exoskeleton

Etymology

From exo- + skeleton.

noun

1. (anatomy) A hard outer structure that provides both structure and protection to creatures such as insects and Crustacea.
   This is the case not only with all forms provided with exoskeleta and endoskeleta, into the composition of which lime largely enters, but also with those which exercise the precipitating effect on the calcium salts they absorb from sea water, the precipitation rarely going so far as to form a distinct deposit in the cells or tissues of the organism. 17 January 1903, A[rchibald] B[yron] Macallum, “The Palæochemistry of the Ocean in Relation to Animal and Vegetable Protoplasm”, in Transactions of the Canadian Institute, volume VII, Toronto, Ont.: […] for the Canadian Institute by Murray Printing Company, published 1904, section IV (The Composition of the Primeval Ocean), page 551
   Ordinarily, allergy to animals is due to either their fine dander which becomes aerosolized or to the exoskeleta, pupae, or feces of their ectoparasites. 1982, R. V. Lynch, Jr., R. Burrell, “Primate Dander Allergy of Lesser Bushbaby (Galago): A Case Report”, in D[uane] E. Haines, editor, The Lesser Bushbaby (Galago) as an Animal Model: Selected Topics, Boca Raton, Fla.: CRC Press, Inc., page 304
   After separation, the next generation of daughters resumes the photosynthetic fixation (reduction) of carbon, the sequestration of phosphorus, nitrogen, and mineral nutrients (up to a score), and the synthesis of the proteins that will contribute to the generational doubling of biomass. Structures such as flagella, scales, and exoskeleta also have to be reallocated or copied. 2009, Klement Tockner, Gene E[lden] Likens, editors, Encyclopedia of Inland Waters, Academic Press