INTERNATIONAL JOURNAL OF AGRICULTURE & BIOLOGY ISSN Print: 1560–8530; ISSN Online: 1814–9596 07–404/SAE/2008/10–5–475–480 http://www.fspublishers.org Full Length Article To cite this paper: Ghoneim, K.S., R.F. Bakr, M.A. Tanani, A.G. Al Dali and A.S. Bream, 2008. An ultrastructural study on the desert locust (Schistocerca gregaria) as affected by Tebufenozide (RH-5992). Int. J. Agri. Biol., 10: 479–80 An Ultrastructural Study on the Desert Locust (Schistocerca gregaria) as Affected by Tebufenozide (RH-5992) K.S. GHONEIM 1 , R.F. BAKR†, M.A. TANANI, A.G. AL DALI AND A.S. BREAM Department of Zoology, Faculty of Science, Al-Azhar University, Cairo, Egypt †Department of Entomology, Faculty of Science, Ain Shams University, Cairo, Egypt 1 Corresponding author’s e-mail: kar_ghoneim@yahoo.com ABSTRACT Tebufenozide exhibited some histopathological effects on the integument of last instar nymphs of desert locust (Schistocerca gregaria Forsk) such as: detachment of the cuticle from epidermis, undistinguishable epicuticle. Tebufenozide treatments affected the ultrastructural configuration of thoracic muscles such as disrupted organization of A, I and H bands and the degeneration of Z disc varied from one half of the disc to small central or peripheral degenerated areas. Tebufenozide treatments resulted in the loss of normal architecture of the majority of mid-gut epithelial cells, which had dwarf and deformed microvilli. The most important ultrastructural changes in the intracellular organelles by the action of Tebufenozide, as shown in the electron micrographs, were elongation of mitochondria, which appeared with prominent cristae, the lysosomes were supposedly autophagic, Golgi bodies had a bullet shape and the cytoplasm contained scattered granules. Kew Words: Schistocerca gregaria; Tebufenozide; Nymphal instar; Ultrastructure; Histopathology; Integument; Muscles INTRODUCTION Development and reproduction in insects are affected by a number of hormones, including juvenile hormone and ecdysone. Insect growth regulators (IGRs) are synthetic analogues, which mimic the naturally occurring hormones for affecting the physiological processes of insects and are generally classified as juvenile hormone analogues and ecdysone agonists (Sehnal, 1983; Mohandass et al., 2006). The ecdysone agonists, or ecdysteroids, are synthetic products interfering with the natural insect moulting hormone (20-hydroxyecdysone), which controls several physiological and biochemical processes of growth and development. They have attracted the attention of many researchers all over the world (Hagedron, 1985; Silhacek et al., 1990; Ghoneim et al., 1991 & 98; Smagghe et al., 1996; Cadogan et al., 1997). Tebufenozide (RH-5992) represents a novel class of IGRs, which directly stimulate the ecdysteroid receptors as the molecular level initiating the moulting process by gene regulation especially in larval Lepidoptera (Wing et al., 1988). Although considerable interest has been shown in the use of hormone analogues as agents for insect pest control, studies have tended to concentrate on morphometric changes and on assessing pesticidal activity. Hence, information concerning the effects of such compounds at the cellular or subcellular level is somewhat limited. In the present work, the histopathological effects of Tebufenozide, as well as the ultrastructural changes in the desert locust (Schistocerca gregaria Forsk) were investigated aiming to shed some light on its roles at the cellular and subcellular levels. MATERIALS AND METHODS Experimental insect. A gregarious stock culture of desert locust [Schistocerca gregaria Forsk. (Orthoptera: Acrididae)] was raised by a sample from the established culture of Locust and Grasshopper Res. Division, Agric. Res. Center, Giza, Egypt. The insects were reared under crowded breeding conditions outlined by Hunter-Jones (1961) and Hassanein (1965). Newly hatched hoppers were kept in wooden cages with wire-gauze sides (40 x 40 x 60 cm) and small door in the upper-side to allow the daily feeding and cleaning routine. The bottom was covered with 20 cm layer of sterilized sand. Cages were equipped internally with 60 W electric bulb for lightening (17:7 LD) and warming (32±2 o C.). Successive generations were raised before obtaining the nymphs for the present experimental work. Fresh food plant was clover Medicago sativa along the period of study except few weeks every year, because of the absence of this plant species. During these weeks, insects were fed on Sesbania egyptiaca. All experiments were conducted with Medicago sativa only. Administration of the hormone analogues. A technical grade of the non-steroidal ecdysone agonist Tebufenozide