Reproductive cycle of the house gecko, Hemidactylus flaviviridis, in Oman in relation to morphological and ultrastructural changes and plasma steroid concentrations with reference to localisation of progesterone receptors

Abstract

In Oman, a comprehensive study of the annual reproductive cycles of male and female house geckos, Hemidactylus flaviviridis was conducted. Circulating testosterone (T), oestradiol (E₂) and progesterone (P) concentrations were measured using a sensitive HPLC-MS/MS detection technique. Data were collected from a natural population over two consecutive seasons. The annual patterns of circulating concentrations of T, E₂ and P were measured for both sexes. In males, peak plasma T, E₂ and P concentrations occurred in the active phase, coinciding with the stages of spermatogenesis, courtship and mating, but gradually declined in the second half of the mating period with a significant drop in the quiescent phase, coinciding with testicular regression. In females, elevated plasma E₂ and T concentrations in the active phase were associated with vitellogenesis and mating. Plasma E₂ concentrations decreased significantly during the quiescent phase, coinciding with follicular regression. Plasma P concentrations were elevated during gravidity but fell significantly prior to oviposition.
The plasma steroid concentrations were related to the steroidogenic ultrastructural features and expression of progesterone receptors (PR) throughout the reproductive cycle. The steroidogenic ultrastructural features were characterized by the presence of smooth endoplasmic reticulum (SER) in the form of cisternal whorls and tubular cisternae, presence of swollen vesiculated mitochondria and association between SER, mitochondria, and lipid droplets. In the male, the rise in the three plasma steroid concentrations during the active phase was closely associated with the development of the ultrastructural features and strong PR expression in Leydig and Sertoli cells. During the quiescent phase, there was a significant decline in plasma steroid concentrations, undeveloped steroidogenic features and weakly expressed PR. In the female, the appearance of the steroidogenic ultrastructural features in the preovulatory and lutein granulosa cells was correlated with the significant rise in the three steroid concentrations and the strong expression of PR. As the steroid concentrations declined, the granulosa cells underwent general degeneration and disruption of the ultrastructural steroidogenic features. These detailed findings are the first to be reported for this species in the Arabian Peninsula.
Based on histological and gross morphological observations, the house gecko ovulates two eggs at a time, one from each ovary. This is followed by a second two egg clutch, suggesting that this species lays two clutches of eggs annually, each clutch containing two eggs.
The comprehensive data obtained from this study may be of some value for comparison with reproductive cycles of other closely related species in this region. In addition, conservation awareness for the protection of this widely distributed species may be beneficial for the protection of other wildlife.

Date of Award	Mar 2012
Original language	English
Awarding Institution	University of Portsmouth
Supervisor	Colin Peter Waring (Supervisor)