Biological factors controlling developmental duration, growth and metamorphosis of the larval green toad, Bufo viridis viridis

Abstract

The present study in a controlled laboratory setting provided important insights into both the degree of plasticity and the proximal environmental cues operating in the response of green toad tadpoles to pond drying, food level. It was concluded that timing of metamorphosis and size at metamorphosis were highly affected by pond duration. The effects of pond desiccation are reflected by shorter developmental duration and smaller size at metamorphosis as a result of increased crowding in the shallow tanks than tadpoles in the deep tanks. Bufo viridis raised on high food supplements grew faster than those raised on low food in low or high population density. In the tanks with decreased water and food levels, the tadpoles accelerate development and metamorphose earlier than tadpoles in higher food and water levels. The obtained data revealed that tadpoles grew faster under conditions of high population density than low one in either high or low food levels. Actual density had limited but significant effects on tadpole size and development. It also suggested that density regulation, acting on the tadpole stage, may be present in the population but was of less short-term importance than abiotic factors. Environmentally induced variation in developmental rates translated to changes in relative hind leg length. Hind leg length plasticity was positively correlated with growth rate plasticity. Finally, documenting the recent results of this study, B. viridis breed in temporary ponds and exhibited plasticity in developmental duration and growth rate in response to a change in water level.