Integument structure and function

Definition

The anatomy, composition, and physiological roles of the integument, the outer covering of an arthropod that serves as both protective armor and active interface with the environment. Structurally, the arthropod integument comprises a single-layered epidermis (hypodermis) beneath a non-living cuticle secreted by epidermal cells. The cuticle itself consists of an inner, flexible procuticle (further divided into chitin-rich endocuticle and protein-sclerotized exocuticle) and an outer, waxy epicuticle that limits water loss. Functionally, the integument provides mechanical support and attachment sites for muscles, protection against predators and pathogens, sensory reception through embedded mechanoreceptors and chemoreceptors, and—via molting (ecdysis)—the only means of growth in arthropods. The integument also mediates critical physiological exchanges: gas exchange in many terrestrial species occurs across thin, modified regions (spiracular atria, tracheal taenidia), while chemical defense compounds, pheromones, and antimicrobial secretions are manufactured and deployed through specialized epidermal glands.

Etymology

From Latin integumentum 'covering' (from tegere 'to cover') + English 'structure' and 'function'

Example

In desert tenebrionid beetles, the integument's epicuticular wax layer and unusually thick exocuticle create a hydrophobic, armor-plated surface that reduces transpirational water loss to less than 1% of body mass per day, while still permitting respiratory gas exchange through the spiracular valve apparatus embedded within the integument's lateral thoracic and abdominal walls.

Related Terms

• Cuticle
• Epidermis
• hypodermis
• Sclerotization
• Ecdysis
• molting
• Spiracle
• Trachea
• epicuticle
• exocuticle
• endocuticle
• Chitin
• Sclerite
• arthropod exoskeleton
• Water balance
• sensilla
• glandular epithelium

Usage Notes

Specialists distinguish between 'integument' (the entire functional system of epidermis plus cuticle) and 'cuticle' (the non-living, secreted portion alone). In soft-bodied larvae, the integument remains flexible and lightly sclerotized, whereas in adult beetles or scorpions, extensive sclerotization and mineralization (calcium carbonate deposition) convert the integument into a rigid exoskeleton. The term is sometimes used interchangeably with 'body wall' in histological contexts, though 'body wall' technically includes underlying musculature and coelomic lining. In medical and veterinary entomology, integument penetration by acaricides or insecticides depends critically on lipophilic passage through the epicuticle and aqueous pore routes through the procuticle—knowledge of integument structure directly informs pesticide formulation.