Species Card of Copepod
Calanoida ( Order )
    Clausocalanoidea ( Superfamily )
        Aetideidae ( Family )
            Chiridius ( Genus )
Chiridius obtusifrons  Sars, 1902   (F,M)
Syn.: Pseudocalanus armatus : Vanhöffen, 1897;
C. armatus : Sars, 1900 (p.64, figs.F, M); Ferrari & Dahms, 2007 (p.22, 27, Rem. N)
C. vanhöffeni Wolfenden, 1904 (p.117, figs.M);
no C. obtusifrons : A. Scott, 1909 (p.43, figs.F); C.B. Wilson, 1950 (p.189)
Sars, 1902 (1903) (p.29, figs.F,M, Rem.); With, 1915 (p.83, figs.F); Rose, 1933 a (p.94, figs.F,M); Jespersen, 1934 (p.56, figs.12, 13); Brodsky, 1950 (1967) (p.155, figs.F,M); Vervoort, 1952 c (n°44, p.3, figs.F,M); Vidal, 1971 a (p.15, 24, 113, figs.F,M); Park, 1975 b (p.289, Rem.); Tupitsky, 1982 a (p.110, figs.); Markhaseva, 1996 (p.116, figs.F,M); G. Harding, 2004 (p.55, figs.F,M)
Species Chiridius obtusifrons - Plate 1 of morphological figuresissued from : E.L. Markhaseva in Proc. Zool. Inst. RAN, St. Petersburg, 1996, 268. [p.117, Fig.88].
Female (specimen from Central part of Arctic Basin). Gn: genital segment (ventral and lateral).

Species Chiridius obtusifrons - Plate 2 of morphological figuresissued from : E.L. Markhaseva in Proc. Zool. Inst. RAN, St. Petersburg, 1996, 268. [p.118, Fig.89].
Female: distal part of metasome and genital segment (dorsal) in specimens from Arctic Basin..

Species Chiridius obtusifrons - Plate 3 of morphological figuresissued from : E.L. Markhaseva in Proc. Zool. Inst. RAN, St. Petersburg, 1996, 268. [p.118, Fig.90].
Male (specimen fron Central part of Arctic Basin)

Species Chiridius obtusifrons - Plate 4 of morphological figuresissued from : G.O. Sars in An Account of the Crustacea of Norway. Vol. IV. Copepoda Calanoida. Published by the Bergen Museum, 1903. [Pl. XVII].
Female & Male.

Species Chiridius obtusifrons - Plate 5 of morphological figuresIssued from : K.A. Brodskii in Calanoida of the Far Eastern Seas and Polar Basin of the USSR. Opred. Fauna SSSR, 1950, 35 (Israel Program for Scientific Translations, Jerusalem, 1967) [p.155, Fig.69].
Female (from Arctic): habitus (dorsal and lateral left side); S1, P1; S2, P2.
Nota: Spikes of terminal thoracic segment short, ending before middle of genital segment, directed somewhat laterally.

Male: habitus (dorsal); S5, P5.
Nota: P5 without traces of endopodites, each leg 5-segmented.

Species Chiridius obtusifrons - Plate 6 of morphological figuresissued from : G. Harding in Key to the adullt pelagic calanoid copepods found over the continental shelf of the Canadian Atlantic coast. Bedford Inst. Oceanogr., Dartmouth, Nova Scotia, 2004. [p.55].
Female & Male.

Nota: Female with tiny point in front (arrowed); urosome 1/2 length of prosome; metasomal points do not reach middle of genital segment (arrowed).
Caudal rami about twice as long as broad in both sexes

Species Chiridius obtusifrons - Plate 7 of morphological figuresChiridius obtusifrons female:1 - Exopod of Mx1 with 10 setae. Points of last thoracic segment reaching to the end of first third of genital segment, rarely reaching its middle.
2 - Endopodal segment 2 of Md with 9 terminal setae.

Species Chiridius obtusifrons - Plate 8 of morphological figuresChiridius obtusifrons male:
1 - Points of last thoracic segment not longer than genital segment.
2 - Right P5 longer than left. Exopodal segments 1 and 2 of P1 with external spines reaching the midlength of the next segment or longer.
3 - Points of last thoracic segment reaching at most the posterior border of genital segment. Endopodal segment 1 of Mxp with 3 medial setae.
4 - Exopodal segment 1 of P1 not reaching the base of following spine.
5 - P5 longer than than half length of P4.
6 - Distal segment of left P5 4.4-5.0 times longer than wide.

Compl. Ref.:
Damas & Koefoed, 1907 (p.398, tab.II, III); Jespersen, 1939 (p.47, Rem., Table 29, 30); Østvedt, 1955 (p.14: Table 3, p.61); Grice, 1962 a (p.101); V.N. Greze, 1963 a (tabl.2); M.W. Johnson, 1963 (p.89, Table 1, 2); Harding, 1966 (p.17, 66); Dunbar & Harding, 1968 (p.319); Shih & al., 1971 (p.32, 201); Björnberg, 1973 (p.323, 385); Kovalev & Schmeleva, 1982 (p.83); Buchanan & Sekerak, 1982 (p.41, vertical distribution); Tremblay & Anderson, 1984 (p.3); Groendahl & Hernroth, 1986 (tab.1); Kosobokova, 1989 (p.27); Mumm, 1993 (tab.1, fig.2); Hanssen, 1997 (tab.3.1); Hirche & Kwasniewski, 1997 (p.299, Table 5); Kosobokova & al., 1998 (tab.2); Auel, 1999 (p.1); Kosobokova & Hirche, 2000 (p.2029, tab.2); d'Elbée, 2001 (tabl. 1); Ringuette & al., 2002 (p.5081, Table 1; Auel & Hagen, 2002 (p.1013, tab.2, 3); Hopcroft & al., 2005 (p.198, table 2); Hop & al., 2006 (p.182, Table 4); Deibel & Daly; 2007 (p.271, Table 1, Rem.: Arctic polynyas); Kosobokova & al., 2007 (p.919, Tab.3, 6, 7, fig.2); Blachowiak-Samolyk & al., 2007 (p.2716, Table 2); Blachowiak-Samolyk & al., 2008 (p.2210, Table 3, biomass); Walkusz & al., 2008 (p.1, Table 3, abundance); Darnis & al., 2008 (p.994, Table 1); Galbraith, 2009 (pers. comm.); Laakmann & al., 2009 (p.741, fig.2, vertical distribution, lipids analysis); Kosobokova & Hopcroft, 2010 (p.96, Table 1, fig.7); Dvoretsky & Dvoretsky, 2010 (p.991, Table 2); 2011 a (p.1231, Table 2: abundance, biomass); Kosobokova & al., 2011 (p.29, Table 2, figs.4, 8, Rem.: Arctic Basins); Matsuno & al., 2012 (Table 2); Laakmann & al., 2012 (p.535, Table 1, fig.2, Rem.: mol. Biol.); Smoot & Hopcroft, 2016 (p.1, fig.7, vertical distribution)
NZ: 5 + 3 doubtful

Distribution map of Chiridius obtusifrons by geographical zones
Species Chiridius obtusifrons - Distribution map 3
Chart of 1996
Species Chiridius obtusifrons - Distribution map 4Issued from : S. Laakmann, M. Kochzius & H. Auel in Deep-Sea Res. I, 2009, 56. [p.745, Fig.2 c].
Vertical distribution abundance of copepodite stages C3 to C6 of Aetideopsis spp. and Chiridius obtusifrons. +: No occurrence; solid line depicts bottom profile (right axis); station 853 over the Yermak Plateau (81°22'N, 6°52'E) is separated from the other stations on the transect; other stations between East Greenland Current, the Fram Strait and the West Spitsbergen Current, into south return Atlantic Current (77°46'N-79°36'N, 6°20'E-7°29'W).
Deep-sea copepods collected from August 20 to September 16, 2006.
North Sea, Norway Sea, Barents Sea, Franz Josef Land, Laptev Sea, Lomonosov Ridge, Canada Basin, Barrow Strait, Baffin Bay, Davis Strait, W Iceland, Greenland Sea, Fram Strait, Spitsbergen, Kongsfjorden, Alaska NW, Arctic (all polar basins), Fletcher's Ice Is., Chukchi Sea, Beaufort Sea, Canadian abyssal plain, Vancouver Is., G. of Maine, Nouvelle-Ecosse, Détr. d'Hudson, ! S Chile (sub-Antarct.) (in Björnberg, 1973), S Bay of Biscay (in d'Elbée, 2001); ? Medit. (Ionian Sea)
N: 59
(7) F: 4,39; (37) F: 4,6-3,5; M: 3,2-2,9; (65) F: 4,2; M: 2,9; (134) F: 4,3; M: 3,3; (1001) F: 3,98-4,52; (1089) F: 3,5-4,2; M: 2,9; {F: 3,50-4,60; M: 2,90-3,30}
Rem.: epi-meso-bathypelagic.
Species considered as arctic-boreal.

The locality records south of Chile, in the southern part of the Bay of Biscay (but possible taking into account the mesopelagic distribution of this species) and in the Mediterranean are doubtful and require confirmation.
The locality record in the NE Atlantic: from 30 to 60° N (in Grice & Hulsemann, 1965, p.223) is not specified.
Last update : 26/01/2017
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Razouls C., Desreumaux N., Kouwenberg J. and de Bovée F., 2005-2021. - Biodiversity of Marine Planktonic Copepods (morphology, geographical distribution and biological data). Sorbonne University, CNRS. Available at http://copepodes.obs-banyuls.fr/en [Accessed February 28, 2021]

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