Oocyte maturation is transformation of oocytes into a fertilizable egg. This study examined the effects of four classes of chemicals: 1) acephate (organophosphate); 2) atrazine (herbicide); 3) cypermethrin and fenvalerate (synthetic pyrethroids); and 4) carbaryl (carbamate) on in vitro germinal vesicle breakdown (GVBD) of Euphlyctis cyanophlyctis oocytes. Follicles were isolated and defolliculated from surgically removed ovaries of E. cyanophlyctis and exposed to either progesterone (1 μM/mL) or graded concentrations (1, 5, 10, 15, and 20 μg/mL) of test chemicals. GVBD was evident by the presence of a white spot in the animal pole as well as the absence of germinal vesicles in sectioned heat-fixed oocytes. Percent GVBD was scored every 4 hours until 24 hours. Progesterone induced 77-84% GVBD, compared to 29-33% in controls, at 24 hours. Acephate induced 46-67% GVBD, whereas atrazine elicited 58-77% of GVBD. In cypermethrin or carbaryl- or fenvalerate-exposed oocytes, GVBD was limited to 22-28, 17-29 and 18-24%, respectively. The study infers that some chemical contaminants in the aquatic system may interfere with GVBD in amphibians. Because oocyte maturation is a prerequisite for the production of fertilizable eggs, any alteration in this process potentially impairs the fecundity of females.

Developmental toxicity effects of endocrine disrupter chemicals, acephate and cypermethrin were studied in Bufo melanostictus tadpoles. Thirty developing eggs of B. melanostictus were exposed to each concentration (0.01, 0.05, 0.1, 0.5, and 1 mg L À1 ) of acephate or cypermethrin in the laboratory (temperature: 23 AE 1 C; photoperiod: 11.5-12.5 h). Eggs maintained in conditioned water alone served as controls. After hatching, larvae were fed on boiled spinach until the completion of metamorphosis. In control group, larvae that hatched on 3rd day were heavily pigmented, voracious feeders, and active swimmers; in these tadpoles, hind limb and forelimb-buds emerged on 16th and 24th day and metamorphosis was complete on 32nd day. Eggs exposed to acephate also hatched on 3rd day but larvae exhibited deformities such as, (i) tail distortions, (ii) laterally crooked trunk, (iii) decreased pigmentation, (iv) inactivity, (v) peeling of the skin, and (vi) delay in emergence of limbs and completion of metamorphosis. Cypermethrin-exposed eggs exhibited a delay (4-8 days) in hatching, there was no mortality, deformities in tail, trunk and head region, delay in the emergence of limbs, and completion of metamorphosis were evident. The demonstrated data indicate that these pesticides interfere with amphibian development when present in the aquatic system.

Novaluron is an insect growth regulator (IGR) used against fruit-borers and domestic pests. In this study, effects of different concentrations (0.5, 0.75, 1.0, 1.5 microg l(-1)) of novaluron on the tail regeneration, limb development and metamorphosis were examined in Bufo melanostictus. Thyroxine (1.0, 2.0, 3.5, 5.0 microg l(-1)), which promotes amphibian development/metamorphosis, and vitamin A (5, 20, 40, 60 IU l(-1)), which disrupts development and induce polymelia, were used for comparison. Bufo melanostictus tadpoles were raised in the laboratory from eggs collected around Dharwad in August 2007. The tail of tadpoles was amputated at limb-bud stage under ether anesthesia. Ten tadpoles were exposed to each concentration of chemicals in triplicate for 5 days and then reared in conditioned water. Tadpoles were fed on boiled spinach. In controls (tadpoles exposed to ringer solution), the tail regenerated on the 5th day, hind-limbs and fore-limbs appeared on days 15 and 24, respectively; metamorphosis was complete on the 30th day. In 1 and 2 microg l(-1) thyroxine exposed tadpoles, regeneration of tail, development of limbs and metamorphosis were preponed to the 4th, 7th, 11th and 23rd day respectively. Exposure to vitamin A resulted in the regeneration of laterally drooped tails, delay in limb development and arrest of metamorphosis in all the concentrations used. Novaluron at lower dose (0.5 microg l(-1)) was not effective, but at 0.75 microg and higher concentrations it elicited results comparable to those of vitamin A. The study indicates that novaluron interferes with amphibian development if found as contaminant in the water bodies where amphibians live and reproduce.

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