EFFECTS OF PROLACTIN AND HCG TREATMENT ON LUTEAL ACTIVITY AND THE CONCEPTUS DURING DELAYED IMPLANTATION IN SCHREIBERS LONG-FINGERED BAT (MINIOPTERUS-SCHREIBERSII)

In Schreibers' long-fingered bat (Miniopterus schueibersii) from South Africa, implantation is delayed from May to August during which time the corpus luteum is inactive and plasma progesterone and LH concentra tions low. Treatment of pregnant long-fingered bats with exogenous pro lactin for 10 days in early delayed implantation (May) resulted in cha nges in luteal ultrastructure that were consistent with increased ster oidogenesis, high plasma progesterone concentrations and the initiatio n of implantation. Treatment of bats with hCG for 10 days in early del ayed implantation induced similar changes in luteal ultrastructure and plasma progesterone concentrations, but did not initiate implantation . Treatment with exogenous progesterone during early delayed implantat ion had no influence on the corpus luteum or the conceptus. We conclud e that prolactin is the most important pituitary hormone in the contro l of delayed implantation, although the route via which it induces imp lantation is unknown.