Ecotoxicity of leaf extracts of Azadirachta indica on chironomids larvae

J.A Adakole

doi:10.17485/ijst/2012/v5i4.10

Abstract

The present study was designed to evaluate acute ecotoxicity of aqueous and ethanolic leaf extracts of Azadirachta indica on Chironomus spp. Exposure of chironomd larvae to the crude aqueous extract (0.0 [control], 25.00, 50.00, 75.00, 150.00 & 200.00 mg/L) and ethanolic (0.0 [control], 6.00, 12.00, 25.00, 50.00 & 100.00 mg/L) concentrations resulted in LC50 of 68.28mg/L and of 6.65mg/L respectively. Other toxic response by the larvae includes avoidance of sediment, impregnation of some segments with dark substances and bleaching/loss of respiratory pigments. Comparatively, mortality rate and other toxic responses was more in the ethanolic extract than in the aqueous extract test tanks. Impregnation of some larvae segments with dark substances suggests that feeding activity was going on during the toxicity test period and mortality of the larvae was partly due to contact with the polluted sediment and ingestion of contaminated particles of the sediment. Keywords. Ecotoxicity, Azadirachta indica, Neem, chironomus larvae, Ecotoxicity

Highlights

Azadirachta indica, family Meliaceae is known to contain a variety of compounds that show insecticidal, antifeedant growth-regulating, and development-modifying properties (Saleh & El-Wakeil, 2007; Abdelouaheb et al, 2009)
In Nigeria, during the dry season/harmattan period, large quantities of neem plant leaves and seeds could be found inside surrounding water bodies
Martinez & Machado-Neo (2007), observed that aqueous extract of neem is extensively used in fish farm as alternative for the control of fish parasites and fish fry predators of Prochilodus lineatus

Summary

Introduction

Azadirachta indica (neem plant), family Meliaceae is known to contain a variety of compounds that show insecticidal, antifeedant growth-regulating, and development-modifying properties (Saleh & El-Wakeil, 2007; Abdelouaheb et al, 2009). Slow moving rivers and streams that bioaccumulate leaves, barks, seeds and fruits of plants pose enormous risk to livestock and aquaculture practices (Makkar et al, 2007) and especially to aquatic macro-invertebrates (Adakole & Balogun, 2011). Some active ingredients in Neem plant includes azadiractin and Limonoids which are toxic to over 500 species of insects including Myzus persicae (aphids) (Khalid et aI., 2002, Martinez & Machado-Neo, 2007; Egho, 2012); Culex pipiens (Abdelouaheb et al, 2009). Quadri and Narasaiah (2005), determined the LC50 of Neem leaves extract against C. fatigans to be 39.0mg/L Though these LC50 differences could probably be attributed to differences in insect species as well as difference in mode of treatment, it could be concluded that azactiachtin is effective to both types of insects. The current excotoxicty investigation was conducted in a modified bioassay tank in the laboratory

Materials and methods

Results

Total observed Total expected Residual probability