Archintodephys longiseta, 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 : 31-34

Archintodephys longiseta sp. nov.

(Figs. 17, 18)

Type material. Holotype (♀, MNHN-IU-2015-12, dissected and mounted on a slide).

Type host. Styela sigma Hartmeyer, 1912 (MNHN-IT-2018-13 = MNHN S1 /STY/322) .

Type locality. French Guiana, GUYANE 2014 cruise, N/ O Hermano Gines, Stn CP 4368 (07°10’N, 52°59’W), depth 397-399 m, MNHN-Convention APA-973-1 coll., 01 August 2014 .

Etymology. The name of the new species, longiseta , refers to the extremely long seta on the apex of the fifth leg which extends beyond the articulation between first and second free abdominal somites.

Female. Body (Fig. 17A) 1.39 mm long. Prosome 727 μm long, cephalosome greatest width 485 μm, wider than pedigerous somites. Urosome (Fig. 17B) 5-segmented. fifth pedigerous somite 170 μm wide. Genital doublesomite 182×136 μm, about 1.3 times longer than wide, gradually narrowing posteriorly; bearing paired genital ap- ertures at 37% of double-somite length. Three free abdominal somites 80×98, 75×93, and 91×86 μm, respectively. Caudal ramus (Fig. 17C) 185×30 μm, about 6.2 times longer than wide; armed with 6 naked setae, outer lateral seta located about at 37% of ramus length.

Rostrum (Fig. 17D) 128×73 μm, elongate, articulated from cephalosome. Antennule (Fig. 17E) 330 μm long and 16-segmented; armature formula 3, 5, 8, 2, 2, 6, 4+aesthetasc, 1, 2, 1, 2, 1+aesthetasc, 1, 2, 2+aesthetasc, and 7+aesthetasc; all setae thin and naked. Antenna (Fig. 17F) with short, unarmed coxa; basis with 2 outer setae distally (1 long and 1 short), representing exopod, both setae naked: endopod 3-segmented; first segment with 1 small seta on middle of inner margin and ornamented with several spinules on subdistal outer margin; second segment with 5 setae (4 distal and 1 subdistal) on inner margin, one of 4 distal setae blunt tipped; third segment 32×19 μm, 2/3 as long as second segment, armed with 1 slender claw and 6 naked setae distally, 3 of distal setae bluntly tipped.

FIG. 17. Archinotodelphys longiseta sp. nov. holotype female. A, habitus, dorsal; B, urosome, dorsal; C, right caudal ramus, dorsal; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, maxillule. Scale bars: A, B, 0.1 mm; C–I, 0.05 mm.

FIG. 18. Archinotodelphys longiseta sp. nov. holotype female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, leg 4; F, leg 5; G, left genital aperture, dorsal. Scale bars: A, B, G, 0.02 mm; C–F, 0.05 mm.

Labrum (Fig. 17G) with setulose posteromedian lobe and 5 or 6 denticles each posterolateral corner. Mandible (Fig. 17H) with 1 major tooth and pectinate medial margin of coxal gnathobase; basis with 1 plumose seta on medial margin; exopod 4-segmented with 5 setae (1, 1, 1, and 2); endopod with 4 and 10 naked setae on first and second segments, respectively. Maxillule (Fig. 17I) with 10 setae on arthrite (one on anterior surface), 1 seta on coxal endite, and 2 setae on epipodite; basis with 6 setae on inner margin; endopod unsegmented with 10 setae (2 distal setae naked); exopod with 4 large setae. Maxilla (Fig. 18A) consisting of precoxa, coxa, basis, and 3-segmented endopod; precoxa with 4 (including small one) and 1 setae on proximal and distal endites, respectively; coxa with 2 and 3 setae on proximal and distal endites, respectively; basis with 2 setae and 1 strong claw ornamented with fine spinules along concave margin; endopod short, 3-segmented, armed with 1, 1, and 4 setae. Maxilliped (Fig. 18B) 4-segmented with 4 (1, 2, and 1), 1, 3, and 2 setae respectively on first to fourth segments; 1 of 3 setae on third segment characteristically located at outer distal corner.

Legs 1–4 with 3-segmented rami; armature formula of legs 1–4 as in family diagnosis. Outer margins of exopods smooth (Fig. 18C–E). Leg 1 with inner distal spine on basis 33 μm long. Outer spines on third exopodal seg- ment of legs 2 and 3 broad, leaf-like.

Leg 5 (Fig. 18F) consisting of protopodal and exopodal segments; protopodal segment wider than long and distinctly articulated from somite, with 1 seta on outer margin; exopod 102×41 μm, about 2.5 times longer than wide and armed with 4 setae (1 outer lateral and 3 distal); lengths of exopodal setae 102, 230, 68, and 81 μm from outer to inner, respectively: innermost seta pinnate proximally and spinulose distally, all other setae naked. Leg 6 (Fig. 18G) in dorsal view represented by 1 naked seta and 1 claw-like spine on genital operculum.

Male. Unknown.

Remarks. The new species carries an armature of 1, 1, 4 setae on the 3-segmented maxillary endopod, a formula shared with A. gurneyi , and three species described below ( A. elegans sp. nov., A. rostralis sp. nov. and A. nudus sp. nov.) (see Table 2). It differs from all of these species in having a setal formula of 4, 1, 3, 2 on the 4-segmented maxilliped. The first three species all have 5 setae on the first segment (syncoxa) whereas the new species has only 4 as in A. nudus sp. nov., but the maxilliped in the latter species is only 3-segmented. One of 3 setae on the third maxilliped segment is located at the outer distal angle of the segment. No other Archinotodelphys species has a seta in such a position. These characteristics are sufficient to justify the establishment of a new species.