The dominant ovarian follicle**The Ayerst Lecture presented at the Thirty-Eighth Annual Meeting of The American Fertility Society, Las Vegas, Nevada, March 23,1982

Provisioning of vitellogenic follicles continues after green turtles arrive at the nesting beach

Understanding the energetic demands of reproduction on female sea turtles is crucial for devising effective conservation strategies aimed at supporting the reproductive health and resilience of populations at nesting habitats. We studied the ovaries of 69 green turtles (Chelonia mydas) preyed upon by jaguars (Panthera onca) during three nesting seasons at Tortuguero, Costa Rica, the main green turtle Atlantic nesting beach. Our findings revealed a bimodal distribution of vitellogenic follicles, with 'dominant' follicles destined for ovulation and 'non-dominant' follicles to be resorbed. Female green turtles lay, on average, six clutches with ~110 eggs each per nesting season, and a size hierarchy was also found within dominant follicles. During the nesting season, the diameter of small dominant follicles increased by 66% prior to ovulation. Analysis of yolk composition showed that small dominant follicles had higher percent water content than large dominant follicles, which indicates dry matter deposition rather than hydration is responsible for the pre-ovulatory increase in diameter of green turtle dominant follicles during the nesting season. Furthermore, percentages of lipid, nitrogen (N) and phosphorus (P) in the yolk dry matter were constant across green turtle vitellogenic follicles, which underscores that the increase in follicle size results from provisioning with yolk containing similar proportions of these nutrients. Atretic follicles had higher water and lower P percentages than dominant follicles, indicating an accelerated resorption of phosphorus over lipids and N, which could be due to the importance of this nutrient for eggshell production. Finally, >49% of the energy required for egg production was still to be invested during the nesting season, and yolk from non-dominant follicles would not have provided sufficient energy for most females to complete yolk deposition. These insights into follicular dynamics and nutrient provisioning clarify the ongoing reproductive investments made by female green turtles at Tortuguero.

Female subfertility

Subfertility is common and affects one in six couples, half of whom lack an explanation for their delay in conceiving. Developments in the diagnosis and treatment of subfertility over the past 50 years have been truly remarkable. Indeed, current generations of couples with subfertility are more fortunate than previous generations, as they have many more opportunities to become parents. The timely access to effective treatment for subfertility is important as many couples have a narrow window of opportunity before the age-related effects of subfertility limit the likelihood of success. Assisted reproduction can overcome the barriers to fertility caused by tubal disease and low sperm count, but little progress has been made in reducing the effect of increasing age on ovarian function. The next 5-10 years will likely see further increases in birth rates in women with subfertility, a greater awareness of lifestyle factors and a possible refinement of current assisted reproduction techniques and the development of new ones. Such progress will bring challenging questions regarding the potential benefits and harms of treatments involving germ cell manipulation, artificial gametes, genetic screening of embryos and gene editing of embryos. We hope to see a major increase in fertility awareness, access to safe and cost-effective fertility care in low-income countries and a reduction in the current disparity of access to fertility care.