Hyalella azteca
Encyclopedia
Hyalella azteca is a widepsread and abundant species
of amphipod
crustacean
in North America
. It reaches 3 millimetre 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
.
, the Caribbean
and North America
, as far north as the Arctic tree line. It lives among vegetation in permanent bodies of freshwater
, including lake
s and river
s, extending into tidal fresh water, and freshwater barrier lagoon
s. It is "the most abundant amphipod of lakes [in North America]".
, H. azteca is extremely common and has wide ecological tolerances. It can tolerate alkaline
waters and brackish water
s, but cannot tolerate a pH
lower (more acid
ic) than 6.0.
The main foodstuffs of H. azteca are filamentous algae and diatom
s, although they may also consume organic detritus
. It cannot assimilate either cellulose
or lignin
, even though these biomolecule
s are a major component of the leaf litter. It can, however, assimilate 60%–90% of the bacteria
l biomass
that it ingests.
Hyalella azteca is an important food for many waterfowl
. In Saskatchewan
, 97% of the diet of female White-winged Scoter
s was observed to be H. azteca, and it also makes up a significant part of the diet of Lesser Scaup
.
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.
s from a "cistern" near Veracruz
, Mexico
. It has also been described under several junior synonyms, including:
When Sidney Irving Smith
erected the genus Hyalella
in 1874, H. azteca was the only included species, and therefore the type species
. The genus now includes dozens of species, mostly in South America.
H. azteca is now thought to represent a species complex
, since there is little gene flow
between populations, and different morphotypes are known to coexist in some areas. Two local populations have been described as separate species – Hyalella texana from the Edwards Plateau
of Texas
, and Hyalella montezuma
from Montezuma Well
, Arizona
.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of amphipod
Amphipoda
Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. The name amphipoda means "different-footed", and refers to the different forms of appendages, unlike isopods, where all the legs are alike. Of the 7,000 species, 5,500 are classified...
crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. It reaches 3 millimetre long, and is found in a range of fresh and brackish waters. It feeds on algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
and diatoms and is a major food of waterfowl
Waterfowl
Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....
.
Description
Hyalella azteca grows to a length of 3–8 mm (0.118110236220472–0.31496062992126 ), 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 AmericaCentral America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
, the Caribbean
Caribbean
The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...
and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, as far north as the Arctic tree line. It lives among vegetation in permanent bodies of freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
, including lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
s and river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
s, extending into tidal fresh water, and freshwater barrier lagoon
Lagoon
A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...
s. It is "the most abundant amphipod of lakes [in North America]".
Ecology
In contrast to other species of HyalellaHyalella
Hyalella is a genus of amphipods, containing the following species:*Hyalella anophthalma Ruffo, 1957*Hyalella araucana Grosso & Peralta, 1999*Hyalella armata *Hyalella azteca...
, H. azteca is extremely common and has wide ecological tolerances. It can tolerate alkaline
Alkalinity
Alkalinity or AT measures the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate. The alkalinity is equal to the stoichiometric sum of the bases in solution...
waters and brackish water
Brackish water
Brackish water is water that has more salinity than fresh water, but not as much as seawater. It may result from mixing of seawater with fresh water, as in estuaries, or it may occur in brackish fossil aquifers. The word comes from the Middle Dutch root "brak," meaning "salty"...
s, but cannot tolerate a pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
lower (more acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
ic) than 6.0.
The main foodstuffs of H. azteca are filamentous algae and diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...
s, although they may also consume organic detritus
Detritus
Detritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...
. It cannot assimilate either cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....
or lignin
Lignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...
, even though these biomolecule
Biomolecule
A biomolecule is any molecule that is produced by a living organism, including large polymeric molecules such as proteins, polysaccharides, lipids, and nucleic acids as well as small molecules such as primary metabolites, secondary metabolites, and natural products...
s are a major component of the leaf litter. It can, however, assimilate 60%–90% of the bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
l biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
that it ingests.
Hyalella azteca is an important food for many waterfowl
Waterfowl
Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....
. In Saskatchewan
Saskatchewan
Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
, 97% of the diet of female White-winged Scoter
White-winged Scoter
The White-winged Scoter is a large sea duck.-Description:It is characterised by its bulky shape and large bill. This is the largest species of scoter. Females range from 950-1950 grams and 48–56 cm , averaging 1180 grams and 52.3 cm . She is brown with pale head patches...
s was observed to be H. azteca, and it also makes up a significant part of the diet of Lesser Scaup
Lesser Scaup
The Lesser Scaup 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...
.
Life cycle
Hyalella azteca passes through a minimum of nine instarInstar
An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, 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.
Taxonomic history
Hyalella azteca was first described by Henri Louis Frédéric de Saussure in 1858, under the name Amphitoe aztecus, based on material collected by AztecAztec
The Aztec people were certain ethnic groups of central Mexico, particularly those groups who spoke the Nahuatl language and who dominated large parts of Mesoamerica in the 14th, 15th and 16th centuries, a period referred to as the late post-classic period in Mesoamerican chronology.Aztec is the...
s from a "cistern" near Veracruz
Veracruz
Veracruz, formally Veracruz de Ignacio de la Llave officially Estado Libre y Soberano de Veracruz de Ignacio de la Llave , is one of the 31 states that, along with the Federal District, comprise the 32 federative entities of Mexico. It is divided in 212 municipalities and its capital city is...
, Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. 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
Sidney Irving Smith 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. Smith married Eugenia Pocahontas Barber in New Haven, Connecticut on June 29, 1882...
erected the genus Hyalella
Hyalella
Hyalella is a genus of amphipods, containing the following species:*Hyalella anophthalma Ruffo, 1957*Hyalella araucana Grosso & Peralta, 1999*Hyalella armata *Hyalella azteca...
in 1874, H. azteca was the only included species, and therefore the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
. The genus now includes dozens of species, mostly in South America.
H. azteca is now thought to represent a species complex
Species complex
A species complex is a group of closely related species, where the exact demarcation between species is often unclear or cryptic owing to their recent and usually still incomplete reproductive isolation. Ring species, superspecies and cryptic species complex are example of species complex...
, since there is little gene flow
Gene flow
In population genetics, gene flow is the transfer of alleles of genes from one population to another.Migration into or out of a population may be responsible for a marked change in allele frequencies...
between populations, and different morphotypes are known to coexist in some areas. Two local populations have been described as separate species – Hyalella texana from the Edwards Plateau
Edwards Plateau
The Edwards Plateau is a region of west-central Texas which is bounded by the Balcones Fault to the south and east, the Llano Uplift and the Llano Estacado to the north, and the Pecos River and Chihuahuan Desert to the west. San Angelo, Austin, San Antonio and Del Rio roughly outline the area...
of Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, and Hyalella montezuma
Hyalella montezuma
Hyalella montezuma is a pelagic amphipod. It lives in Montezuma Well, an oasis in central Arizona. It is the only food of the endemic leech Motobdella montezuma....
from Montezuma Well
Montezuma Well
Montezuma Well , a detached unit of Montezuma Castle National Monument, is a natural limestone sinkhole near Rimrock, Arizona through which some of water flow each day through two underground springs. It is located northeast of Montezuma Castle. The well measures in at across and deep. The...
, Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
.