Comparative evaluation of the acute toxicity and behavioural changes in Clarias gariepinus following exposure to dichlorvos and primextra pesticides

Abstract

Dichlorvos is an organophosphate pesticide used for the control of pests in crops and stored products, while primextra is a commercial herbicide formulation generally used in agriculture for weed control. The present study was designed to evaluate and compare the acute toxicity of dichlorvos and primextra pesticides and assess their effects on mortality and behavioural changes of Clarias gariepinus juveniles. The 24, 48, 72 and 96 h LC₅₀ of dichlorvos were 6.06, 4.96, 1.65 and 1.29 mg l⁻¹, while those of primextra were 9.34, 6.50, 5.41 and 4.67 mg l⁻¹, respectively. The safe levels estimated by different methods varied from 1.29 × 10⁻¹ to 1.29 × 10⁻⁵ mg l⁻¹ in dichlorvos and from 4.67 × 10⁻¹ to 4.67 × 10⁻⁵ mg l⁻¹ in primextra. Behavioural changes, such as hyperactivity, gulping of air, skin discoloration, loss of balance, convulsion, erratic swimming and mucous secretions, were observed in fish exposed to both pesticides. Our study indicated that dichlorvos (96 h LC₅₀ = 1.29 mg l⁻¹) was more toxic to C. gariepinus compared with primextra (96 h LC₅₀ = 4.67 mg l⁻¹). The use of these pesticides in both terrestrial ecosystems and aquatic environments should be subject to strict control and monitoring to prevent potential ecotoxicological hazards to aquatic lives.

Darbo tikslas – įvertinti ir palyginti dichlofoso ir Primextra ūminį toksiškumą bei poveikį Clarias gariepinus jauniklių mirtingumui ir elgsenos pokyčiams. Dichlofosas – organinis fosforo junginys, naudojamas vabzdžių naikinimui laukuose ir sandėliuose, Primextra – herbicidas, dažniausiai naudojamas piktžolių naikinimui žemės ūkyje. Paveikus žuvis tiriamąja medžiaga 24, 48, 72 ir 96 valandas, dichlofoso LC₅₀ koncentracija buvo 6,06, 4,96, 1,65 ir 1,29 mg l⁻¹, Primextra LC₅₀ koncentracija – 9,34, 6,50, 5,41 ir 4,67 mg l⁻¹ atitinkamai. C. gariepinus saugios dichlofoso koncentracijos buvo nuo 1,29 × 10⁻¹ iki 1,29 × 10⁻⁵ mg l⁻¹, Primextra – nuo 4,67 × 10⁻¹ iki 4,67 × 10⁻⁵ mg l⁻¹. Abiem medžiagomis paveiktoms žuvims buvo būdingi elgsenos pokyčiai: hiperaktyvumas, žiopčiojimas ryjant orą, odos spalvos pakitimai, pusiausvyros sutrikimai, konvulsijos, chaotiškas plaukimas ir gleivingos išskyros. Šis tyrimas parodė, kad dichlofosas (96 val. LC₅₀ = 1,29 mg l⁻¹) C. gariepinus yra toksiškesnis negu Primextra (96 val. LC₅₀ = 4,67 mg l⁻¹). Dichlofoso ir Primextra naudojimas turi būti griežtai kontroliuojamas dėl galimo ekotoksikologinio poveikio vandens gyvūnams.

Keywords:

• Clarias gariepinus
• toxicity test
• aquatic environment
• pollution
• dichlorvos
• primextra

Acknowledgements

The authors thank the Department of Zoology and Environmental Biology, University of Nigeria, Nsukka, Nigeria, for the support and material provided for the project.