the variable temperatures. Embryos from 20&degC first hatched at 8 dpf, and at 14 dpf for the 16.3&degC and variable groups. Hatching success was >80% after 10 dpf for 20&degC, but averaged only 32% at 16.3&degC and 35% at variable temperatures. At hatching, larval length did not differ among groups. Larval yolk area and its rate of decrease with dpf did not differ between the 16.3&degC and variable-temperature groups. Thus, fluctuations in temperature had little effect on grunion embryos when compared with the average temperature, but there were expected differences between 16.3 and 20&degC. (funded by NSF-URM)