Chitin contributes to the rigidity of the insect cuticle and serves as an attachment matrix for other cuticular
proteins. Deficiency of chitin results in abnormal embryos, cuticular structural defects and growth arrest.
When chitin is not turned over during molting, the developing insect is trapped inside the old cuticle. Partial
deacetylation of cuticular chitin is also required for proper laminar organization of the cuticle and vertical pore
canals, molting, and locomotion. Thus, chitin and its modifications strongly influence the structure of the exoskeleton
as well as the physiological functions of the insect.
Internal tendons and specialized epithelial cells called “tendon cells” that arise from the outer layer of epidermal
cells provide attachment sites at both ends of adult limb muscles. Membrane processes emanating from both
tendon and muscle cells interdigitate extensively to strengthen the attachment of muscles to the extracellular
matrix (ECM). Protein ligands that bind to membrane-bound integrin complexes further enhance the adhesion
between muscles and tendons. Tendon cells contain F-actin fiber arrays that contribute to their rigidity. In the
cytoplasm of muscle cells, proteins such as talin and other proteins provide attachment sites for cytoskeletal actin,
thereby increasing integrin binding and activation to mechanically couple the ECM with actin in muscle cells.
Mutations in integrins and their ligands, as well as depletion of chitin deacetylases, result in defective locomotion
and muscle detachment from the ECM. Thus, chitin in the cuticle and chitin deacetylases strongly influence the
shape and functions of the exoskeleton as well as locomotion of insects.