Styelicola elongata, 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 : 22-24

Styelicola elongata sp. nov.

( Figs. 10 , 11 )

Type material. Holotype ♀ (MNHN-IU-2018-1943, dissected and mounted on a slide) from mçlycarpa aurẚta (Sluiter, 1890); Plateau des Chesterfield , Coral Sea, west of New Caledonia, CORAIL 2 cruise, R. V. “Coriolis”, Stn CP 90 (19°02.8’S, 158°56.3’E), depth 44 – 48 m, B. Richer de Forges-IRD coll., 26 July 1988.

Etymology. The name of the new species refers to its elongate body.

Description of female. Body ( Fig. 10A ) elongate, cylindrical, slightly curved ventrally. Body length 6.55 mm; maximum width 0.94 mm across third pedigerous somite. Prosome unsegmented, but cephalosome and four pedigerous somites discernible by constrictions and weak dorsal tergites. Prosome-urosome division obscure; fifth pedigerous somite not articulated from prosome. Urosome indistinctly 6-segmented; articulations between somites represented by constrictions and surface wrinkles. Caudal ramus ( Fig. 10B ) about 1.5 times longer than wide (89×58 μm), narrowing distally; armed with 6 setae (1 lateral, 1 subdistal, and 4 distal), all naked and less than half width of ramus; lateral seta positioned at 32% of ramus length.

Rostrum absent. Antennule ( Fig. 10C ) 235 μm long, broad, 1.7 times longer than wide; 5-segmented, second and terminal segments subdivided; armature formula 2, 9, 3, 2, and 12; setae short and naked, some bluntly tipped and aesthetasc-like. Antenna ( Fig. 10D ) consisting of coxbasis and 2-segmented endopod; coxobasis slightly longer than wide, bearing 1 spiniform seta distally; first endopodal segment as long as coxobasis, unarmed; second endopodal segment as long as first, 2.3 times longer than wide (74×32 μm); armed with 5 small setae (2 proximal and 3 distal) plus small terminal claw (23 μm long).

Labrum ( Fig. 10E ) broad, narrowing distally, bearing pair of dentiform processes at each posterolateral corner. Mandible ( Fig. 10F ) consisting of coxa with well-developed gnathobase bearing on medial margin 4 major teeth and 1 or 2 small subsidiary teeth between major teeth, and 2-segmented palp; first segment (fused basis and exopod) with 2 bluntly tipped setae (originally exopodal setae) distally; second segment (endopod) nearly quadrate, with 4 bluntly tipped setae on distal margin. Maxillule ( Fig. 10H, I ) bilobed: inner lobe (precoxal arthrite) bearing 7 setae; outer lobe (palp) bearing 1 seta subdistally and 8 setae distally (3, 2, and 3 setae on 3 small lobes); all setae on maxillule bluntly tipped and subequal in length. Maxilla ( Fig. 10J ) consisting of syncoxa and allobasis; syncoxa broad, unarmed, with 1 small pore (opening of maxillary gland) on inner surface; allobasis terminating in spiniform claw, armed with 4 spines (1 on outer margin and 3 on inner margin) near base of terminal claw. Maxilliped ( Fig. 10K ) as blunt, unarmed digitiform lobe.

Leg 1 ( Fig. 11A ) consisting of unarmed coxa, basis bearing outer seta, and 2-segmented exopod and endopod. Outer spines on exopod small, rudimentary. Second exopodal segment tapering and terminating in spiniform process. Endopod broad, both segments unarmed; second segment blunt, with broadly rounded distal margin. Legs 2-4 shaped and armed as in leg 1, but larger than leg 1, increasing in size from leg 2 to leg 4. Armature formula for legs 1-4 as follows:

	Coxa	Basis	Exopod	Endopod
Legs 1-4	0-0	1-0	I-0; III, 0	0-0; 0

Leg 5 ( Fig. 11B ) consisting of lamellate protopod and small exopod: protopod 558×818 μm, directed dorsally, bearing 1 small seta dorsodistally; exopod 91×89 μm, inserting on ventral margin of protopod, strongly tapering, partially subdivided on ventral side; armed distally with 1 large and 3 minute setae. Leg 6 not observed.

Male. Unknown.

Remarks. The distinctive features of Styelẚcçla elçngata sp. nov. are as follows: (1) the body of the female is large,

6.55 mm long; (2) the caudal ramus is broad, about 1.5 times longer than wide; (3) the mandibular palp is 2-segmented; (4) the maxilla lacks an endite; (5) the endopods of legs 1-4 are unarmed; and (6) the exopod of leg 5 is distinctly tapering and armed with 1 large and 3 small setae. Character states (4) and (5) are shared with S. çmphalus, but the others are exhibited exclusively by S. elçngata sp. nov. In congeners, such as S. çmphalus, the body is at most 4.35 mm long, the caudal ramus is at least twice as long as wide, the mandibular palp is single-segmented, and the exopod of leg 5 is nearly rectangular and bears 5 or 6 setae.

Figures

FIG. 10. Styelẚcçla elçngata sp. nov., female. A, habitus, right; B, right caudal ramus, dorsal; C, antennule; D, antenna; E, labrum; F, mandible; G, paragnath; H, maxillule; I, palp of maxillule; J, maxilla; K, maxilliped. Scale bars: A, 0.5 mm; B-K, 0.05 mm.

FIG. 11. Styelẚcçla elçngata sp. nov., female. A, leg 1; B, leg 5; C, exopod of leg 5. Scale bars: A, C, 0.05 mm; B, 0.2 mm.