Female Reproductive Tract and Dynamics of the Only Unisexual Lizard of Pleurodonta (Iguania: Liolaemidae)

Abstract

Liolaemus parthenos is the only unisexual species of Pleurodonta. It is conjectured that this lizard is parthenogenetic; however, its sexual cycleand ecological and anatomical aspects inherent to its reproduction are unknown. The main objective of this study was to provide information on themonthly progression of the gonads during the active period of this species. Anatomical characteristics of the genital tract were described in specimenswith different reproductive conditions. The sexual cycle of L. parthenos is seasonal, with gonadal activity concentrated between spring and summer. Theovaries and oviducts reach their maximum development in October, at the beginning of spring. Through scanning electron microscopy, five anatomicaland ultrastructural regions were identified in the oviduct, none of which showed the presence of sperm. The abdominal fat body cycle was described toestimate the energetic investment in reproduction. The weight of these organs showed an inverse variation pattern relative to the gonads, with reproductionconsuming most of their fat stores, followed by brumation. This study expands knowledge of the reproductive biology of Liolaemus. It indicatesthat L. parthenos has a reproductive pattern similar to other temperate Squamata, with a conserved gonadal dynamic compared to oviparous species inthe L. darwinii group, to which it belongs. However, the hybrid origin and unisexual condition of this lizard raise new questions and highlight the need forfurther reproductive studies, such as identifying parental species and determining whether reproduction depends on sperm to initiate embryogenesis.