Growth and metamorphosis of Bufo gargarizans gargarizans larvae: effects of water volume and food diversity

Organisms can evolve and produce different phenotypes in respond to local environmental conditions. Abiotic factors, such as water volume and food diversity in breeding ponds, also play significant roles in the survival and age at metamorphosis of amphibians. Here, we experimentally examined the plasticity of growth rate, survival rate, larval mass, age, and body size at metamorphosis in Bufo gargarizans gargarizans in response to varying combinations of water volume and food diversity. The interaction between water volume and food diversity had no effect on larval growth and development. However, food diversity had a significant impact on the age at metamorphosis, with two food resources resulting in a shorter larval period and earlier metamorphosis, particularly in larger water volumes. Our findings demonstrated that tadpoles raised in larger water volumes had larger body sizes at metamorphosis compared to those in smaller water volumes. Additionally, tadpoles in larger water volumes exhibited higher growth rates and shorter larval periods than those in smaller water volumes. We suggest that the increased frequency of physical encounters between tadpoles and the vessel walls in smaller volumes, akin to high-density conditions, causes psychological stress due to crowding, which hinders larval growth and development.