sclerite

A sclerite is a hard plate or element of the skeleton in various invertebrates, most notably arthropods, and also in some echinoderms. In arthropods, the exoskeleton is divided into sclerites—typically dorsal tergites, lateral pleurites, and ventral sternites—that provide rigidity and shape to body segments. Each sclerite is a plate of cuticle that has been hardened through sclerotization, a chemical process in which cross-links form between structural proteins and chitin; in some groups, mineralization adds calcium carbonate to increase stiffness. Joints between adjacent sclerites allow movement of limbs and body segments.

Growth occurs through molting (ecdysis), during which old sclerites are shed and new, larger sclerites are produced to accommodate growth. The arrangement and fusion of sclerites contribute to the distinctive exoskeletal architecture of different taxa and can influence locomotion and protection.

In addition to arthropods, the term sclerite is used in some echinoderms to describe calcareous ossicles—small skeletal plates that form the internal endoskeleton. These sclerites vary in size and shape and help support and protect soft tissues, while contributing to the overall rigidity of the skeleton.

Overall, sclerites are fundamental structural elements that integrate protective armor, mechanical support, and muscle attachment in invertebrates, while also serving as useful features in taxonomic and paleontological descriptions.