Bathycopola setifera, Kim & Boxshall, 2021

Kim, Il-Hoi & Boxshall, Geoff A., 2021, Copepods (Cyclopoida) associated with ascidian hosts: Ascidicolidae, Buproridae, Botryllophilidae, and Enteropsidae, with descriptions of 84 new species, Zootaxa 1, pp. 1-286 : 38-41

Bathycopola setifera gen. et sp. nov.

( Figs. 20 , 21 )

Type material. Holotype ♀ (MNHN-IU-2018-1948, dissected and mounted on a slide) from Cnemẚdçcarpa dẚgçnas Monniot C. & Monniot F., 1968; Bay of Biscay, BIOGAS 3 Expedition, RV “Jean Charcot”, Stn DS 45 (47°33.9´N, 09°38.4´W), depth 4260 m, September 1973.

Etymology. The specific name refers to the presence of a seta on the proximal margin of the coxal gnathobase of the mandible.

Description of female. Body ( Fig. 20A, B ) narrow, 1.28 mm long. Prosome cylindrical, longer than urosome, consisting of cephalosome and 4 pedigerous somites; maximum width of body 339 μm at level of second pediger- ous somite. Pedigerous somites discernible by 3 dorsal suture lines, becoming longer from anterior to posterior; posterodorsal border of fourth pedigerous somite produced posterodorsally, with rounded posterodorsal margin. Urosome ( Fig. 20C ) 5-segmented; fifth pedigerous somite short, indistinctly demarcated from prosome. Genital somite as long as wide (170×170 μm), bearing copulatory pore on ventral surface. Three abdominal somites 110×143, 70×127, and 60×110 μm, respectively. Caudal ramus ( Fig. 20D ) about 2.3 times longer than wide (55×24 μm), slightly shorter than anal somite, with convex inner margin; armed with 1 lateral seta, 1 inner subdistal seta, and 3 spines plus 1 seta distally; lateral seta positioned at 40% of ramus length; lateral and inner subdistal setae more than half length of ramus; distal spines small, outer spine longest (15 μm); small distal seta spiniform.

Rostrum as blunt anterior prominence of cephalosome ( Fig. 20A, B ). Antennule ( Fig. 20E ) slender, 85 μm long, 6-segmented; armature formula 2, 7, 3, 6+aesthetasc, 2+aesthetasc, and 11+2 aesthetascs; aesthetascs small and setiform. Antenna ( Fig. 20F ) 3-segmented, consisting of coxobasis and 2-segmented endopod; coxobasis 54×33 μm, with 1 large, spinulose spine (31 μm long); first endopodal segment 44×27 μm, with 1 seta on inner margin; second endopodal segment 2.12 times longer than wide (36×17 μm); armed with 2 setae in middle of inner margin and 3 setae distally plus terminal claw 36 μm long, as long as second endopodal segment.

Labrum ( Fig. 20G ) forming 2 tapering posterior lobes, with deep and wide posteromedian incision; both lobes bearing medially facing pair of teeth at apex. Mandible ( Fig. 20H ) consisting of coxa and palp: coxal gnathobase bearing strong distal tooth and 5 spiniform denticles on medial margin and 1 spinulose seta (arrowed) on proximal margin; palp biramous, bearing 3 setae on mediodistal corner of basis, 4 setae on exopod and 6 setae on endopod; endopod distinctly articulated from basis, but exopod not articulated at base. Maxillule ( Fig. 20I ) consisting of precoxa with 9 setae on arthrite, and biramous palp with 6 setae on medial margin of basis; exopod and endopod lobate, not articulated from basis, bearing 2 and 4 setae, respectively; 1 seta present between basis and arthrite. Maxilla ( Fig. 21A ) 3-segmented; syncoxa bearing 2 endites, each tipped with 1 seta, seta on proximal endite not articulated at base; basis with strong claw plus 2 setae; endopod small, 1-segmented, with 6 setae (1 inserted in middle of segment). Maxilliped ( Fig. 21B ) as tapering lobe bearing 6 setae (4 medial and 2 apical) and 2 rows of minute spinules.

Legs 1-2 ( Fig. 21 C-F) biramous with 2-segmented rami; coxa lacking inner seta. Legs 3 and 4 ( Fig. 21E, F ) with 2-segmented exopods and 1-segmented endopods; coxa of legs 3 and 4 bearing inner seta; endopods subdivided by partial suture line on outer side. Outer spine on first exopodal segment of legs 2-4 elongated. Most of spines on rami of legs 1-4 spinulose distally. Legs 3 and 4 with same armature; armature formula for legs 1-4 as follows:

	Coxa	Basis	Exopod	Endopod
Leg 1	0-0	1-I	I-0; III, I, III	0-0; I, II, I
Leg 2	0-0	1-0	I-0; III, I, III+1	0-0; I, II, II
Legs 3 & 4	0-1	1-0	I-0; III, I, IV	I, II, II

Leg 5 ( Fig. 21G ) consisting of lamellate protopod and small exopod; protopod oval, 375×257 μm, extending beyond distal margin of first abdominal somite, armed with 1 minute seta on ventral side of distal margin; exopod about 2.2 times longer than wide (86×39 μm), bearing 6 unequal setae (1 on ventral margin and 5 on distal margin); left and right legs fused with each other proximally on ventral surface ( Fig. 20C ). Leg 6 ( Fig. 21H ) represented by 3 small spines on genital operculum.

Male. Unknown.

Remarks. In Bathycçpçla gen. nov. the leg armature seems to be a robust taxonomic character that can be used to differentiate between species, but B. setẚfera gen. et sp. nov. and B. brevẚcaudata gen. et sp. nov. have the same armature formula for the rami of legs 2-4. In addition, both species share a 3-segmented maxilla. The major differences between the two species are in the number of setae on the maxillary endopod and the maxilliped, and the presence or absence of the inner coxal seta on leg 3 ( Table 1 ). The segmentation of legs 3 and 4 and the length of some of the exopodal spines on these legs also differ significantly between the two species.

Figures

FIG. 20. Bathycçpçla setẚfera gen. et sp. nov., female.A, habitus, dorsal; B, habitus, right; C, urosome, ventral; D, right caudal ramus, dorsal; E, antennule; F, antenna; G, labrum; H, mandible; I, maxillule. Scale bars: A-C, 0.1 mm; D-I, 0.02 mm.

FIG. 21. Bathycçpçla setẚfera gen. et sp. nov., female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, leg 3; F, leg 4; G, leg 5; H, genital aperture. Scale bars: A-F, H, 0.02 mm; G, 0.1 mm.