Abstract
The Ultrastructural effects of chlorpyrifos and phenthoate on midgut of third larval instar of Chrysomya albiceps was illustrated with the aid of transmission electron microscope. It was clear that chlorpyrifos considered to be most potent than phenthoate. The number of pupae and emerged adults were reduced after treatments with all concentrations of the two insecticides. There was a predominance of males over female (ratio, 4.5:1), respectively after treatment with 15 ppm chlorpyrifos. Based on ultrastructural changes, after treatment with phenthoate, densely compressed cells with irregular shrank nucleus that has fragmented nucleoli and lacked condensed chromatin were observed in the midgut cells. The rough endoplasmic reticulum becomes swallowed. The microvilli clumped and shrunk. After treatment with chlorpyrifos, Numerous number of large vacuoles observed at the periphery of the midgut cells. The mitochondria show different degrees of deformation from clumping of cristae to rupture of mitochondrial membrane. The cells of midgut possessing short, shrunk or atrophied microvilli. Lysis of most cellular organelles is the most characteristic features after chlorpyrifos treatments.
Highlights
Chrysomya albiceps is a species belonging to the blowfly family, Calliphoridae (Queiroz, 1991& 1996; Povolny, 2002)
Toxicological Studies: The LC50, LC90 and LC95 values resulted from treatment of third larval instar of Chrysomya albiceps with chlorpyrifos and phenthoate insecticides were reported in the table (1)
The number of pupae is reduced after treatment of third larval instar with the two selected compounds; it reaches 4.6±0.67 and 0.0 ±0.0 after treatment with 25 ppm chlorpyrifos and 250 ppm phenthoate, respectively compared with 19.8±0.2 in control (Table 2)
Summary
Chrysomya albiceps is a species belonging to the blowfly family, Calliphoridae (Queiroz, 1991& 1996; Povolny, 2002). It causes economic damage to cattle breeding by causing primary myiasis (Queiroz, 1996) This blowfly species considered being an important vector in spreading of the carbuncle which is caused by Bacillus anthracis in South Africa (Braack and Retief, 1986). In Africa, it plays a significant role as a predator of other dipteran larvae They may seriously alter the qualitative and quantitative species composition on a corpse (Grassberger et al, 2003). Chlorpyrifos [0, O-diethyl 0-(3,5,6-trichloro-2-pyridyl) phosphorothioate] is a broad-spectrum organophosphorothioate insecticide which shows activity against many insects. Phenthoate is Khater, K.S [S-alpha-ethoxycarbonylbenzyl O,O-methyl phosphoro dithioate], an organothiophosphate insecticide It is used in controlling mosquitoes, blowflies and houseflies. The strong pungent odor of phenthoate repelled adults and egg laying can be prevented
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