Archinotodelphys antarcticus, 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 : 20-24

Archinotodelphys antarcticus sp. nov.

(Figs. 9-11)

Type Material. Holotype ♀ (MNHN-IU-2014-21196) and 4 paratype ♀♀ (MNHN-IU-2014-21197). 1 dissected paratype ♀ in the collection of IHK.

Type host. Molgula pedunculata (Herdman, 1881) (MNHN-IT-2008-5650 = MNHN S3/MOL.A/35).

Type locality. South Georgia, cruise of SOSC Islas Orcadas, Stn 131 (59°27’S, 27°02’W), depth 86-101 m, trawl, 27 February 1976 .

Etymology. The new name refers to the type locality of this species, the Antarctic.

Additional non-type material. 1♀ (intact) (MNHN-IU-2018-1923) in Molgula hodgsoni Herdman, 1910 (MNHN-IT-2008-5550 = MNHN S3 /MOL.A/152), South Georgia, Cruise 575 of SOSC Islas Orcadas, Stn 26 (53°43.1’S- 36°49.3’W), depth 188-192 m, 17 May 1975 . 1 ♀ (dissected) (MNHN-IU-2009-5726) in M. hodgsoni (MNHN-IT-2018-16 = MNHN S3 /MOL.A/381), Antarctic , Terre Adelie , CEAMARC cruise, R. V. Aurora Australis, Stn 26AEV436 (66°32´S, 140°03´E), depth 176–288 m, IPEV-AAD-MNHN coll., 13 January 2008 .

1♀ 1♂ (both dissected) in Molgula euplicata Herdman, 1923 (MNHN-IT-2008-5499 = MNHN S3 /MOL.A/286), Weddell Sea, EPOS 3 cruise, RV Polarstern, Stn GSN 14 (71°06.2´S, 12°33.5´W), depth 499-515 m, 19 February 1989 .

Female. Body (Fig. 9A) narrow, large, 3.32 mm long; prosome 1.74 mm long; cephalosome 969 μm long, with angular posterolateral corners on dorsal cephalosomic shield; first pedigerous somite 704 μm wide, distinctly narrower than cephalosome and second pedigerous somite. Urosome (Fig. 9B) 5-segmented: fifth pedigerous so FIG. 9. Archinotodelphys antarcticus sp. nov. paratype female. A, habitus, dorsal; B, urosome, dorsal; C, right caudal ramus, dorsal; D, egg sac; E, rostrum; F, antennule; G, antenna; H, labrum; I, paragnath; J, maxillule. Scale bars: A, D, 0.5 mm; B, 0.2 mm; C, E, F, 0.1 mm; G, H, 0.05 mm.

FIG. 10. Archinotodelphys antarcticus sp. nov. paratype female. A, mandible; B, maxilla; C, maxilliped; D, leg 1; E, leg 2; F, leg 4; G, leg 5; H, genital aperture on right side, dorsal. Scale bars: A–G, 0.1 mm; H, 0.05 mm.

FIG. 11. Archinotodelphys antarcticus sp. nov. male. A, habitus, dorsal; B, urosome, ventral; C, antennule; D, leg 5; E, leg 6. Scale bars: A, 0.2 mm; B, 0.1 mm; C–E, 0.05 mm.

mite 436 μm wide, with tapering lateral margins. Genital double-somite 473×327 μm, with nearly parallel lateral margins; bearing paired genital apertures dorsolaterally at anterior third. Three free abdominal somites 297×255, 242×224, and 212×218 μm, respectively. Caudal ramus (Fig. 9C), about 5.9 times longer than wide (400×68 μm), armed with 6 naked setae; outer lateral seta located at mid-length of ramus. Egg sac (Fig. 9D) oval, 836×518 μm; each egg about 170 μm in diameter.

Rostrum (Fig. 9E) longer than wide, evenly tapering with small lobe at blunt tip. Antennule (Fig. 9F) 723 μm long, gradually narrowing distally, 17-segmented; armature formula 3, 5, 8, 2, 2, 6, 4+aesthetasc, 2, 2, 2, 2, 1+aesthetasc, 1, 1, 2, 2+aesthetasc, and 7+aesthetasc; all setae thin and naked; aesthetascs thin and short. Antenna (Fig. 9G) with short, unarmed coxa; basis with inner seta and 2 outer exopodal setae; first endopodal segment with 1 seta on inner margin; second with 4 setae, 3 at inner distal corner (1 with blunt tip) and 1 in middle of inner margin; third segment with 1 curved claw plus 6 setae, 3 of which bluntly tipped; setae on endopod remarkably short.

Labrum (Fig. 9H) strongly tapering, with spinulose posteromedian lobe and posterolateral corners. Mandible (Fig. 10A) with 2 setae and 7 teeth on coxal gnathobase; basis with 1 seta on medial margin; exopod 4-segmented with 1, 1, 1, and 2 setae; 2-segmented endopod with 4 setae on first segment and 10 setae on second. Paragnath (Fig. 9I) forming tapering lobe, obliquely truncate distally, ornamented with setules on medial surface. Maxillule (Fig. 9J) with 11 setae on precoxal arthrite (1 located at tip of digitiform lobe on ventral surface), 1 seta on coxal endite, 2 unequal setae on coxal epipodite, 8 setae on medial margin of basis, 4 setae distally on exopod; endopod incompletely 2-segmented with 6 setae on first segment and 4 setae on second. Maxilla (Fig. 10B) 5-segmented; suture line between precoxa and coxa distinct; precoxa with 1 spiniform process and 3 setae on proximal endite, and 1 seta on distal endite; coxa with 3 setae each on proximal and distal endites; basis with large claw bearing spinules along concave margin and 2 unequal setae; endopod 2-segmented, with 1 and 5 setae respectively on first and second segments. Maxilliped 4-segmented (Fig. 10C); incomplete transverse fold partially subdividing proximal segment; proximal segment with 1, 5, and 4 setae; basis with 1 seta; armature formula of endopod 3 and 3.

Legs 1–4 biramous with 3-segmented rami (Fig. 10D–F) and with same armature formula as preceding species. Inner distal spine on basis of leg 1 stout, 52 μm long, not extending beyond distal margin of first endopodal seg- ment.

Leg 5 (Fig. 10G) 2-segmented; protopodal segment clearly articulated with somite, wider than long, with 1 seta on outer margin; exopodal segment nearly rhomboidal, about 2.0 times longer than wide (218×112 μm), armed with 4 slender setae of very unequal lengths; longest apical seta 545 μm, extending to posterior margin of first free abdominal somite. Leg 6 (Fig. 10H) represented by 1 spine and 1 seta in genital aperture.

Male. Body (Fig. 11A) much smaller than female, 1.59 mm long. Cephalosome with extended posterolateral corners bearing blunt tip. Urosome (Fig. 11B) 6-segmented; fifth pedigerous 195 μm wide; genital somite 123×193 μm, slightly narrowing distally; four free abdominal somites 104×127, 95×111, 75×98, and 90×97 μm, respectively. Caudal ramus about 6.8 times as long as wide (204×30 μm).

Rostrum as in female.Antennule (Fig. 11C) 15-segmented, with geniculation between antepenultimate and penultimate segments; terminal segment attenuated; armature formula 3, 5, 6, 2, 2, 2, 2, 2, 2, 4, 2, 2, 4, 2, and 10+aesthetasc. Antenna, labrum, mandible, paragnath, maxillule, maxilla, maxilliped, and legs 1–4 as in female.

Leg 5 (Fig. 11D) exopodal segment 1.5 times longer than wide (60×39 μm), armed with 1 spine (inner distal ele- ment, 60 μm long) and 5 setae. Leg 6 (Fig. 11E) represented by 2 naked setae and 1 spinule on genital operculum.

Remarks. Only two species of Archinotodelphys are known to possess a 2-segmented endopod on the maxilla, A. hexasetosus sp. nov. and A. antarcticus sp. nov. In all other species the endopod is 3-segmented. The setation of the endopod varies: in A. hexasetosus sp. nov. the setation formula is 2, 6, whereas in A. antarcticus sp. nov. it is 1, 5. The total number of setae (6) is the same as reported here for several new species described below, but the setal formula for the 3-segmented endopod in these cases is either 1, 1, 4 ( A. gurneyi comb. nov. plus four of the new species) or 1, 2, 3 (two species). The total number of setae on the 4-segmented maxilliped is 17 (10, 1, 3, and 3 per segment) which is the highest total for any species in the genus. The highest total setation recorded for any other species is 16, found in A. monnioti sp. nov. (see Table 2).