Effects of Nicotina tobacum (Linnaeus) on the survival and behavioral response of the freshwater leeches, Hirudinaria sp.

Abstract

We investigated the efficacy of Nicotina tobacum as an anti-parasitic chemical to freshwater leeches of the genus Hirudinea, by assessing their behavioral and survival responses to different concentrations and ages of N. tobacum (i.e. 2.5, 5.0, 7.5, 10.0, 12.5, 15.0, 17.5 and 20.0 g L -1) at 25±1oC. We observed longer escape time from freshly prepared tobacco solutions compared to 1- day 2- day and 3- day-old solutions, suggesting a gradual degradation of nicotine toxicity with time. The percentage survival decreased significantly (P<0.05) with increasing concentrations of N. tobacum and exposure time. Concentrations of 15.0, 17.5 and 20.0 g L-1 recorded highest hazard ratios and low survival rates of leeches. The lethal concentration (LC50) and time (LT50) at which 50 % of leeches died were 15.0 gL-1 and 73 min respectively. This finding can be applied to control leeches, which are potential human disease vectors in aquatic ecosystems. Further investigations should target effects of nicotine on cultured animals and water quality parameters.