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Histopathological Changes in Heliothis Armigera Infected with Bacillus Thuringiensis as Detected by Electron Microscopy

  • H. S. Salama
  • A. Sharaby
Research Article

Abstract

The histopathological changes caused by Bacillus thuringiensis var. entomocidus HD-635 in the cotton bollworm, Heliothis armigera, have been investigated using electron microscopy. Death of the larvae due to infection was a gradual process involving a sequence of symptoms. Most of the histopathological changes that occurred on the fourth day after treatment with B. thuringiensis were mainly localized in the midgut, where the epithelium was greatly affected losing its integrity; the peritrophic membrane and microvilli were degenerated; and the musculosa was also affected. Other associated effects were observed in the integument, nerve ganglion, fat body cells, tracheoles and Malpighian tubules. In the integument, the exo- and endocuticles were clumped with an obvious separation from each other. An obvious degeneration of the nerve cells surrounding the second abdominal nerve ganglion as well as the neurilemma of the nerve fibres occurred. Vacuolization of the fat body cells, degeneration of their nuclei and destruction of the membraneous sheath surrounding these cells occurred. Tracheoles showed excessive cellular hypertrophy with disintegration of its mitochondria. The Malpighian tubules showed a reduction in their lumen, with nuclei degeneration and nuclear chromatin clumping. Uric acid crystals were released in the lumen of the tubules and a rupture was observed in some parts of the microvilli. A rapid phagocytosis occurred in the haemocytes. The plasmatocytes and granular haemocytes phagocytosed the bacteria. The counts of haemocytes were at a minimum and bacterial numbers at a maximum on the fourth day after feeding the larvae on B. thuringiensis-contaminated diet.

Key Words

Histopathology Heliothis armigera Bacillus thuringiensis electron microscopy 

Résumé

Les changements histopathologiquea causeś par Bacillus thuringiensis var. entomocidus HD-635 sur Heliothus armígera ont ete étudiés par microscope électronique. La mortalité larvaire due a l’infection, reflete un syndrome des symptômes progressivement gradues. Les changements histopathologiques observes au 4eme jour de traitement sout principallement localises dans l’intestin moyen. C’est montre par l’epithelium largement touche qui perd son intégrité en plus. La membrane peritrophic ainsi que les microvillosités sont assez dégrades, Les muscles sont aussi touches, avec quelques effets sur le teguments, ganglions nerveuses, cellules du corps gras, trachés et les tubes de Malpighies.

L’effét sur tégument est caractérisé par des changements phisiques de l’exo et endocuticle qui séparent chaqun de l’autre. Une degradation nette est observee dans les cellules nerveuses entourant le second ganglion nerveuse abdominale, ausi les nerfs fibreux. Sur tissu adipeux, les vacuoles dans les cellules, degradation des noyaux et destruction de l’enveloppe de tissue est egalement distincte. Les cellules trachéoles sont excessivement hypertrophiées avec une désintégration de leur mitochondries. Les tubes de Malpighian montrent une reduction de volume de leure lumière, degradation des noyaux et en particulier la nucléole. Dans le lumière des tubes on observe des crystaux d’acide (uric acide), de ruptures son aussi remarqués sur quelques parties de microvillosité. Les haemocytes sont nettement phagocites. Des bactéries sont aussi phagocites par des haemocytes granulaires et de plasmocytes. Après 4 jours de traitement, le nombre des haemocytes est arrivée au minimum, par contre, de nombre de bactéries augment au maximum chez les larves infectées par contamination sue milieu artificiel.

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Copyright information

© ICIPE 1985

Authors and Affiliations

  • H. S. Salama
    • 1
  • A. Sharaby
    • 1
  1. 1.Laboratory of Plant ProtectionNational Research CentreDokki, CairoEgypt

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