Boreomysis G. O. Sars, 1869

Daneliya, Mikhail E., 2023, Mysid Subfamily Boreomysinae (Crustacea: Mysida: Mysidae) in the Southeast Australian Deep-sea, Records of the Australian Museum (Rec. Aust. Mus.) 75 (2), pp. 87-124 : 92

Boreomysis G. O. Sars, 1869

Boreomysis G. O. Sars, 1869: 330 ; 1879a: 8, 9; 1883: 34; 1885a: 11, 173, 177; 1885b: 54.—Czerniavsky, 1882:

56, 61, 69.—Hansen, 1887: 212; 1908: 100; 1910: 3–5,

7, 24, 25, 26, 28; 1921: 71; 1925: pl. 6; 1927: 22, 23, 24.— Perrier, 1893: 1026.— Stebbing, 1893: 269.—

Faxon, 1893: 218.— Ortmann, 1894: 105–106.— Ohlin, 1901: 69, 70, 72, 90.—Gerstaecker & Ortmann, 1901:

619, 625, 643, 654, 666, 674, 680, 682, 683.— Zimmer, 1904: 427, 428, 429, 473, 486, 489; 1909: 45, 48, 52, 60, 66; 1914: 386.—Fowler, 1912: 540.—W. M. Tattersall, 1913: 869; 1939: 230; 1951: 45, 47.—Holt & W. M. Tattersall, 1906: 21, 22, 45.— Linko, 1908: 39, 41.— Illig, 1930: 413, 559–560.—Coifmann, 1937: 17.— Nouvel, 1943: 45, 71.—Banner, 1948: 352, 361, 362; 1954: 579, 580.—W. M. Tattersall & O. S. Tattersall, 1951: 67, 70, 127–128, 131, 269.—O. S. Tattersall, 1955: 4, 25, 66, 67.—Holmquist, 1956: 428, 429, 432, 442, 443, 445;

1957: 4, 9, 45, 49.—Birstein & Tchindonova, 1958:

279, 335, 348, 351.—Birstein & Tchindonova, 1962: 64.— Ii, 1964: 16, 282, partim.— Pillai, 1965: 1682,

1686, 1687.—Băcescu, 1971: 7.12; 1981: 38.—Elofsson

& Hallberg, 1977: 177.— Mauchline & Murano, 1977: 49.— Mauchline, 1980: 9, 19, 226.— Tchindonova,

1981: 26.—Băcescu, 1981: 38.—Staff of the Zoological Society of London, 1985: 398, 399.—Hargreaves, 1985: 255–258.— Kathman et al., 1986: 41, 103, partim.— Fenton, 1986: 33.—Ariani et al., 1993: 401.— Müller,

1993: 22.— Saltzman & Bowman, 1993: 325, 330.— Petryashov, 1993a: 90, 103; 1993b: 71; 2004a: 125;

2005b: 963, 965, 967, 970; 2014a: 186; 2014b: 149.— Katağan & Kokataş, 1995: 396.— Ledoyer, 1995: 603, 615.—Hargreaves & Murano, 1996: 665.—Brattegard & Meland, 1997: 77.—Hargreaves, 1997: 52–62.—Brandt et al., 1998: 4, 5.—Lowry & Stodart, 2003: 428, 429.— Meland & Willassen, 2007: 1096, partim.— Fukuoka,

2009: 419.— Jocque & Blom, 2009: 4, 17.—Biju & Panampunnayil, 2011: 335.— Wittmann et al., 2014: 24, 207, 225, 228, 240, 245, 247, 253, 296, 332.— Ortiz et al., 2017: 113.— Wittmann, 2020: 15.—Hendrickx et al., 2020: 20.—Hernández-Payán & Hendrickx, 2020: 2. Arctomysis Czerniavsky, 1882: 61 , 69 (synonymized by Hansen, 1910: 3, 24).

Pseudanchialus Caullery, 1896: 368 (synonymized by W. M. Tattersall, 1951: 45).

Type species. Mysis arctica Krøyer, 1861 , by original designation.

Diagnosis. Telson not broad in central part, narrower than in anterior part. Eyes with cornea, not concave.

Distribution and habitat. Cosmopolitan. Petryashov (2014a) considered its centre of diversity as Western Pacific. Epi-bathypelagic (0–6000 m).

DNA divergence. The mtDNA COI gene divergence between all the studied species of the genus Boreomysis was 16–84% of model corrected distance. The divergence between Boreomysis and Neobirsteiniamysis was 67–116%.

Remarks. The genus Boreomysis was described in detail by G. O. Sars (1869, 1879a) for two species, B. arctica (Krøyer, 1861) and B. tridens G. O. Sars, 1870 . The genus was distinguished from other mysids (except Petalophthalmus ) by the larger number of marsupial plates (seven against three). Additionally, it had long, natatory male pleopods (shared with several other subfamilies) and reduced statocyst. Hansen (1910) noticed that carpus was jointed with propodus via vertical articulation.

Numerous species have been described since then, but most of them rather inadequately, and already Holmquist (1957) suggested that the genus required a revision. Ii (1964) provided an updated diagnosis of the genus, although no other boreomysine genera were known at that time; and therefore, none of the characters counts to be diagnostic in comparison with Neobirsteiniamysis . Describing new species of Boreomysis, Ii could not cope with the amount of variation. Expressing the feeling that he could equally be able to merge them with other known species, Ii eventually decided to maintain their separateness not to cause future difficulties in identification. He was particularly skeptical concerning the use of eyes in diagnostics. The taxonomy of the genus has been outstandingly problematic ( Mauchline, 1980).

After the description of Neobirsteiniamysis it appeared that the eye structure has been crucial in the separation of the genera. The eye shape is indeed variable with age of individuals, but adult specimens of the species of Boreomysis can often be rather clearly distinguished by this character. Certain species of a designated here Petryashovia subgen. nov. are distinguished above all by quite large eyes, with the cornea dominating over the stalk, lacking any traces the eye papilla. Thus, the structure of eyes does, in fact, play taxonomic role in the subfamily. I compose here a new generic diagnosis, which compares Boreomysis with Neobirsteiniamysis .

Composition. The genus Boreomysis contains 38 species, which I propose here to split into two subgenera, Boreomysis sensu stricto and Petryashovia subgen. nov. Members of both subgenera are found in the Australian waters.