Archinotodelphys cinctus, Kim & Boxshall, 2020

Kim, Il-Hoi & Boxshall, Geoff A., 2020, A revision of the family Archinotodelphyidae Lang, 1949 (Copepoda: Cyclopoida Oithonida), with the recognition of 15 new species, Zootaxa 4801 (1), pp. 1-56 : 17-20

Archinotodelphys cinctus sp. nov.

(Figs. 7, 8)

T ype material. Holotype ♀ (MNHN-IU-2014-21195; dissected and mounted on a slide).

Type host. Bathystyeloides enderbyanus (Michaelsen, 1904) (MNHN-IT-2008-1441 = MNHN S1 /BAT.B/36) .

Type locality. Atlantique Tropical Campagne EUMELI 2 cruise, RV Atalante, Cape Verde basin, Stn CHP 07 (18°30’0’’N, 21°1’0.012’’W), depth 3120 m, IFREMER coll., 10 February 1991 .

Etymology. The name of the species refers to the presence of 5 setae on the first endopodal segment of the mandible.

Female. Body (Fig. 7A) length 1.62 mm; prosome 879 μm long; cephalosome 436×600 μm, dorsal cephaloso- mic shield with posteriorly extended posterolateral corners and distinctly broader than free pedigerous somites. Urosome (Fig. 7B) 5-segmented: fifth pedigerous somite 218 μm wide. Genital double somite 222×189 μm, gradually narrowing posteriorly; bearing paired genital apertures dorsolaterally at 38% of double-somite length. Three free abdominal somites 91×127, 76×124, and 109×127 μm, respectively; anal somite ornamented with minute spinules along posteroventral border near base of caudal rami (Fig. 7C). Caudal ramus (Fig. 7C) about 4.8 times longer than wide (203×42 μm) and armed with 6 setae; lateral seta located about at mid-length of ramus.

Rostrum (Fig. 7D) about 127×117 μm, tapering to pointed apex. Antennule (Fig. 7E) 450 μm long and 17-seg- mented; third segment with trace of subdivision; setation not observed due to loss of setae. Antenna (Fig. 7F) with inner seta on basis, plus 2 exopodal setae (1 small and setule-like); first endopodal segment with 1 seta on inner margin; second with 5 setae (4 at inner distal corner and 1 on inner margin); third 73×23 μm, longer than second, and armed with slender curved claw plus 6 setae.

FIG. 7. Archinotodelphys cinctus sp. nov. holotype female. A, habitus, dorsal; B, urosome, dorsal; C, right caudal ramus, ventral; D, rostrum; E, antennule segmentation pattern; F, antenna; G, labrum; H, mandible; I, paragnath; J, maxillule. Scale bars: A, 0.2 mm; B, 0.1 mm; C–I, 0.05 mm.

FIG. 8. Archinotodelphys cinctus sp. nov. holotype female. A, biting edge of coxal gnathobase of mandible; B, maxilla; C, maxilliped; D, leg 1; E, leg 2; F, leg 4; G, leg 5. Scale bars: A, 0.02 mm; B–G, 0.05 mm.

Labrum (Fig. 7G) tapering posteriorly with broad posteromedian lobe; posterolateral corners and posteromedian lobe setulose. Mandible (Fig. 7H) with 8 teeth, 2 setae, and rows of spinules on coxal gnathobase (Fig. 8A), three proximal teeth spinulose; basis with 1 seta on medial margin: exopod 4-segmented, armed with 1, 1, 1, and 2 setae; endopod with 5 setae on first segment and 10 setae on second. Paragnath (Fig. 7I) ornamented with 1 small denticle at outer distal region, minute spinules apically, and setules on inner surface. Maxillule (Fig. 7J) with 11 setae (including 1 on ventral surface) on precoxal arthrite, 1 seta on coxal endite, 2 unequal setae on coxal epipodite, 1 spine and 6 setae on medial margin of basis, 4 setae on exopod and 9 setae on 2-segmented endopod (5 and 4 on first and second segments, respectively); all setae on endopod and 3 distal setae on basis naked. Maxilla (Fig. 8B) 6-segmented with suture line between precoxa and coxa; precoxa with 4 and 1 setae on proximal and distal endites, respectively; 3 setae present on each of proximal and distal coxal endites; basis bearing large claw ornamented with fine spinules along concave margin and bearing 2 unequal setae; endopod 3-segmented, with 2, 2, and 4 setae on first to third segments. Maxilliped (Fig. 8C) 4-segmented with setal formula 6, 2, 3, and 3; first segment partly subdivided by fold into proximal and distal parts bearing 4 and 2 setae, respectively.

Legs 1–4 with 3-segmented rami; armature formula as in family diagnosis. Outer basal seta of leg 1 large but outer basal seta on legs 2 to 4, small, all outer setae on basis naked (Fig. 8D–F). Inner distal spine on basis of leg 1 55 μm long and with smooth margins.

Leg 5 (Fig. 8G) 2-segmented; protopodal segment wider than long and clearly articulated from somite; exopodal segment about 1.9 times as long as wide (100×53 μm), outer margin convex, but inner margin straight; armed with 4 setae 205, 202, 69, and 149 μm in length from outermost to inner. Leg 6 represented by 1 spine and 1 seta in genital aperture.

Remarks. Archinotodelphys cinctus sp. nov. is similar to A. illgi sp. nov. in having 5 setae (4 + 1) on the second endopodal segment of the antenna and 2, 2, and 4 setae respectively on the first to third endopodal segments of the maxilla. The body form, the shape of the genital double-somite, and the segmentation and setation of the maxilliped are also similar in these two species. However, they can readily be distinguished by the presence of 5 setae on the first endopodal segment of the mandible in A. cinctus sp. nov. The possession of 5 setae is unique in the genus; most other species have 4 or 6 setae (see Table 2), with only a single new species, A. nudus sp. nov., bearing just a single seta. A total of 9 setae is carried on the endopod of the maxillule of A. cinctus sp. nov. compared to 10 in A. gurneyi , A. momus sp. nov., A. hexasetosus sp. nov. and A. illgi sp. nov., and 11 in A. curtus sp. nov. and A. polynesiensis . These differences justify the establishment of a new species to accommodate the material from Bathystyeloides enderbyanus .