kitiinikuori

Kitiinikuori is the external covering of many arthropods, as well as some other organisms, consisting primarily of the polysaccharide chitin bound with proteins. In Finnish biology, the term literally means a chitinous shell or cuticle. The kitiinikuori provides both shape and protection, supports muscle attachment, and forms a barrier against dehydration and pathogens.

Chitin, a long polymer of N-acetylglucosamine, forms multiple layers in the cuticle. The outer epicuticle minimizes water loss and houses waxy compounds; beneath it the exocuticle and endocuticle provide strength and flexibility. In crustaceans and some myriapods, minerals such as calcium carbonate may reinforce the cuticle, making it harder and more resistant to damage.

Growth occurs through molting (ecdysis), when the old kitiinikuori is shed and a new one secreted by the epidermis beneath. This process is tightly regulated by hormonal signals and temporarily leaves the animal vulnerable. The degree of sclerotization—cross-linking of proteins within the cuticle—determines stiffness and protection level.

Beyond its biological role, the kitiinikuori has inspired biomaterials research because it combines lightness with toughness and can be tuned by chemical cross-linking. Studying its structure helps understand insect locomotion, pest resistance, and fossilization, while also informing the development of bio-based composites and coatings.