Plasma concentrations of progesterone and estradiol and the relation to reproduction in Galapagos land iguanas, Conolophus marthae and C. subcristatus (Squamata, Iguanidae)

In a combined approach, endocrine and ultrasonic analyses were performed to assess reproduction of two syntopic populations of terrestrial Galapagos iguanas the Conolophus marthae (the Galapagos Pink Land Iguana) and C. subcristatus on the Volcan Wolf (Isabela Island). The ELISA methods (enzyme-linked immunosorbent assay) were used to measure plasma concentrations of progesterone (P4) and 17β-estradiol (E2) from samples collected over the course of three different seasons: July 2010, June 2012–2014. As for C. subcristatus, the large number of females with eggs in 2012 and 2014 were associated with increased plasma P4 concentrations and the corresponding absence of females with eggs in July 2010 when concentrations of both hormones levels were basal indicating reproduction was still ongoing in June and had ended in July. In C. marthae, even though there was a positive relationship between egg-development stages and hormone concentrations, P4 concentrations were basal through the three years that samples were collected, with some females having a lesser number of eggs compared with C. subcristatus. In C. marthae P4 and E2 patterns did not allow for defining a specific breeding season.