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Porous channels in the cuticle of the head‐arrester system in dragon/damselflies (Insecta: Odonata)
Author(s) -
Gorb Stanislav N.
Publication year - 1997
Publication title -
microscopy research and technique
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.536
H-Index - 118
eISSN - 1097-0029
pISSN - 1059-910X
DOI - 10.1002/(sici)1097-0029(19970601)37:5/6<583::aid-jemt18>3.0.co;2-m
Subject(s) - arthropod cuticle , perpendicular , cuticle (hair) , ultrastructure , materials science , rod , microfibril , anatomy , composite material , biophysics , chemistry , biology , geometry , insect , botany , medicine , cellulose , pathology , mathematics , alternative medicine , organic chemistry
The ultrastructure of the porous channels (PC) of the postcervical sclerite (SPC), which provides additional head fixation to the neck in adult odonates, was studied using TEM and high resolution SEM microscopy. Single chitin‐protein microfibrils, about 0.14 μm thick, are arranged into channels with cylinder‐like shapes. The axial rod of the chitin fiber (0.04 μm thick) is located in the center of the cylinder. The orientation of the axial rods was three‐dimensionally demonstrated after dissolving the protein cover with NaOH. The PCs are arranged vertically to the surface and pass from the epidermal cells through all the cuticular layers to the surface of the cuticle. In the exo‐ and endocuticle, the PCs are usually oval in cross‐section and about 0.3 μm thick. In the endocuticle, the cross‐sectional area of the PCs varies widely, from 0.01–0.15 μm 2 . The shape of the PC is determined by the macromolecular organization of the chitin‐protein microfibrils: the long axis of the channel is orientated parallel to the axis of the preferred orientation of the cuticular microfibrils. The microfibrils tend to follow the line of the channel very closely. In fractures orientated perpendicular to the surface, the PC resembles a ribbon‐like construction, which was clearly demonstrated by casts. The strongly parallel orientation of PCs in the deep layers of the cuticle changes within the microtrichia (MT), and they begin to be curved. Numerous PCs pass through the microtrichium, and most of them end on its side wall. PCs usually contain channel filaments about 0.09 μm thick. Usually, a single channel contained one filament, but channels located in the deep layers of the endocuticle have from one to five single filaments. The filaments were observed in the intact cuticle and in the cuticle enzymatically treated with chitinase, while in the cuticle treated with NaOH filaments were absent. The porous channel system of the odonate arrester is interpreted as a device transporting adhesive excretions from the epidermal cells to the cuticular surface. Microsc. Res. Tech. 37:583–591, 1997. © 1997 Wiley‐Liss, Inc.