Archinotodelphys longicaudatus, 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 : 44-47

Archinotodelphys longicaudatus sp. nov.

(Figs. 26-28)

Type material. Holotype (♀, MNHN-IU-2014-21207, intact). Dissected paratypes (1 ♀, 1 ♂) in the collection of IHK.

Type host. Microcosmus longicloa Monniot C. & Monniot F., 1991 (MNHN-IT-2008-5256 = MNHN S2 / MIC/96 ) .

Type locality. The Philippines, N. Lubang, MUSORSTOM 2 cruise 17, R. V. Coriolis, Stn CP 04 (13°59’N, 120°18’E), depth 183-190m, Bouchet coll., 20 November 1980 .

17 CP 04, The Philippines (CPA 944).

Etymology. The name of the new species refers to the elongate caudal rami, which are more than 9 times as long as wide in the adult female.

Female. Body (Fig. 26A) 1.98 mm long; prosome 880 μm long; cephalosome 305×545 μm. Urosome (Fig. 26B) 5-segmented; fifth pedigerous somite 196 μm wide. Genital double-somite about 1.2 times as long as wide (240×196 μm); paired genital apertures located dorsolaterally at about 23% of somite length. Three free abdominal somites 152×138, 160×125, and 127×109 μm, respectively; second free abdominal somite longest. Caudal ramus (Fig. 26C) slender and elongate, about 9.4 times longer than wide (339×36 μm); lateral seta small, located at 23% of ramus length; dorsal seta small; other setae missing.

Rostrum (Fig. 26D) elongate (142×65 μm) tapering in distal part; directed antero-ventrally. Antennule (Fig. 26E) 376 μm long and 14-segmented; armature formula 3, 5, 6, 2, 2, 6, 4, 1, 1, 3, 2+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; all setae naked except for 2 setae on first segment; aesthetascs thin, setiform. Antenna (Fig. 26F) with unarmed coxa; basis with 1 pinnate seta and 1 minute seta representing exopod at outer distal corner, and ornamented with setules on both margins: endopod 3-segmented with 1, 4 +1, and 6+claw on first to third segments; second segment with minute seta on inner margin.

Labrum (Fig. 26G) with weakly developed posteromedian lobe; both sides of labrum and posteromedian lobe ornamented with distal margin spinules and setules. Mandible (Fig. 26H) with 4 major teeth and 1 seta on coxal gnathobase; one small subsidiary tooth present between distal 2 teeth: basis with 1 seta on medial margin and row of fine spinules near base of exopod; exopod 4-segmented, each segment with 1 seta: endopod 2-segmented with 4 setae on first segment and 9 setae on second. Paragnath not observed. Maxillule (Fig. 27A) with 9 setae on precoxal arthrite; coxa with 1 seta on endite and 2 unequal setae on epipodite; basis with 4 setae on medial margin (2 proximal and 2 distal); exopod with 4 setae; endopod with 8 setae (4 medial, naked and 4 distal, weakly pinnate). Maxilla (Fig. 26I) 5-segmented; syncoxa with 4, 1, 2, and 3 setae on first to fourth endites; basis with 1 large claw and 1 seta; endopod 3-segmented with 1, 2, and 3 setae on first to third segments. Maxilliped (Fig. 27B) 3-segmented with 5 (grouped as 1, 2, and 2), 1, and 4 setae on first to third segments, respectively; second segment ornamented with tuft of needle-like spinules near base of seta.

FIG. 26. Archinotodelphys longicaudatus sp. nov. paratype female. A, habitus, dorsal; B, urosome, dorsal; C, left caudal ramus, dorsal; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, maxilla. Scale bars: A, B, 0.2 mm; C, 0.1 mm; D–F, H, 0.05 mm; G, I, 0.02 mm.

FIG. 27. Archinotodelphys longicaudatus sp. nov. paratype female. A, maxillule; B, maxilliped; C, leg 1; D, leg 2; E, leg 4; F, leg 5; G, right genital aperture, dorsal. Scale bars: A–F, 0.05 mm; G, 0.02 mm.

FIG. 28. Archinotodelphys longicaudatus sp. nov. paratype male. A, habitus without caudal rami, dorsal; B, Urosome without caudal rami, ventral; C, antennule. Scale bars: A, B, 0.1 mm; C, 0.05 mm.

Legs 1–4 biramous with 3-segmented rami (Fig. 27C–E); armature formula as in generic diagnosis. Outer seta on basis naked in leg 1 but pinnate in legs 2–4. Inner distal spine on basis of leg 1 smooth, 38 μm long, longer than first endopodal segment.

Leg 5 (Fig. 27F) protopodal segment wider than long with 1 outer seta; exopodal segment 2 times longer than wide (90×45 μm), with 4 setae. Leg 6 (Fig. 27G) represented by 1 spine (curved distally) and 1 seta on genital operculum.

Male. Body (Fig. 28A) length 1.23 mm. Urosome (Fig. 28B) 6-segmented; fifth pedigerous somite 145 μm wide; genital somite wider than long (102×141 μm); four free abdominal somites 109×110, 118×94, 107×86, and 91×72 μm, respectively. Caudal rami missing.

Rostrum as in female. Antennule (Fig. 28C) 290 μm long, 13-segmented, and geniculate between eleventh and twelfth segments; armature formula 3, 5, 8, 2, 2, 4, 2, 4+aesthetasc, 1, 1, 2, 2+aesthetasc, and 9+aesthetasc.Antenna, labrum, mandible, maxillule, maxilla, maxilliped, and legs 1–5 as in female. Leg 6 represented by 2 setae on genital operculum.

Remarks. The extremely elongate caudal rami (L/W ratio is 9.4: 1 in the female) distinguishes this species from all of its congeners: in other known species this ratio does not exceed 6.3:1 as found in A. reductus sp. nov. The 14-segmented antennule of the female is a unique condition: in the great majority of species the antennule is 17- segmented, but it is 16-segmented in A. gurneyi comb. nov., and A. longiseta sp. nov., 15-segmented in A. elegans sp. nov., A. rostralis sp. nov. and A. nudus sp. nov., 12-segmented in A. unisetosus sp. nov., and apparently 10-segmented in A. profundus according to Monniot (1968). The armature (1, 2, 3) on the three endopodal segments of the maxilla is shared only with A. unisetosus sp. nov. (described below), but these species can be distinguished by the 1, 7 formula of the mandibular endopod in the latter (cf. 4, 9 in A. longicaudatus sp. nov.). The other species that bear a total of 6 setae on the maxillary endopod have a setal formula of either 1, 1, 4 (as in A. gurneyi , A. elegans sp. nov., A. rostralis sp. nov., A. nudus sp. nov., and A. longiseta sp. nov.), or 1, 5 (as in A. antarcticus sp. nov.). These differences support the recognition of a new species to accommodate the material from Microcosmus longicloa .