ABSTRACT Studies on the thermal biology of fossorial reptiles that examine the relationship between the body temperature and thermal environment are needed to determine the extent of their thermoregulation abilities. This study assessed the thermal biology of Amphisbaena munoai Klappenbach, 1969 in the rocky fields of the Rio Grande do Sul and in the laboratory. The body temperature of most individuals was between 24 and 30 °C, both in the field (n = 81) and laboratory (n = 19). More individuals were caught in winter (n = 55) and spring (n = 60) than in summer (n = 25) and fall (n = 45), and in spring, individuals showed similar nocturnal and diurnal activities. In the laboratory, we found individuals with body temperatures up to 5 °C higher than the ambient temperature (n = 4), suggesting that some physiological mechanisms participate in the thermoregulation of these animals. Amphisbaena munoai is a thigmothermic species that is capable of actively regulating its temperature by selecting microhabitats such that its various activities occur within an ideal temperature range. This study is the first to evaluate the effect of seasonality and diurnal and nocturnal variations on the thermoregulation of an amphisbaenid.

Apesar de machos e fêmeas de serpentes nascerem com o mesmo tamanho, as taxas de crescimento e a idade da maturação sexual podem ser diferentes, determinando dimorfismo sexual em estágios posteriores da vida. Avaliamos a ocorrência de variação morfométrica sexual e ontogenética em Bothropoides jararaca (Wied, 1824), explorando as relações entre tamanho corporal e amadurecimento sexual através de 14 variáveis morfométricas. Foram analisados 142 espécimes provenientes do estado do Rio Grande do Sul, sul do Brasil. Os dados morfométricos - comprimento da cabeça, rostro-cloacal, da cauda, comprimento total; largura da cabeça, ocular, nasal, loreal, da cauda; distância ocular-nasal, ocular-loreal, loreal-nasal, ventral-sinfisal e rostral-labial - e comprimento/diâmetro dos folículos ovarianos, foram tomados em milímetros, através de régua simples e paquímetro analógico de precisão 0,05 mm. A determinação sexual foi realizada por inspeção das gônadas. A classificação etária foi associada à maturidade sexual. Para as análises estatísticas foram utilizadas análises de variância (ANOVA) com teste de Tukey post hoc, regressão linear e análise discriminante canônica (ADC). A maioria das medidas indicou dimorfismo sexual (ANOVA, P<0,05) apenas em adultos (Tukey, P<0,05). As análises de regressão mostram que o comprimento rostro-cloacal explica o comportamento das demais variáveis (P<0,001) e que em todas as medidas as fêmeas crescem mais que os machos. A ADC foi exitosa em separar as classes sexuais e etárias, apresentando significado biológico, considerando 79,2% dos casos como corretamente classificados.

Although male and female snakes are born with the same size, growth rates and age of sexual maturation may be different, thus determining sexual dimorphism in the later stages of life. We evaluated the incidence of sexual and ontogenetic morphometric variation in Bothropoides jararaca (Wied, 1824), exploring relationships involving body size and sexual maturity through 14 morphometric variables. We analyzed 142 specimens from the state of Rio Grande do Sul, southern Brazil. Morphometric data - head length, snout-vent length, tail length, total length; head width, ocular width, nasal-loreal width, tail width; nasal-ocular distance, ocular-loreal distance, loreal-nasal distance, ventral-sinfisal distance and rostral-labial distance - and length/diameter of ovarian follicles, were taken in millimeters by simple rule and analogical caliper, precision 0.05 mm. Sex determination was performed by inspection of the gonads. Age was associated to sexual maturity. For the statistical analysis the analysis of variance (ANOVA) with Tukey's post hoc test was used with, linear regression and canonical discriminant analysis (CDA). Most measures indicated sexual dimorphism (ANOVA, P<0.05) only in adults (Tukey, P<0.05). Regression analysis showed that snout-vent length explains the behavior of other variables (P< 0.001) and in all measures, females grow more than males. The ADC has been successful in separating the genders and age groups, with biological meaning, whereas 79.2% of cases were correctly classified.