The cuticle is the most external part of the body wall in nematodes. It is an elastic, proteinaceous, layered secretion of the epidermis. Four main layers can be distinguished: epicuticula, exocuticula, mesocuticula and endocuticula. The last three are also called cortical, median and basal layers.
The cuticle covers the entire body surface of the nematode and penetrates inside through various openings such as mouth and pharynx (stomodeum), anus and rectum or cloaca (proctodeum), vulva and vagina, excretory pore, external sensilla and glands. The body cuticle is semi-permeable and metabolically active. Liquids can pass thorugh it and pore-canals have been demonstrated in a number of species. At the same time the cuticle forms a barrier that protects the nematode against biotic and abiotic factors from its environment.
The ornamentation of the cuticle is one of the most important caracteristics in the identification of a nematode and usually is easy to be seen in light microscopy. There are many variations of the ornamentation however the three most common cuticle types in marine nematodes are:
Smooth:
Striated:
Pointed (with dots):
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