"Cuticle" - what is it, definition of the term
«cuticle» is a thin, hardened, non‑cellular covering composed mainly of chitin‑protein complexes, forming the outer protective barrier of arthropods such as ticks, true bugs, lice and fleas; it shields underlying tissues, prevents desiccation, and provides structural support for locomotion and attachment.
Detailed information
The outer protective layer of arthropods consists of a multi‑laminate structure primarily composed of chitin fibers embedded in a protein matrix. This covering provides mechanical rigidity, limits water loss, and serves as a barrier to pathogens and environmental chemicals. Its surface is often coated with lipids that form a waterproof film, while underlying layers may undergo periodic molting to permit growth.
In ticks, the exoskeletal sheath includes an epicuticular waxy layer that reduces desiccation during prolonged attachment to hosts. Beneath this, a flexible cuticular matrix allows expansion when engorged with blood. The rigidity of the dorsal plates protects internal organs during locomotion through vegetation and host fur.
True bugs possess a hardened dorsal shield that incorporates pigments and structural proteins, imparting species‑specific coloration and resistance to abrasion. The ventral side features a thinner, more pliable section that facilitates movement through plant tissue and accommodates the insertion of stylet mouthparts.
Lice exhibit a highly flexible outer coating, enabling close conformity to the host’s hair or feather shafts. Microstructures on the surface increase friction, enhancing grip during rapid host movements. Periodic shedding of this layer allows removal of accumulated debris and parasites.
Fleas display a heavily sclerotized exterior that endures repeated jumping and contact with host skin. The surface is reinforced with cross‑linked proteins, providing durability against mechanical stress. A dense array of setae embedded in the outer layer assists in detecting host vibrations and maintaining stability during leaps.
Key structural characteristics across these groups:
- Multi‑layered composition: chitin‑protein matrix with an overlying lipid film.
- Variable rigidity: hardened dorsal plates in ticks and fleas; flexible ventral sections in lice and bugs.
- Specialized surface features: waxes for water retention (ticks), pigments for camouflage (bugs), micro‑setae for adhesion (lice), sclerotization for impact resistance (fleas).
- Periodic molting: enables growth and removal of contaminants in all examined taxa.