Serpentirhabdias mexicanus n. sp. (Nematoda: Rhabdiasidae), a parasitic lungworm of the nauyaca viper Bothrops asper (Serpentes: Viperidae) in the Mexican Neotropics.

Serpentirhabdias mexicanus n. sp. (Nematoda: Rhabdiasidae) is described from the lung of the nauyaca viper Bothrops asper in Puebla State, central Mexico. This new species is the fifth of the genus described having onchia. Among the species included in this group, the new species is morphologically closest to S. viperidicus and S. atroxi. However, it differs from both species mainly by having only one excretory gland (compared to two present in S. viperidicus and S. atroxi). In addition, S. mexicanus n. sp. can be separated of S. viperidicus by tail length, shape of vulval lips, geographic distribution and host species and from S. atroxi by body length, number of papillae in the cephalic region, as well as the host species and geographic distribution. In the present study, we propose the new species based on morphological, host spectrum and genetic evidence. Phylogenetic analysis indicated Serpentirhabdias as a monophyletic group, with two subgroups that are congruent with the presence/absence of onchia in the esophagostome, host association and other relevant morphological characters.

Trade-off between thermal preference and sperm maturation in a montane lizard.

Temperature is a key abiotic factor that influences performance of several physiological traits in ectotherms. Organisms regulate their body temperature within a range of temperatures to enhance physiological function. The capacity of ectotherms, such as lizards, to maintain their body temperature within their preferred range influences physiological traits such as speed, various reproductive patterns, and critical fitness components, such as growth rates or survival. Here, we evaluate the influence of temperature on locomotor performance, sperm morphology and viability in a high elevation lizard species (Sceloporus aeneus). Whereas maximal values for sprint speed coincides with field active and preferred body temperature, short-term exposure at the same range of temperatures produces abnormalities in sperm morphology, lower sperm concentration and diminishes sperm motility and viability. In conclusion, we confirmed that although locomotor performance is maximized at preferred temperatures, there is a trade-off with male reproductive attributes, which may cause infertility. As a consequence, prolonged exposure to preferred temperatures could threaten the persistence of the species through reduced fertility. Persistence of the species is favored in environments with access to cooler, thermal microhabitats that enhance reproductive parameters.