Larva cuticle

Table VI. Comparison of Larvae Cuticle Fatty Acids...

M. Zhang, A. Haga, H. Sekiguchi, S. Hirano, Structure of insect chitin isolated from beetle larva cuticle and silkworm (Bombyx mori) pupa exuvia, Int. J. Biol. Macromol. 27 (2000) 99-105. 

Hurst (19) discusses the similarity in action of the pyrethrins and of DDT as indicated by a dispersant action on the lipids of insect cuticle and internal tissue. He has developed an elaborate theory of contact insecticidal action but provides no experimental data. Hurst believes that the susceptibility to insecticides depends partially on the cuticular permeability, but more fundamentally on the effects on internal tissue receptors which control oxidative metabolism or oxidative enzyme systems. The access of pyrethrins to insects, for example, is facilitated by adsorption and storage in the lipophilic layers of the epicuticle. The epicuticle is to be regarded as a lipoprotein mosaic consisting of alternating patches of lipid and protein receptors which are sites of oxidase activity. Such a condition exists in both the hydrophilic type of cuticle found in larvae of Calliphora and Phormia and in the waxy cuticle of Tenebrio larvae. Hurst explains pyrethrinization as a preliminary narcosis or knockdown phase in which oxidase action is blocked by adsorption of the insecticide on the lipoprotein tissue components, followed by death when further dispersant action of the insecticide results in an irreversible increase in the phenoloxidase activity as a result of the displacement of protective lipids. This increase in phenoloxidase activity is accompanied by the accumulation of toxic quinoid metabolites in the blood and tissues—for example, O-quinones which would block substrate access to normal enzyme systems. The varying degrees of susceptibility shown by different insect species to an insecticide may be explainable not only in terms of differences in cuticle make-up but also as internal factors associated with the stability of oxidase systems. 

Fig. 8.5. Transmission electron micrograph of a transverse section through an infective dauer larva of Anguina agrostis (funesta) showing Clavibacter toxicus adhering to the cuticle and causing pathological changes to the cuticle surface (arrows). Scale bar = 1 pm.

The identity of TES-32 and CTL-1 was confirmed by polyclonal antibodies to recombinant CTL-1, which bound to native TES-32, and by monoclonal antibody Tcn-3, raised to native TES-32 (Maizels et al, 1987), which specifically recognized recombinant CTL-1. The CTL-1 sequence also contained three sites for Afglycosylation, which had previously been shown to be present on TES-32 (Page and Maizels, 1992). Both Tcn-3 and polyclonal antibody to the recombinant CTL-1 protein localize to the cuticle of the infective larvae by immunoelectron microscopy (Fig. 12.2). 

Histopathology of cuticle and anal gills in 4th instar larvae after 24-h exposure of 3rd instar larvae 6... 

Christiansen, M.E. 1986. Effect of diflubenzuron on the cuticle of crab larvae. Pages 175-181 in International Conference on Chitin and Chitosan. Plenum Press, New York. 

Christiansen, M.E., E. Gosling, and M.A. Williams. 1984. Effect of the insect growth regulator diflubenzuron (dimilin) on the uptake of glucose and V-acetylglucosamine into the cuticle of crab larvae. Mar. Biol. 83 225-230. 

The nematodes are themselves insect parasitoids that are not very particular about their hosts. Fly maggots, moth larvae and pupae, beetle larvae, and numerous other hosts are all acceptable to them. Some of these nematodes do have narrow preferences, but one widespread species invades more than two hundred different kinds of insects. Juvenile nematodes infected with their bacteria seek out a host to parasitize, typically gaining entry through one of its body orifices. Some species enter through a hole they scrape in the insect s cuticle using a "tooth" on their head. Once inside the insect, the worms force their way through soft tissues and into their host s central body cavity. 

In addition to the sensilla styloconica, lepidopterous larvae possess gustatory sensilla on the maxillary palps. Eight basiconic sensilla are located on top of each palpus (see Figure 1). Five of them possess a terminal pore, and for that reason these sensilla might be considered as contact chemoreceptors. The remaining three show numerous small perforations all over the cuticle, which indicates an olfactory function (.8). The response spectra of these sensilla are, however, still obscure. 

Ecdysone stimulates the synthesis of RNA in tissues. Visual demonstration of the effect is provided by its action on polytene chromosomes of fly larvae (Fig. 26-14).361 Fifteen minutes after the application of ecdysone, a puff is induced on one band of the chromosome a second puff forms at a later time while a preexisting puff diminishes. Thus, like steroid hormones in mammals, ecdysone appears to have a direct controlling effect on transcription. The cuticle-shedding process (ecdysis) is initiated by the brain peptide eclosian. However, the brain may be responding to the ecdysis-triggeiing hormone, a peptide that is secreted by a series of epitracheal glands located in various segments of the body.362... 

The one millimeter long adult nematode Cae-norhabditis elegans contains only 959 somatic cells. Tire lineal descent of all of these has been traced.236-240 Tire development follows an almost exactly defined pathway with 113 programmed cell deaths during formation of the 558-cell newly hatched larva. In addition, each adult worm contains 302 neurons that make about 8000 synapses. This little nematode also has an alternative developmental pathway. The larvae shed their cuticles in four consecutive molts. If the food supply is inadequate, they enter a persistent nonfeeding state in which they may survive for months and are able to resume development when conditions are appropriate.241... 

Mohanty et al. (2008) studied the efficacy of the virulent M. anisopliae strain 892 -isolated from Pyrausta nubilalis - against mosquito larvae. LC50 values of M. anisopliae 892 for Culex quinquefasciatus, Anopheles stephensi and Aedes aegypti were examined. M. anisopliae 892 was found to cause approximately 50% mortality of C. quinquefasciatus 4 days post inoculation. The production of subtilisin-like (Prl) and trypsin-like protease (Pr2) was measured in the presence of certain inducers. Significant differences in the production of Prl and Pr2 were found following the addition of inducers i.e. cuticles of the three... 

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