Tadpole Survival and Metamorphosis in the Granular Spiny Frog, <i>Quasipaa verrucospinosa</i> (Dicroglossidae, Anura, Amphibia) in Central Vietnam

Abstract

Little is known about many aspects of the tadpole ecology of Quasipaa verrucospinosa (Bourret, 1937), whereas this species has also been classified as Near Threatened (NT) due to habitat change and degradation, loss of forest and stream habitats and overexploitation. We conducted experiments in the field and collected tadpole data to estimate survival rates, growth rates, and age at metamorphosis. The average number of tadpoles per clutch was 518, the average survival ratio at the final stage of metamorphosis was 80%, and the total time to metamorphosis averaged 55.8 days. Multiple regression results for possible effects of water temperature, dissolved oxygen, and pH values on survival rates and the total time of tadpole metamorphosis were significant among localities. Water temperature and dissolved oxygen, but not pH values, were negatively associated with the survival ratio and metamorphosis time of tadpoles. At the beginning stage of metamorphosis (41 – 42), tadpoles had an average body weight of 2.7 g, a snout-vent length (SVL) of 24.8 mm, a tail length of 40.5 mm, and a total length of 65.3 mm. The process of metamorphosis is completed in stage 46, at which juvenile frogs had a mean body weight of 2.3 g and a mean SVL of 25.8 mm. We used a two-way multivariate analysis of variance to examine the effects of year and site factors on the variance in morphological measurements and body weightes of tadpoles. This analysis revealed that body sizes of tadpoles varied significantly among years, sites, and by site-year interaction. Water temperature and dissolved oxygen have major impacts on rates of growth, timing of metamorphosis, and body size of tadpoles at metamorphosis.