Gammarus
Gammarus is a genus of small crustaceans commonly known as scuds or freshwater shrimp. They are widely distributed in freshwater and brackish habitats around the world, with over 300 known species. These amphipods play a crucial role in aquatic ecosystems as detritivores, feeding on dead plant and animal matter, and are also an important food source for fish and other aquatic organisms.
Characteristics
Gammarus species are typically 5-20 mm long, with elongated bodies that are laterally compressed. Their exoskeletons are transparent or translucent, often with a greenish or brownish hue. They have seven pairs of legs, with the first pair modified into grasping appendages, and two pairs of antennae. Gammarus species are distinguished by their elongated uropods, which are the last pair of appendages at the end of the abdomen.
Environments
Gammarus species are found in a wide range of freshwater and brackish habitats, including rivers, lakes, ponds, and estuaries. They prefer environments with moderate to high levels of dissolved oxygen, and are often found in association with submerged vegetation, rocks, and debris. Some species are particularly tolerant of pollution, while others are sensitive to water quality changes.
Life Cycle
Gammarus species have a complex life cycle that includes several stages. The females carry their eggs in a brood pouch located beneath the abdomen. After hatching, the young, known as larvae, undergo several molts before reaching adulthood. The lifespan of Gammarus species varies, but most live for 1-2 years.
Ecological Importance
Gammarus species are important members of aquatic food webs. They are primary consumers, feeding on dead plant and animal matter, and are an important food source for fish, amphibians, birds, and other invertebrates. Some Gammarus species have been used as bioindicators, meaning that their presence or absence can indicate the health of an aquatic ecosystem.
References
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