The effect of sublethal exposure to temephos and propoxur on reproductive fitness and its influence on circadian rhythms of pupation and adult emergence in Anopheles stephensi Liston—a malaria vector

Abstract

The present study was undertaken to investigate the effects of organophosphate and carbamate insecticides namely, temephos and propoxur respectively, on the life history of Anopheles stephensi Liston (Culicidae) under laboratory conditions. The late third instar larvae of the mosquito were exposed to sublethal concentrations of temephos and propoxur at LC(10), LC(30) and LC(50), respectively, and adult survivors were evaluated for fitness parameters. Sublethal effects were also evaluated in subsequent generations. Fecundity, egg hatchability, sex ratio, adult longevity and morphology of gonads were the end points studied and compared to the untreated control. Adverse changes in developmental traits were mainly observed in fecundity, egg hatchability and sex ratio. However, significant differences in adult longevity were observed in the insecticide-exposed population. Pleiotropic effects through prolonged larval duration and enhanced longevity of adults were observed. Morphology of gonads in the insecticide-exposed population was severely affected and is represented by rudimentary and atrophied testes, and the size of the vas deferens was very much reduced when compared to that of the control. In another set of experiments, circadian rhythm (for pupation and adult emergence) of LC(10), LC(30) and LC(50) values to abovementioned insecticides exposed to late third instar larvae was studied. Pupation and adult emergence rhythms were found to be disturbed with an increase in concentrations of insecticides when compared to that of untreated control.

The Stressor Effect of Ethanol and Water Extracts of the Magical Herb <i>Phytolacca dodecandra</i> (Herit) on Life History of <i>Anopheles gambiae</i> (Diptera: Culicidae) Mosquitoes

“…Indeed it was reported that when exposed to insecticides containing temephos and propoxur, Anopheles stephensi females produced less viable eggs (Sanil and Shetty, 2012).…”

Assessment of Gluta renghas L. and Mangifera indica L. (Sapindales: Anacardiaceae) extracts on the sublethal effects of dengue vector

“…Insecticides have morphological effect on the reproductive organs of insects and effects on the reproductive capability is based on the mosquito response to the insecticides, inherent toxicity and mosquito species (Zin and Shetty, 2008). Application of insecticides resulted in the decreasing of the population, either by killing the susceptible strains and/or by decreasing the reproductive ability of the resistant strains (Sanil and Shetty, 2012). Anacardiaceae plants used in this study contain various compounds such as alkaloids, coumarins, saponins, tannins, reducing sugars, avonones, triterpenoids and steroids (Bbosa et al, 2007;Elumalai et al, 2012), which are previously reported for antifeedant, acute toxicity, repellent, fumigant and inhibiting reproduction of many insect species (Cox, 2004;Kubo, 2006).…”

“…The reduction in the number of offspring of the toxic compounds is due to the change in behavior for mate positioning and oviposition which affecting the egg fertilization, ovulation and sperm motility (Ali et al, 2006). Having less fertile adults treated with toxic compounds will resulted in less fertile or unfertilized eggs, also will reduce the percentage of larval emergence (Sanil and Shetty, 2012). Sublethal effects on egg hatchability at higher doses and delayed on larval development are strongly reported for malaria and dengue vectors exposed to the methanolic extracts of Calotropis procure F. Aiton (Ramos et al, 2006).…”

“…Synthetic chemicals like temephos and propoxur showed to have sublethal exposure to different mosquito species causing modifications in life history behaviors (Sanil and Shetty, 2012). Reduction in the number of eggs and fecundity indicated the disadvantages in the reproductive systems of mosquitoes caused by these synthetic insecticides (Sanil and Shetty, 2012).…”

“…Exposure to temephos increased average longevity of adults of An. stephensi after exposure (Sanil and Shetty, 2012). Comparison between the synthetic insecticides of fenitrothion and lambda-cyhalothrin and the natural plant extracts of Callitris glaucophylla J. Tomps & L.A.S.…”