REPRODUCTIVE PHYSIOLOGICAL VARIATION IN LATITUDINALLY SEPARATED POPULATIONS OF THE BAY SCALLOP,AEQUIPECTEN IRRADIANSLAMARCK

1. The geographically separated populations of the bay scallop A. irradians from Woods Hole, Massachusetts, and Beaufort, North Carolina, vary in their timing of reproductive events. These events occur earlier in the year at Woods Hole than at Beaufort.2. The monthly gonad index values of the populations are fitted with three-term Fourier curves to show the cyclical trend of gonad activity response within the year. Periodic regression analysis of the data indicates that displacement of maximum gonad response is a significant difference between the two populations.3. The reproductive physiological variation in the populations of scallops may have been favored through selection as an adaptive response to the geographical differences in temperature and time of abundant food production.4. The variation could be either phenotypic or truly genetic.