Branchinecta gigas
Encyclopedia
Branchinecta gigas is a species
of fairy shrimp that lives in western Canada
and the United States
. It is the largest species of fairy shrimp, growing up to 86 mm (3.4 in) long. It lives in turbid, hyposaline waters, and hunts smaller fairy shrimp by feel.
when they are 45–50 mm (1.8–2 ) long, and grow up to 86 mm (3.4 in) long; males reach only 66 mm (2.6 in). Unpublished records exist of individuals up to 180 mm (7.1 in) long. Despite being the largest species, B. gigas has the smallest eyes of any species in the family, and possibly in all Anostraca.
, Saskatchewan
, Washington, Montana
, Oregon
, North Dakota
, Utah
, Nevada
and California
. A related species, Branchinecta raptor, occurs in Idaho
.
ranging from 1.8‰ to 5.8‰. These waters often have high turbidity
(low visibility), and so B. gigas hunts by feel rather than by sight. When feeding, B. gigas adopts a "hunting posture", with the body bent double. The animal swims dorsal side down, with the abdomen nearly parallel with the thorax, so that the sensitive antennae
and caudal rami all extends forwards. The thoracic limbs are held wide open, ready to close on any prey which enters. This response appears to be entirely by feel, which correlates with the turbidity
of the waters where B. gigas and its prey live. The prey taken by B. gigas is chiefly other species of Anostraca, especially Branchinecta mackini, although it also eats copepod
s, cladocera
ns and sometimes green algae
.
. These specimens were sent to James E. Lynch of the University of Washington
in Seattle, who visited sites between Coulee City and the Grand Coulee Dam
in 1936, and discovered further specimens. Lynch described the species
as Branchinecta gigas in 1937.
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 fairy shrimp that lives in western Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
and the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. It is the largest species of fairy shrimp, growing up to 86 mm (3.4 in) long. It lives in turbid, hyposaline waters, and hunts smaller fairy shrimp by feel.
Description
Females reach sexual maturitySexual 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...
when they are 45–50 mm (1.8–2 ) long, and grow up to 86 mm (3.4 in) long; males reach only 66 mm (2.6 in). Unpublished records exist of individuals up to 180 mm (7.1 in) long. Despite being the largest species, B. gigas has the smallest eyes of any species in the family, and possibly in all Anostraca.
Distribution
Branchinecta gigas has been found in AlbertaAlberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
, 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....
, Washington, Montana
Montana
Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...
, Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
, North Dakota
North Dakota
North Dakota is a state located in the Midwestern region of the United States of America, along the Canadian border. The state is bordered by Canada to the north, Minnesota to the east, South Dakota to the south and Montana to the west. North Dakota is the 19th-largest state by area in the U.S....
, Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
, Nevada
Nevada
Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...
and California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
. A related species, Branchinecta raptor, occurs in Idaho
Idaho
Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....
.
Ecology and behaviour
B. gigas lives in hyposaline lakes and rivers, with salinitySalinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
ranging from 1.8‰ to 5.8‰. These waters often have high turbidity
Turbidity
Turbidity is the cloudiness or haziness of a fluid caused by individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality....
(low visibility), and so B. gigas hunts by feel rather than by sight. When feeding, B. gigas adopts a "hunting posture", with the body bent double. The animal swims dorsal side down, with the abdomen nearly parallel with the thorax, so that the sensitive antennae
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
and caudal rami all extends forwards. The thoracic limbs are held wide open, ready to close on any prey which enters. This response appears to be entirely by feel, which correlates with the turbidity
Turbidity
Turbidity is the cloudiness or haziness of a fluid caused by individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality....
of the waters where B. gigas and its prey live. The prey taken by B. gigas is chiefly other species of Anostraca, especially Branchinecta mackini, although it also eats copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s, cladocera
Cladocera
Cladocera is an order of small crustaceans commonly called water fleas. Around 620 species have been recognised so far, with many more undescribed. They are ubiquitous in inland aquatic habitats, but rare in the oceans. Most are long, with a down-turned head, and a carapace covering the apparently...
ns and sometimes green algae
Green algae
The green algae are the large group of algae from which the embryophytes emerged. As such, they form a paraphyletic group, although the group including both green algae and embryophytes is monophyletic...
.
Taxonomy
In 1935, J. F. Clark collected two specimens of a large branchiopod near Coulee City, WashingtonCoulee City, Washington
Coulee City is a town in Grant County, Washington, United States. The population was 600 at the 2000 census.-Geography:Coulee City is located at ....
. These specimens were sent to James E. Lynch of the University of Washington
University of Washington
University of Washington is a public research university, founded in 1861 in Seattle, Washington, United States. The UW is the largest university in the Northwest and the oldest public university on the West Coast. The university has three campuses, with its largest campus in the University...
in Seattle, who visited sites between Coulee City and the Grand Coulee Dam
Grand Coulee Dam
Grand Coulee Dam is a gravity dam on the Columbia River in the U.S. state of Washington built to produce hydroelectric power and provide irrigation. It was constructed between 1933 and 1942, originally with two power plants. A third power station was completed in 1974 to increase its energy...
in 1936, and discovered further specimens. Lynch described the species
Alpha taxonomy
Alpha taxonomy is the discipline concerned with finding, describing and naming species of living or fossil organisms. This field is supported by institutions holding collections of these organisms, with relevant data, carefully curated: such institutes include natural history museums, herbaria and...
as Branchinecta gigas in 1937.