Enterocola seticaudus Kim & Boxshall 2021, sp. nov.
Creators: name: Kim, Il-Hoi
name: Boxshall, Geoff A.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Maxillopoda
Cyclopoida
Ascidicolidae
Enterocola
Enterocola seticaudus

description: Enterocola seticaudus sp. nov.   
(Figs. 131-133)  
 Type material. Holotype ♀ (MNHN-IU-2014-21544), 3 ♀♀ paratypes (MNHN-IU-2014-21545), and 1 ♀, 1 ♂ paratypes (dissected, MNHN-IU-2014-17396) from mharyngçdẚctyçn caulẚfçrmẚs Monniot C. & Monniot F., 1991 (MNHN-IT-2008-6229 = MNHN A1 / PHA/7); New Caledonia, between Île des Pins and Récif S., SMIB 4 cruise, RV “Alis”, Stn DW 60 (23°00’S, 167°21.6’E), depth 500 m, B. Richer de Forges-IRD coll., 10 March 1989.   
 Etymology. The specific name refers to the presence of a seta on the caudal rami.   
 Description of female. Body (Fig. 131A, B) eruciform, cylindrical, consisting of cephalosome, trunk, and genitoabdomen. Body length 1.42 mm in dissected largest specimen (other 4 specimens 1.08, 1.32, 1.33, and 1.41 mm); maximum width 370 μm (across fourth pedigerous somite). Cephalosome much wider than long (212×321 μm), defined from trunk by lateral constriction. Trunk unsegmented, gradually broadening posteriorly, with weak constrictions between somites. First to fourth pedigerous somites each with paired dorsolateral tergal folds; these tergal folds variously developed depending on individuals, usually becoming smaller from anterior to posterior. On ventral surface, each pedigerous somite with pair of interpodal protrusions; protrusions becoming larger from anterior to posterior. Genitoabdomen (Fig. 131C) 5-segmented; articulations distinct ventrally, but obscure dorsally; anal prominence distinct. Caudal rami (Fig. 131D) inserted close to each other; each ramus about 2.0 times longer than wide (91×45 μm), gradually narrowing distally, with rounded distal margin, and tipped with 1 small, naked seta 28 μm long.   
Rostrum absent. Antennule (Fig. 131E) tapering, 74 μm long, 2-segmented; articulation between segments in- distinct, but segments clearly defined by width difference; broad proximal segment 54×48 μm, armed with 4 setae distally; small distal segment 23×15 μm, armed with 3 setae (distal seta larger than others). Antenna (Fig. 131F) 144×68 μm, indistinctly 2-segmented; proximal segment unarmed; distal segment longer than proximal segment, armed with 6 naked setae (1 small medial margin and 5 large on distal margin); lengths of setae I-VI (medial to lateral) 24, 55, 70, 83, 97, and 106 μm, respectively; setae V and VI longer than distal segment; medial seta positioned at about 80% along medial margin of segment.  
Labrum (Fig. 131G) sub-rectangular, with patch of spinules on both sides; palp spinulose, curved laterally. Mandible (Fig. 131G) tapering, spinulose, slightly longer than labral palp. Maxillule consisting of precoxa and palp: precoxa (Fig. 131H) distally bilobed and strongly sclerotized, with endite bearing 1 slender, spinulose seta and more than 10 long setules: palp (Fig. 131I) with 5 spinulose, spiniform setae on distal margin and 1 shorter seta on lateral margin. Maxilla (Fig. 131J) 2-segmented; proximal segment with mediodistal endite bearing distally bifurcate and spinulose process; distal segment bluntly bifurcate distally, with 1 small seta proximally on posterior surface. Maxilliped absent.  
Legs 1-4 each with 2-segmented protopod and unsegmented rami (Fig. 131K, L); protopods with 1 small outer seta on basis. Exopods shorter than endopods in legs 1, 2, and 4, but as long as endopod in leg 3. Endopods 53×37, 61×30, 60×34, and 57×36 μm, respectively, in legs 1-4; outer margin of endopods convex. Lengths of laterodistal and mediodistal setae on endopods 106 and 83, 105 and 90, 109 and 85, and 114 and 83 μm, respectively, in legs 1-4. All endopodal setae longer than endopodal segment. Laterodistal seta 1.28 times longer than mediodistal seta in leg 1.  
Leg 5 (Fig. 131M) much wider than long (125×216 μm); armed with 2 small setae on distal margin, separated by distance of 148 μm.  
 Description of male. Body (Fig. 132A) cyclopiform, narrow, with distinct prosome-urosome division. Body length 1.24 mm; maximum width 342 μm (across cephalosome). Prosome consisting of cephalosome and first to fourth pedigerous somites. Cephalosome 313 μm long, slightly wider than long, with truncate anterior apex. Fourth pedigerous somite distinctly narrower than anterior somites, with convex lateral margins. Urosome (Fig. 132B) slender, shorter than prosome, consisting of fifth pedigerous somite, genital somite, and 4 abdominal somites. Fifth pedigerous somite 113 μm wide; genital somite 153×112 μm, with well-developed genital opercula ventrally. Four abdominal somites 64×76, 47×71, 45×74, and 29×80 μm, respectively; anal somite shorter than penultimate ab- dominal somite; anal operculum not seen. Caudal rami (Fig. 132B) broad, 1.18 times longer than wide (45×38 μm), armed with 6 pinnate setae; lateral seta shortest.   
Rostrum (Fig. 132C) large, 151×78 μm, tapering, slightly constricted near proximal third, with minutely bi- fid apex. Antennule (Fig. 132D) 237 μm long, 7-segmented; first segment broader than other segments; armature formula 12, 2, 3, 0, 2, 1, and 9+aesthetasc; 2 setae on first and 1 on sixth segments pinnate, all other setae naked. Antenna (Fig. 132E) 3-segmented; first segment 82 μm long, armed with 1 naked seta subdistally; second segment as long as first, unarmed, but ornamented with setules along outer margin; third segment about 3.7 times longer than wide (67×18 μm), distinctly narrower than proximal segments, ornamented with setules on proximal outer margin; armed with 5 setae plus claw (29 μm long), subdistal seta 90 μm long, much longer than others.  
Labrum (Fig. 132F) very small, but well-sclerotized. Mandible (Fig. 132G) forming unarmed and unornamented digitiform process. Maxillule (Fig. 132H) 2-segmented; broad proximal segment unarmed; distal segment nearly circular, armed with 6 large, pinnate setae. Maxilla (Fig. 130I) lobate, tipped with 1 pinnate seta. Maxilliped absent.  
Legs 1-4 (Fig. 132J, 133 A-C) biramous, with 2-segmented protopod; coxa unarmed; basis with pinnate outer seta; basis of leg 1 with inner distal spine (27 μm long). Leg 1 with 2-segmented exopod and 3-segmented endopod. Legs 2-4 with 3-segmented exopods and endopods. First and second endopodal segments of leg 1 unarmed. Most setae on exopods and endopods geniculate proximally. Armature formula for legs 1-4 as follows:  
     Coxa  Basis  Exopod  Endopod      Leg 1:  0-0  1-I  I-0; I, I, 3  0-0; 0-0; 1, 2, 2      Leg 2:  0-0  1-0  I-1; I-1; II, I, 4  0-1; 0-2; 1, 2, 3      Leg 3:  0-0  1-0  I-1; I-1; II, I, 5  0-1; 0-2; 1, 2, 3      Leg 4:  0-0  1-0  I-1; I-1; II, I, 4  0-1; 0-2; 1, 2, 2      
Leg 5 (Fig. 132B) consisting of small lateral seta on somite and small free exopodal segment tipped with 1 small seta. Leg 6 (Fig. 132B) represented by 2 small setae on proximal lateral margin of genital operculum.  
 Remarks. The female of bK setẚcaudus sp. nov. can be distinguished from existing congeneric species by the unique setation of its antennule and by the presence of a prominent seta on the caudal ramus. The antennule of the new species is 2-segmented with 4 and 3 setae on the proximal and distal segments, respectively. This setation pattern is unique, although the antennulary armature of female b. ẚanthẚnus Illg & Dudley, 1980 is similar, with 4 setae on the proximal but only 2 setae on the distal segment (Ooishi, 2014a). The presence of a caudal seta was recorded in b. latẚceps Illg & Dudley, 1980 by Illg & Dudley (1980) and in b. ẚanthẚnus by Ooishi (2014a), but the caudal seta of these two species is very small and spinule-like, unlike b. setẚcaudus sp. nov. bnterçcçla latẚceps and b. ẚanthẚnus can be distinguished from the new species by additional differences: b. latẚceps has 2-segmented rami in legs 1-4 (cf. unsegmented in the new species) and b. ẚanthẚnus carries 2 almost equal distal setae on the endopods of legs 1-4 (cf. unequal).   
 Males of bnterçcçla are known in only four species, b. fulgens, b. fertẚlẚs Illg & Dudley, 1980, b. gçttçẚ Conradi, López-González & García-Gómez, 1992, and b. sydnẚẚ Chatton & Harant, 1924 (Ooishi, 2011). The males of all these species exhibit a uniform segmentation and setation pattern in the swimming legs, and in most other appendages. The most notable features of the male of b. setẚcaudus sp. nov. are that the terminal segment of the antenna is armed with 5 setae including 1 large subdistal seta (cf. only 4 small setae in the four congeners), and the armature formula of the antennule, which appears to be species-specific in this genus.
description: Published as part of Kim, Il-Hoi & Boxshall, Geoff A., 2021, Copepods (Cyclopoida) associated with ascidian hosts: Ascidicolidae, Buproridae, Botryllophilidae, and Enteropsidae, with descriptions of 84 new species, pp. 1-286 in Zootaxa 1 on pages 205-209, DOI: 10.11646/zootaxa.4978.1.1, http://zenodo.org/record/4820443