Variação morfométrica em Bothropoides jararaca (Serpentes, Viperidae) no Rio Grande do Sul

Abstract

ABSTRACT. Morphometric variation in Bothropoides jararaca (Snakes, Viperidae) in Rio Grande do Sul. 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. KEYWORDS.Ontogeny, morphology, dimorphism. RESUMO.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...

Morphological variation of Philodryas patagoniensis (Girard, 1858) (Serpentes, Dipsadidae) from Brazil, based on the study of pholidosis, coloration and morphometric features

“…We observed that the adult females of P. patagoniensis have a largest body size that than adult males (Table 1). A similar pattern of females were reported in several other species of snakes (Solorzano & Cerdas 1989, Shine 1993, Rivas & Burghardt 2001, Gregory 2004, Pinto & Fernandes 2004, Matias et al 2011, Mesquita et al 2011, Henao-Duque & Ceballos 2013.…”

“…Several authors observed that the fertility is considered one of the main selective agents for the larger size of females for some species of snakes; however, the largest size of males in another species of snakes can be considered as a significant feature of males of species that possesses the behaviour of competition for territory and for females in reproductive period (Shine 1978, 2000, Zug et al 2001, Matias et al 2011, Henao-Duque & Ceballos 2013.…”

“…Research on sexual dimorphism performed in several species of snakes of the families Colubridae and Dipsadidae demonstrate that the females have a highest snout-vent length compared to males (Solorzano & Cerdas 1989, Rivas & Burghardt 2001, Zug et al 2001, and males have a highest tail length than females (King 1989, López & Giraudo 2008, Matias et al 2011.…”

Morphological variation in the common lancehead populations: Sexual dimorphism and ontogenetic patterns

“…Some studies have discovered populations with larger body sizes or marked sexual dimorphism (e.g. Matias et al., 2011; Siqueira & Marques, 2018). Although studies addressing morphological divergences in snakes have been published extensively, many are focused only on one population, sympatric species or address only adults.…”

Evolução das estratégias reprodutivas de Bothrops jararaca (Serpentes: Viperidae)

“…Machos de Bothrops jararaca de ambos os clados e das ilhas estudadas atingem a maturidade sexual com menor tamanho corporal do que as fêmeas, assim como observado em outras espécies do gênero Bothrops (VALDUJO et al, 2002;HARTMANN et al, 2004;MONTEIRO et al, 2006;NUNES et al, 2010;BARROS, 2011 HOGE et al, 1959;SOLÓRZANO;CERDAS, 1989;JANEIRO-CINQUINI et al, 1992;MANZANI, 1998;NOGUEIRA et al, 2003HARTMANN et al, 2004MONTEIRO et al, 2006;KASPEROVICZUS, 2009;NUNES et al, 2010;BARROS, 2011;MATIAS et al, 2011), mas também em outras espécies de serpentes PLUMMER, 1987;SCARTOZZONI, 2009;GOMES;. Essa característica ocorre provavelmente devido ao custo energético relacionado à fecundidade ser maior nas fêmeas (SHINE, 1978;BELL, 1980;FORD, 1987).…”