Mesocletodes robustus Por, 1965

Menzel, Lena & George, Kai Horst, 2009, Description of four new species of Mesocletodes Sars, 1909 (Copepoda, Harpacticoida, Argestidae) and redescription of Mesocletodes robustus Por, 1965 from the South Atlantic, including remarks on the Mesocletodes abyssicola- group *, Zootaxa 2096 (1), pp. 214-256 : 245-251

Redescription of Mesocletodes robustus Por, 1965

( Figs 25–30 )

Type material (used for comparison):

Paratype: 1 female dissected, mounted on 2 slides, coll. no. Cop 52 1–2, Hebrew University of Jerusalem, Israel

Redescription is based on collected material: Angola Basin, 27.07.2000. 1 female, dissected, mounted on 6 slides, coll. no. SMF 31422/1–6 at station 346/1 (16°17.0’S / 05°27.0’E, 5389m) , 1 female, dissected, mounted on 7 slides, coll. no. SMF 31423/1–7 at station 346/7 (16°17.0’S / 05°27.0’E, 5389m) , 1 female mounted on 1 slide, coll. no. SMF 31435/1 at station 346/6 (16°17.0’S / 05°27.0’E, 5389m) .

Description of female. Habitus ( Figs 25B ) of cylindrical shape, no clear distinction between prosome and urosome. Body length 1327µm. Rostrum tipped, slightly protruding, with 2 sensilla. Cphth blotched as depicted, with several setules and with dorsal triangular cuticular process, which is curved and points in a posterior direction. Process with 4 distal apertures. Distal margins of cphth and prosomites with denticulated hyaline frill, urosomites with bare hyaline frill. Long sensilla on distal margins of body somites, except the penultimate one. P2–P4 bearing body somites dorsally with rows of spinules, P5-bearing somite and urosomites with additional lateral rows of spinules. Telson square, with dorsal cuticular process peaking in a small spine (like M. abyssicola ), 1 sensillum on each side of the process. Somites covered by spinules. Genital double-somite incompletely fused. P2–P4 bearing body somites with thickened cuticula at the insertions of legs.

A1 ( Fig. 26A ) 8-segmented, acrothek on segments 4 and 8. First segment without setae, proximally and medially with 1 row each of spinules. Second segment with a strong protrusion bearing a strong, bipinnate seta. Spines of A1 with 1 STE each.

Setal formula: I:0, II:8, III:6, IV:3+Aes, V:1, VI:2, VII:3, VIII:7 +Aes.

A2 ( Fig. 26B ) basis with spinules. Exp 1-segmented with 2 bipinnate setae of unequal length. Enp1 with corona of spinules. Enp2 with long, outer spinules, 2 bipinnate, medial spines with 1 STE each and 6 terminal elements. 1 outer unequal bipinnate spine, 3 geniculated, coarse bipinnate setae, 1 annulated, bipinnate seta fused to 1 fine, unipinnate inner seta at its base. Enp2 with terminal spinules of different length.

Md lost during preparation.

Mxl ( Fig. 27A ) arthrite of the praecoxa with 10 armature elements: 2 surface setae (depicted beneath). 2 toothlike setae with strong terminal spinules, 1 undulated, tooth like seta with strong spinules terminally, 2 brushlike setae, 1 depressed, swung, unipinnate seta, 1 unipinnate seta on a protrusion, 1 single, unipinnate seta, very long spinules on the surface (depicted beneath). Coxal endite with 5 setae, incompletely fused to pinnate terminal seta. Corona of spinules at the base of coxal endite. Basis with 7 setae, segments of enp and exp not expressed.

Mx ( Fig. 27B ) syncoxa with several rows of spinules and 2 endites. Proximal endite with 1 bare seta, distal endite with 3 setae: 1 strongly bipinnate and 2 bare setae. Basis with 3 setae: 2 pinnate setae, incompletely fused to basis and 1 bare seta. Enp small, 1-segmented, with 2 long, bipinnate setae.

Mxp ( Fig. 27C ) syncoxa with 2 long, bipinnate setae. Enp 1 segmented and fused to strong claw. Basis and enp lost during dissection.

P1 ( Fig. 28A ) coxa with several spinules. Basis with 1 inner and 1 outer spine, net-like structure close to the insertion of outer seta. Exp 3-segmented. Exp1 and exp2 without inner armature. Exp3 with 1 outer and 2 terminal, bipinnate spines with distal tube pores and 1 short bipinnate inner seta. Enp 1-segmented, extremely long and broad. Enp with 1 bare inner seta, 1 bipinnate, terminal seta and 1 bipinnate, terminal spine. Intercoxal sclerite ( Fig. 27B ) with 2 triangular holes, covered with many long strong spinules. Setal formula as in Table 5.

P 2–P 4 ( Figs 28C, D ; 29A, B ) coxae with several spinules. Bases with outer seta and inner setular tufts. Net-like structure close to the outer seta of P2, P3 and P4 with a lateral porus. Exp 3- segmented, increasing in length posteriorly. Exp1 without inner armature, but with inner spinules. Exp2 with inner seta and 5 long, inner spinules. Exp3 with 2 bipinnate outer spines, 1 bipinnate, terminal spine, 1 bipinnate seta terminally and 2 (P2 and P3) or 1 (P4) inner, bipinnate setae. P2–P4 Enp 1-segmented, decreasing in length and broadness posteriorly. Enp with 1 bare seta, 3 bipinnate setae and 1 bipinnate spine (P2 and P3) or 2 bare and 2 bipinnate setae (P4). All spines with spinules close to their insertions. Intercoxal sclerites as depicted for P2. Setal formula as in Table 5.

P5 ( Fig. 30) outer lobe of basenp with spinules and setophore. Inner lobe of basenp barely protruding, with inner setular tuft, spinules and 1 long inner seta, 1 long, median seta and one short, outer seta. The outer and median seta are close to each other, the long, inner seta separated from the former two elements. Net-like structure close to exp insertion. Exp approximately 9 times longer than broad, with 5 setae and 1 terminal tube pore. Exp covered by spinules, especially in the proximal part. Setal formula as in Table 5.

Furcal rami ( Fig. 25A ) approximately 13 times longer than broad (the widest part measured at its base), the insertion surrounded by spinules of anal somite. Furcal ramus with spinules and 7 setae: I and II close to the beginning (ventral and lateral) III subdistally, IV and V terminally, VI ventrally terminal, VII in the middle of furcal ramus. Setae I, II, III, VI are bare, IV lost during sample treatment, V bipinnate (lost during preparation) VII triarticulate and bare.

Male unknown.

Figures

FIGURE 25: Mesocletodes robustus, female. A, telson and furcal rami lateral view; B, habitus lateral view, with detail of surface structure of Cephalothorax and overall surface structure illustrated; scale bars: 50µm.

FIGURE 26: Mesocletodes robustus, female. A, antennula; B, antenna; scale bars: 50µm.

FIGURE 27: Mesocletodes robustus, female. A, maxillula; B, maxilla; C, syncoxa of maxilliped; scale bar: 50µm.

FIGURE 28: Mesocletodes robustus, female. A, P1; B, P1 intercoxal sclerite; C, P2 intercoxal sclerite; D, P2; scale bars: 50µm.

FIGURE 29: Mesocletodes robustus, female. A, P3; B, P4; scale bar: 50µm.