Reproductive traits vary widely within and among snake species, and are influenced by a range of factors. However, additional studies are needed on several species, especially on tropical snake faunas, to fully understand the patterns of reproductive variation in snakes. Here, we characterized the reproductive biology of B. jararacussu from southeastern and southern Brazil. We combined macroscopic and microscopic examinations of the reproductive system of museum specimens with observations of free-ranging snakes to characterize size at sexual maturity, sexual size dimorphism (SSD), reproductive output, and male and female reproductive cycles. We compared our data with published literature and discuss the factors that may play a role in shaping the reproductive patterns in the species and the genus. Bothrops jararacussu shares several characteristics with its congeners such as autumn mating season, obligatory sperm storage in the female reproductive tract, seasonal timing of parturition (summer-autumn), female-biased SSD, maturity at larger body sizes in females, and a positive relationship between body size and litter size. These characteristics seem phylogenetically conserved in Bothrops. On the other hand, B. jararacussu exhibits some unique characteristics such as a high degree of SSD (one of the highest values recorded in snakes), a large female body size, and a large litter and offspring size, which are among the largest recorded in the genus. Moreover, larger females reproduce more frequently than smaller conspecifics. These characteristics may be collectively interpreted as the result of a strong selection for increased fecundity. Other peculiarities of the species include an asynchrony between spermiogenesis (summer-autumn) and the peak of SSK hypertrophy (autumn to spring) and a prolonged production of SSK granules. Because SSK hypertrophy and mating are androgen-dependent in snakes, the prolonged SSK hypertrophy suggests that male B. jararacussu may prolong their potential to mate (compared with its congeners), which may increase their reproductive success. Our results and previous literature collectively suggest that, in Bothrops, the evolution of SSD is driven by fecundity selection, variation in reproductive output is influenced by variation in female body size, and the timing of spermiogenesis is influenced by other factors in addition to temperature. We also suggest that male Bothrops have undergone multiple evolutionary shifts in the timing of spermiogenesis.

中文翻译：

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pitviper Bothrops jararacussu 的繁殖：大型雌性增加了它们的繁殖量，而小型雄性增加了它们的交配潜力

蛇种内部和之间的生殖特征差异很大，并受一系列因素的影响。然而，需要对几个物种进行额外的研究，尤其是热带蛇动物群，以充分了解蛇的生殖变异模式。在这里，我们描述了来自巴西东南部和南部的 B. jararacussu 的生殖生物学特征。我们将博物馆标本生殖系统的宏观和微观检查与对自由放养蛇的观察相结合，以表征性成熟时的大小、性别大小二态性 (SSD)、生殖输出以及雄性和雌性生殖周期。我们将我们的数据与已发表的文献进行了比较，并讨论了可能在塑造物种和属的生殖模式方面发挥作用的因素。Bothrops jararacussu 与其同类具有几个共同特征，例如秋季交配季节、雌性生殖道中的强制性精子储存、季节性分娩时间（夏秋季）、偏向雌性的 SSD、雌性体型较大时的成熟以及正相关在体型和窝产仔数之间。这些特征在 Bothrops 中似乎在系统发育上是保守的。另一方面，B. jararacussu 表现出一些独特的特征，例如高度的 SSD（蛇中记录的最高值之​​一）、较大的雌性体型以及较大的窝和后代大小，这些都是记录中最大的属中。此外，较大的雌性比较小的同种繁殖更频繁。这些特征可以共同解释为增加繁殖力的强烈选择的结果。该物种的其他特性包括精子发生（夏秋）与 SSK 肥大高峰（秋季至春季）之间的不同步以及 SSK 颗粒的长时间产生。由于蛇的 SSK 肥大和交配依赖于雄激素，延长的 SSK 肥大表明雄性 B. jararacussu 可能会延长它们的交配潜力（与其同类相比），这可能会增加它们的繁殖成功率。我们的结果和以前的文献共同表明，在 Bothrops 中，SSD 的进化是由繁殖力选择驱动的，生殖输出的变化受雌性体型变化的影响，精子发生的时间除温度外还受其他因素的影响。我们还建议雄性双龙鱼在精子发生的时间上经历了多次进化转变。