Efect of cadmium cloride on the gonads of bulfrog tadpole (Lithobates catesbeianus)

Abstract

In past few years the amount of xenobiotics in the aquatic ecosystems has alarming increased, due the anthropic action on environments. Such substances are able to interact with the living organism, causing multiple organic changes causing serious consequences on populations, communities or various biomes. Several studies have pointed to a drastic decline of amphibians populations in the world. Among the factors supposed to be responsible for the decline of amphibians is the exposure to xenobiotics. In recent decades, the cadmium shows the highest increase rates in the environment, and this rate keeps rising. Cadmium has high penetrance between ecosystems, being bioaccumulative and persistent in the environment and may be biomagnified in the food chain. There are several effects of cadmium exposure on amphibian, such as delay and/or inhibition of metamorphosis, sex reversal, reduced growth in tadpoles, and sterility in adults. Recently, it has been pointed as a cause of endocrine disruptors, including effects on the morphology and reproductive function in both genders. Despite the literature on the influence of xenobiotics in the gonads of tadpoles, the influence of cadmium is poorly studied. The aim of this project is to contribute contribute to obtain effective results, through structural and functional biology, about the action of the cadmium on the gonadal development of bullfrog tadpoles exposed to acute (2 and 4 days) and chronic (16 days) concentrations at 1 ppb of cadmium chloride on the gonads of tadpoles Lithobates catesbeianus, during Gosner (1960) stage 25, contributing to the knowledge about the interference of the metal trace in gonadal development of tadpoles and, consequently, the reproduction of adults. This study aims to provide not only advances in the understanding of the effect of these substances on frogs, but also allows monitoring the the cadmium concentrations given as environmentally safe by the Brazilian National Environment Council (CONAMA-2005) for rivers of class 1 and 2 (1 ppb) in an attempt to establish appropriate policies to ensure the preservation and protection of the natural balance of aquatic communities. Additionally, it is the first step to understand the main damages that this trace metal exposure on the gonadal development in a "standard" amphibian to support futures studies with native species.