Changes in LH and progesterone associated with the nesting cycle and ovulation in the olive ridley sea turtle, Lepidochelys olivacea

Studies on a large nesting population of olive ridley sea turtles on the Pacific coast of Mexico established that ovulation is completed in most animals within a few days after nesting in this multiclutched species. By 3 days postoviposition, eggs in the oviduct contain thin partially calcified shells, even though eggs may not be laid for up to a month. Analysis of serum samples demonstrated the presence of a pronounced “ovulatory surge” in luteinizing hormone (LH) and progesterone (Pro). Levels of both hormones increase by more than an order of magnitude within a day after oviposition and hormonal levels return to near baseline levels within 2 to 3 days, by the time that the egg shell membrane appears. Testosterone and estradiol levels show little change in the periovulatory period. These increases in LH and Pro are highly correlated in both time and magnitude. Increases in Pro comparable to the ovulatory surge could not be induced by injection of extracts of homologous pituitaries into preovulatory animals before nesting. Also, gonadotropin releasing hormone and a potent agonistic analog were inactive in both sexes of the adult breeding ridley turtle.