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The study was aimed to determine the toxicity of cypermethrin, a synthetic pyrethroid pesticide on the freshwater catfish Heteropneustes fossilis. The experiment was conducted in two parts for a period of 96 h, under static conditions. In the first part, the LC 50 value of cypermethrin for 24, 48, 72 and 96 h was estimated. Behavioral changes in fish such as increased frequency of surfacing and gulping of atmospheric air, decrease in opercular movement (OCM), alteration in swimming pattern, violent shaking and jerking of head and gradual loss of balance due to cypermethrin exposure were regularly monitored for 96 h. In the second part of the study, the fish were subjected to short term (96 h) exposure of 3.42 µg/l (75% of 96 h LC 50 ) cypermethrin. Thereafter, fish were released in the cypermethrin-free water in order to study the recovery patterns in serum electrolyte levels. The data obtained from the acute toxicity tests were evaluated using EPA Probit analysis, Version 1.5, software based on Finney's Probit Analysis method. The LC 50 values for cypermethrin 24, 48, 72 and 96 h were 5.43, 5.12, 4.82 and 4.56 µg/l, respectively. The Ca +2 levels decreased in the exposed fishes up to 96 h, whereas, Mg +2 and Pi recorded an increase. During recovery period the serum electrolytes recorded a pattern towards normalcy when compared with 96 h exposed fishes.

Amphibians living partially or totally in a terrestrial environment are the first tetrapods to possess parathyroid glands. Purely aquatic amphibians and amphibian larvae lack these endocrine glands. The parathyroids develop at the time of metamorphosis. The parathyroid glands in caecilians consist of a single cell type, that of urodeles may be composed of basal (supporting) cells and suprabasal (chief) cells, and that of anurans of small and large chief cells. Parathyroid glands of caecilians and anurans lack connective tissue, blood vessels, and nerves. The parathyroid cells become activated in response to decreased blood calcium concentration and undergo changes indicating increased parathyroid hormone secretion. Increased blood calcium concentration suppresses secretory activity. Usually, parathyroidectomy elicits hypocalcemia in most amphibians. Such operations have no effect in lower urodeles. Parathyroid hormone administration provokes hypercalcemia in most amphibians. The parathyroids of caecilians have not been studied in detail. The urodeles and anurans exhibit seasonal changes in the parathyroid glands. These changes may be initiated by environmental stimuli such as light, temperature, or alterations in blood calcium levels caused by natural hibernation.

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