Cerviniella hitoshii Kihara & Arbizu, 2012, sp. nov.

Cerviniella hitoshii sp. nov.

(Figs 11–15, 20–21)

Type locality. Arctic Ocean, Laptev Sea (78°08.19' N, 133°19.94' E), 796 m depth.

Type material. Holotype female dissected on 16 slides (reg. no. SMF 37031) from station PS27#038/2458-1, multi corer 6, collected 05/09/1993. Undissected paratypes consist of 3 copepodites (CII, CIII and CIV with reg. nos. SMF 37032, 37033 and 37034, respectively) from station PS27#047/2465-1, multi corer 1–4, collected 08/09/ 1993. All material collected by the junior author during the Expedition ARCTIC’93, Leg ARK-IX/4 of RV Polarstern.

Description. FEMALE. Total body length 772.0 μm. Largest width measured at posterior margin of cephalic shield: 272.0 μm. Body (Figs 11 A, 20A–C) with no clear distinction between prosome and urosome, body somites gradually tapering posteriorly.

Prosome (Figs 11 A, 20A–C, 21D) 4-segmented, with first pedigerous somite incorporated into cephalothorax. Cephalothorax with anastomosing pattern near rostrum (Fig. 21 C) and along margins (Figs 11 A, 20A–B); additional ornamentation consisting of sensilla and pores as illustrated in Figure 11 A; posterior margin smooth. Pedigerous somites with reticulation along posterior margins and ornamentation consisting of sensilla as illustrated in Figure 11 A; epimera of second and third pedigerous somites expanded posteriorly; posterior margins serrate. Gonads extending from posterior region of mouth parts until middle area of somite bearing P2 (Fig. 21 D).

Urosome (Figs 11 A, 12A–B, 20A–C) 5-segmented, comprising P5-bearing somite, genital double-somite, 2 free abdominal somites and anal somite. Urosomites with surface ornamentation consisting of sensilla and minute spinules as illustrated in Figures 12 A–B; posterior margin serrate.

Genital double-somite (Figs 11 A, 12A–B, 20A–B) original segmentation indicated by transverse, serrate surface ridge with reticulation and sensilla dorsally, and hook-like projections laterally (Fig. 21 B), completely fused ventrally; genital field (Fig. 12 C) with surface smooth, copulatory pore located in median depression; gonopores covered by opercula derived from sixth legs and by anteriorly directed flap arising from somite wall; P6 bearing 3 pinnate setae.

Anal somite (Figs 11 A–B, 12A–B, 20A–C) with reduced anal operculum with large anal opening; surface ornamentation consisting of pair of sensilla dorsally and setules ventrally; posterior margin smooth.

Caudal rami (Figs 11 A, C–D) slightly asymmetrical; 3.5X as long as maximum width, tapering posteriorly. Each ramus with 7 setae: seta I closely set to seta II, both pinnate and inserted at proximal third; seta III pinnate and positioned ventrolaterally; setae IV and V fused basally, seta IV pinnate and seta V naked, both bases covered by membranous extension; seta VI minute and flattened, displaced ventrally; seta VII tri-articulate at base and pinnate.

Rostrum (Figs 11 E, 21C) fused to cephalic shield; bluntly triangular; with midventral tube-pore near apex.

Antennule (Figs 12 D, 21A) 5-segmented, and surface ornamentation consisting of small denticles as shown in Figure 12 D. Segment I with pointed projection on posterior distal corner; segment II longest, double segment completely fused dorsally but with original segmentation apparent in ventral view, with aesthetasc fused basally to seta and set on distinct pedestal; segment V with aesthetasc fused basally to pinnate seta. Armature formula: I-[1 pinnate spine], II-[15 pinnate + 7 pinnate spines + (1 + ae)], III-[3 pinnate], IV-[4 pinnate], V-[5 pinnate + (1 pinnate + ae)].

Antenna (Fig. 13 A) 3-segmented, comprising coxa, allobasis, and 1-segmented endopod. Coxa small, with no ornamentation. Basis and enp-1 fused, forming elongate allobasis, with spinules along abexopodal margin and patch of spinules and denticles as shown in Figure 13 A, abexopodal seta pinnate. Free endopod about half length of allobasis; ornamented with row of spinules proximally, row of spinules along distal corner and sparse spinules on posterior surface; medial armature consisting of 2 pinnate setae and 1 spine; apical armature consisting of 4 spines and 3 setae (2 naked and 1 pinnate), subdistal seta shortest. Exopod 4-segmented; exp-1 as long as next 3 segments combined; armature formula: I-[2 pinnate], II-[1 pinnate], III-[1 pinnate], IV-[3 pinnate].

Mandible (Fig. 13 B). Coxa with well developed gnathobase bearing several multicuspidate teeth and 1 pinnate seta (detailed drawing in Fig. 13 B) around distal margin. Palp well developed, comprising basis, endopod and exopod. Basis with 4 pinnate setae and surface ornamentation as indicated in Figure 13 B. Endopod 1-segmented; medial armature consisting of 3 setae (1 naked and 2 pinnate); apical armature consisting of 5 setae (4 naked and 1 pinnate). Exopod 3-segmented; armature formula: I-[2 pinnate], II-[1 pinnate], III-[3 pinnate].

Maxillule (Fig. 13 C). Praecoxa with transverse fold and rows of spinules as shown in Figure 13 C; arthrite well developed, with 2 setae (1 naked and 1 pinnate) on anterior surface, with 7 spines (3 pinnate and 4 striated) and 3 pinnate setae along distal margin, posterior surface with 2 pinnate setae. Coxa with cylindrical endite, bearing 6 setae (5 naked and 1 pinnate) distally; epipodite represented by 1 pinnate seta. Basis and endopod fused, with row of spinules on anterior surface (not represented); basis with 11 naked setae; endopod incorporated into basis, represented by 3 naked setae. Exopod 1-segmented, with 3 pinnate setae.

Maxilla (Fig. 13 D) comprising syncoxa, allobasis and 3-segmented endopod. Syncoxa with 4 endites; proximal praecoxal endite with 4 setae (1 naked and 3 pinnate); distal praecoxal endite almost completely incorporated into syncoxa, with 3 setae (1 pinnate and 3 naked); proximal coxal endite with 3 naked setae; distal coxal endite with 2 naked setae and 1 pinnate spine; rows of spinules and setules along outer margin and additional ornamentation as shown in Figure 13 D. Allobasis endite forming strong claw; accessory armature consisting of 2 naked setae and 1 pinnate spine; endopodal armature of maxillar allobasis represented by 1 seta and 1 spine. Endopod with armature formula: I-[1 + 1 geniculate], II-[2 geniculate], III-[3 + 1 geniculate].

Maxilliped (Fig. 14 A, 21D) with elongated protopod and 2-segmented endopod. Protopod with rows of long setules along outer margin and rows of spinules on anterior surface; each syncoxal endite with 1 pinnate seta and 1 pinnate spine; basal endite represented by 1 pinnate seta and 1 pinnate spine. Endopod with spinules along outer margin and anterior surface; armature formula: I-[1 pinnate], II-[2 pinnate spines + 2 pinnate setae].

P1 (Figs 14 B, 21D) biramous. Intercoxal sclerite well developed, and with reticulated surface. Praecoxa with row of spinules along outer margin. Coxa with rows of spinules on anterior surface, small setules along distal margin, and long spinules along outer margin. Basis with 1 pinnate seta on inner corner of anterior surface and 1 pinnate seta on outer distal margin (not illustrated); ornamentation consisting of patches of setules on anterior surface. Exopod 1-segmented; with rows of setules on proximal area, and rows of minute spinules around bases of outer setae; 5 setae (with setules proximally and pinnate distally) along outer margin, 2 pinnate setae apically, and 3 pinnate setae along inner margin. Endopod 1-segmented, half length of exopod, and with rows of spinules along outer margin; 2 pinnate setae along inner margin, 2 elements apically (outer apical element 1 pinnate seta and inner apical element missing on both sides of holotype) and 1 pinnate seta on distal outer corner.

P2–P4 (Figs 14 C, 15A–B) biramous. Intercoxal sclerite well developed (cordiform in P2 and almost rectangular in P3–P4), with reticulated surface and row of setules along distal margin. Praecoxa well developed (not illustrated). Coxa with rows of spinules and setules on anterior surface, small setules along distal and outer margins (P2–P3). Basis with scattered spinules on anterior surface (P2), distal margin with acute projection (P2–P3) and row of spinules (P2–P4), 1 pinnate seta on outer margin. Exopod-1 segmented; with row of setules along inner and outer margins, anterior surface with patch of setules proximally; outer and distal margins with acute projections. Endopod 2-segmented; enp-1 outer corner drawn out into blunt (P2) or acute (P3–P4) projection, with row of setules along outer margin, and 1 pinnate seta on inner distal corner; enp-2 outer margin with rows of setules (P2–P3) and conspicuous acute projection at midlength of the segment (P2–P3).

P1–P4 spine and seta formulae as follows:

P5 (Figs 14 D, 21B). Protopod fused to supporting somite and with 1 outer pinnate seta. Exopod with spinules along inner and outer margins; with 1 apical and 2 outer pinnate setae.

MALE. Unknown.

Etymology. The specific name hitoshii is dedicated to the senior author’s father, Getulio Hitoshi Kihara.