Plastron

A plastron is the underside or belly part of a turtle or turtle-like creature’s shell. It provides protection for the creature’s vital organs, such as the heart and lungs. In some aquatic animals, like certain insects or diving beetles, a plastron is a specialized layer of air trapped against their bodies, allowing them to breathe underwater for extended periods. Essentially, it serves as a protective or breathing structure, depending on the animal, contributing to their safety, buoyancy, or respiration.