Asterocheres tridentatus, Lee, 2024

Lee, Il-Hoi Kim and Taekjun, 2024, Copepods of the genus Asterocheres Boeck, 1859 (Siphonostomatoida: Asterocheridae) from Korean waters, Journal of Species Research 13 (2), pp. 185-254 : 228-232

publication ID	https://doi.org/ 10.12651/JSR.2024.13.2.185
persistent identifier	https://treatment.plazi.org/id/ED1887CB-FFD5-FFC4-FF41-B455B4B861D7
treatment provided by	Felipe
scientific name	Asterocheres tridentatus
status	sp. nov.

Treatment

Asterocheres tridentatus n. sp. ( Figs. 27-29 View Fig View Fig View Fig )

https://zoobank.org/urn:lsid:zoobank.org:act:46F57

BFA-D91F-4342-9733-79E407B8F132

Type material. Holotype (intact ♀; NIBRIV 0000 909863), intact paratypes (16♀♀; NIBRIV0000909864 ), and dissected paratype (1♀) from washings of unidentified sponges, SCUBA diving, depth 24.2 m, Dokdo Island in the Korean east sea (37°14 ʹ 50.8 ʺ N, 131°51 ʹ 49.28 ʺ E), coll. T. Lee, 25 May 2023 GoogleMaps . Holotype and intact paratypes have been deposited in the National Institute of Biological Resources ( NIBR). Incheon, Korea. Dissected paratype is kept in the collection of I.-H. Kim. Etymology. The name tridentatus refers to the presence of three teeth on the mandibular stylet .

Female. Body ( Fig. 27A View Fig ) rather broad. Mean body length 815 μm (797-835 μm), based on 7 specimens. Figured and described specimen 835 μm long. Prosome 585 μm long, 0.70 times as long as body length. Cephalothorax 370 × 476 μm; its posterolateral corners angular. Second to fourth pedigerous somite with rounded lateral corners. Urosome ( Fig. 27B View Fig ) 4-segmented. Fifth pedigerous somite slightly wider than genital double-somite 115 μm wide, bearing several spinules on lateral margins. Genital double-somite as long as wide (106 × 106 μm); genital apertures positioned laterally at middle of double-somite length; posterior region posterior to genital apertures gradually narrowing; postgenital lateral margin bearing 2 groups of spinules, proximal group consisting of 2 or 3 longer spinules and distal group consisting of 2-6 shorter spinules ( Fig. 27K, L View Fig ). Two free abdominal somites 36 × 62 and 33 × 61 μm, respectively; Anal somite with spinules on posteroventral margin ( Fig. 27C View Fig ). Caudal ramus ( Fig. 27C View Fig ) wider than long (25 × 29 μm), armed with 6 setae and ornamented with spinules (or scales) on lateral and posteroventral margins.

Rostrum ( Fig. 27D View Fig ) as tapering ridge, without posteri- or apex. Antennule ( Fig. 27E View Fig ) 324 μm long, 20-segment- ed; 9th, 18th, and terminal segments bearing 7 setae, 2 setae + aesthetasc, and 11 setae, respectively; all other segments each with 2 setae; several setae on proximal segment bearing minute spinules on margins; anterior margin of first segment with fine spinules. Antenna ( Fig. 27F View Fig ) with short, unarmed coxa; basis 75 μm long, unarmed ornamented with longitudinal row of fine spinules near exopod and several spinules on inner margin; exopod small, 10 × 5.5 μm, bearing 3 setae; first endopodal segment 53 μm long, unarmed but ornamented with 2 rows of fine spinules on outer surface; small second endopodal segment with 1 seta distally; third endopodal segment with 3 setae (including 1 minute seta); terminal claw 83 μm long, 1.62 times longer than first endopodal segment.

Oral siphon ( Fig. 27G View Fig ) 183 μm long, reaching between maxilliped and leg 1. Mandible ( Fig. 27H View Fig ) consisting of stylet and palp; stylet 190 μm long, bearing 3 teeth (2 distal and 1 subdistal); palp 2-segmented; proximal and distal segments 36 and 21 μm long, respectively, 2 distal setae 135 and 64 μm long, feebly pinnate; palp segments plus longer distal seta 193 μm long, as long as stylet. Maxillule ( Fig. 27I View Fig ) bilobed; smaller outer lobe 25 μm long, with 4 setae, longest one of them 97 μm long; inner lobe about 82 μm long, tipped with 1 small and 4 large setae, longest one of them 105 μm long. Maxilla ( Fig. 27J View Fig ) slender, 2-segmented; proximal segment unornamented; distal segment 1.3 times longer than proximal segment, with 1 group of setules near middle followed distally by row of fine spinules. Maxilliped ( Fig. 28A View Fig ) slender, 6-segmented; armature formula 1, 1, 2, 1, 1, and 1 + claw; first segment with 1 patch of spinules at outer subdistal region and several spinules at outer distal corner; inner seta on second segment rudimentary; terminal segment 38 μm long; terminal claw 91 μm long, 2.4 times longer than terminal segment.

Leg 1 ( Fig. 28B View Fig ), 2 ( Fig. 28C View Fig ), 3, and 4 ( Fig. 28E View Fig ) biramous with 3-segmented rami. Posterior margin of intercoxal plate smooth in all swimming legs. Inner coxal seta small, naked in leg 1, large and pinnate in legs 2 and 3, but absent in leg 4. Leg 3 same as leg 2, except bearing 1 spine plus 5 setae on third endopodal segment ( Fig. 28D View Fig ). Inner distal corner of basis of leg 1 spinulose, but naked in other swimming legs. Inner distal seta on basis of leg 1 slender, not broadened at its proximal region, pinnate along both margins. Second endopodal segment of all swimming legs bearing bicuspid outer distal corner. Armature formula for legs 1-4 as in A. processus n. sp.

Leg 5 ( Fig. 27B View Fig ) consisting of dorsolateral seta on fifth pedigerous somite and free exopod; exopodal segment ( Fig. 28F View Fig ) fusiform with convex, spinulose outer and inner margins, 2.07 times longer than wide (58 × 28 μm), armed with 3 setae; these setae 59, 38, and 31 μm long, respectively, from outer to inner. Leg 6 ( Fig. 27K, L View Fig ) represented by 2 naked setae and 1 denticle on genital operculum.

Male. Body ( Fig. 29A View Fig ) similar in form to that of female. Body length 582 μm. Prosome 387 μm long. Cephalothorax 237 × 294 μm, bearing angular posterolateral corners. Urosome ( Fig. 29B View Fig ) 5-segmented. Fifth pedigerous somite 77 μm wide. Genital somite 76 × 96 μm; with well-developed genital operculum. Three abdominal somites 22 × 53, 24 × 46, and 22 × 46 μm, respectively. Caudal ramus 18× 23 μm.

Rostrum as in female. Antennule ( Fig. 29C View Fig ) 17-segmented, slightly geniculate between 15th and 16th segments; 9th, 12th,16th, and terminal segments bearing 6 setae, 4 setae, 1 seta + aesthetasc, and 11 setae, respectively; anterodistal corner of 16th segment pointed; aesthetasc on penultimate segment constricted at 60% region. Antenna as in female.

Oral siphon, mandible, maxillule, and maxilla as in female. Maxilliped ( Fig. 29D View Fig ) with 1 guttiform process near inner distal seta of first segment (indicated by arrowhead); second segment bearing 2 small pronouncements on inner margin.

Legs 1 and 2 showing sexual dimorphisms. Second endopodal segment of leg 1 ( Fig. 29E View Fig ) bearing produced, distally directed outer distal corner and 3 rows of small spinules on outer surface. Third exopodal segment of leg 2 ( Fig. 29F View Fig ) expanded; its second outer spine bearing subsidiary denticle on outer margin; third outer spine bearing membrane on distal part of inner margin; both spines naked, without spinules.

Exopodal segment of leg 5 ( Fig. 29G View Fig ) 1.77 times longer than wide (23 × 13 μm), bearing few spinules on out- er and inner margins and 3 unequal naked setae. Leg 6 ( Fig. 29B View Fig ) probably represented by 2 unequal setae on distal region of genital operculum.

Remarks. Nine species of Asterocheres are selected as relatives of A. tridentatus n. sp. after comparing the new species with its congeners based on the character states of 17 characters ( Table 2). These nine species are A. alter Eiselt, 1965 ; A. canui ; A. cubensis Varela, 2010 ; A. fernadezmilerai Varela, 2010 ; A. halichondriae Stock, 1966 ; A. manaarensis Thompson & A. Scott, 1903 ; A. proboscideus ; A. tenuipes Kim, 2010 ; and A. tetrasetosus Johnsson, 1999 and distinguished from the new species by their different features. The oral siphon extends before the maxilliped in A. alter , to the maxilliped in A. canui , A. halichondriae , and A. tetrasetosus , to leg 1 in A. tenuipes , and over leg 1 in A. proboscideus (vs. the oral siphon extends between the maxilliped and leg 1 in A. tridentatus n. sp.). Therefore, these six species are distinguished from the new species by having different lengths of the oral siphon. Asterocheres cubensis and A. fernandezmilerai both described from the West Indies ( Varela, 2010a) have 19-segmented female antennule (vs. 20-segmented in A. tridentatus n. sp.) and an inner coxal seta on leg 4 (vs. the seta is absent in A. tridentatus n. sp.). Therefore, the latter two species are also distinguished from the new species.