Behavioral Toxicity Of Monocrotophos And γ-BHC To A Marine Nematode Chromadorina Gemanica

Monocrotophos (MCP) is a high toxic organophosphorus pesticides extensively used in agriculture and animal husbandry in many developing countries. This pesticide can enter into aquatic environment through agriculture runoff, washing from the atmospheric precipitation and industrial point sources etc. Lindan (γ-BHC) is the principle components of hexachloro-cyclohexane soprocide, which was also widely used in agriculture. Althoughγ-BHC has been forbidden in most of countries, it is still detected in many environmental samples due to high fat-solubility, the hard biodegradability and long residence time. Hence,γ-BHC, together with the organic phosphorus pesticides, may cause combined pollution in aquatic ecosystem. Previous study has proved that MCP can inhibit acetylcholinesterase (AChE) activity.γ-BHC can promote acetylcholine release and inhibit GABA receptor. That is, MCP andγ-BHC are potent neurotoxicants, which may elicit abnormal behavior. Behaviors of Caenorhabditis elegans (C.elegens) has been widely applied to evaluate soil and water pollution, while information is missing about behavioral toxicity of MCP andγ-BHC to marine nematode. In the present study, we reported the behavioral toxicity of MCP andγ-BHC to a marine nematode Chromadorina gemanica (C.gemanica) using several behavioral paradigms― body bends, head thrashes, food attainment levels and egg-laying rates following a 72 hr exposure to MCP andγ-BHC standards in static culture plate. Our results showed as follows:⑴10μg/L treatment did not decreased the body bends and head thrashes statistically. However, when the worms were exposed to 100μg/L and 1000μg/L for 72 hr, their body bends were decreased by 16.7 %, 47 % and their head thrashes were decreased by 17.8 %,41.5 %. 0.5μg/Lγ-BHC significantly decreased the head thrashes. The body bends were also reduced, but there was no noticeably differences compared to the control. When the worms were exposed to 5μg/L and 50μg/Lγ-BHC for 72 hr, their body bends were decreased by 29.2%, 37.8% and their head thrashes were decreased by 26.7%, 41.1%; The joint treatment of MCP andγ-BHC caused very significant inhibition on locomotion behavior of C.gemanica. The body bends were reduced by 32.9%, 45.4% and 86.5%, the head thrashes were decreased by 37.3%, 48% and 94.4%. The results indicate that MCP andγ-BHC exposures caused significant inhibition on locomotion behavior of C.gemanica.⑵After exposure to 10μg/L MCP, the food attainment levels were reduced very significantly at 2, 4 hr and significantly at 6, 8, 10 hr. The food attainment levels of the animals exposed to 100μg/L and 1000μg/L MCP were very significantly reduced at all observation points; After exposure to 0.5μg/Lγ-BHC, the food attainment levels were decreased only at 2 hr. However, it was reduced very significantly at all observation points after exposure to 5μg/L and 50μg/L; The joint treatment of MCP andγ-BHC caused very significant inhibition on the food attainment levels of C.gemanica at all joint group: 10&0.5μg/L, 100&5μg/L and 1000&50μg/L. The results indicate that MCP andγ-BHC could also noticeably decrease the food attainment levels in a concentration-dependent fashion.⑶When the worms were exposed to 10μg/L, 100μg/L and 1000μg/L MCP, the egg-laying rates were decreased by 18.3%, 67.7% and 81.7%, respectively; When the nematodes were exposed to 5μg/L and 50μg/Lγ-BHC, the egg-laying rates were decreased by 62.5% and 83.3%, respectively. Treatment with 0.5μg/Lγ-BHC also reduced the egg-laying rates, but there was no noticeably differences compared to the control. The joint treatment of MCP andγ-BHC caused very significant inhibition on the egg-laying rates of C.gemanica at all joint group: 10&0.5μg/L, 100&5μg/L and 1000&50μg/L. The results indicate that treatment with MCP andγ-BHC also inhibited egg-laying behavior of C.gemanica.By comparing the results of monocrotophos,γ-BHC separate treatment to the joint treatment, additive effects on the locomotion, feeding and egg-laying behaviors of C.germanica were found, after joint treated by monocrotophos andγ-BHC.In conclusion, our research indicates that locomotion, feeding and egg-laying behavior in the marine nematode C.gemanica are very sensitive to MCP andγ-BHC and the MCP andγ-BHC noticeably inhibited the body bends. head thrashes, food attainment levels and egg-laying rates, exhibiting behavioral toxicity. The model nematode C.elegens has been extensively applied to assess soil and fresh water pollution caused by heavy metals and pesticides. Our works propose that the marine nematode C.gemanica is an attractive test organism that provides us an informative test system to evaluate the marine pollution.