Species Card of Copepod
Cyclopoida ( Order )
    Oithonidae ( Family )
        Oithona ( Genus )
Oithona robertsoni  McKinnon, 2000   (F,M)
Ref.:
McKinnon, 2000 (p.105, 108, figs.F,M)
Species Oithona robertsoni - Plate 1 of morphological figuresissued from : A.D. McKinnon in Plankton Biol. Ecol.,2000, 47 (2). [p.107, Fig.7].
Female (from 12°30.35'S, 143°15.45'E): a-b, habitus (dorsal and lateral, respectively); c, urosome (dorsal); d, genital complex and P5 (lateral).


Species Oithona robertsoni - Plate 2 of morphological figuresissued from : A.D. McKinnon in Plankton Biol. Ecol.,2000, 47 (2). [p.109, Fig.8].
Female: a, A1; b, A2; c, Md (mandibular palp); d, Mx1; e, Mx2; f, Mxp.

Nota: A1 symmetrical, 14-segmented. A2 esopod segment 1 with 1 proximal, 1 medial and3 terminal setae, distal segment (segment 2) with 7 terminal setae. Md basis bearing 2 sharp recurved spines, each armed with spinules; endopod with 5 setae, proximal hirsute; exopod 3-segmented with 1, 1, 3 setae. Mx1 praecoxal endite with 8 plumose seta; 1st basal endite with 3 setae; exopod with 4. Mx2 comprises praecoxa, coxa and endopod 3-segmented. Mxp with praecoxa distinct, coxa basis with row of setules on inner surface, 2 setae distally and endopod


Species Oithona robertsoni - Plate 3 of morphological figuresissued from : A.D. McKinnon in Plankton Biol. Ecol.,2000, 47 (2). [p.110, Fig.9].
Female: a-d, P1 to P4.

Nota: Two inner setae of P4 endopod segment and proximal seta of endopod segment 3 modified, with denticulate membranous flange on medial tip. Intercoxal plate of P4 with long setules. P5 comprises dorsal seta of basis and exopod segment with crown seta.


Species Oithona robertsoni - Plate 4 of morphological figuresissued from : A.D. McKinnon in Plankton Biol. Ecol.,2000, 47 (2). [p.111, Fig.10].
Male: a-b, habitus (dorsal and lateral, respectively); c, urosome (dorsal); d, anal somite and caudal rami; e, genital somite and P5; f, A1.

Forehead blunt in dorsal and lateral views. Urosome somites 3, 4, 5 distal margins coarsely denticulate.Proportional lengths of urosomites and caudal rami 0.92:1.50:1.08:0.96:0.79:0.96: 1.0. Anal somite length 1.0 times width.Caudal ramus length 2.30 times width, 1.09 times anal somite.


Species Oithona robertsoni - Plate 5 of morphological figuresissued from : A.D. McKinnon in Plankton Biol. Ecol.,2000, 47 (2). [p.112, Fig.11].
Male: a, A2; b, Md (mandibular palp); c, Mx1; d, P1; e, P2 exopod; f, P3 exopod; g, P4.


Species Oithona robertsoni - Plate 6 of morphological figuresissued from : A.D. McKinnon in Plankton Biol. Ecol.,2000, 47 (2). [p.113, Fig.12].
Male: a, cephalosome flap organ (lateral); b, idem, nested shield-like integumental organs, with remnants of sensilla.

Nota: Cephalosome flap organ extending to the posterior margin of thoracic segment 2. Pore signature pattern similar to that described for . Cilia have been lost from the integumental organs in specimens prepared for SEM, but some gragments remained adhered to the integument (b) suggesting a similar arrangement of cilia within integumental organs to that seen in O. nishidai.


Species Oithona robertsoni - Plate 7 of morphological figuresissued from : A.D. McKinnon in Plankton Biol. Ecol.,2000, 47 (2). [p.107, Fig.7].
A comparison of O. robertsoni with other species of Oithona possessing 5 setae on the endopod of the mandible, and 1 seta on the free segment of P5 (excluding Dioithona).
PR : UR = prosome : urosome length ratio; CR L : W = caudal ramus length : width ratio; Md B2 = mandible palp basipod armament; Md Ri = armature of mandible endopod; L1-L4 = armament of legs P1-P4; R = round; B = blunt; P = pointed; Ri = endopod; Re = exopod.


Species Oithona robertsoni - Plate 8 of morphological figuresissued from : A.D. McKinnon in Plankton Biol. Ecol., 2000, 47 (2). [p.108, Table 2].
Morphological characteristics useful in the discrimination of the females of co-occuring species of Oithona from coastal waters of Northern Australia.
PR : UR = prosome : urosome length ratio; CR L : W = caudal ramus length : width ratio; Md B2 = mandible palp basipod armament; Md Ri = armature of mandible endopod; L1-L4 = armament of legs P1-P4; B = blunt; P = pointed; Ri = endopod; Re = exopod.

NZ: 1

Distribution map of Oithona robertsoni by geographical zones
Loc:
E Australia (N Queensland: mangrove)
N: 1
Lg.:
(847) F: 0,54-0,60; M: 0,51-0,54; {F: 0,54-0,60; M: 0,51-0,54}
Rem.: For McKinnon (2000, p.107) this species is one of the 5 species of Oithona sensu sticto (i.e excluding Dioithona) having 5 setae on the endopod of Md, the other being O. amazonica, O. colcarva, O. dissimilis and O. oswaldocruzi. O. fonsecae has 6 setae on the endopod of Md, 5 around the apex and 1 small seta near the base. It is difficult to ascertain the taxonomic affinities of O. robertsoni, through it has charaxters in common with O. aruensis, O. brevicornis, O. davisae, O. spinulosa, O. wellershausi/ In general body form it is most similar to the smaller form of O. brevicornis described by Nishida (1985) and to O. aruensis. However, the blunt rostrum of O. robertsoni and the structure of the mouthparts is quite different. Of the Indo-Pacific species, only O. dissimilis resembles O. robertsoni in the possession of 5 setae on the endopod of Md.
Last update : 08/12/2016
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