Chemistry Reference
In-Depth Information
Figure 12.3
Helicoidal (a) and plywood - like (b)
arranged layers in arthropod cuticles and shells;
ordered (c) and random-felt like (d) microfi bril
textures of arthropod peritrophic matrices.
[13]. However, depending on cuticle function, other patterns have also been
observed, including unidirectional and plywood-like arrangements of the fi bers
(Figure 12.3 b).
12.3.3
Peritrophic Matrices and Cocoons
The peritrophic matrix is a membrane-like secretion product of gut epithelial cells
and lines the inner surface of the intestine of many different organisms, including
insects, nematodes, annelids and mollusks [14]. Its precise function is still unclear,
but it might aid digestion and could protect the gut epithelium from mechanical
damage, radical oxygen species and infection by pathogenic microorganisms.
Peritrophic matrixes can be formed by either the entire midgut (type I peritrophic
matrices) or by specialized cells of the anterior midgut (type II peritrophic matri-
ces). In most cases chitin has been detected as a structural component of the
peritrophic matrix. The chitin microfi brils (
α
- ,
β
- or
γ
-chitin) are embedded in a
