Branchinecta gigas

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Branchinecta gigas
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Branchiopoda
Order: Anostraca
Family: Branchinectidae
Genus: Branchinecta
Species: B. gigas
Binomial name
Branchinecta gigas
Lynch, 1937

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.

Description

Females reach sexual maturity when they are 45–50 millimetres (1.8–2.0 in) long, and grow up to 86 mm (3.4 in) long; males reach only 66 mm (2.6 in).[2] Unpublished records exist of individuals up to 180 mm (7.1 in) long.[3] Despite being the largest species, B. gigas has the smallest eyes of any species in the family, and possibly in all Anostraca.[3]

Distribution

Branchinecta gigas has been found in Alberta, Saskatchewan, Washington, Montana, Oregon, North Dakota, Utah, Nevada and California.[4] A related species, Branchinecta raptor, occurs in Idaho.[5]

Ecology and behaviour

B. gigas lives in hyposaline lakes and rivers, with salinity ranging from 1.8 to 5.8‰.[4] These waters often have high turbidity (low visibility), and so B. gigas hunts by feel rather than by sight.[3] 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.[6] This response appears to be entirely by feel, which correlates with the turbidity of the waters where B. gigas and its prey live.[6] The prey taken by B. gigas is chiefly other species of Anostraca,[7] especially Branchinecta mackini,[3] although it also eats copepods, cladocerans and sometimes green algae.[5]

Taxonomy

In 1935, J. F. Clark collected two specimens of a large branchiopod near Coulee City, Washington. 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.[8]

References

  1. Inland Water Crustacean Specialist Group (1996). "Branchinecta gigas". IUCN Red List of Threatened Species. Version 2.3. International Union for Conservation of Nature. Retrieved March 3, 2011.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
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  4. 4.0 4.1 Ulrich Theodore Hammer (1986). "The plankton communities of saline lakes". Saline Lake Ecosystems of the World. Volume 59 of Monographiae Biologicae. Springer. pp. 171–336. ISBN 978-90-6193-535-3.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
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