Gammarus hyalelloides
Encyclopedia
Gammarus hyalelloides is a species of amphipod
crustacean
in the family Gammaridae
. It is endemic to four springs
in Jeff Davis County
and Reeves County
, Texas
, and is listed as a vulnerable species
on the IUCN Red List
.
females are 5 millimetre. They live in beds of Chara at the mouth of Phantom Lake Spring.
G. hyalelloides makes up more than 70% of the diet of Gambusia nobilis in the Phantom Lake Spring refuge in Jeff Davis County, Texas. Other biota found in the Phantom Lake Spring include the snails Pyrgulopsis texana
and Lyrodes cheatumi. The absence of Hyalella azteca
may have allowed speciation to take place in the genus Gammarus
, with one species entering the vacant niche, and reducing in size to become G. hyalelloides.
, but were later recognized as a new and distinct species of Gammarus
.
The type specimens were deposited in the United States National Museum (holotype
male: USNM 151957; paratype
female: USNM 151958). Further paratype series were deposited at the same museum, and at the National Museum of Canada
.
G. hyalelloides is part of the Gammarus pecos species complex
, alongside Gammarus pecos
and Gammarus desperatus
; all three species are restricted to the Pecos River
basin of Texas
and New Mexico
.
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 the family Gammaridae
Gammaridae
Gammaridae is a family of amphipods. In North America they are included among the folk taxonomic category of "scuds", and otherwise gammarids is usually used as a common name....
. It is endemic to four springs
Spring (hydrosphere)
A spring—also known as a rising or resurgence—is a component of the hydrosphere. Specifically, it is any natural situation where water flows to the surface of the earth from underground...
in Jeff Davis County
Jeff Davis County, Texas
Jeff Davis County is a county in the U.S. state of Texas. It is named for Jefferson Davis, the president of the Confederate States of America. It is one of the nine counties that comprise the Trans-Pecos region of West Texas. In 2000, its population was 2,207, and 2,258 by 2009...
and Reeves County
Reeves County, Texas
Reeves County is a county located in the US state of Texas. It is one of the nine counties that comprise the Trans-Pecos region of West Texas. In 2000, its population was 13,137. Its seat is Pecos. Reeves County is named for George R. Reeves, a Texas state legislator and colonel in the...
, 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 is listed as a vulnerable species
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...
on the IUCN Red List
IUCN Red List
The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...
.
Description and ecology
G. hyalelloides is the smallest freshwater amphipod in North America. Males are 5.8 millimetre long, while sexually matureSexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
females are 5 millimetre. They live in beds of Chara at the mouth of Phantom Lake Spring.
G. hyalelloides makes up more than 70% of the diet of Gambusia nobilis in the Phantom Lake Spring refuge in Jeff Davis County, Texas. Other biota found in the Phantom Lake Spring include the snails Pyrgulopsis texana
Phantom cave snail
The phantom cave snail or phantom cavesnail is a species of very small freshwater snail with an operculum, an aquatic gastropod in the family Hydrobiidae.- Distribution :...
and Lyrodes cheatumi. The absence of Hyalella azteca
Hyalella azteca
Hyalella azteca is a widepsread and abundant species of amphipod crustacean in North America. It reaches 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.-Description:...
may have allowed speciation to take place in the genus Gammarus
Gammarus
Gammarus is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most speciose genera of crustaceans...
, with one species entering the vacant niche, and reducing in size to become G. hyalelloides.
Taxonomic history
The first collections of G. hyalelloides were made in 1967 at the Phantom Lake Spring. The amphipods were originally thought to be the common and widespread Hyalella aztecaHyalella azteca
Hyalella azteca is a widepsread and abundant species of amphipod crustacean in North America. It reaches 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.-Description:...
, but were later recognized as a new and distinct species of Gammarus
Gammarus
Gammarus is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most speciose genera of crustaceans...
.
The type specimens were deposited in the United States National Museum (holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
male: USNM 151957; paratype
Paratype
Paratype is a technical term used in the scientific naming of species and other taxa of organisms. The exact meaning of the term paratype when it is used in zoology is not the same as the meaning when it is used in botany...
female: USNM 151958). Further paratype series were deposited at the same museum, and at the National Museum of Canada
Canadian Museum of Nature
The Canadian Museum of Nature is a natural history museum in Ottawa, Ontario, Canada. Its collections, which were started by the Geological Survey of Canada in 1856, include all aspects of the intersection of human society and nature, from gardening to gene-splicing...
.
G. hyalelloides is part of the Gammarus pecos 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...
, alongside Gammarus pecos
Gammarus pecos
Gammarus pecos is a species of crustacean in family Gammaridae. It is endemic to the United States.-Source:* Inland Water Crustacean Specialist Group 1996. . Downloaded on 9 August 2007....
and Gammarus desperatus
Gammarus desperatus
Gammarus desperatus is a species of amphipod crustacean in the family Gammaridae.G. desperatus was formerly found at three sites in New Mexico, but it has since been extirpated from two of these sites. G. desperatus only survives within Bitter Lake National Wildlife Refuge...
; all three species are restricted to the Pecos River
Pecos River
The headwaters of the Pecos River are located north of Pecos, New Mexico, United States, at an elevation of over 12,000 feet on the western slope of the Sangre de Cristo mountain range in Mora County. The river flows for through the eastern portion of that state and neighboring Texas before it...
basin 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 New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
.