''Hyalella azteca'' is a widespread and abundant

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of amphipod

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can ...

in North America. It reaches long, and is found in a range of fresh and brackish waters. It feeds on algae and

diatoms A diatom (New Latin, Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group com ...

and is a major food of

waterfowl Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which i ...

Description

''Hyalella azteca'' grows to a length of , with males being larger than females. Their colour is variable, but the most frequent hues are white, green and brown.

Distribution

''Hyalella azteca'' is found across

Central America Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. ...

, the Caribbean and North America, as far north as the Arctic tree line. It lives among vegetation in permanent bodies of freshwater, including

lake A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much large ...

s and

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of w ...

s, extending into tidal fresh water, and freshwater barrier

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') ...

s. It is "the most abundant amphipod of lakes n North America, with golf course ponds sometimes supporting large populations.

Ecology

In contrast to other species of '' Hyalella'', ''H. azteca'' is extremely common and has wide ecological tolerances. It can tolerate alkaline waters and

brackish water Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

s, but cannot tolerate a pH lower (more acidic) than 6.0. The main foodstuffs of ''H. azteca'' are

filamentous algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular micr ...

and diatoms, although they may also consume organic detritus. It cannot assimilate either

cellulose Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell w ...

or lignin, even though these biomolecules are a major component of the

leaf litter Plant litter (also leaf litter, tree litter, soil litter, litterfall or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that have fallen to the ground. This detritus or dead organic material and its constituent ...

. It can, however, assimilate 60%–90% of the

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...

l biomass that it ingests. ''Hyalella azteca'' is an important food for many

. In

Saskatchewan Saskatchewan ( ; ) is a province in western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on the south by the U.S. states of Montana and North Dak ...

, 97% of the diet of female

white-winged scoter The white-winged scoter (''Melanitta deglandi'') is a large sea duck. The genus name is derived from Ancient Greek ''melas'' "black" and ''netta'' "duck". The species name commemorates French ornithologist Côme Damien Degland. Description The ...

s was observed to be ''H. azteca'', and it also makes up a significant part of the diet of

lesser scaup The lesser scaup (''Aythya affinis'') is a small North American diving duck that migrates south as far as Central America in winter. It is colloquially known as the little bluebill or broadbill because of its distinctive blue bill. The origin of ...

Insecticide resistance

Some ''H. azteca'' have evolved

insecticide resistance Pesticide resistance describes the decreased susceptibility of a pest population to a pesticide that was previously effective at controlling the pest. Pest species evolve pesticide resistance via natural selection: the most resistant specimens s ...

. This does however conflict with their need to adapt to climate change: Fulton et al 2021 finds some of their mechanisms of resistance impose a fitness cost under higher temperatures.

Life cycle

''Hyalella azteca'' passes through a minimum of nine

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...

s 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.

Uses

''Hyalella azteca'' are used in various aquatic

bioassay A bioassay is an analytical method to determine the concentration or potency of a substance by its effect on living animals or plants (''in vivo''), or on living cells or tissues(''in vitro''). A bioassay can be either quantal or quantitative, dir ...

s (also called toxicity tests). Because of their wide distribution, ease of captive reproduction, and its niche in lake sediments, ''Hyalella azteca'' are used in aquatic toxicology assays in sediments Hyalella azteca have been used to test bioaccumulation of different contaminants such as manufactured nanomaterial

pesticide

and metal

https://doi.org/10.1016/j.envpol.2008.03.001]

Taxonomic history

''Hyalella azteca'' was first described by

Henri Louis Frédéric de Saussure Henri Louis Frédéric de Saussure (; ; 27 November 1829 – 20 February 1905) was a Swiss mineralogist and entomologist specialising in studies of Hymenoptera and Orthopteroid insects. He also was a prolific taxonomist. Biography Sauss ...

in 1858, under the name ''Amphitoe aztecus'', based on material collected by

Aztec The Aztecs () were a Mesoamerican culture that flourished in central Mexico in the post-classic period from 1300 to 1521. The Aztec people included different ethnic groups of central Mexico, particularly those groups who spoke the Nahuatl ...

s from a "cistern" near

Veracruz Veracruz (), formally Veracruz de Ignacio de la Llave (), officially the Free and Sovereign State of Veracruz de Ignacio de la Llave ( es, Estado Libre y Soberano de Veracruz de Ignacio de la Llave), is one of the 31 states which, along with Me ...

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

. It has also been described under several junior synonyms, including: *''Hyalella dentata'' S. I. Smith, 1874 *''Hyalella fluvialis'' Lockington, 1877 *''Hyalella inermis'' S. I. Smith, 1875 *''Hyalella knickerbockeri'' Bate, 1862 *''Hyalella ornata'' Pearse, 1911 When

Sidney Irving Smith Sidney Irving Smith (February 18, 1843 in Norway, Maine – May 6, 1926 in New Haven, Connecticut) was an American zoologist. Private life Sidney Smith was the son of Elliot Smith and Lavinia Barton. His brother in law was Addison Emery Verrill. ...

erected the genus '' Hyalella'' in 1874, ''H. azteca'' was the only included species, and therefore the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...

. The genus now includes dozens of species, mostly in South America. ''H. azteca'' is now thought to represent a

species complex In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

, since there is little gene flow between populations, and different

morphotype In biology, polymorphism is the occurrence of two or more clearly different morphs or forms, also referred to as alternative ''phenotypes'', in the population of a species. To be classified as such, morphs must occupy the same habitat at the s ...

s are known to coexist in some areas. Two local populations have been described as separate species – '' Hyalella texana'' from the

Edwards Plateau The Edwards Plateau is a geographic region at the crossroads of Central Texas, Central, South Texas, South, and West Texas. It is bounded by the Balcones Fault to the south and east, the Llano Uplift and the Llano Estacado to the north, and the ...

Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...

, and '' Hyalella montezuma'' from

Montezuma Well Montezuma Well ( yuf-x-yav, ʼHakthkyayva), a detached unit of Montezuma Castle National Monument, is a natural limestone sinkhole near the town of Lake Montezuma, Arizona, through which some of water emerge each day from an underground s ...

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

. In addition to being a species complex, laboratory work sequencing and analyzing the genome of lab populations of Hyalella azteca revealed Hyalella azteca shares characteristics of other model organisms. How these crustaceans interact with contaminants can provide insight about how other species will interact with those same contaminants.

Genome Sequencing Project

There is an ongoing ''Hyalella azteca'' genome sequencing project. This is part of a larger project being led by the Baylor college of Medicine Human Genome Sequencing Center (BCM-HGSC) ; in which 28 arthropod genomes are being sequenced. The sequencing of these genomes serves as a beginning to the larger i5k initiative, which has an end goal of sequencing 5,000 Arthropoda. Scientists looking to contribute to this research are able to nominate species to sequence, and download and share data to i5k website. Data can also be submitted to the Global Genome biodiversity workshop Biodiversity Repository.

References

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