This superorder is characterized by the presence of a marsupium (an abdominal sac sheltering the eggs) formed by the oostegites, the flat and flared parts of the proximal segments of the legs.

[2] Pierre-André Latreille (1762-1833), an important French entomologist specialized in the taxonomy of arthropods, coined the term Amphipoda in 1816.

This term is coined in opposition to the Isopoda, another order of the Peracarida, which only present a single type of leg.

[7] Gammarus mucronatus is eurytopic, which means that it is capable of tolerating a wide range of ecological conditions.

[6] It is generally found in the endemic shallow waters and coasts of the North American Atlantic seaboard and the Gulf of Mexico.

It is therefore found in very different habitat: algae,[1] grass beds, sponges, spartina marshes, soft bottoms with shells or cobbles, oysters bar and open beaches.

[1][6] Gammarus mucronatus has a diversified diet: it is detritivore but also eats microalgae and macroalgae, and possibly some other macrofauna.

[6] Moreover, large decapods, crustaceans, juvenile and adult fishes prey on G. mucronatus,[6] like the stripped killfish, Fundulus majalis.

The presence of macroalgua reduces the predation of G. mucronatus by fish, which directly has a positive effect on their population’ size[8] and could create ternate stable states.