Reproductive biology of the Sword Snake Tomodon dorsatus (Serpentes: Dipsadidae) in South Brazil: comparisons within the tribe Tachymenini

Abstract

We described the reproductive cycle, size-fecundity relationships, reproductive effort, and sexual maturity of Tomodon dorsatus in South Brazil. We examined 87 individuals (25 males and 62 females) from herpetological collections. The description of the reproductive cycle was based on the morpho-anatomical and histological changes in male testes, ductus deferens, and kidney and in female ovary and oviduct. The age at the onset of sexual maturity was estimated by skeletochronology of the caudal vertebra. The reproduction is seasonal semi-synchronous with most of the individuals showing a reproductive peak in the spring. Males and females have developed sperm storage strategies, increasing the reproductive success. Males store sperm in the ductus deferens during the autumn and winter, while females storage takes place in the utero-vaginal junction furrows during the autumn and early winter. Larger females produce a higher number of larger follicles and eggs. Females invest more in growth before reaching sexual maturity than males. Females reach sexual maturity earlier (4 years old) than males (5 years old) and have larger bodies but lower longevity. Reproductive strategies of Tachymenini specie are highly conserved.

How sexual differences affect locomotor performance and metabolism of the Sword Snake: An integrated view from energetics

“…This effort corresponds to the metabolic costs of vitellogenesis (MCV) and the maintenance cost of pregnancy (MCP), occurring in other species of viviparous Squamata reptiles (Robert & Thompson, 2000; Schultz et al ., 2008; Van Dyke & Beaupre, 2011). Tomodon dorsatus is a viviparous snake with a longer development period until it reaches sexual maturity, a high fecundity potential (Loebens et al ., 2020) and biennial reproduction (Bizerra, 1998). Thus, the analysis of the reproductive stage may be an important aspect to be consider in order to explain the difference of our results (Lima‐Santos et al .…”

“…Thus, the aerobic metabolic rate of T. dorsatus males may be the result of its sexual dimorphism. On the other hand, the reproductive effort of males of T. dorsatus is also lower than that of females (Loebens et al, 2020). In females of viviparous snakes, the reproductive effort may represent an increase in metabolic demand (Schultz et al, 2008;Van Dyke & Beaupre, 2011; The results are expressed as mean AE SD for the sample size (N) indicated in parenthesis.…”

“…Afterward, we froze the tissues and organs in liquid nitrogen and stored them in a freezer at −80°C for the enzymatic assays (more details ahead). We considered females and males adults when are larger than 416 mm and 345 mm SVL, respectively, as well as we considered vitellogenic females when they presented follicles larger than 3.35 mm (Loebens et al ., 2020).…”

Seasonal variations of male reproductive parameters of Tomodon dorsatus from Southeastern Brazil

“…In addition, the histological analysis of the gonadal tissue for the verification of cellular processes such as gametogenesis is essential for the determination of a reproductive cycle (Rojas et al 2013, Almeida-Santos et al 2014, Loebens et al 2017. Loebens et al (2020) claimed that the combined morpho-anatomical and histological analyses allowed to precisely describe the reproductive cycle in males and females. According to Tsai & Tu (2000), the studies of the reproductive features of tropical and subtropical snakes were limited.…”

“…These authors presented a macroscopical study about reproductive cycle of this snake and claimed that this snake presents a post-nuptial reproductive cycle, that is, the production of the gametes occurs after copulation, occurring sperm storage in the ductus deferens until the next copulation (Bizerra 1998, Bizerra et al 2005. The reproductive biology of T. dorsatus males and females from the south region of Brazil was studied based on morpho-anatomical and histological features (Loebens et al 2020). To these authors, this snake has a seasonal pattern of reproduction, with a strong peak in spring.…”