procutícula

Procutícula, in arthropod biology, is the inner portion of the cuticle located beneath the epicuticle. It encompasses the exocuticle and endocuticle, two sublayers secreted by epidermal cells during molt. The procuticle forms the bulk of the new exoskeleton after shedding the old cuticle.

The exocuticle is typically more sclerotized or even mineralized, contributing to rigidity in parts of the body that require support. The endocuticle is usually less sclerotized and more flexible, allowing movement. Both sublayers consist mainly of chitin–protein fibers arranged in a layered matrix, with cross-links produced by sclerotizing enzymes. The procuticle's composition and degree of hardening vary by region and developmental stage.

The epicuticle, by contrast, is thin and rich in lipids, serving as a barrier to water loss and chemical invasion; together with the procuticle, it forms the functional exoskeleton. The procuticle is secreted by the epidermis and undergoes molting cycles as the animal grows. Molting involves degradation of the old cuticle, synthesis of a new procuticle and epicuticle, then shedding.

In addition to insects, similar terminology applies to other arthropods, though structural details vary among groups. Overall, the procuticle provides mechanical strength, protection, and housing for epidermal tissues, and its properties influence the shape and mobility of the animal.