Meeting Abstract

P3.84  Thursday, Jan. 6  Changing sexes in a complex environment – shifts in skeletal myosin isoforms in coastal populations of California sheephead BARTLETT, J N*; LOKE, K M; YOUNG, K; LOWE, C; ROURKE, B C; CSU Long Beach; CSU Long Beach; CSU Long Beach; CSU Long Beach; CSU Long Beach jinae.bartlett@gmail.com

Myosin heavy chain (MyHC) isoform expression was investigated in California sheephead, Semicossyphus pulcher, a protogynous hermaphroditic fish found in coastal Southern California and Northern Mexico. This species was collected from nine capture sites near the Channel Islands where both overall size, and size of individuals at the transitional sexual stage, varies considerably. We therefore cloned MyHC isoforms and analyzed proteins by SDS-PAGE to determine if gender, size, water temperature, or geographic location influenced contractile protein expression. The relative percentage of the slow MyHC isoform increased as sheephead transitioned from female to male with the highest expression of slow MyHC isoform observed in male sheephead. Northern and off-shore island populations were exposed to significantly colder average monthly water temperatures than Southern and near-shore island populations. The lowest expression of slow MyHC was seen in the cold water female populations, when compared to the warm water female populations. Relative percentage of slow MyHC isoform positively correlated with standard length in populations where sex change increases mass. No significant differences were observed between red mid-line and white body wall MyHC expression. Swimming fins had the highest expression of slow MyHC overall. Thus, in this interesting system where muscle mass undergoes dramatic growth accompanying gender transitions, MyHC isoforms are likely influenced by both sexual development and environment.