Acarapace is adorsal (upper) section of theexoskeleton or shell in a number of animal groups, includingarthropods, such ascrustaceans andarachnids, as well as vertebrates, such asturtles andtortoises. In turtles and tortoises, the underside is called theplastron.
Incrustaceans, the carapace functions as a protective cover over thecephalothorax (i.e., the fused head andthorax, as distinct from theabdomen behind). Where it projects forward beyond the eyes, this projection is called arostrum. The carapace iscalcified to varying degrees in different crustaceans.[1]
Zooplankton within the phylum Crustacea also have a carapace. These includeCladocera,ostracods, andisopods, but isopods only have a developed "cephalic shield" carapace covering the head.
Inarachnids, the carapace is formed by the fusion of prosomaltergites into a singleplate which carries the eyes, ocularium,ozopores (a pair of openings of the scent gland ofOpiliones) and diverse phaneres.[2]
In a few orders, such asSolifugae andSchizomida, the carapace may be subdivided. In Opiliones, some authors prefer to use the term carapace interchangeably with the term cephalothorax, which is incorrect usage, because carapace refers only to the dorsal part of the exoskeleton of the cephalothorax.
Alternative terms for the carapace of arachnids and their relatives, which avoids confusion with crustaceans, areprosomal dorsal shield andpeltidium.
The carapace is thedorsal (back) convex part of the shell structure of aturtle, consisting primarily of the animal'srib cage, dermal armor, andscutes.[3][4]
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