Histological changes in the bullfrog (Lithobates catesbeianus) myocardium induced by severe hypoxia during embryonic development

Amphibians are organisms that suffer high damage from ecological imbalance, since they necessarily have aquatic reproduction and larval phase, being, due to the fragility of this development stage, more susceptible to harmful changes in the environment. The occurrence of environmental hypoxia during development can play an important role in the involvement of serious abnormalities of the central nervous system and heart defects. Bullfrog eggs ( Lithobates catesbeianus ) ( n = 24) were kept in aquariums, with a volume of 5 L, and were divided into two experimental groups: Control Group and Hypoxia Group. The treated groups were kept in experimental conditions during the initial two days of development, being then relocated to aquariums with dechlorinated water and constant aeration. After 12 days the tadpoles had their measurements of mass and length taken and then they were anesthetized by hypothermia, euthanized, and fixed for histological preparation. Animals exposed to hypoxia showed a reduction in body mass and length, as well as a decrease in the mean thickness of the trabeculae of the cardiac tissue. The results show that the acute exposure of bullfrog tadpoles to severe hypoxia has deleterious effects on their development.