Cuticle

Definition

The non-living, outermost layer of the arthropod integument, secreted by the underlying epidermis and serving as the primary structural component of the exoskeleton. Composed of proteins (notably sclerotin) and often chitin, the cuticle consists of multiple layers—typically the thin, waxy epicuticle externally and the thicker, lamellate procuticle beneath—that provide mechanical support, protection against desiccation and pathogens, and sites for muscle attachment. Its composition and thickness vary regionally (sclerotized plates versus flexible membranes) and taxonomically; it is shed entirely during ecdysis.

Etymology

From Latin cuticula, diminutive of cutis 'skin'

Example

The freshly moulted woodlouse leaves behind its entire cuticle as an exuvia; the new cuticle beneath is initially soft and pale, hardening and darkening over hours as sclerotization and tanning cross-link its proteins.

Synonyms

• cuticula

Related Terms

• Exoskeleton
• Integument
• epicuticle
• procuticle
• Chitin
• Sclerotization
• Ecdysis
• exuvia
• apolysis

Usage Notes

In entomology, 'cuticle' refers specifically to the acellular outer secretion of the epidermis, not the whole exoskeleton (which includes underlying cellular and muscular components). The term is sometimes used more broadly in botany and other fields for unrelated non-homologous coverings; in arthropod contexts, precision matters. Contrast with 'shell' (often calcareous in crustaceans) and 'skin' (loose, usually refers to vertebrate integument). Regional variations in cuticle structure create the arthrodial membranes between sclerites that permit movement.