uropods

Uropods are paired, posterior appendages found on the last abdominal segment of many crustaceans, forming part of the tail fan together with the telson. In decapods such as shrimp, lobsters and crabs, the uropods are often flattened and bear a series of spines or setae that aid in steering and stabilising the animal during rapid swimming or reversed locomotion. In isopods and amphipods the uropods may be more robust, sometimes articulated, and can function in burrowing, anchoring to substrates, or creating water currents for respiration.

Morphologically, each uropod consists of a basal protopodite, which bears muscle attachments, and one or two distal branches (exopodite and endopodite) that may be fused or separate. The degree of development varies widely among taxa, reflecting ecological specialisation; pelagic species tend to have elongated, paddle‑like uropods, while benthic forms often possess shorter, sturdier structures. In some crustaceans the uropods carry sensory setae that detect changes in water flow, contributing to predator avoidance and habitat orientation.

Uropods are considered homologous to the abdominal appendages of other arthropods and provide insight into the evolution of limb specialization within Crustacea. Their fossil record, preserved in carapace impressions and soft‑tissue fossils, helps reconstruct phylogenetic relationships among early mandibulate lineages. Research on uropod biomechanics informs the design of bio‑inspired propulsion systems, while their ecological roles continue to be examined in studies of locomotion, sediment interaction, and species‑specific behavioral adaptations.