Boreomysinae
{{Short description|Subfamily of crustaceans}}
{{Automatic taxobox
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| taxon = Boreomysinae
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Boreomysinae is a subfamily of large, mostly deep-water oceanic mysid crustaceans from the family Mysidae. The name, which can be translated as "northern mysids", comes from the genus Boreomysis G.O. Sars, 1869, established for Boreomysis arctica (Krøyer, 1861) from the boreal waters of Atlantic. As more species have been discovered subsequently, the subfamily is considered panoceanic, and includes 38 species from two genera, Boreomysis and Neobirsteiniamysis Hendrickx et Tchindonova, 2020.{{cite WoRMS |author1=Jan Mees |author2=Kenneth Meland|year=2012 |title=Boreomysinae |id=154152 |accessdate=July 28, 2023}}{{cite journal |author=Daneliya, M. E. |title=Mysid subfamily Boreomysinae (Crustacea: Mysida: Mysidae) |journal=Records of the Australian Museum |volume=75 |issue=2|doi=10.3853/j.2201-4349.75.2023.1845 |doi-access=free |hdl=10138/357511 |hdl-access=free }}
Boreomysinae is a primitive group, uniquely distinguished from other subfamilies of Mysidae by the presence of the seven pairs of oostegites, which can be maximum four in other subfamilies, and by the incomplete proximal suture on the uropodal exopods (either complete and distal or completely absent in the rest of subfamilies).
Boreomysinaes show wide diversity in the structure of eyes, from rather reduced to large with well-developed cornea.{{cite journal |last1=Holt |first1=E.W.L. |last2=Tattersall |first2=W.M. |date=1906 |title=Schizopodous Crustacea from the north-east Atlantic slope |journal=Supplement. Fisheries, Ireland, Scientific Investigations, 1904 |volume=V |pages=1–50}}
Being an ancient group of crustaceans,{{cite journal |last1 =Petryashov |first1=V.V. |date=1993 |title=Deep-sea mysids (Crustacea, Mysidacea) of the Arctic Basin (Arctic Ocean) |journal= Morskoi Plankton. Sistematica, Ekologiya I Rasprostranenie, II. Issledovaniya Fauny Morei |volume =45 |issue =53 |pages = 70–89 [in Russian, with English abstract.]}} possibly originated in the beginning of Mesozoic era, boreomysines are considered living fossils.
Description
Abdominal pleomeres lacking pleural plates. Telson not armed in anterior part, but having apical cleft, lacking plumose setae.{{cite journal |last1=Kathman |first1=R.D. |last2=Austin |first2=W.C. |last3=Saltman |first3=J.C. |last4=Fulton |first4=J.D. |date=1986 |title=Identification Manual to the Mysidacea and Euphausiacea of the Northeast Pacific |journal=Canadian Special Publication of Fisheries and Aquatic Sciences |volume=93 |pages=1–411}} Appendix masculina present as slight tubercle with a bunch of setae.{{cite journal |last1=Hansen |first1=H.J. |title=The Schizopoda of the Siboga Expedition |journal=Siboga Expeditie |volume=37| pages=1–123 |date=1910 |doi=10.5962/bhl.title.10421|doi-access=free }}
Labrum not armed apically; thought its right lobe with inward-bent process. Antennal scale with smooth outer margin, terminating with non-articulated spine.Wittmann, K. J., A. P. Ariani, and J.-P. Lagardère. (2014) Orders
Lophogastrida Boas, 1883, Stygiomysida Tchindonova, 1981,
and Mysida Boas, 1883 (also known collectively as Mysidacea),
pp. 189–396, 404–406. In Treatise on Zoology—Anatomy, Taxonomy, Biology. The Crustacea. Revised and updated, as well as extended from the Traité de Zoologie, ed. J. C. von Vaupel Klein, M. Charmantier-Daures, and F. R. Schram, Vol.
4 Part B (54) Pereopod endopods not differentiated; only pereopod 1 slightly stronger than others; carpus and propodus divided by oblique articulation;{{cite book|last=Hansen|first=H J.|title=Studies on Arthropoda. II.|year=1925|publisher=Copenhagen, Gyldendalske Boghandel}} internal articulation of the propodus transverse. Marsupium (brood pouch) made of seven plates (oostegites), present
on maxillipeds 2 and all six pereopods of females. Penes tubular. Pleopods reduced to unsegmented plates in females. In males pleopods always well-developed,Zimmer, C. 1909. Die nordischen Schizopoden (inkl. Nachtrag zu Mysis oculata (Fabr.). In Nordisches Plankton, ed. K. Brandt and
C. Apstein. Kiel and Leipzig: Lipsius und Tischer, 12: 1–179 biramous; endopod 1 non-segmented; other endopods and all five exopods multisegmented; endopods with movable preudobranchial lobe; exopod 3, and sometimes
also exopod 2 modified, with stronger and shorter setae on terminal segments. Uropodal exopod with incomplete proximal suture, its segment 1 bearing distolateral spiniform setae;{{cite journal |last1=Holt |first1= E. W. L. |last2=Tattersall |first2=W.M. |title=Schizopodous Crustacea from the north-east Atlantic slope |journal=Reports on the Sea and Inland Fisheries of Ireland, 1902–1903 |date=1905 |volume=2 |issue=4 |pages=99–152}} endopod entire, without signs of articulation. Balance organ (statolith) in the endopod of organic composition,{{cite journal |last1=Ariani |first1=A.P. |last2=Wittmann |first2=K.J. |last3=Franco |first3=E. |date=1993 |title=A comparative study of static bodies in mysid crustaceans: Evolutionary implications of crystallographic characteristics |journal=The Biological Bulletin |volume=185 |issue=3 |pages=393−404| doi=10.2307/1542480|jstor=1542480 |pmid=29300627 |url=https://www.biodiversitylibrary.org/part/6870 }} somewhat reduced{{cite journal |last1=Banner |first1=A. H. |title=A taxonomic study of the Mysidacea and Euphausiacea (Crustacea) of the northeastern Pacific, Part II. Mysidacea, from tribe Mysini through subfamily Mysidellinae |journal=Transactions of the Royal Canadian Institute |volume=27 |pages=65−124 |date=1948}}{{cite journal |last1=Daneliya |first1=Mikhail E. |title=Mysid subfamily Boreomysinae (Crustacea: Mysida: Mysidae) in the southeast Australian deep-sea |journal=Records of the Australian Museum |date=26 April 2023 |volume=75 |issue=2 |pages=87–124 |doi=10.3853/j.2201-4349.75.2023.1845 |url=https://journals.australian.museum/daneliya-2023-rec-aust-mus-752-87124/ |access-date=3 August 2023 |language=en |issn=2201-4349|hdl=10138/357511 |s2cid=258369187 |hdl-access=free }} {{Creative Commons text attribution notice|cc=by4|from this source=yes}}
Boremysine individuals are the largest mysids: body length of some species reaches up to 85 cm.
Taxonomy
Type genus of the subfamily is Boreomysis G.O. Sars, 1869; by original monotypy.
Some authors suggested the suborder or the full family status for boreomysines, but only the subfamily level rank is currently supported.
Classification
The subfamily contains two genera:
- Boreomysis G.O. Sars, 1869
- Neobirsteiniamysis Hendrickx et Tchindonova, 2020
Phylogeny
Boreomysines were originally thought to be close to Leptomysinae, another subfamily with well-developed biramous pleopods. According to molecular genetic studies, Boreomysinae form a monophyletic clade, basal to most of Mysidae, and somewhat close to Rhopalophthalminae, also with articulated uropodal exopod and organic statolith.{{cite journal |last1=Meland |first1=K.|last2=Willassen |first2=E. |date=2007 |title=The disunity of "Mysidacea" (Crustacea) |journal=Molecular Phylogenetics and Evolution |volume=44 |issue=3 |pages=1083–1104 |doi=10.1016/j.ympev.2007.02.009|pmid=17398121 }} A detailed comparison suggests them to be structurally more similar to Siriellinae, sharing uropodal exopod articulation, its armature, non-differentiation of pereopods, non-reduction of pleopods and their apical modification.
Their basal position, corresponds to their primitive structure. Estimates of the molecular clock make boremysines some 242,7 million years old.{{cite journal |last1=Kou |first1=Q. |last2=Meland |first2=K. |last3=Li |first3=X. |last4=He |first4=L. |last5=Wang |first5=Y. |date=2020 |title="Unicorn from Hades", a new genus of Mysidae (Malacostraca: Mysida) from the Mariana Trench, with a systematic analysis of the deep-sea mysids |journal=Molecular Phylogenetics and Evolution |volume=143:106666 |doi=10.1016/j.ympev.2019.106666|pmid=31669817 |s2cid=204969925 }}
Distribution
The subfamily is generally cosmopolitan. Boreomysine species are among the most widely distributed mysids.{{cite journal |last1=Holmquist |first1=C. |date=1957 |title=Mysidacea of Chile. Reports of the Lund University Chile Expedition 1948–49. (Report 28) |journal=Lunds Universitets Årsskrift 2 |volume=53 |issue=6 |pages=1–52}} For example, Neobirsteiniamysis inermis is a rare case of bipolar amphitropical species, found in the deep water from Arctic to Antarctic.
Habitat
Boreomysine mysids are mostly deep-water oceanic crustaceans. Certain species, however, have been described from relatively shallow epi- and mesopelagic waters (members of the subgenus Boreomysis (Petryashovia). Some deep-water species also occasionally penetrate epipelagic zone. Some species have also been found in inland seas, like Marmora Sea, thus deviating from purely oceanic habits.