38
MICHAEL LOCKE
granules discharging between the microvilli at the surface. The granules
arise in vesicles of Golgi complexes.
S. The Lamellate Cuticle
Below the protein epicuticle, the cuticle becomes fibrous. The fibers
are at first irregular, but this soon changes to a repeating pattern of
lamellae (Figs. 4 and 5). The lamellae vary in thickness from several
microns down to a few hundred angstroms, but are typically 0.1-1 μ wide.
The fibers composing the lamellae may be single chitin chains with associated protein (see the discussion in Rudall, 1963). They are arranged in
the characteristic pattern shown in Fig. 6 ; this pattern has been observed
in the lamellate cuticle of a wide variety of material (Locke, 1960a,
1961, 1964). For an interpretation of this appearance see the section
on microcycles of deposition (Section II,C,3). In some cuticles, the
lamellae may be interleaved with the elastic cuticle called resilin
(Neville, 1963a; Weis-Fogh, 1960, 1961a,b). After its deposition, the
lamellate cuticle may be stabilized in various ways with a change in
color and staining properties to become exocuticle or mesocuticle.
4- Reticulate Fibrous Cuticle
The tracheae are cuticular tubes in which the epicuticle is folded
in an annular or helical "concertina-like" pattern. The cuticle of the
taenidia, which fill the folds, provides resistance to lateral deformation,
while the folds, which are often quite deep, allow extensions in length
of as much as 200-300%. The inner face of the epicuticle is firmly
attached to the underlying taenidial cuticle, but the taenidia are separated from the sides of the folds by a reticulate meshwork of fibers or
filaments (Beaulaton, 1964). See Figs. 7 and 8. A similar structure has
also been seen below the epicuticle in the bellows section of the ducts
of repugnatorial glands in a Tenebrionid beetle (Eisner et al., 1964).
The randomly arranged meshwork of fibers and the distribution of this
sort of cuticle suggest that it may function as an elastic pad.
5. Resilin
A structural protein, resilin, has been described from some wing hinges
and muscle insertions. It shows long-range rubberlike elasticity, with no
permanent deformation and probably has a wide distribution wherever
an elastic component is needed (Weis-Fogh, 1960, 1961a,b,c; Andersen
and Weis-Fogh, 1964). It is built from randomly coiled peptide chains
linked together in a stable three-dimensional network by two aromatic
α-amino acids containing a phenolic group, one of which is a diaminothe protein epicuticle is penetrated by filaments and the epidermis is secreting
unoriented fibers. Abbreviations : c, cuticulin ; p, protein epicuticle ; v, vesicles giving
rise to the protein epicuticle. X 40,000.
MICHAEL LOCKE
granules discharging between the microvilli at the surface. The granules
arise in vesicles of Golgi complexes.
S. The Lamellate Cuticle
Below the protein epicuticle, the cuticle becomes fibrous. The fibers
are at first irregular, but this soon changes to a repeating pattern of
lamellae (Figs. 4 and 5). The lamellae vary in thickness from several
microns down to a few hundred angstroms, but are typically 0.1-1 μ wide.
The fibers composing the lamellae may be single chitin chains with associated protein (see the discussion in Rudall, 1963). They are arranged in
the characteristic pattern shown in Fig. 6 ; this pattern has been observed
in the lamellate cuticle of a wide variety of material (Locke, 1960a,
1961, 1964). For an interpretation of this appearance see the section
on microcycles of deposition (Section II,C,3). In some cuticles, the
lamellae may be interleaved with the elastic cuticle called resilin
(Neville, 1963a; Weis-Fogh, 1960, 1961a,b). After its deposition, the
lamellate cuticle may be stabilized in various ways with a change in
color and staining properties to become exocuticle or mesocuticle.
4- Reticulate Fibrous Cuticle
The tracheae are cuticular tubes in which the epicuticle is folded
in an annular or helical "concertina-like" pattern. The cuticle of the
taenidia, which fill the folds, provides resistance to lateral deformation,
while the folds, which are often quite deep, allow extensions in length
of as much as 200-300%. The inner face of the epicuticle is firmly
attached to the underlying taenidial cuticle, but the taenidia are separated from the sides of the folds by a reticulate meshwork of fibers or
filaments (Beaulaton, 1964). See Figs. 7 and 8. A similar structure has
also been seen below the epicuticle in the bellows section of the ducts
of repugnatorial glands in a Tenebrionid beetle (Eisner et al., 1964).
The randomly arranged meshwork of fibers and the distribution of this
sort of cuticle suggest that it may function as an elastic pad.
5. Resilin
A structural protein, resilin, has been described from some wing hinges
and muscle insertions. It shows long-range rubberlike elasticity, with no
permanent deformation and probably has a wide distribution wherever
an elastic component is needed (Weis-Fogh, 1960, 1961a,b,c; Andersen
and Weis-Fogh, 1964). It is built from randomly coiled peptide chains
linked together in a stable three-dimensional network by two aromatic
α-amino acids containing a phenolic group, one of which is a diaminothe protein epicuticle is penetrated by filaments and the epidermis is secreting
unoriented fibers. Abbreviations : c, cuticulin ; p, protein epicuticle ; v, vesicles giving
rise to the protein epicuticle. X 40,000.