Foram analisadas as gônadas de 124 exemplares de Cercosaura schreibersii e 192 exemplares de Cnemidophorus lacertoides do Escudo Sul-Riograndense, Rio Grande do Sul, Brasil. Ambas as espécies apresentaram reprodução tipicamente sazonal com fêmeas vitelogênicas no final do inverno e primavera, ovígeras na primavera e verão e o recrutamento ocorrendo nos meses com médias mais altas de temperatura na região. Não foi observada variação no volume médio ajustado dos testículos de machos de C. schreibersii ao longo do ano, contudo, o volume médio ajustado dos testículos de machos adultos de C. lacertoides alcançaram os maiores valores na primavera. Todas as desovas de C. schreibersii apresentaram número fixo de 2 ovos (n = 8) havendo correlação positiva entre o CRC das fêmeas e o tamanho dos ovos (R² = 0,55; p < 0,05). Em C. lacertoides o tamanho das desovas variou de 2 a 6 ovos (<img src="/img/revistas/bn/v10n1/x4_barra.gif" align="absmiddle" width="10" height="10"> = 3,75 ± 1,24; n = 15) e foi observada correlação positiva entre o CRC das fêmeas e o tamanho das desovas (R² = 0,50; p < 0,001). Em ambas as espécies, fêmeas maduras apresentam CRC significativamente maiores que machos (Teste t; p < 0,001). Por outro lado, machos maduros apresentam o comprimento (Ancova; p < 0,001) e largura da cabeça (Ancova; p < 0,001) maiores que as das fêmeas. Fêmeas juvenis podem alcançar tamanho compatível ao de exemplares maduros em aproximadamente 7 meses de vida para C. schreibersii e 8 meses para C. lacertoides durante a primeira estação reprodutiva após o nascimento. Não foi possível estimar a idade de maturação sexual dos machos, contudo, pode-se inferir que amadureçam antes e com menor tamanho que as fêmeas em ambas as espécies.

Gonads of 124 specimens of Cercosaura schreibersii (Wiegmann, 1834) and 192 specimens of Cnemidophorus lacertoides Duméril & Bibron, 1839 from the Sul-Riograndense Shield, Rio Grande do Sul, Brazil were analyzed. Both species presented seasonal reproduction, with vitellogenic females found at the end of winter and spring, gravid females in spring and summer and recruitment recorded during the months with the higher mean temperatures in the region. Variation of testis volume was not observed in males of C. schreibersii throughout the year, while adult males of C. lacertoides had variation, with larger testis found in spring. All clutches of C. schreibersii comprised two eggs and data suggest positive correlation between female SVL and egg size (R² = 0.55; p < 0.05). Clutch size of C. lacertoides varied from 2 to 6 eggs (3.75 ± 1.24, n = 15) and positive correlation between female SVL and clutch size was also observed (R² = 0.50; p < 0.001). Females of C. schreibersii had significantly larger SVL than mature males (t-test; p < 0.0001). Head length and width of mature females and males of C. schreibersii were not significantly different. Sexually mature females of C. lacertoides had significantly larger SVL than mature males (t test; p < 0.001), however, males had larger head than females, with significant differences in head length (Ancova; p < 0.001) and width (Ancova; p < 0.001). Juvenile females can attain the size of mature specimens after seven months for C. schreibersii and eight months for C. lacertoides. It was not possible to estimate the sexual maturation age of males, but it is possible to estimate that males are mature earlier and with smaller size than females in both species.

In May 1987, a female of Bothrops jararaca (Wied, 1824), from Carazinho, Rio Grande do Sul (RS), Brazil, was placed in the same vivarium with a male of Bothrops neuwiedi Wagler, 1824 coming from Guaíba, RS. There, they stayed for aproximately ten months. In March 1988, it was observed a delivery of five live and two still born, among them six presented morphologic characteristics of B. neuwiedi and one of B. jararaca. After the female died, in April 1988, through necropsy, two fetusus were found, one near the cloaca and, both identified as B. neuwiedi. The morphologic analysis and the origin of the progenitors suggest the hypothesis that the litter was resulted of cross-breeding.