Characterizing seasonal transitions: Breeding-like morphology and behavior during the late non-breeding season in green anole lizards

Neural control of reproduction in reptiles

Reptiles display considerable diversity in reproductive behavior, making them great models to study the neuroendocrine control of reproductive behavior. Many reptile species are seasonally breeding, such that they become reproductively active during their breeding season and regress to a nonreproductive state during their nonbreeding season, with this transition often prompted by environmental cues. In this review, we will focus on summarizing the neural and neuroendocrine mechanisms controlling reproductive behavior. Three major areas of the brain are involved in reproductive behavior: the preoptic area (POA), amygdala, and ventromedial hypothalamus (VMH). The POA and VMH are sexually dimorphic areas, regulating behaviors in males and females respectively, and all three areas display seasonal plasticity. Lesions to these areas disrupt the onset and maintenance of reproductive behaviors, but the exact roles of these regions vary between sexes and species. Different hormones influence these regions to elicit seasonal transitions. Circulating testosterone (T) and estradiol (E2) peak during the breeding season and their influence on reproduction is well-documented across vertebrates. The conversion of T into E2 and 5α-dihydrotestosterone can also affect behavior. Melatonin and corticosterone have generally inhibitory effects on reproductive behavior, while serotonin and other neurohormones seem to stimulate it. In general, there is relatively little information on the neuroendocrine control of reproduction in reptiles compared to other vertebrate groups. This review highlights areas that should be considered for future areas of research.

Cycle of the sexual segment of the kidney: histological insights into the role of the urinary tract in the reproduction of male Notomabuya frenata (Squamata: Scincidae)

The kidneys of male Squamata have an important reproductive function as some portions of the nephron may undergo hypertrophy, characterizing the sexual segment of the kidney (SSK). Although its function is still not completely understood, it is believed that the secretions produced by the SSK may act in the maintenance of spermatozoa. In this study, we investigated the reproductive biology of males of Notomabuya frenata based on the seasonal variation of the SSK. We performed macroscopic and microscopic evaluations of the male reproductive tract of museum specimens to characterize the SSK cycle. The nephron portion in which hypertrophy was observed was the collecting duct with secretory granules accumulation in the apical portion. SSK hypertrophy was observed in all seasons, with the tubule diameter in autumn differing from spring and the epithelium height showing no variation. Alcian Blue reacted positively to acid mucopolysaccharides in all seasons. Periodic acid-Schiff's reacted positively to neutral mucopolysaccharides in all seasons, except autumn. Both stains reacted only in the collecting duct. In addition, spermatozoa were found in the lumen of the SSK of one specimen examined. Cycle of the SSK varied seasonally as does the chemical composition of the secretions produced by the collecting duct. The reflux of spermatozoa into SSK may indicate that (1) these secretions act in sperm maintenance, and (2) possibly there is communication between the seminal and urinary ducts.