Branchinecta gigas

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 is known commonly as the giant fairy shrimp.[1]

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

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they are 45–50 millimetres (1.8–2.0 in) long, and grow up to 86 mm (3.4 in) long; males reach only 66 mm (2.6 in).[2] Unpublished records exist of individuals up to 180 mm (7.1 in) long.[3] Despite being the largest species, B. gigas has the proportionally smallest eyes of any species in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, B. raptor, occurs in Idaho.[5]

Ecology and behaviour

B. gigas lives in hypersaline 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 touch 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 touch, 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 fairy shrimp,[7] especially B. 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. 1996: e.T3041A9545649. doi:10.2305/IUCN.UK.1996.RLTS.T3041A9545649.en.
  2. Graham R. Daborn (1975). "Life history and energy relations of the giant fairy shrimp Branchinecta gigas Lynch 1937 (Crustacea: Anostraca)". Ecology. 56 (5): 1025–1039. doi:10.2307/1936144. JSTOR 1936144.
  3. Michel A. Boudrias & Jammieson Pires (2002). "Unusual sensory setae of the raptorial Branchinecta gigas (Branchiopoda: Anostraca)". Hydrobiologia. 486 (1): 19–27. doi:10.1023/A:1021317927643.
  4. 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.
  5. D. Christopher Rogers; Dana L. Quinney; James Weaver & Jørgen Olesen (2006). "A new giant species of predatory fairy shrimp from Idaho, USA (Branchiopoda: Anostraca)" (PDF). Journal of Crustacean Biology. 26 (1): 1–12. doi:10.1651/C-2509.1. Archived from the original (PDF) on 2018-10-09. Retrieved 2011-03-25.
  6. G. E. White; G. Fabris & R. Hartland-Rowe (1969). "The method of prey capture by Branchinecta gigas Lynch, 1937 (Anostraca)". Crustaceana. 16 (2): 158–160. doi:10.1163/156854069X00411. JSTOR 20101576.
  7. Geoffrey Fryer (1966). "Branchinecta gigas Lynch, a non-filter-feeding raptatory anostracan, with notes on the feeding habits of certain other anostracans". Proceedings of the Linnean Society of London. 177 (1): 19–34. doi:10.1111/j.1095-8312.1966.tb00948.x.
  8. James E. Lynch (1937). "A giant new species of fairy shrimp of the genus Branchinecta from the state of Washington". Proceedings of the United States National Museum. 84 (3205): 555–562, pls. 77–80. doi:10.5479/si.00963801.84-3025.555.
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