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 angolaensis sp. nov. ( Figs 2–6 ) Etymology. The species name refers to the sampling location, the Angola Basin. Locus typicus : Angola Basin (off Angola ), RV „Meteor“, Cruise M-48/1, 27.07.2000 . Holotype : 1 male , dissected, mounted on 9 slides, coll. no. SMF 31430/1–9 at station 346/1 ( 16°17’S , 05°27’E , 5389m ). Description of male. Habitus ( Figs 2 A, C, D ) of cylindrical shape. Body length 642µm. No clear distinction between prosome and urosome. Distal margins of cphth and free thoracic somites with denticulated, textured hyaline frill ( Fig. 2B ) and, except the penultimate somite, with fine, long sensilla. Urosomites with long spinules inserting just anteriorly of the hyaline frill. Rostrum not protruding, with 2 sensilla. Cphth without cuticular process, dorsally and laterally with slight depressions, cuticula with nearly symmetric pattern and symmetrically arranged sensilla. Ventral margin of cphth with small spinules and few sensilla. Telson nearly square from dorsal view, slightly tapering posteriorly, ventrally with spinules, dorsally with strong, cuticular process ( Fig. 6A ). Cuticular process on telson with basal swelling, distally peaked, long and narrow. Laterally with 1 sensillum on each side. Lateral edges of pleurotergites of P2–P4 bearing prosomites with thickened cuticula and several spinules. P3–P4 bearing somites with 2 dorsal hyaline protrusions each bearing a long sensillum and, laterally of these, a row of spinules. P5 bearing somite laterally with 2 rows of small spinules and few strong spinules close to the hyaline frill. A1 ( Fig. 3A ) 7-segmented, haplocer, acrothek on segments IV and VII. First segment without seta, ornamented with strong spinules proximally and subdistally, with small spinules subdistally on anterior face. Second segment with a strong protrusion bearing a strong, bipinnate seta. Segment III very short. Aes of segment IV extremely elongate and large. Segments IV and V with 2 and 1 tripinnate seta(e) respectively. Segments IV–VII arranged in a loop. Spines of A1 with 1 STE each. Setal Formula: I:0, II:7, III:3, IV:5+Aes, V:2, VI:2, VII:7+Aes. A2 ( Fig. 3B ) with basis, seemingly without exp. Enp1 with 6 long spinules. Enp2 with 3 long and several small spinules, 2 medial spines with 1 STE each, terminally with 4 bipinnate setae, 2 of which geniculated. Mouthparts atrophied, could not be traced due to their strong reduction. FIGURE 2: Mesocletodes angolaensis sp. nov. , male. A, habitus dorsal view, cephalothorax and thorax; B, structure of hyaline frill at distal margins of body somites; C, habitus lateral view, cephalothorax and thorax; D, habitus lateral view, urosome; scale bars: 50µm. FIGURE 3: Mesocletodes angolaensis sp. nov. , male. A, antennula; B, antenna; scale bars: 50µm. FIGURE 4: Mesocletodes angolaensis sp. nov. , male. A, P1; B, P2; scale bars: 50µm. FIGURE 5: Mesocletodes angolaensis sp. nov. , male. A, P3; B, P4; C, P4 coxa and basis; scale bar: 50µm. FIGURE 6: Mesocletodes angolaensis sp. nov. , male. A, telson and furcal rami lateral view, arrow highlighting distal tube pore; B, P5; scale bars: 50µm. P1 ( Fig. 4A ) coxa with several rows of spinules, with fine spinules close to inner and with coarser spinules close to outer margin. Basis at inner margin with setular tuft, with 1 inner and 1 outer spine. Exp 3- segmented. Exp1 and Exp2 without inner armature. Exp3 with 1 outer bipinnate spine with STE, 2 terminal and 1 inner, bipinnate seta. Enp 2-segmented. Enp1 without inner seta, Enp2 with 1 inner, 1 terminal and 1 outer, bipinnate seta. Outer seta short and with STE. All segments with inner setules and outer spinules. Spinules near insertion of spines. Intercoxal sclerites are U-shaped and bare. Setal formula as in Table 1. TABLE 1 : Mesocletodes angolaensis sp. nov. setal formula of swimming legs P1–P5

Exp	Enp
P1
P2
P3
P4
P5	2-1-1	1-1-0

P 2–P 4 ( Figs 4B ; 5A, B, C ) coxa with spinules as shown for P3. Basis with inner setular tufts and outer seta (as illustrated for P4). Exp 3-segmented. Exp1 with fine spinules at inner margin. Exp2 with inner, bipinnate seta. Exp3 with 2 outer, bipinnate spines, 1 terminal, unequally bipinnate spine and 1 bipinnate seta, with 2 (P2 and P3) or 1 (P4) inner, bipinnate seta(e). Enp biarticulate. Enp1 with inner, bipinnate seta and fine, outer spinules. Enp2 of P2 and P3 with 4 bipinnate setae, Enp2 of P4 lost during dissection. Spinules near insertion of spines. Intercoxal sclerite as in P1. Setal formula as in Table 1. P 5 ( Fig. 6B ) outer part of basenp with setophore, 3 spinules and long bipinnate seta. Inner part of basenp barely protruding, with 1 long, strong, inner seta and 1 short, bare, outer seta. Exp about 4 times longer than basal width, proximally with 2 long spinules, 2 outer, 1 terminal and 1 inner setae and 1 STE. Setal formula as in Table 1. P 6 reduced to 1 seta. Furcal rami ( Fig. 6A ) about 13 times longer than wide at their insertion. Entirely covered by spinules, insertion surrounded by coarse spinules of anal somite. Furcal ramus with 7 setae: I and II close together laterally in proximal third, seta III inserted subdistally dorsolaterally, IV, V and VI inserting terminally, VII dorsally in the middle. Setae I, II, III, IV and VI bare, Seta V broken, seta VII triarticulated and bare. Furcal ramus with tube pore terminolaterally (highlighted by arrow in Fig. 6A ). Female unknown.