Styelicola bahusia Lützen, 1968

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 : 19-21

Styelicola bahusia Lützen, 1968

( Figs. 8 , 9 )

Material examined. 1 ♀ (MNHN-IU-2015-7, dissected) in Styela sẚgma Hartmeyer, 1912; off French Guiana, GUYANE 2014 cruise, RV “Hermano Gines”, Stn CP 4366 (07°09´N, 53°05´W), depth 300-301 m, MNHN coll., 01 August 2014 .

Description of female. Body ( Fig. 8A ) elongate, curved dorsally, with weakly sclerotized, rather soft exoskeleton; body length 2.62 mm. Prosome longer than urosome, slightly depressed, and unsegmented, but cephalosome defined by cephalic shield and 4 pedigerous somites recognizable by weak dorsal tergites. Urosome ( Fig. 8B ) 5-segmented, gradually narrowing posteriorly. Articulation between fifth pedigerous somite and genital somite obscure; genital somite longer than wide; genital apertures positioned dorsally. Anal somite slightly longer than wide, longer than second abdominal somite, with deep posteromedian incision; anal operculum distinct. Caudal ramus ( Fig. 8C ) nearly fusiform, 2.09 times longer than wide (117×56 μm), 0.63 times as long as anal somite, with strongly convex inner margin: armed with 6 small setae (1 lateral and 5 distal); lateral seta positioned at 36% of ramus length; all setae naked and shorter than width of ramus.

Rostrum absent. Antennule ( Fig. 8D ) stout, 228 μm long, 7-segmented, gradually narrowing distally; armature formula 2, 11, 3, 2, 2, 2, and 12; setae small and naked; 2 of setae on terminal segment aesthetasc-like. Antenna ( Fig. 8E ) consisting of coxobasis and 2-segmented endopod; coxobasis broadening distally, longer than wide, armed with 1 broad spine distally: first endopodal segment unarmed, but ornamented with patch of minute spinules near anterodistal corner; second endopodal segment as long as first, bearing 3 small setae (1 proximal and 2 distal) plus acutely pointed claw; ornamented with minute spinules proximally on anterior surface.

Labrum not observed (destroyed). Mandible ( Fig. 8F ) consisting of coxa and unsegmented palp: coxal gnathobase with 4 major and 3 subsidiary teeth on medial margin; palp about 2.2 times longer than wide, with slightly convex outer margin, armed distally with 4 short setae. Paragnath ( Fig. 8G ) broadening distally, with 3 setiform elements proximally on medial margin, 1 dentiform process at distal third of medial margin and angular mediodistal corner. Maxillule ( Fig. 8H ) consisting of precoxa and palp: precoxal arthrite armed with 7 spines and 1 proximal seta; palp 2-segmented; first segment subdivided proximally, bearing 7 blunt setae (3 proximal and 2 distal setae on medial margin, and 2 longer setae at outer distal corner); second segment (?endopod) quadrate, bearing 4 setae on distal margin. Maxilla ( Fig. 8I ) consisting of syncoxa and allobasis; syncoxa broad, bearing single endite tipped with 2 unequal setae, both articulated at base; allobasis armed with 6 unequal spiniform elements (largest element distally). Maxilliped ( Fig. 8J, K ) as digitiform lobe tipped with 1 seta and ornamented with several rows of minute spinules.

Legs 1-4 biramous with 2-segmented rami; coxa lacking inner seta; second exopodal segment conical ( Fig. 9A, B ). Outer spines on exopods and endopods usually rudimentary. Endopods stout, expanded, with incomplete articulation between segments; distal margin of second segment rounded. Legs 3 and 4 shaped and armed as in leg 2. Armature formula for legs 1-4 as follows:

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

Leg 5 ( Fig. 8L ) 2-segmented, consisting of lamellate protopod and small exopod; protopod 318×303 μm, subcircu- lar, extending to middle of genital somite ( Fig. 8B ), bearing 1 small seta distally; exopod ( Fig. 8M ) about 1.3 times longer than wide (68×52 μm), inserting on ventral margin of protopod and armed with 6 unequal setae (2 dorsal setae distinctly longer than other 4). Leg 6 ( Fig. 8N ) represented by 3 spiniform processes on genital operculum

Male. Unknown.

Remarks. The single female specimen examined here is elongate and contrasts with the body form in the original description of Styelẚcçla bahusẚa by Lützen (1968) who described the female body as short, thick and broad. This difference is almost certainly due to the different methods of specimen preservation: we consider that our specimens became inflated after fixation, whereas the type specimens probably contracted. There are other differences: in the type specimens the antennule is 8-segmented, the maxillular palp is unsegmented, and the swimming legs have a different armature formula. However, we consider it likely that these differences are artefacts or possibly represent intraspecific variation. The shape of the caudal ramus and the armature of the mandible, maxillule, and maxilliped of our West Atlantic specimen all coincide exactly with the description of the type specimens and, it is on the basis of this evidence that we identify them as SK bahusẚa.

Figures

FIG. 8. Styelẚcçla bahusẚa Lützen, 1968, female.A, habitus, right; B, urosome, dorsal; C, right caudal ramus, ventral; D, antennule; E, antenna; F, mandible; G, paragnath; H, maxillule; I, maxilla; J, K, maxilliped; L, leg 5, medial; M, exopod of leg 5; N, genital aperture. Scale bars: A, 0.5 mm; B, L, M, 0.1 mm; C, D, G, I, 0.05 mm; E, F, H, J, K, N, 0.02 mm.

FIG. 9. Styelẚcçla bahusẚa Lützen, 1968, female. A, Leg 1; B, leg 2. Scale bars: 0.05 mm.