Abstract
To explore the mechanisms by which the wasp Scleroderma sichuanensis Xiao regulates the physiology and biochemistry of its host, effects of S. sichuanensis venom and parasitism on host the Tenebrio molitor L. pupae were examined. Significant differences in nutritional content were noted between parasitized and non-parasitized pupae and between venom- and phosphate buffered saline-injected pupae. When pupae were injected with venom, the fat body could not be disintegrated into granules; however, when pupae were parasitized, fat-body disintegration occurred. Electrophoresis showed no differences in hemolymph protein content between parasitized pupae and those injected with venom, indicating that the wasp did not have narrow-spectrum peptides. These findings confirmed that S. sichuanensis was a typical idiobiont ectoparasitoid wasp, and that nutrient regulation was similar between idiobiont and koinobiont wasps. The strong similarities between the two treatments suggest that venom injection is a major factor responsible for changes in host nutrient content. The wasp fed mainly on reducing sugars, free amino acids, and fat-body tissues; larval fat bodies were derived from hemolymph and from host tissue. Our findings suggest that lipid catabolism might be accelerated, and that lipid biosynthesis might be inhibited, when host pupae are parasitized or injected with venom. In addition to venom, physiological and biochemical changes that occur during the parasitic process might be caused by venom, ovarian proteins, saliva, or secretions.
Highlights
No significant differences were found between venom- and PBSinjected pupae (P > 0.05) treated on the first or second day
Trehalose content was significantly lower in venom- than in phosphate buffered saline (PBS)-injected pupae from the third to the sixth day (Fig. 1A)
To explore the regulatory mechanism of parasitic wasps on host physiology and biochemistry, we examined the effects of venom injection and parasitism by S. sichuanensis on T. molitor pupae
Summary
When Pieris rapae was parasitized by Cotesia rubecula, its hemolymph phenol oxidase (tyrosinase) activity was significantly reduced (Asgari et al 2003). Cai et al (2004) showed that venom of Pteromalus puparum could significantly inhibit the extension and encapsulation functions of hemocytes in P. rapae pupae, and could lead to hemocyte death. Webb and Luckhart (1994) suggested that venom and ovarian proteins of Campoletis sonorensis could inhibit the host’s early response by destroying the skeleton of host plasmatocytes and granulocytes. The venom of Nasonia vitripennis accelerated host fat synthesis (Rivers and Denlinger 1995).
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