''Hyalella azteca'' is a widespread and abundant

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 ...

amphipod Amphipoda () is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods () range in size from and are mostly detritivores or scavengers. There are more than 10,700 amphipod species cur ...

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

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

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

and

diatoms A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...

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'' has body plan similar to most

amphipods Amphipoda () is an order (biology), order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods () range in size from and are mostly detritivores or scavengers. There are more than 10,700 amphip ...

and is a classic freshwater example of the order. They grow to a length of , with males being larger than females. Their color is variable, but the most frequent hues are white, green and brown. They are identified from other similar species by antenna 1 being equal or shorter than antenna 2, 1 spine on pleosome 1 and pleosome 2, Pereopod I and II are gnathopod with males having a visibly larger gnathopod.

Distribution

''Hyalella azteca'' is found across

Central America Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually ...

, the

Caribbean The Caribbean ( , ; ; ; ) is a region in the middle of the Americas centered around the Caribbean Sea in the Atlantic Ocean, North Atlantic Ocean, mostly overlapping with the West Indies. Bordered by North America to the north, Central America ...

and

, as far north as the Arctic tree line. It lives among vegetation and sediments in permanent bodies of

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...

, including

lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...

s and

river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...

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'') an ...

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 ''Hyalella'' is a genus of amphipods Amphipoda () is an order (biology), order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods () range in size from and are mostly detritivores or scave ...

'', ''H. azteca'' is extremely common and has wide ecological tolerances. It can tolerate

alkaline In chemistry, an alkali (; from the Arabic word , ) is a basic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The ...

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 estuary ...

s, but cannot tolerate a pH lower (more

acid An acid is a molecule or ion capable of either donating a proton (i.e. Hydron, hydrogen cation, H+), known as a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis ...

ic) than 6.0. The main foodstuffs of ''H. azteca'' are

filamentous algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular microalgae, suc ...

and

diatom A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...

s, although they may also consume organic

detritus In biology, detritus ( or ) is organic matter made up of the decomposition, decomposing remains of organisms and plants, and also of feces. Detritus usually hosts communities of microorganisms that colonize and decomposition, decompose (Reminera ...

. It cannot assimilate either

cellulose Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important s ...

lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidit ...

, even though these

biomolecule A biomolecule or biological molecule is loosely defined as a molecule produced by a living organism and essential to one or more typically biological processes. Biomolecules include large macromolecules such as proteins, carbohydrates, lipids ...

s 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 has fallen to the ground. This detritus or dead organic material and its constituen ...

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

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

biomass Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...

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

. In

Saskatchewan Saskatchewan is a Provinces and territories of Canada, province in Western Canada. It is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and to the south by the ...

, 97% of the diet of female

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

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

''Hyalella azteca'' is widely used in ecotoxicology due to its sensitivity to pollutants; however, recent studies suggest that populations may develop tolerance to insecticides over few generations. For instance, a 2024 study found that after just two generations of exposure to thiacloprid, tolerance levels increased significantly, highlighting the potential role of developmental plasticity in rapid adaptation to pesticide pollution. However, evolved resistance to insecticides may conflict with the species' ability to adapt to climate change. Fulton et al. (2021) demonstrated that some resistance mechanisms in ''H. azteca'' impose a fitness cost under higher temperatures, raising concerns about the trade-offs between pesticide tolerance and thermal adaptability in a changing environment. Some ''H. azteca'' have evolved

insecticide resistance Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, ...

. 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 Fitness (often denoted w or ω in population genetics models) is a quantitative representation of individual reproductive success. It is also equal to the average contribution to the gene pool of the next generation, made by the same individuals ...

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, which occurs between each moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the exoskeleton in order to ...

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 potency or effect of a substance by its effect on animal testing, living animals or plants (''in vivo''), or on living cells or tissues (''in vitro''). A bioassay can be either quantal or quantit ...

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 Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance faster than it can be lost or eliminated by catabolism and excretion. T ...

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 people, Swiss mineralogist, taxonomist and entomologist specialising in studies of hymenopteroid and Polyneoptera, orthopteroid insects. Education, ca ...

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

Aztec The Aztecs ( ) were a Mesoamerican civilization that flourished in central Mexico in the Post-Classic stage, post-classic period from 1300 to 1521. The Aztec people included different Indigenous peoples of Mexico, ethnic groups of central ...

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, is one of the 31 states which, along with Mexico City, comprise the 32 Political divisions of Mexico, Federal Entit ...

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

. It has also been described under several

junior synonym In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...

s, 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 Verri ...

erected the genus ''

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

type species In International_Code_of_Zoological_Nomenclature, 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 spe ...

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

, since there is little

gene flow In population genetics, gene flow (also known as migration and allele flow) is the transfer of genetic variation, genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent ...

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 forming the crossroads of Central, South and West Texas, United States. It is named in honor of Haden Edwards. It is bounded by the Balcones Fault to the south and east; the Llano Uplift and the Lla ...

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

, and '' Hyalella montezuma'' from

Montezuma Well Montezuma Well (), a detached unit of Montezuma Castle National Monument, is a natural limestone sinkhole near the town of Rimrock, Arizona, through which some of water emerge each day from an spring (hydrology), underground spring. It is l ...

Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...

. 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

1] "Aquatic Invertebrates: Amphipods". The Nature of the Rideau River. Canadian Museum of Nature. May 18, 2007. Retrieved October 5, 2010. Mark D. Sytsma; Jeffery R. Cordell; John W. Chapman; Robyn C. Draheim (October 2004). "Final Technical Report: Appendices" (PDF). Lower Columbia River Aquatic Nonindigenous Species Survey 2001–2004. United States Fish and Wildlife Service. Archived from the original (PDF) on June 4, 2010. Retrieved October 6, 2010. C. F. Mason (2002). "Acidification". Biology of Freshwater Pollution (4th ed.). Pearson Education. pp. 175–204. . Douglas Grant Smith (2001). "Amphipoda". Pennak's freshwater invertebrates of the United States: Porifera to Crustacea (4th ed.). John Wiley and Sons. pp. 569–584. . N. Kaushik (1975). "Decomposition of allochthonous organic matter and secondary production in stream ecosystems". Productivity of World Ecosystems: Proceedings of a Symposium Presented August 31–September 1, 1972, at the V General Assembly of the Special Committee for the International Biological Program, Seattle, Washington. United States National Academy of Sciences. pp. 90–95. . Gary L. Krapu; Kenneth J. Reinecke (1992). "Foraging ecology and nutrition". In Bruce D. J. Batt (ed.). Ecology and Management of Breeding Waterfowl. University of Minnesota Press. pp. 1–29. . Robert Jay Goldstein; Rodney W. Harper; Richard Edwards (2000). "Foods and feeding". American Aquarium Fishes. Volume 28 of W. L. Moody, Jr., natural history series. Texas A&M University Press. pp. 43–51. . Poynton, H. et al. (2018). The Toxicogenome of Hyalella azteca: A Model for Sediment Ecotoxicology and Evolutionary Toxicology. Environmental Science and Technology, 52(10), 6009–6022. https://doi.org/10.1021/acs.est.8b00837 Nebeker, A; Miller, C. "Use of the amphipod crustacean Hyalella azteca in freshwater and estuarine sediment toxicity tests". EPA Science Inventory. Environmental Protection Agency. Retrieved 22 August 2017. 0Kuehr, S et al. (2020). Testing the bioaccumulation potential of manufactured nanomaterials in the freshwater amphipod Hyalella azteca. Chemosphere 263(2021),1. https://doi.org/10.1016/j.chemosphere.2020.127961 1Fulton, C et al. (2020). Fitness costs of pesticide resistance in Hyalella azteca under future climate change scenarios. Science of the Total Environment, 753(2021), 1. https://doi.org/10.1016/j.scitotenv.2020.141945 2Couillard, Y et al. (2008). The amphipod Hyalella azteca as a biomonitor in field deployment studies for metal mining. Environmental Pollution, 156(2008), 1314–1324. https://doi.org/10.1016/j.envpol.2008.03.001 3Yihao Duan; Sheldon I. Guttman; James T. Oris; A. John Bailer (2000). "Genetic structure and relationships among populations of Hyalella azteca and H. montezuma (Crustacea:Amphipoda)". Journal of the North American Benthological Society. 19 (2): 308–320. doi:10.2307/1468073. JSTOR 1468073. 4Exequiel R. Gonzalez & Les Watling; Watling (2002). "Redescription of Hyalella azteca from its type locality, Vera Cruz, Mexico (Amphipoda: Hyalellidae)". Journal of Crustacean Biology. 22 (1): 173–183. doi:10.1651/0278-0372(2002)022 173:ROHAFI.0.CO;2. JSTOR 1549618. 5. Lowry (2010). J. Lowry (ed.). "Hyalella azteca (Saussure, 1858)". World Amphipoda