Boreomysis

Boreomysis (from Greek Boreas, the god of the northern winds, and the genus name Mysis) is a mysid crustacean genus, the type of the subfamily Boreomysinae of the family Mysidae. Majority of the species are found in the ocean deep water. Cosmopolitan. 38 species.

Description
Compared to another genus of the subfamily, Neobirsteiniamysis, the members of the genus Boreomysis have narrower telson, not expanded in the central part, being always narrower than in the anterior part. Also the eyes are mostly normally developed. Although in certain species the eyes may be reduced to certain extent, they still always possess cornea, unlike in Neobirsteiniamysis.

Taxonomy
The originally designated type species is Mysis arctica Krøyer, 1861.

Boreomysis is one of the most difficult mysid genera, mostly due to considerable variation with age.

Classification
The species of Boreomysis are distributed among two subgenera:
 * Boreomysis sensu stricto, 34 species, and
 * Petryashovia Daneliya, 2023, 4 species

Subgenus Boreomysis sensu stricto
The nominate subgenus combines most of the species of Boreomysis sensu lato, found in epi-bathypelagic waters, which have pointed rostrum and large ventrolateral projections of the carapace. Nearly all its species have 2-segmented propodus of pereopods (the exception is Boreomysis dubia, which has only one segment).

Subgenus Petryashovia
Subgenus Petryashovia, with the type species Boreomysis megalops G. O. Sars, 1872, includes epi-mesopelagic species with somewhat less developed carapace projections (no rostrum and rather short ventrolateral lobes) and undevided propodus of pereopods.

The name is dedicated to a carcinologist Victor Vladimirovich Petryashov (1956–2018).

Distribution
Members of the genus are found in all oceans, and Boreomysis can be considered cosmopolitan.

Habitat
Most of the species are oceanic deep-water. Some, however, penetrate deep parts of inland seas. The depth is from surface or subsurface waters (epipelagic) down to 6000 m (bathypelagic).