Toxicity of endosulfan to tadpoles of Fejervarya spp. (Anura: Dicroglossidae): mortality and morphological deformities Ngangom Nganbi Devi • Abhik Gupta Accepted: 4 September 2013 / Published online: 26 September 2013 Ó Springer Science+Business Media New York 2013 Abstract The acute toxicity of endosulfan to the tadpoles of three coexisting species of the anuran genus Fejervarya revealed 96 h LC 50 values of 46.715, 6.596, and 3.015 lgl -1 for Fejervarya sp.1, F. teraiensis and Fejer- varya sp.2, respectively. Toxicity of endosulfan was also tested at the sublethal concentrations of 5 and 0.5, and 0.3 and 0.03 lgl -1 (c 10 and 1 % of their respective 96 h LC 50 values) in Fejervarya sp.1 and Fejervarya sp.2, and 0.35 and 0.18 lgl -1 (c 5 and 2.5 % of 96 h LC 50 ) in F. teraiensis. Endosulfan was observed to cause mortality at concentrations as low as c 1, 2.5 and 10 % of their respective 96 h LC 50 values in Fejervarya sp.2, F. terai- ensis, and Fejervarya sp.1. Such vulnerabilities are likely to have implications for the survival of natural populations of these co-existing species as well as other anurans present in the study area where pesticide use is relatively high in the tea plantations. Morphological deformities caused by endosulfan comprised failure to develop one or both fore- limb in Fejervarya sp.1 and F. teraiensis, stunted hindlimb growth in Fejervarya sp.1, and axial malformation in Fe- jervarya sp.1 and Fejervarya sp.2. Fore- and hind-limb deformities were likely to have occurred due to the impairment of thyroid metabolism by endosulfan. These effects illustrate the threat that continued endosulfan use poses to natural populations of anuran amphibians. Keywords Anura  Endosulfan  Mortality  Sublethal toxicity  Deformity Introduction As opposed to 1,211 species of birds and 1,130 of mam- mals, 1,856 species of amphibians are threatened to vary- ing degrees, making them currently the most vulnerable class of vertebrates on the IUCN Red List (Stuart et al. 2004). There is growing evidence that environmental pol- lution and agrochemical toxicity are important factors among those responsible for the amphibian decline that has been drastic enough during the last 25 years (Sparling et al. 2001; Blaustein et al. 2003). Pesticides and other contam- inants were found to play a significant role in the decline of Rana muscosa in California (Fellers et al. 2004). Amphibians have permeable skin and lay eggs that readily absorb chemicals from the polluted environment, making them vulnerable to pesticides and other chemicals (Hayes et al. 2003). India has a rich amphibian diversity comprising 342 species, of which 306 are anurans. According to an IUCN estimate, 4.97 % of the Indian amphibians are critically endangered, 9.36 % endangered, and 7.02 % vulnerable, although the number of threatened taxa is likely to increase because 23.68 % are Data Deficient, and 21.93 % have not been evaluated (Dinesh et al. 2012). Indiscriminate use of pesticides such as DDT, dieldrin and malathion, herbicides such as atrazine, and other forms of pollution have been held responsible, among other factors, for this precarious status (IUCN 2009). The test chemical, endosulfan, is a broad-spectrum organochlorine cyclodiene pesticide (Broomhall and Shine 2003) that has neurotoxic action in a variety of organisms, can damage gill tissues and cause eye abnormalities (Harris et al. 2000; Bernabo` et al. 2008). Endosulfan was reported to be highly toxic to fish, amphibians and crustaceans and its residues were detected in amphibian and fish tissues N. N. Devi  A. Gupta (&) Department of Ecology and Environmental Science, Assam University, Silchar 788011, Assam, India e-mail: abhik.eco@gmail.com 123 Ecotoxicology (2013) 22:1395–1402 DOI 10.1007/s10646-013-1125-2