Bioaccumulation of potentially toxic trace elements (As, Cd, Hg, In, Ni, Pb, Se, Zn) and methylmercury in an Indian tarantula Thrigmopoeus truculentus (Pocock 1899) of the Western Ghats

Spiders are good bioindicators of ecological contamination by potentially toxic trace elements such as As, Cd, Hg, In, Ni, Pb, Se Zn and methylmercury (MeHg). Here, we investigated their bioaccumulation in an Indian tarantula, Theraphosidae spider Thrigmopoeus truculentus inhabiting mud embankments along a national highway in the Western Ghats mountains, and the soil contamination. Concentrations in soil were higher than the soil environmental quality criteria of different countries for Cd, Zn and Ni. Concentrations in whole-body of tarantulas (n = 7) were Zn > Se > [Cd, As, Pb, Ni] > In > total mercury (THg) > MeHg. Concentrations of Zn, Cd, Se, THg and MeHg were significantly higher (p < 0.05) compared to soil, suggesting biomagnification. Our work and the review of past data suggest that spiders can biomagnify Zn, Cd, Se, THg and MeHg; but not Pb, As, In and Ni. For As, Zn, Se, Cd, In and THg, correlations between concentrations in tarantula appendages and whole-body were significant (p < 0.05), suggesting that a non-lethal approach be explored where only appendages of larger tarantulas are analysed. Overall, the Theraphosidae species showed the potential to be used as an indicator of bioaccumulation, and their usefulness should be further explored.