SPONTANEOUS OVARIAN CONTRACTIONS IN FUNDULUS-HETEROCLITUS

Spontaneous contractions of Fundulus heteroclitus ovaries were observed and quantified using 2 methods. Contractions were measured as increases in intraovarian pressure in ovaries retained in the fish and as tension changes in ovaries removed from the fish, suspended in a smooth muscle bath, and connected to a force transducer. Spontaneous contractions were observed in approximately one-half the ovaries tested, using both methods. The occurrence of spontaneous contractions was dependent on the reproductive stage of the fish, with more sexually mature fish exhibiting a greater incidence of spontaneous activity. The rate of contraction increased linearly with temperature over the range 20-35-degrees-C. Although the physiological significance of ovarian contractions in F. heteroclitus is unclear, possible functions include the facilitation of ovulation, egg release during spawning, and the movement of eggs or fluid within the ovary.