''Aega psora'' is a species of

isopod Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, an ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

that parasitises a number of

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

species in the North Atlantic. It is a serious ectoparasite of larger species of fish, particularly when they are injured.

Description

''Aega psora'' is the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

of the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

''Aega'' and was first described by

Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...

1758 Events January–March * January 1 – Swedish biologist Carl Linnaeus (Carl von Linné) publishes in Stockholm the first volume (''Animalia'') of the 10th edition of Systema Naturae, 10th edition of ''Systema Naturae'', the sta ...

. It reaches in length and is mostly grey, with a faint dorsal stripe. It has slender mandibles and

maxillae The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

adapted for sucking blood and some of the setae (bristles) are hooked. The front three pairs of

pereiopod The decapod (crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various g ...

s (legs) cling on to its host, it inserts its mouthparts and blood is pumped rapidly into the gut. Other adaptations for this method of feeding include strong muscles in its

oesophagus The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the ...

and large salivary

gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland). Structure De ...

Distribution

''Aega psora'' is widespread throughout the North Atlantic Ocean and has been found in the

Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain. The sea stretches from 53°N to 66°N latitude and from ...

, the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

and the

Irish Sea The Irish Sea or , gv, Y Keayn Yernagh, sco, Erse Sie, gd, Muir Èireann , Ulster-Scots: ''Airish Sea'', cy, Môr Iwerddon . is an extensive body of water that separates the islands of Ireland and Great Britain. It is linked to the Ce ...

. In the northwestern Atlantic it is found between the

Bay of Fundy The Bay of Fundy (french: Baie de Fundy) is a bay between the Canadian provinces of New Brunswick and Nova Scotia, with a small portion touching the U.S. state of Maine. It is an arm of the Gulf of Maine. Its extremely high tidal range is the hi ...

and

Cape Cod Cape Cod is a peninsula extending into the Atlantic Ocean from the southeastern corner of mainland Massachusetts, in the northeastern United States. Its historic, maritime character and ample beaches attract heavy tourism during the summer mont ...

Hosts

''Aega psora'' is a facultative parasite which temporarily attaches itself to its host and is able to survive independently. It probably spends the rest of the time resting on the seabed. It has been found as an external parasite on the Atlantic cod (''Gadus morhua''), the

Greenland shark The Greenland shark (''Somniosus microcephalus''), also known as the gurry shark, grey shark, or by the Kalaallisut name ''eqalussuaq'', is a large shark of the family Somniosidae ("sleeper sharks"), closely related to the Pacific and southern s ...

(''Somniosus microcephalus''), a shark in the genus ''

Squalus ''Squalus'' is a genus of dogfish sharks in the family Squalidae. Commonly known as spurdogs, these sharks are characterized by smooth dorsal fin spines, teeth in upper and lower jaws similar in size, caudal peduncle with lateral keels; upper pr ...

'', the

common skate The common skate (''Dipturus batis''), also known as the blue skate, is the largest skate in the world, attaining a length of up to .Griffiths AM, Sims DW, Cotterell SJ, El Nagar A, Ellis JR, Lynghammar A, McHugh M, Neat FC, Pade NG, Queiroz N, ...

(''Raja batis''), the

thorny skate The thorny skate (''Amblyraja radiata'') is a species of fish in the family Rajidae. This bottom-living Skate (fish), skate lives in the North and south-eastern Atlantic Ocean in depths ranging from and water temperatures from . Species descrip ...

(''Amblyraja radiata'') and the barndoor skate (''Dipturus laevis''). Large numbers have also been found in the stomach of a Greenland shark, though whether living as a parasite or as a commensal is unclear. It was also found for the first time on the goldstripe sardinella (''Sardinella gibbosa'') off the coast of Egypt in 2007.

References

{{Taxonbar, from=Q1954046 Cymothoida Crustaceans of the Atlantic Ocean Crustaceans described in 1758 Taxa named by Carl Linnaeus