OPEN ACCESS International Journal of Aquatic Science ISSN: 2008-8019 Vol. 7, No. 1, 19-24, 2016 () erioch2006@yahoo.com; erick.ogello@gmail.com Effects of Nicotina tobacum (Linnaeus) on the survival and behavioral response of the freshwater leeches, Hirudinaria sp. Erick Ochieng Ogello 1* , Elija Migiro Kembenya 1 , Kevin Odhiambo Obiero 2 and Jonathan Mbonge Munguti 3 1) Kenya Marine and Fisheries Research Institute (KMFRI), Kegati Aquaculture Research Station, P.O.Box 3259 - 40200, Kisii, Kenya 2) Kenya Marine & Fisheries Research Institute (KMFRI), Sangoro Aquaculture Research Station, P.O.Box 136, Pap Onditi, Kenya 3)Kenya Marine and Fisheries Research Institute (KMFRI), National Aquaculture Research Development and Training Center, P.O.Box 26 Sagana, Kenya Received: 17 July 2015 Accepted: 25 September 2015 Published: 01 January 2016 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±1 o C. 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. Key words: Hirudinea sp., Nicotina tobacum, leeches, lethal concentration, lethal time Introduction Leeches are hermaphroditic invertebrates (phylum: annelid, genus: Hirudinea), often found in terrestrial and aquatic habitats (Sasaki and Tani, 1997; Sket and Trontelj, 2008). Leeches reproduce by egg deposition in their cocoons secreted by the clitellum through direct ontogeny without larval stages (Sawyer, 1986; Sket and Trontelj, 2008). In aquatic ecosystems, the parasitic leeches affect growth and survival of fishes (Sakiti et al., 1999; Iyaji and Eyo, 2008). For example, the genus Hirudinea have been reported in a wider range of African fishes e.g. Clariidae, Synodontidae, mugilidae, Mormyridae and Cichlidae (Mann, 1962; Oosthuizen, 1989; FAO, 1996), where it causes haemorrhage, fibrin deposition and oedema (Volonterio et al., 2004). The leeches also erode mucus membrane and damages the fish skin (Roubal, 1986; Volonterio et al., 2004), hence become a predisposing factor to opportunistic bacterial and fungal infections (Kabata, 1985). In humans, leeches can cause aenemia and haemorrhage (Kazemi and Bajoghli, 2002; Yaghmaee, 2002) thanks to their anti-coagulant histamine chemical (Bahmani et al., 2012). They also cause ophthalmorrhagia (Davari, 2008), pain, itching, hypersensitivity, and anaphylactic reactions (Ahmadiz- adeh, 2001). To control such incidences, chemical drugs have been commonly used (Bahmani et al., 2012). However, these chemicals have longer residual effects on the environment and may affect non-target organisms. Therefore, studies are needed to investigate environmentally safe chemicals (Sasaki and Tani, 1997). Nicotina tobacum is an agricultural product processed from the leaves of plants in the genus Nicotina. Studies have documented that nicotine; a highly toxic substance found in tobacco leaves, can kill and repel different pests and predators (Bahmani et al., 2012) including molluscs (Spector, 1956; FAO, 1970; Aleem, 1988; FAO, 1997;