Why do some crustaceans have clamlike shells with two valves?

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crustacean The American lobster (*Homarus americanus*) is among the largest crustaceans.

Some crustaceans, such as clam shrimp and ostracods (also known as mussel shrimp), possess a clamlike appearance because their bodies are enclosed within a bivalved carapace.123

This shell structure is an adaptation that arises during development as a fold from the back of the head, which splits into two valves to protect the animal's trunk, limbs, and gills. While these crustaceans resemble bivalve mollusks, their "shells" are distinct in origin and function as part of the crustacean body plan. In many of these species, the carapace serves as a protective enclosure, and in some, it may even form a brood pouch for developing eggs.234