propodus

Propodus is a segment of the limbs in many crustaceans, lying between the carpus and the dactylus. It is typically the penultimate segment and, in many decapods, forms the major part of the claw when paired with the movable dactylus. The propodus, together with the dactylus, often constitutes a chelate structure that enables grasping and manipulation of objects, prey, or substrates.

In crustacean limb anatomy, the standard progression from proximal to distal segments is coxa, basis, ischium, merus, carpus, propodus, and dactylus. The propodus varies in size and shape across taxa; in some forms it is expanded and may bear spines, denticles, or a fixed process that interacts with the dactylus to produce a pinching claw. Its morphology reflects functional demands, such as feeding, defense, or locomotion.

Propodus is used across multiple crustacean groups, including decapods (crabs, lobsters, and their relatives) as well as isopods and amphipods, where it serves as the distal base of the limb. While its specific form can differ markedly, the propodus generally functions as a sturdy platform for the more mobile dactylus, contributing to the limb’s grip, manipulation, and, in some species, predatory actions.