Species Card of Copepod
Calanoida ( Order )
    Clausocalanoidea ( Superfamily )
        Stephidae ( Family )
            Stephos ( Genus )
Stephos arcticus  Sars, 1909   (F,M)
Syn.: ? Stephos sinuatus Willey, 1923 a (p.325, fig.M)
Sars, 1909 b (p.16, figs.F,M); Fosshagen, 1970 (p.43, Rem.); Bradford-Grieve, 1999 a (p.25, Table1: Rem.); Kos, 2016 (p.14, figs.F, M, Rem.)
Species Stephos arcticus - Plate 1 of morphological figuresissued from : G.O. Sars in Rep. 2nd Norw. Arctic Exped. \"Fram\", 1909, N°18. [Pl. I].
Female (from Bay Land's End): 1, habitus (dorsal); 3, A2; 4, Md (masticatory edge); 5, Md (mandibular palp); 6, Mx2; 7, Mxp; 8, P1; 9, P2; 10, P3; 11, P5.
Nota: Last pedigerous segment not wholly confluent with the preceding one, a slight notch on each side indicating the limit between the two; lateral lobes rounded off and slightly unequal, the right one somewhat more prominent than the left.
Urosome slender and narrow, attaining almost half the length of the prosome.
Genital segment slightly asymmetrical, bulging somewhat on left side.
Caudal rami about the length of the last segment, apical setae rather slender, the innermost but one much the longest, and attaining about half the length of the body.
A1 shorter than the prosome, 24-segmented.
P5 extremely small, with the distal segment conical in form and scarcely denticulated.

Male: 2, habitus (lateral left side); 12, P5 (posterior surface); 13, terminal segment of left leg (viewed from the outer side, magnified).
Nota: Urosome 5-segmented; 2nd segment the largest and produced bemow to a conical decurved projection.
A1 as in female.
P5 gratly developed. Right leg more slender than left, and consisting of 4 segments, the penultimate one long and slender, sublinear in form, and produced at the end outside to a conical projection, terminal segment divided into 3 unequal lappets, the middle one the largest and somewhat spoon-shaped. Left leg angularly bent in frontof the middle, and distinctly5-segmented, penultimate segment large and tumid, oval in form, and provided at the base inside a slender spiniform appendage, outside which another much smaller projection occurs, lower face provided, in front of the middle, with a rounded projecting tubercle, terminal segment somewhat club-shaped, and provided at the end outside with about 6 lanceolate, leaf-like appendages, tip rounded off and fringed with a comb-like series of delicate, somewhat compressed spinules.

Species Stephos arcticus - Plate 2 of morphological figuresIssued from : A. Willey in Contr. Canad. Biol. Ottawa, 1923, N.S.1, N°16. [p.25, Fig.19]. As Stephos sinuatus. With doubt.
Male (from Canada: James Bay): P5.

Nota : Characters male : Last thoracic segment rounded on the left side, bluntly produced on the right.
2nd abdominal segment produced below into a blunt process.
P5 : right and left legs equally long but the left le gis more evenly hinged, its segment consisting of 2 basal pieces and a 3-segmented ramus, the inner branch being suppressed. The end-segment of the left leg commonly terminates in a cluster of spines. The right leg has one of its proximal segments (the 3rd, corresponding to exopodite 1) greatly elongated, while the end-segment has a deep, bay-like emargination which possibly serves for threading the spermatophore .

Nota : Characters female : the last thoracic segment is asymmetrical and evenly rounded behind.
The genital segment is asymmetrical, convexly protuberant below.
P5 3-segmented, counting the basal pieces which are confluent across the middle line ; the terminal segment, less than twice the length of the middle segment, consists of a tumid proximal portion, withn convex inner border, separated on the outside by a distinct shoulder from the curved, sharp-pointed distal portion with concave inner border ; the points of the feet meet like finger-tips in the middle line in situ ; on the outer side of the distal portion , about the end of the first third of it, there is a delicate spinule beyond which the nearly even outer border appears to be obscurely and minutely ciliate.

Species Stephos arcticus - Plate 3 of morphological figuresIssued from : M.S. Kos in Zoological Institut RAS, St. Petersburg, 2016, 179. [p.14, Fig.2]. Stephos arcticus female and male (Redrawn from Sars, 1909).

Compl. Ref.:
Shih & al., 1971 (p.207); Park & Ferrari, 2009 (p.143, fig.2, biogeography)
NZ: 1

Distribution map of Stephos arcticus by geographical zones
Arct. (Canada: Jones Sound, ? James Bay, Land’s End Bay)
locality: 75°N, 86°W
N: 3
(551) F: 1,2; M: 1,05; {F: 1,20; M: 1,05}
Rem.: After Bradford-Grieve (1999 a, p.25) this species belongs to type II (see Genus Stephos).
Last update : 05/02/2019
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Razouls C., Desreumaux N., Kouwenberg J. and de Bovée F., 2005-2024. - Biodiversity of Marine Planktonic Copepods (morphology, geographical distribution and biological data). Sorbonne University, CNRS. Available at http://copepodes.obs-banyuls.fr/en [Accessed May 29, 2024]

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