• G K Karnavar

      Articles written in Proceedings – Animal Sciences

    • Influence of azadirachtin on insect nutrition and reproduction

      G K Karnavar

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      Neem extracts and pure azadirachtin influence the behaviour and physiology of large number of insects. These compounds affect the sensory receptors, thereby inhibit food intake. This anti-feedant property is exploited by using neem extracts and azadirachtin for plant protection. The gut motility and movement of food in the digestive tube are regulated by azadirachtin.Holotrichia serrata, the beetle of the ‘white grub’ feeds on neem leaves and no ill-effect of azadirachtin is reported.

      Azadirachtin and neem extracts regulate the reproductive functions of insects through their endocrine system. Morphogenesis, ovarian development, fecundity, egg viability and moulting are adversely affected by azadirachtin. Radioimmunoassays show that the ecdysteroid level falls drastically on azadirachtin treatment. Juvenile hormone synthesis also is inhibited inLocusta on administration of azadirachtin. InOncopeltus fasciatus, high doses of azadirachtin inhibit adult development resulting in permanent larvae which show oocyte differentiation with yolk incorporation equivalent to day 4 of adult development.

    • Influence of precocene-I on the development of vitellogenic oocytes inTrogoderma granarium Everts (Coleoptera: Dermestidae)

      S Chellayan G K Karnavar

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      FemaleTrogoderma granarium pupae, 0–96 h old, were treated with precocene-I at 6 h intervals. Reduction in the vitellogenic oocyte number was observed in adults after precocene treatment at specific ages. Precocene-I was effective when applied to 6, 18, 30, 42, 54 and 90 h old pupae while in 0, 12, 24, 36, 48, 60, 66, 72, 78, 84 and 96 h old pupae this compound was not significantly effective. Corpus allatum activity is a major contributory factor towards precocene susceptibility. The results suggest that pupae at different ages exhibit periodic changes in corpus allatum activity that might be related to cycles of development in the reproductive system.

    • Influence of neem kernel extract on morphogenesis and vitellogenic oocyte development inTrogoderma granarium everts

      S Chellayan G K Karnavar

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      Neem seed kernel extracts adversely affect the growth and morphogenesis of insects. InTrogoderma granarium, neem seed kernel extract was found to inhibit normal pupal-adult development. The malformed adults comprised a heterogenous group of transitory forms between the pupal and adult types. Older pupae were less sensitive to the compound. In the seemingly normal surviving adults ofTrogoderma granarium a reduction in the number of vitellogenic oocytes was found. The active compound(s) in the neem seed kernel extracts is proposed to produce the observed effects by regulating morphogenetic hormone titres, though the precise mode of action cannot be safely defined.

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