Reprodução do anfisbênio amazônico Amphisbaena brasiliana (Gray, 1865) (Squamata, Amphisbaenidae)

Abstract

We study the sexual dimorphism and reproductive cycle of A. brasiliana, based on specimens from the region of Santarém, Pará, Brazil, and test whether precipitation affects the cycle. We accessed and analysed 143 individuals (73 males, 70 females), deposited in scientific collection between 1999 and 2021. We analysed the following morphological data from each specimen: snout-vent length (SVL), testicular length, width, and height, condition of the ductus deferens (convoluted or non-convoluted), diameter of the ductus deferens in the medial and distal portion, condition of the oviducts (convoluted or non-convoluted), length of the largest follicle and number of primary and secondary follicles. The SVL of females ranged from 149.10 – 363.11 mm, with 46 specimens (65.61%) being mature (smallest adult female = 246.46 mm). Male SVL ranged from 123.31 – 337.26 mm, with 42 (54.16%) being mature (smallest adult male = 241.98 mm). The sample not present significant variation in sexual dimorphism analysed in SVL (P = 0.93232). Testicle volume and ductus deferens diameter varied seasonally, with highest values recorded from August to December, during the low rainfall period. Spermatozoa were recorded in the ductus deferens during the low rainfall months in the region, especially in September, when we observed more individuals with ductus deferens convoluted, which may indicate spermatozoa storage. The testicular volume and the diameter of the ductus deferens in the medial and distal portions (P < 0.01) are related to the period of greatest precipitation. We did not record oviductal eggs in the specimens analysed; however, the presence of vitellogenic follicles in April, in much smaller numbers than those observed in September and December, can be interpreted as a peak of development in the period of least precipitation, coinciding with the results for males of the species. Our results suggest that the reproductive cycle of the population of A. brasiliana analysed may be influenced by regional rainfall, being seasonal.