Carapace

Definition

The hardened, dorsal (upper) portion of the exoskeleton that covers the cephalothorax in arachnids, crustaceans, and some other arthropods; formed by fusion or close articulation of tergites and often bearing eyes, ozopores, or other sensory structures. In arachnids, the carapace is typically a single sclerotized plate that shields the prosoma and provides attachment sites for leg muscles and the stomach.

Etymology

French carapace, from Spanish carapacho, of uncertain origin; originally referring to tortoise shells, later extended to arthropod dorsal armor.

Example

In spiders (Araneae), the carapace is usually pear-shaped and distinct from the soft, segmented abdomen; in scorpions, it is broad and bears the median and lateral eyes.

Synonyms

• dorsal shield
• prosomal shield
• cephalothoracic shield

Related Terms

• Cephalothorax
• prosoma
• tergite
• Exoskeleton
• Plastron
• Sclerite
• opisthosoma
• Cuticle

Usage Notes

In arachnology, 'carapace' specifically denotes the dorsal shield of the prosoma and is never used for the abdomen (opisthosoma). The term is sometimes applied more broadly in crustacean biology to include fused head-thoracic covering, but specialists distinguish between the true carapace (covering cephalothorax) and the rostrum or other projections. Not used for insects, which lack this structure; the analogous dorsal covering of insect thoracic segments is referred to as 'tergites' or 'nota.' Contrast with plastron, the ventral shell in turtles.