ISSN:
1432-0878
Keywords:
Epicuticle
;
Insects
;
Tenebrio molitor
;
Development
;
Structure
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Description / Table of Contents:
Résumé L'épicuticule de l'adulte de Tenebrio molitor est composée de deux couches distinctes dénommées épicuticule externe et épicuticule interne. L'épicuticule externe est la première couche cuticulaire sécrétée sous forme de petites plaques s'agrandissant par leurs bords pour recouvrir toute la surface cellulaire. Au moment de sa sécrétion, cette couche est formée de quatre lames denses A, B, C1 et C2. La lame B, très fine, disparaît par la suite et les lames C1 et C2 deviennent très nettes. L'épicuticule externe de l'adulte est donc formée de trois lames denses séparées par deux lames claires. L'épicuticule interne est formée de lames superposées denses et claires de structure complexe, qui sont masquées pendant la sécrétion des premières couches de cuticule lamellée (procuticule). Cette structure correspond à un arrangement moléculaire hautement organisé. La forme de la surface cuticulaire des sternites est déterminée par la forme de la surface cellulaire avant le dépôt de l'épicuticule.
Notes:
Summary The epicuticle of adult Tenebrio consists of two distinct layers named outer and inner epicuticle. The outer epicuticle is the first cuticular layer to be deposited in form of small patches on top of the microvilli. These initial patches are composed of four dense laminae (A, B, C1 and C2) separated by three light spaces. The outer epicuticle grows by densification of diffuse material at the edges of the patches until the entire area is covered. The thickness of outer epicuticle remains constant (175 Å) during the development of the pharate adult, lamina B however rapidly disappears. Thus, the adult outer epicuticle is fivelayered (three dense laminae: A, C1 and C2). After being deposited, the inner epicuticle shows a complex laminar structure interpreted to represent a highly organized molecular system. The laminae are masked during the formation of the first procuticle lamellae. During the deposition of the epicuticle, lamina A is covered by a component of the moulting fluid, forming an irregular dense layer which disappears after the resorption of this fluid. Perhaps this layer protects the new epicuticle from lytic enzymes of the moulting fluid. In adult animals, there is an additional superficial layer, the signification of which is not clear. The possibility of remains of cement or wax is discussed. The development of the surface patterns of the sternal and pleural cuticle is determined before the epicuticle formation by the shape of the epidermal surface. The rate of outer epicuticle deposition appears to depend on the size of the microvilli: epicuticle deposition seems to proceed faster over high microvilli.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00336526
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