gammarus

Gammarus is a genus of small crustaceans in the family Gammaridae, comprising numerous amphipod species found in a variety of aquatic habitats. Members of the genus occur in freshwater, brackish, and coastal marine environments, with a wide distribution in temperate regions of Europe, North America, and parts of Asia.

Morphology and lifestyle: Gammarus species are typically small and laterally compressed, with a body divided into a head, thorax, and abdomen. They lack a carapace and use their many legs to crawl and maneuver along substrates such as stones, leaf litter, and detritus. They are generally omnivorous, feeding on decaying plant material, algae, and small invertebrates, and play a role in the breakdown of organic matter and nutrient cycling in aquatic ecosystems.

Ecology and importance: These amphipods are common prey for fish, amphibians, and waterfowl, making them an integral component of aquatic food webs. Their abundance and health are often used as indicators of water quality, as they tend to decline in polluted or poorly oxygenated conditions.

Reproduction: Reproduction is sexual, and in many species females carry eggs in a brood pouch on thoracic appendages until hatching. The early juveniles undergo direct development, gradually reaching adulthood through molts.

Taxonomy and notable species: The genus includes many species such as Gammarus pulex (a widespread freshwater species in Europe) and Gammarus lacustris (found in North American lakes). Other notable members include Gammarus duebeni and various marine forms.