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 * Author Menzel, Lena Author George, Kai Horst text Zootaxa 2009 2009-05-11 2096 1 214 256 https://biotaxa.org/Zootaxa/article/view/zootaxa.2096.1.14 journal article 10.11646/zootaxa.2096.1.14 1175-5326 5320482 Mesocletodes meteorensis sp. nov. ( Figs 18–24 ) Etymology. The name refers to the RV “Meteor”, on board of which the sample containing this species was taken. Locus typicus : Angola Basin , (off Angola ), RV „Meteor“, Cruise M-48/1, 27.07.2000 . Holotype : 1 female , dissected, mounted on 7 slides, coll. no. SMF 31424/1–7; at station 346/1 ( 16°17.0’S / 05°27.0’E , 5389m ). Paratype : 1 female , dissected, mounted on 10 slides, coll. no SMF 31425/1–10 at station 346/3 ( 16°17.0’S / 05°27.0’E , 5389m ) . Description of female . Habitus ( Fig. 18 ) of cylindrical shape, no clear distinction between prosome and urosome. Body length 627µm. Rostrum small, not protruding, with 2 sensilla. Cphth with a dorsal cuticular process which is triangular, curved and pointing backwards. Process with several spinules. Cphth with several fine spinules. Distal margins of cphth and bodysomites with smooth hyaline frill. Long sensilla on distal margins of body somites, except the penultimate one. Spinules arranged in rows and decreasing in length posteriorly. Body blotched with small depressions (as depicted for telson). Genital double somite incompletely fused. Telson square, dorsally with bifid cuticular process peaked backwards: robust at the insertion, anterior and posterior peaks short, of equal length. Caudal region of telson with several rows of spinules, lateral to the process 1 sensillum on each side. A1 ( Fig. 19A ) 8-segmented, acrothek on segments 4 and 8. First segment without seta but with 2 rows 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:6, III:6, IV:2+Aes, V:1, VI:2, VII:4, VIII:6+Aes. A2 ( Fig. 19B ) basis with fine spinules. Exp small, 1-segmented with 2 bipinnate setae of unequal length. Enp1 with few outer spinules. Enp2 covered by spinules, with 2 medial bipinnate spines with 1 STE each and 6 terminal elements. 1 outer bipinnate spine, 2 geniculated setae, 1 bipinnate seta, 1 bipinnate seta with STE, this seta fused to a small bare seta at the base. Md ( Figs 20E, F ) gnathobase with broad grinding face and 3 rows of spinules. Grinding face composed of 1 imbricate, distally carved seta, beneath 1 bare, spoon like seta, followed by several fused toothlike elements. Strong bare seta ventrally. Palpus 2- segmented with spinules. Basis with 1 seta (seta lost during preparation). Enp 1- segmented, with 4 terminal and 1 subterminal setae. Exopodal lobe with 2 bipinnate setae. Mxl ( Figs 20B, C ) arthrite of the praecoxa with long spinules and 10 armature elements: 2 bare surface setae (depicted beneath), 2 strong, tooth like setae with spinules, 1 strong, unarmed tooth like seta, 1 strong, undulated unipinnate seta, 1 brushlike seta, 1 compact, unipinnate seta, 1 slender, unipinnate seta, 1 strong, unipinnate seta. Coxa with long spinules and 5 setae, strongest seta brushlike, incompletely fused to coxa. Basis with 7 setae and several spinules. Mx ( Fig. 20A ) syncoxa with 2 endites. Proximal endite with 1 bare seta, distal endite with 3 setae: 1 strongly bipinnate and 2 bare setae. Basis with 2 strongly bipinnate setae and 2 bare setae. Enp 1-segmented, very small, with 2 bipinnate setae. Mxp ( Fig. 20D ) syncoxa with many fine spinules and 2 bipinnate setae of unequal length. Basis with fine outer and coarse inner spinules. Enp 1-segmented, fused to strong claw. P1 ( Fig. 21A ) coxa with several spinules. Basis with 1 inner and 1 outer spine, net-like structure close to outer seta. Exp 3-segmented. Exp1 and 2 without inner armature. Exp3 proximally with inner tube pore, 3 bipinnate spines with 1 STE each and 1 bare inner seta. Enp biarticulate. Enp1 with inner seta. Enp2 with 1 terminal, bipinnate spine, 1 terminal, bipinnate seta and 1 bare, inner seta. Setal formula as in Table 4. P 2–P 4 ( Figs 21B ; 22A, B ) coxae with several spinules, bases with outer seta and inner setular tufts, netlike structure close to outer seta. Exp 3-segmented, increasing in length and decreasing in breadth from P2 to P4. Exp1 with 5 (P3) or 4 (P4) fine, inner spinules. Exp1 without inner seta. Exp2 with inner, bipinnate seta and outer spine. Exp3 of P2 and P3 with 2 bipinnate, outer spines and 2 bipinnate setae terminally. P4 Exp3 with 2 outer, bipinnate spines, 1 terminal bipinnate and 1 inner, bipinnate seta. Second terminal seta probably lost during sample treatment. Enp biarticulate. Enp1 with inner bipinnate seta. P2–P4 Enp2 with 1 outer, 2 terminal and 1 inner setae. Spines with spinules at their insertion points. Setal formula as in Table 4. FIGURE 18: Mesocletodes meteorensis sp. nov. , female (holotype). Habitus lateral view, with detail of overall surface structure illustrated on telson; scale bar: 50µm. FIGURE 19: Mesocletodes meteorensis sp. nov. , female (paratype). A, antennula; B, antenna; scale bars: 50µm. FIGURE 20: Mesocletodes meteorensis sp. nov. , female (holotype). A, maxilla; B, maxillula; C, maxillular palpus; D, maxilliped; E, mandibula gnathobasis; F, mandibular palpus; scale bar: 50µm. FIGURE 21: Mesocletodes meteorensis sp. nov. , female (paratype). A, P1; B, P2; scale bars: 50µm. FIGURE 22: Mesocletodes meteorensis sp. nov. , female (paratype). A, P3; B, P4; scale bars: 50µm. FIGURE 23: Mesocletodes meteorensis sp. nov. , female (holotype). P5; scale bar: 50µm. FIGURE 24: Mesocletodes meteorensis sp. nov. , female (holotype). telson and furcal rami lateral view; scale bar: 50µm. 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. TABLE 4 : Mesocletodes meteorensis sp. nov. setal formula of P1–P5. P 5 ( Fig. 23 ) basenp with several spinules. Outer lobe of basenp with setophore bearing 3 spinules and 1 outer seta. Inner lobe not protruding, with 1 inner, 1 median and 1 outer seta. The outer and median seta are close to each other, the long inner seta separated from the former two elements. Exp approximately 3 times longer than broad, with 5 setae and 1 terminal tube pore. Exp sparsely covered with spinules. Net-like structure between outer and inner lobe of basenp. Setal formula as in Table 4 . Furcal rami ( Fig. 24 ) approximately 3 times longer than wide (width measured at its base), insertion surrounded by spinules of anal somite. Furcal ramus with 7 setae: setae I and II ventral and lateral accompanied by 1 spinule each close to the insertion, seta III dorsally subterminal, setae IV and V terminal, seta VI ventrally terminal, seta VII in the middle of furcal ramus. Setae I, II, III, VI are bare, seta IV long and bipinnate, seta V short and bipinnate, seta VII triarticulate and bare. Male unknown.