Asterocheres spiniventer, 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 : 215-220

publication ID	https://doi.org/ 10.12651/JSR.2024.13.2.185
persistent identifier	https://treatment.plazi.org/id/ED1887CB-FFE0-FFC8-FF7F-B537B2646154
treatment provided by	Felipe
scientific name	Asterocheres spiniventer
status	sp. nov.

Treatment

Asterocheres spiniventer n. sp. ( Figs. 18-20 View Fig View Fig View Fig )

https://zoobank.org/urn:lsid:zoobank.org:act:7D4DC

C69-1AC4-4F6F-B4D9-563737235A56

Type material. Holotype (intact ♀; HNIBRIV2398), intact paratypes (5♀♀, 3♂♂; HNIBRIV2399), and dissected paratypes (1♀, 1♂) from washings of mixed species of sponges. SCUBA diving, depth 20.3 m, Beomseom, Seogwipo, Jeju Island (33°13 ʹ 28.7 ʺ N, 126°30 ʹ 46.9 ʺ E), coll. T. W. Jung, 20 July 2022. Intact type specimens have been deposited in the Honam National Institute of Biological Resources ( HNIBR), Mokpo, Korea, Dissect- ed paratypes are kept in the collection of I.-H. Kim Additional non-type material. 10♀♀ and 1♂ from washings of an unidentified sponge, SCUBA diving, depth 28.1 m, Munseom , Seogwipo , Jeju Island, 33°13 ʹ 41.1 ʺ N, 126°34 ʹ 05.9 ʺ E, coll. T. Lee, 06 April 2023. GoogleMaps

Etymology. The specific name (noun) is a combination of the Latins spini -(= spiny) and venter (= belly) refers to the presence of many spinules on the lateral margins of the genital double-somite.

Female. Body ( Fig. 18A View Fig ) moderately broad. Body length of figured and described specimen 807 μm. Prosome ovoid, 552 μm long, representing about 68% of body length. Cephalothorax wider than long (356 × 418 μm). All prosomal somite bearing rounded lateral corners. Urosome ( Fig. 18B View Fig ) 4-segmented. Fifth pedigerous somite 114 μm wide. Genital double-somite 1.06 times longer than wide (114 × 108 μm); genital apertures positioned dorsolaterally at widest, 40% region of double-somite; postgenital part tapering posteriorly; postgenital lateral margins each bearing about 27 small spinules grouped as 8, 6-8, 7-8, and 4 from proximal to distal ( Fig. 19F View Fig ). Two free abdominal somites 38 × 56 and 33 × 52 μm, respectively. Anal somite bearing several minute spinules on posteroventral margin ( Fig. 18C View Fig ). Caudal ramus ( Fig. 18C View Fig ) 1.52 times longer than wide (35 × 23 μm), armed with 6 setae, and ornamented with 5 transverse row of minute spinules on both sides; distal margin smooth, lacking any spinule.

Rostrum ( Fig. 18D View Fig ) small, as tapering ridge, without distal apex. Antennule ( Fig. 18E View Fig ) 314 μm long, 21-segmented; 9th, 18th, 20th, and terminal segments bearing 7 setae, 2 setae+ aesthetasc, 4 setae, and 7 setae, respectively; all other segments each bearing 2 setae; several setae on proximal segments weakly pinnate. Antenna ( Fig. 18F View Fig ) bearing short, unarmed coxa; basis unarmed but bearing longitudinal row of fine spinules; exopodal segment 11 × 5 μm, bearing 3 setae; first endopodal segment 49 μm long, unarmed but ornamented with fine spinules (or setules) along outer margin; short second endopodal segment tipped with 1 small seta; third endopodal segment bearing 3 unequal setae; terminal claw of 49 μm long.

Oral siphon ( Fig. 18G View Fig ) 139 × 62 μm, reaching insertions of maxillipeds; broader proximal third with parallel lateral margins, distal two-thirds tapering. Mandible ( Fig. 18H View Fig ) with stylet of 137 μm long, bearing longitudinal row of about 6 denticles at distal region; palp 1-segmented, 32 μm long, distally tipped with 2 extremely unequal setae; longer seta 120 μm long, pinnate; shorter seta 20 μm long, naked; palp segment plus longer distal seta 140 μm long, about 1.1 times longer than stylet. Maxillule ( Fig. 18I View Fig ) bilobed; outer lobe 20 μm long, with 4 setae distally, longest one 65 μm long; inner lobe 55 μm long, with 4 large and 1 minute setae distally, longest seta 79 μm long. Maxilla ( Fig. 18J View Fig ) stout; proximal segment bearing row of thin, needle-like spinules at proximal region; distal segment longer than proximal segment, with few spinules and setules in distal region. Maxilliped ( Fig. 19G View Fig ) 6-segmented; armature formula 1, 1, 2, 1, 1, and 1 + claw; second segment with spinules on outer margin; terminal segment and claw 24 and 53 μm long, respectively.

Legs 1 ( Fig. 19A View Fig ), 2 ( Fig. 19B View Fig ), 3, and 4 ( Fig. 19D View Fig ) biramous with 3-segmented rami. Distal margin of intercoxal plate spinulose in legs 1 and 2, but smooth in legs 3 and 4. Inner distal seta on basis of leg 1 thin and naked. Leg 3 similar to leg 2, except bearing 1 spine and 5 setae on third endopodal segment ( Fig. 19C View Fig ). Second endopodal segment of all swimming legs bearing bicuspid outer distal corner. Inner coxal seta of leg 4 small but distinct. Armature formula for legs 1-4 as in A. aesthetes .

Leg 5 ( Fig. 18B View Fig ) comprising dorsolateral seta on fifth pedigerous somite and exopod; exopodal segment ( Fig. 19E View Fig ) 1.85 times longer than wide (37 × 20 μm), with 3 setae and spinulose outer and inner margins; lengths of setae 55, 48, and 20 from outer to inner. Leg 6 ( Fig. 19F View Fig ) represented by 1 small pinnate seta and 1 minute spinule on genital operculum.

Male. Body ( Fig. 20A View Fig ) narrower than that of female. Body length 575 μm. Prosome 367 μm long. Cephalothorax 242 × 245 μm, with nearly parallel lateral margins. Urosome ( Fig. 20B View Fig ) 5-segmented. Fifth pedigerous somite 69 μm wide. Genital somite 80 × 109 μm, with numerous fine spinules on lateral surfaces. Three abdominal somites 20 × 45, 20 × 41, and 23 × 39 μm, respectively. Caudal ramus 1.22 times longer than wide (22 × 18 μm).

Rostrum as in female. Antennule ( Fig. 20C View Fig ) 17-segmented, geniculate between 15th and 16th segments; 9th, 12th, 15th, 16th, and terminal segments bearing 5 setae, 4 setae, 4 setae, 2 setae + aesthetasc, and 11 setae, respectively; all other segments each with 2 setae; penultimate segment with pointed anterodistal corner; all setae naked. Antenna as in female.

Oral siphon, mandible, maxillule, maxilla as in female. Maxilliped ( Fig. 20D View Fig ) bearing blunt, beak-like inner process at proximal region of second segment.

Leg 1 ( Fig. 20E View Fig ) segmented and armed as in female, but endopod different from that of female; second endopodal segment bearing unicuspid outer distal corner and thick setules on outer distal region; third endopodal segment distally with 1 strong, spiniform outer process bearing spinules on its outer margin and 1 smaller, curved inner process bearing truncate tip. Legs 2-4 as in female.

Leg 5 ( Fig. 20F View Fig ) armed as in female; exopodal segment short, 1.33 times longer than wide (16 × 12 μm); 2 larger distal setae 40 μm (pinnate outer seta) and 27 μm (naked inner seta), respectively. Leg 6 ( Fig. 20G View Fig ) represented by 2 unequal naked seta on genital operculum.

Remarks. Five species of Asterocheres are selected for a comparison with A. spiniventer n. sp., as the new species exhibits higher similarity values with these species (more than 75% values) than with other species ( Table 2). These five species are A. canui Giesbrecht, 1897 ; A. suberitis ; A. uncinatus ; A. faroensis Crescenti, Baviera & Zaccone, 2010 ; and A. intermedius ( Hansen, 1923) . However, they are clearly distinguished from the new species by their diagnostic features exhibited in the mandibular palp and oral siphon, since the first three species have a 2-segmented mandibular palp (vs. 1-segmented in A. spiniventer n. sp.) and the remaining two species, A. faroensis and A. intermedius , have a longer oral siphon that approaches over the insertion of the maxilliped in the former species ( Crescenti et al., 2010) or over leg 1 in the latter species ( Hansen, 1923) (vs. the oral siphon approaches to the insertion of the maxilliped in A. spiniventer n. sp.).

As key characters of A. spiniventer n. sp., the caudal ramus is 1.5 times longer than wide, two distal setae on the mandibular palp are extremely unequal in length (longer seta six times longer than shorter one), and the genital double-somite of the female is ornamented with about 25 spinules arranged along the entire postgenital lateral margin. Most of all, the nature of the sexually dimorphic morphological transformation of the endopod of male leg 1 is unique to the new species.