Hyalella azteca

Hyalella azteca is a widespread and abundant species of amphipod crustacean in North America. It reaches 3–8 mm (0.12–0.31 in) long, and is found in a range of fresh and brackish waters. It feeds on algae and diatoms and is a major food of waterfowl. Hyalella azteca grows to a length of 3–8 millimetres (0.12–0.31 in), with males being larger than females. Their colour is variable, but the most frequent hues are white, green and brown. Hyalella azteca is found across Central America, the Caribbean and North America, as far north as the Arctic tree line. It lives among vegetation in permanent bodies of freshwater, including lakes and rivers, extending into tidal fresh water, and freshwater barrier lagoons. It is 'the most abundant amphipod of lakes ', with golf course ponds sometimes supporting large populations. In contrast to other species of Hyalella, H. azteca is extremely common and has wide ecological tolerances. It can tolerate alkaline waters and brackish waters, but cannot tolerate a pH lower (more acidic) than 6.0. The main foodstuffs of H. azteca are filamentous algae and diatoms, although they may also consume organic detritus. It cannot assimilate either cellulose or lignin, even though these biomolecules are a major component of the leaf litter. It can, however, assimilate 60%–90% of the bacterial biomass that it ingests. Hyalella azteca is an important food for many waterfowl. In Saskatchewan, 97% of the diet of female white-winged scoters was observed to be H. azteca, and it also makes up a significant part of the diet of lesser scaup. Hyalella azteca passes through a minimum of nine instars during its development. Sexes can first be distinguished at the 6th instar, with the first mating occurring in the 8th instar. Subsequent instars, of which there may be 15–20, are considered adulthood. Hyalella azteca is used in various aquatic bioassays. Because of their wide distribution, ease of captive reproduction, and its niche in lake sediments, Hyalella azteca is used in aquatic toxicology assays in sediments