STRUCTURE
AND
etegans CUTICLE
Christina
Alves
FUNCTION
OF THE
Caenohzbditis
Peixoto
Departamento de Patologia e Biologia Celular, Centro de Pesquisas Aggeu Magalhaes, Av.
Moraes Rego s/n, Recife, Brazil.
Caenorhabditis elegans is one of the most studied metazoans because of the invariance of
the cellular development of this nematode, which has made possible the precise analyses of its
anatomy, developmental biology and behaviour.
The cuticle of nematodes is an extracellular multilayered structure that plays roles in nutrition,
resistance to desiccation, and defense against the host’s immune system for parasitic species and
free-living nematodes (bacteria and nematophagous fungi).
Examination of thin sections of adult nematodes of C. elegans cuticle shows the presence of six
layers: epicuticle, external cortical, internal cortical, intermediate, fibrous and basal (Peixoto and De
Souza. 1992).
Deep-etched replicas of C. elegaMS cuticle showed a matrix composed of a network of filamentous
and globular structures that had empty spaces probably occupied by an intracuticuiar fluid in the
living specimen (Peixoto and De Souza, 1995; Peixoto et al, 1997) (Fig 1 and 2).
Recently, new elements of the fibrous layer of the C. elegans cuticle were identified. When thin
sections were made using a very oblique low angle, showed wavy fibers around 300 nm in length
located above the fibrous layer. Deep-etching views of C. eleguns showed that those fibers are
organized in a honeycomb fashion figures composed of 5 sides (Peixoto et al, 1997).
Roller mutants of C. elegans rotate around their long axis and move in circular paths. isolation and
sequence of the rol-6 gene of C. elegans has previously been shown to encode a cuticle collagen. In
deep-etched replicas of the right roller mutant rol-6 (~~1006) showed that the honeycomb elements
completly fill the intermediate layer of the cuticle, which is observed to largely empty spaces in the
wild type strain. The honeycomb elements appear to connect the cortical and basal regions of the
mutant cuticle and may well to be involved in generating the helical twist of the mutant animals
(Peixoto et al, 1998, in press) (Fig 3 and 4).
References:
Peixoto CA, Melo JV, Kramer JW, and De Souza W. 1998.Ultrastructural analyses of the C. efeguns rof-6(su1006)
mutant, which produces abnormal cuticle collagen. J Parasitol (in press).
Peixoto CA, Kramer JW, and De Souza W. 1997. Caenorhabditis elegam cuticle: a description of new elements of the
fibrous layer. J Parasitol 83(3): 368-372.
Peixoto and De Souza. 1995. Freeze-fracture and deep-etched view of the cuticle of Caenorhabditis
efegans. Tissue &
Cell 27:56 l-568.
1992. Cytochemical characterization of the cuticle of Cuenorhabdits
elegans (Nematoda:
Rhabditoidea). J Submicrosc Cytol and Pathol24: 425-435.
Figure 1 - Deep-etched view of an adult nematode. We can observe the particulated inner face of the epicuticle (IF),
and the meshwork of filamentous and globular particles of the cortical layer (CL). The honeycomb elements (arrow)
are located above the esqueletal fibrous layer (FL). The intermediate layer (IL), struts (S), basal layer (BL) and
hypodermis are also indicated (peixoto et al 1997). 40,000X.
Figure 2 - Schematic view of the cuticle of an adult of C. elegcms based mainly cm observations made in deep-etched
replicas (Peixoto and De Sowa, 1995).
Figure 3 - Scuming electron micrograph of C. elegant rol-6 (~~1006) adult. Note the hellicaly twisted body of the
nematode (arrow). 2,200X. (Peixoto et al, 1998)
Figure 4 - Deep-etched view of the C. &guns ~01-6 (~~1006) adult cuticle. Note the honeycomb elements completely
filling the intermediate layer. 46,000X. (Peixoto et al, 1998)
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