Meeting Abstract

P2.98  Friday, Jan. 4  Sexually Regressed Mummichog (Fundulus heteroclitus) Lack Spontaneous Ovarian Contractions. JENSEN, BH; LAI, M*; MARINO, CL; BRYCE, B; The College of Saint Rose, Albany, NY jensenb@strose.edu

The function of spontaneous ovarian contractions in teleost fish is poorly understood. All fish studied to date; whether the fish spawn on a daily, semi-lunar, or seasonal reproductive pattern, have ovaries that spontaneously contract. This variability in reproductive pattern combined with the fact that all fish have spontaneously contracting ovaries has made it difficult to elucidate the reason for the contractions. It is possible that the contractions have no reproductive function, are for mechanically separating the oocytes, or are for mixing the contents of the ovary. In the current study, sexually regressed mummichog ovaries were used to determine if the spontaneous ovarian contractions occur prior to seasonal development of the ovary. Mummichog were collected in Eastham, MA late in the spawning cycle, were maintained on a natural light cycle (August and September 2007) at room temperature and fed ad libitum twice daily. Ovaries were removed from fish and hung in smooth muscle baths containing teleost ringers solution. Spontaneous contractions were measured prior to and after sunrise and set to determine if spontaneous ovarian contractions occurred in sexually regressed fish and if there was a diel pattern to those contractions. At the termination of each experiment, acetylcholine was added to the smooth muscle bath. No spontaneous ovarian contractions (defined as 10% of acetylcholine induced contraction) were observed in sexually regressed mummichog. Based upon the results to date, it is likely that spontaneous ovarian contractions do have a reproductive function. Studies are currently under way to determine at what stage prior to the reproductive season mummichog ovaries become active, and if ovaries are always equally responsive to hormonal stimulation.