Environmentally relevant concentrations of Cadmium impair morpho-physiological development and metamorphosis in Polypedates maculatus (Anura, Rhacophoridae) tadpoles

Abstract

Cadmium (Cd) poisoning has been globally reported causing detrimental health issues with severe toxic effects on certain physiological systems. Here the effects of different concentrations of Cadmium were assessed on the metamorphosis and development of common Indian tree frogs (Polypedates maculatus, Gray 1830). The tadpoles were exposed to environmentally relevant concentrations (up to 0.7 mg/l) of Cd in dechlorinated water from the larval stage to adulthood. Survival, growth traits (body length and body mass), external deformities and movement were some of the morpho-physiological characters compared between control and experimental samples. Followed by the determination of acute toxicity (median lethal concentration–LC50– after 24 h (5.603 mg/l) and 48 h (4.811 mg/l) of exposure), impacts associated with chronic toxicity of Cd to the tadpoles were inspected. The study showed multiple physiological deformities in the tadpoles chronically exposed to 0.5 and 0.7 mg/l Cd that included morphological malformations, pale skin colour, insipid motility, delayed metamorphosis and even high mortality. In addition to that, the tadpoles treated with 0.5 and 0.7 mg/l Cd showed significantly lesser growth traits than the controls over the study period. The paper aims to contribute in increasing ecotoxicological knowledge of an anuran species from which there is not much information of this type. Given the wide geographical distribution of the study species, it can serve as a bio-indicator of cadmium contamination, considering its applicability across a large swath of aquatic ecosystems in the Indian subcontinent.

Keywords

• Cadmium
• LC50
• Metamorphosis
• Polypedates maculatus
• Toxicity
• Tumours