Gladius (cephalopod)
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The gladius, or pen, is a hard internal bodypart found in many cephalopods of the superorder Decapodiformes and in a single extant member of the Octopodiformes, the vampire squid. It is so named for i
Gladius, showing measurement of rachis and vane
Paralarva chiroteuthids (such as the Chiroteuthis veranyi pictured) are unusual in that they possess a greatly elongated gladius extending well beyond the fins; this supports a long, trailing tail-like structure.
Trachyteuthis
Teudopsis
Chitin
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Chitin n is a long-chain polymer of N-acetylglucosamine, an amide derivative of glucose. Chitin is the second most abundant polysaccharide in nature; an estimated 1 billion tons of chitin are produced
Gladius (cephalopod)
…mollusc shell, which was external. The gladius is located dorsally within the mantle and usually extends for its entire length. Composed primarily of chitin, it lies within the shell sac, which is responsible for its secretion. Some species, like the bigfin reef squid, still has a gladius with some degree…
A close-up of the wing of a leafhopper; the wing is composed of chitin.
A cicada emerges from its nymphal exoskeleton; the shed exoskeleton is mostly modified chitin (sclerotin) but the wings and much of the adult body are still unsclerotized chitin at this stage