American bullfrog
In multiple animal studies, it has been shown that stress causes increases in glucocorticoid levels). Frogs release corticosteroids in response to many environmental factors and this pattern of release is often species-specific within Amphibia More specifically, increased stocking density and hypoxia cause changes in cortisol (one of the glucocorticoids) and white blood cells in American bullfrog tadpoles ("Lithobates catesbeianus") indicative of stress.