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Adaptive features of the exoskeleton and pigment deposits in Demodex spp. (Demodicidae)

Stromberg, B.E. and Nutting, W.B.

1972 - Volume: 14 Issue: 4 pages: 605-611


Acari Demodicidae Demodex cuticle chemical composition physical properties pigments


The democlicid exoskeleton shows the three (epicuticle, exocuticle, endocuticle) layers typical of the arthropod exoskeleton. It is remarkably thin (under 0.6 fL) in ali stages of the life cycle, relatively non-porous, and highly chitinous. A keratin-Iike protein present in the mid-layer (exocuticle) is apparently of adaptive significance in lencling fiexibility, especially in the egg and in mature stages, to the exoskeleton. The epicuticle is very thin and, in part, lipid in nature. The endocuticle was most reactive to ali tests for chitin. The pigment granules found in ali stages (even ova) of the democlicid life cycle are not guanine. They seem to play a dual role as (r) inert repositories of waste material and (z) elements used in ’excretory cocling’ - since they are incorporated in the egg and probably forma substrate for waste immobilization during development. Members of the three genera, Demodex, Harpyrhynch~ts, and Psorergates, show birefringence on polariscopic examination and so fall within Grandjean s phylogenetic grouping of Actinochitinosi.

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1972 Stromberg, B.E. and Nutting, W.B.
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