Gammaridea

Gammaridea is a large and diverse infraorder of amphipods, a group of crustaceans. Amphipods are characterized by their laterally compressed bodies and the presence of both thoracic and abdominal limbs. Gammarideans, in particular, are distinguished by their typically seven pairs of thoracic appendages, called peraeopods, and their distinctive uropods, which are used for swimming and balancing.

These crustaceans are found in a wide range of aquatic environments across the globe, from freshwater streams and lakes to brackish estuaries and the deep sea. They exhibit a remarkable variety of lifestyles and feeding habits. Many gammarideans are scavengers, feeding on dead organic matter. Others are detritivores, consuming decaying plant material. Some species are predators, actively hunting smaller invertebrates, while a few are herbivorous or parasitic.

The morphology of gammarideans can vary significantly, reflecting their diverse adaptations. Body shapes can range from elongated and slender to more robust and compact. Their antennae are often well-developed and used for sensing their environment. The first two pairs of thoracic appendages, called gnathopods, are often modified for grasping prey or for other specific functions.

Gammarideans play important roles in aquatic ecosystems. They are a significant food source for many fish and other larger invertebrates. Their scavenging and detritivorous activities contribute to nutrient cycling and the breakdown of organic matter. Due to their widespread distribution and sensitivity to environmental changes, some gammaridean species are used as bioindicators to assess water quality.