Species Card of Copepod
Calanoida ( Order )
    Clausocalanoidea ( Superfamily )
        Mesaiokeratidae ( Family )
            Mesaiokeras ( Genus )
Mesaiokeras hurei  Krsinic, 2003   (F,M)
Krsinic, 2003 (p.940, figs.F,M); Vives & Shmeleva, 2007 (p.675, figs.F,M, Rem.)
Species Mesaiokeras hurei - Plate 1 of morphological figuresissued from : F. Krsinic in J. Plankton Res., 2003, 25 (8). [p.941, Fig.1].
Female (from 42°46'02''N, 17°22'02'' E): A-B, habitus (dorsal and lateral, respectively); C, genital double-somite (ventral); D, urosome (lateral); E, A1; F, position of P56; G, forehead (ventral).

Nota: Rostral area rounded without filament. Cephalosome and pedigerous somite 1 fused, 4th and 5th fused, asymmetrical in dorsal view, posterior right margin of 5th pedigerous somite longer than left, covering 1/2 of genital double-somite. Urosome of 4 free somites. Proportional lengths of urosomites and caudal rami 39 : 14 : 16 : 11 : 20 = 100. Ratio of length of prosome to length of urosome (with caudal rami) 3 : 1. Genital area located medioventrally and symmetrical; the opercula are fused, the genital apertures and seminal receptacles are paired; ventro-distal margin of genital double-somite armed with 4 longer processes; some median long, smaller spinules and a tuft of spinumes on the left side. A1 symmetrical, 21-segmented, reaching almost to end of prosome

Species Mesaiokeras hurei - Plate 2 of morphological figuresissued from : F. Krsinic in J. Plankton Res., 2003, 25 (8). [p.942, Fig.2].
Female: A, urosome (dorsal); B, urosome with attached spermatophore (lateral, left side).

Nota: Posterior margins of urosomites 3-4 fringed with very fine spines. Caudal rami asymmetrical, longer than wide, right ramus slightly longer than left.

Species Mesaiokeras hurei - Plate 3 of morphological figuresissued from : F. Krsinic in J. Plankton Res., 2003, 25 (8). [p.943, Fig.3].
Female: A, A2; B, Md; C, Mx1; D, Mx2; E, Mxp.

Nota : A2 : coxa with 1 setule ; basis with 2 setules at inner angle ; exopod 6-segmented with setal armature 1, 4, 1, 1, 1, 1 + 3 terminal setae ; endopod 2-segmented. Md : gnathobase with 8 teeth ; basis with 3 curved setae ; endopod 2-segmented ; exopod 5-segmented, seta on 2nd segment twice as long as on others. Mx1 : praecoxal arthrite bearing 10 elements ; coxal epipodite armed with 7 longer and 2 smaller setae and coxal endite 2 spinulose setae, respectively ; basal endite with 3 setae ; exopod bearing 8 longer and 3 smaller setae ; endopod 3-segmeted, 1st segment bearing 2 setae, 2nd with 2 setae, 3rd with 5 setae. Mx2 : praecoxa with 2 endites, each with 3 setae ; 2 coxal endites each with 2 longer spinulose and 1 shorter seta ; allobasis armed with 4 setae ; endopodal segments with 5 spinulose setae. Mxp : coxa longer than basis ; endopod 6-segmented.

Species Mesaiokeras hurei - Plate 4 of morphological figuresissued from : F. Krsinic in J. Plankton Res., 2003, 25 (8). [p.944, Fig.4].
Female: A-D, P1 to P4; E, P5.

Nota : P5 asymmetrical, left leg 2-segmented, right leg represented by short rounded stump.

Species Mesaiokeras hurei - Plate 5 of morphological figuresissued from : F. Krsinic in J. Plankton Res., 2003, 25 (8). [p.945, Fig.3].
Male: A, habitus (dorsal); B, forehead (ventral); C, urosome (dorsal); D, A1.Nota : Proportional lengths of urosome somites and caudal rami 36 : 15 : 13 : 13 : 13 = 100. A1 non geniculate, right A1 longer than left, reaching almost to end of prosome, comprising 21 free segments. A2 and all of mouthparts identical to those of female.

Species Mesaiokeras hurei - Plate 6 of morphological figuresissued from : F. Krsinic in J. Plankton Res., 2003, 25 (8). [p.947, Fig.6].
Male: A-D, P1 to P4; E, P5.

Nota : Swimming legs P1-P3 identical to those of female ; P4 with outer spine of exopod segment 1 much smaller than in female. Right P5 reduced to a short rounded stump ; left leg uniramous, 5-segmented, longer than prosome, proportional lengths of segment 10 : 28 : 28 : 19 : 15 = 100.

Compl. Ref.:
Belmonte & al., 2013 (p.222, Table 2, abundance vs stations); Belmonte, 2018 (p.273, Table I: Italian zones)
NZ: 1

Distribution map of Mesaiokeras hurei by geographical zones
Adriatic Sea (Veliko Jezero, Mljet Is., Croatia), Gulf of Taranto (S Italy)
N: 3
(891) F: 0,345-0,375; M: 0,325-0,35; {F: 0,345-0,375; M: 0,325-0,350}
Rem.: Interior marine lake (depth: 46 m); specimens at 1-11 m above the bottom in suspended detrital material.
According to Krsinic (2003, p.948) both sexes have 21 free antennule segments; this suggests that they may be the most advanced representatives of this genus (also see the antennulary setation patterns), whereas females of most species have 23-segmented antennules, and the most primitive according to Fosshagen (1978) Mesaiokeras hepneri with 24-segmented antennules.
Last update : 05/02/2020
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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 19, 2024]

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