The Use of Hormone Antagonists to Inhibit Reproduction in the Lizard, Eublepharus macularius

Abstract

With the increase in popularity of reptiles as personal pets, there is an increasing desire to inhibit reproduction and the associated, and often times undesirable, effects. In an attempt to develop a therapeutic treatment to induce a temporary inhibition of reproduction, we implanted time-released pellets of tamoxifen, an estrogen binding inhibitor, or indomethacin, a prostaglandin synthesis inhibitor, intracoelomically into leopard geckos, Eublepharis macularius. All females treated with either tamoxifen or indomethacin (n = 6 for each group) at the onset of the reproductive season failed to show any follicular yolk deposition for the duration of the 60-day life span of the pellets, whereas 15 of indomethacin treated females were completely inhibited for the entire reproductive season, but 50% of the females developed a generalized edema. Fifty percent of tamoxifen treated females showed some follicular vitellogenesis after the expiration of the pellet, but no female successfully laid a viable clutch. Treatment with tamoxifen during active vitellogenesis was ineffective at inhibiting further follicular growth or ovulation. Eight of nine tamoxifen females successfully reproduced in the year following treatment and their reproductive output (i.e., number of total clutches, number of fertile clutches) was similar to that of control females. These results suggest that tamoxifen may be a viable treatment to induce temporary reproductive inhibition in reptiles, and further study is warranted.

Assessment of the reproductive status of female veiled chameleons (Chamaeleo calyptratus) using hormonal, behavioural and physical traits

“…They do not face seasonal alterations in temperature, humidity, prey availability, and photoperiod as they would in the wild. As a result, in some egg‐laying species, females continue to cycle and produce non‐viable eggs year‐round (rather than seasonally), and in many species this occurs even in the absence of a male and breeding [Rivera, ], as observed in the commonly kept green iguana; Iguana iguana [DeNardo and Helmenski, ] and veiled chameleon; Chameleo calyptratus [Kummrow et al, ,]. In addition, they produce larger clutches with larger eggs compared to wildlife counterparts, which can put increased strain on the females' bodily reserves, and the potential of developing reproductive complications [Cuadrado et al, ; Rivera, ; Sykes, ].…”

“…Reproductive disorders are a common cause of death in captive female reptiles [Cuadrado et al, ; Rivera, ; Sykes, ], particularly in C. calyptratus [Kummrow et al, ,], I. iguana [DeNardo and Helmenski, ], and members of the Varanidae family [Stacy et al, ]. The most commonly observed condition, known as egg binding refers to the failure to lay eggs at the expected time based on cycle or breeding history [Cuadrado, 2002; Rivera, ; Kummrow et al, ; Sykes, ].…”