Species Card of Copepod
Calanoida ( Order )
    Ryocalanoidea ( Superfamily )
        Ryocalanidae ( Family )
            Ryocalanus ( Genus )
Ryocalanus spinifrons  Shimode, Toda & Kikuchi, 2000   (F)
Shimode & al., 2000 (p.128, Descr.F, figs.F); Boxshall & Halsey, 2004 (p.184, p.183: fig.F); Renz & al., 2013 (p.257)
Species Ryocalanus spinifrons - Plate 1 of morphological figuresissued from : S. Shimode, T. Toda & T. Kikuchi in Hydrobiologia, 2000, 432. [ p.129, Fig.1].
Female (from 35°00'N, 139°20'E): a, habitus (dorsal); b, idem (lateral); c, forehead (ventral); d, urosome (dorsal); e, genital double-somite (ventral); f, idem (lateral); g, head (arrangement of appendages; La = labrum, Pa = paragnaths).
Arrow: ventral inner side of last somite with 12 long spinules on both sides, without spinules on the ventral margin.

Nota: Prosome of 6 somites; cephalosome and 1st pedigerous somite separate, 4th and 5th separate. 5th pedigerous somite protrudes posteriorly into an acute spine reaching the posterior border of the genital double-somite on both sides. Urosome with 4 somites, dorsal posterior margins of genital double-somite to 3rd urosomal somite each with row of spinules. Genital double-somite almost symmetrical., with ventromedially genital opening; pair of copulatory pores located posteriorly in genital opening. Anal somite longer than preceding two somites. Caudal rami symmetrical, wider than long, ramus bearing tuft of fine spinules on posterior dorsal surface, fringed with minute spinules along inner margin and 6 setae along posterior margin; all setae with long lateral setules except short inner and outer setae.

Species Ryocalanus spinifrons - Plate 2 of morphological figuresissued from : S. Shimode, T. Toda & T. Kikuchi in Hydrobiologia, 2000, 432. [p.130, Fig.2].
Female: a, left A1 (segments I-XIV); b, idem (segments XV-XXV); c, idem (segments XXIII-XXV); d, right A2; e, labrum; f, left Md (mandibular cutting edge); g, right Md; h, left paragnath.

Nota: The paragnaths are quite complex and comparatively large relative to the labrum. The row of 5 robust spines on the inner margin is a distinct character; tese may be involved in feeding. A cave-dwelling species, Enantiosis cavernicola Barr (1984) has similar robust spines on the paragnaths and a relationship with food items is suspected. A1 25-segmented. Endopod of A2 2-segmented, exopod incompletely 7-segmented. Mandibular palp with basis bearing 3 inner setae; endopod 2-segmented; exopod 4-segmented

Species Ryocalanus spinifrons - Plate 3 of morphological figuresissued from : S. Shimode, T. Toda & T. Kikuchi in Hydrobiologia, 2000, 432. [p.131, Fig.3].
Female: a, right Mx1; b, right Mx2; c, right Mxp; d-g, P1 to P4 (right legs).

Nota: Mx1 praecoxal arthrite with 14 setae on proximal margin and fine spinules on surface; coxal epipodite missing in holotype, but coxal epipodite of paratype with 9 setae; coxal endite with 4 setae; 1st endite with 4 setae; 2nd basal endite almost coalescent with endopod, armed with 4 setae and fine spinules on surface (like praecoxal arthrite); endopod 2-segmented, 1st and 2nd segments with 5 and 6 setae, respectively; exopod bearing fan-like array of 11 setae.Mx2: 1st praecoxal endite bearing 5 setae, 2nd endite with 3 setae; epipodite seta lost, but maxilla of paratype having epipodite seta; both 1st and 2nd coxal endites with 3 setae; basal endite bearing 3 setae; endopod incompletely 4-segmented, almost coalescent, bearing total of 8 setae; inner surface of 2nd praecoxal endite to basal endite with patches of fine spinules. Mxp: coxa with 9 setae; basis longer than coxa, with 3 setae; endopod 6-segmented, 1st to 6th bearing 2, 4, 4, 3, 2+12 and 4 setae, respectively.

Species Ryocalanus spinifrons - Plate 4 of morphological figuresissued from : S. Shimode, T. Toda & T. Kikuchi in Hydrobiologia, 2000, 432. [p.132].
Female: Sera and spine formula of the swimming legs. (Romann numerals = spines; Arabic numerals = setae).

Compl. Ref.:
Bradford-Grieve, 2004 (p.283); Shimode & al., 2005 (p.113 + poster)
NZ: 1

Distribution map of Ryocalanus spinifrons by geographical zones
Japan (SW Sagami Bay)
N: 2
(850) F: 2,27; 2,29; { F: 2,27-2,29}
Rem.: bathyal (1500 m), hyperbenthic.
For Shimode & al. (2000, p.132) the data concerning the various species of Ryocalanus suggest that the family Ryocalanidae has diversified in the deep-sea benthopelagic habitat.
Last update : 08/01/2014
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Razouls C., Desreumaux N., Kouwenberg J. and de Bovée F., 2005-2022. - Biodiversity of Marine Planktonic Copepods (morphology, geographical distribution and biological data). Sorbonne University, CNRS. Available at http://copepodes.obs-banyuls.fr/en [Accessed May 23, 2022]

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