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 bicornis sp. nov. ( Figs 7–11 ) Etymology. The name refers to the double cuticular process on the cephalothorax. Locus typicus : Angola Basin , (off Angola ), RV „Meteor“, Cruise M-48/1, 27.07.2000 . Holotype : 1 female , mounted on 1 slide, coll. no. SMF 31426/1 at station 346/4 ( 16°16.9’S / 05°27.0’E , 5389m ). Paratypes : 1 female , dissected, mounted on 12 slides, coll. no. SMF 31427/1–12 at station 346/2 ( 16°17.0’S / 05°27.0’E , 5389m ) ; 1 female , dissected, mounted on 6 slides, coll. no. SMF 31431/1–6 at station 346/8( 16°17.0’S / 05°27.0’E , 5390m ) ; 1 female , mounted on 1 slide, coll. no. SMF 31432/1 at station 346/2 ( 16°17.0’S / 05°27.0’E , 5389m ) ; 1 female , mounted on 1 slide, coll. no. SMF 31433/1 at station 346/5 ( 16°17.0’S / 05°27.0’E , 5389m ) ; 1 female , mounted on 1 slide, coll. no. SMF 31434/1 at station 346/1 ( 16°17.0’S / 05°27.0’E , 5389m ) . FIGURE 7: Mesocletodes bicornis sp. nov. , female (holotype). A, habitus lateral view; B, telson and furcal rami, lateral view; scale bar: 50µm. FIGURE 8: Mesocletodes bicornis sp. nov. , female (paratype). A, antennula; B, antenna; scale bars: 50µm. FIGURE 9: Mesocletodes bicornis sp. nov. , female (paratype). A, maxillula; B, maxilla; C, mandibula; D, maxilliped; E, P1; scale bars: 50µm. Description of female. Habitus ( Fig. 7A ) of cylindrical shape, no clear distinction between prosome and urosome. Body length 660µm. Rostrum small, not protruding, with 2 sensilla. Cphth dorsally with bifid, cuticular process, anterior part triangular, curved and pointing posteriorly, posterior part small and stout, triangular. Distal margins of cphth to second urosomite with denticulated, hyaline frill, the remaining urosomites with bare hyaline frill. Long sensilla on distal margins of body somites, except the penultimate one. P3–P5 bearing somites and second urosomite dorsally with bifid cuticular processes. Rows of spinules along posterior margins of somites, spinules increasing in length posteriorly. Telson square, dorsally with bifid, cuticular process peaked upward with posterior tip longer than the anterior one. A1 ( Fig. 8A ) 8-segmented, acrothek on segments 4 and 8. First segment without seta, proximally with corona of spinules and several spinules spread over the segment. Second segment with a strong protrusion bearing a strong, bipinnate seta. Third segment elongate, with 5 fine, long spinules at inner margin of the segment. Spines of A1 with 1 STE each. Setal formula: I:0, II:7, III:5, IV:2+Aes, V:1, VI:2, VII:3, VIII:6+Aes. A2 ( Fig. 8B ) basis with fine spinules. Exp incompletely fused to basis, 1-segmented, with 1 long, bipinnate and 1 short, bare seta. Enp1 with many fine, long spinules, a corona of spinules in the distal part and 3 strong spinules at the outer margin. Enp2 with 4 strong outer spinules, 2 medial bipinnate spines with 1 STE each and 6 terminal elements: 1 outer, bipinnate spine, 1 annulate seta, 2 geniculated setae with 3 pinnae each, 1 annulate seta distally with STE, seta fused to a small, bare seta at the base. Md ( Fig. 9C ) gnathobase with broad grinding face. Dorsally with transformed denticulated seta, beneath 2 spoonlike setae, followed by several strong toothlike elements. Palpus 1-segmented, with 1 bipinnate basal seta, 1 bipinnate exopodal seta and 4 endopodal setae, 3 of these located terminally. Mxl ( Fig. 9A ) arthrite of the praecoxa with long spinules and 10 armature elements: 2 bare surface setae (depicted beneath), 2 strong, tooth like setae with 1 strong spinule each, 1 strong, tooth like seta with 1 spinule and several strong pinnae, 2 brushlike setae, 1 unipinnate seta, 1 bare, 1 unipinnate, single seta. Coxa with spinules at the base of arthrite, with long spinules and 5 setae, strongest seta fused to coxa. Basis with 5 bipinnate setae and 4 spinules. Mx ( Fig. 9B ) syncoxa with 2 endites. Proximal endite with 1 seta (seta lost during dissection), distal endite with 3 setae: Endite drawn out into strong claw with two accompanying bare setae. Basis with a row of small spinules and 3 setae: main seta incompletely fused to basis, 1 strongly bipinnate seta and 1 bare slender seta subterminally. Enp 1-segmented, very small, with 2 bipinnate setae. Mxp ( Fig. 9D ) syncoxa lost during preparation. Basis with many fine spinules, unarmed. Enp 1- segmented, fused to strong claw. P1 ( Fig. 9E ) coxa with several spinules. Basis with 1 inner and 1 outer spine. Exp 3-segmented. Exp1 and exp2 without inner armature. Exp3 inner seta transformed to tube pore. Exp3 with 3 bipinnate spines with 1 STE each. Enp biarticulate. Enp1 with inner seta. Enp2 with 2 terminal setae. Setal formula as in Table 2. P2–P 4 ( Figs 10A–C ) coxae with several spinules (P2 lost during preparation. However, it was observed that P2 and P3 were identical with respect to the setation). Bases with outer seta and inner setular tufts. Exp 3- segmented. Exp1 P3 and P4 with few fine, inner spinules. Exp2 with inner, bipinnate seta and outer spine. Exp3 with 2 bipinnate, outer spines, 2 bipinnate setae terminally and 2 (P2 and P3) or 1 (P4) inner bipinnate setae. Enp biarticulate. Enp1 without seta. Enp2 with 4 bare setae. Spines with spinules at their insertionpoints. Setal formula as in Table 2. TABLE 2 : Mesocletodes bicornis sp. nov. setal formula of swimming legs P1–P5.
P1
P2
P3
P4
P5
FIGURE 10: Mesocletodes bicornis sp. nov. , female (paratype). A, P3; B, P3 coxa and basis; C, P4; scale bar: 50µm. P 5 ( Fig. 11 ) basenp with several spinules. Outer lobe of basenp with setophore bearing 3 spinules and 1 outer seta. Inner lobe not protruding, with 1 long inner, 1 long median, bipinnate and 1 short, outer seta. The outer and median seta are close to each other, the long, inner seta separated from the former two elements. Exp approximately 5 times longer than broad, with 5 setae and 1 apical tube pore. Exp sparsely covered with spinules. Setal formula as in Table 2 . Furcal rami ( Fig. 7B ) approximately 13 times longer than broad (the widest part measured at its base), the insertion surrounded by spinules of anal somite. Furcal ramus with distal tube pore and 7 setae: setae I and II in the middle of caudal ramus with spinules at their insertions, seta III subdistally, setae IV and V distally, seta VI distally and arising ventrally, seta VII dorsally in distal half. Setae I and II bare, setae III, IV, V lost during sample treatment, seta VI bare, VII triarticulate and bare. Male unknown.