Asterocheres aesthetes Ho, 1984

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 : 190-191

publication ID	https://doi.org/ 10.12651/JSR.2024.13.2.185
persistent identifier	https://treatment.plazi.org/id/ED1887CB-FFFB-FFE1-FCF8-B33FB0C16328
treatment provided by	Felipe
scientific name	Asterocheres aesthetes Ho, 1984
status

Treatment

Asterocheres aesthetes Ho, 1984 View in CoL ( Fig. 1-3 View Fig View Fig View Fig )

Syn.: Asterocheres aesthetes Ho, 1984: 47 , figs. 17-20; Boxshall, 1990: 537, fig. 8C- F; Kim, 1998: 628, figs. 292-294.

Material examined. 40♀♀, 20♂♂ from washings of unidentified sponges, Munseom, Seogwipo, Jeju Island (33°13 ʹ 39.4 ʺ N, 126°33 ʹ 48.2 ʺ E), SCUBA diving, depth 22 m, coll. T. Lee, 06 April 2023 GoogleMaps ; 20♀♀, 10♂♂ from washings of unidentified sponges, Munseom, Seogwipo, Jeju Island (33°13 ʹ 30.6 ʺ N, 126°34 ʹ 09.62 ʺ E), trimix diving, depth 56 m, coll. T. Lee, 26 April 2023 GoogleMaps .

Female. Body ( Fig. 1A View Fig ) cyclopiform. Body length of largest described specimen 936 μm. Mean body length 857 μm (763-936 μm), based on 10 specimens. Prosome 659 μm long, occupying 70% of body length. Cephalothorax wider than long (418 × 488 μm). All prosomal somites with rounded lateral corners. Urosome ( Fig. 1B View Fig ) 4-segmented. Fifth pedigerous somite (first urosomal somite) 148 μm wide, bearing minute spinules scattered on lateral surface. Genital double-somite slightly wider than long (123 × 126 μm), gradually narrowing along posterior half; genital apertures positioned dorsolaterally at about 40% region of double-somite length; postgenital lateral margin ornamented with 2 groups of spinules ( Fig. 2F View Fig ), anterior group comprising about 12 longer spinules and posterior group comprising 4 or 5 shorter and thicker spinules; posterodorsal margins of double-somite bearing row of minute spinules. Two free abdominal somites 45× 70, and 45 × 67 μm, respectively, each with 3 or 4 spiniform scales on each lateral margin. Posteroventral margin of anal somite bearing row of spinules ( Fig. 1C View Fig ). Caudal ramus ( Fig. 1C View Fig ) slightly wider than long (28 × 30 μm), with longer outer margin, shorter inner margin, armed with 6 setae, and ornament- ed with spinules along oblique posterior margin.

Rostrum ( Fig. 1D View Fig ) as tapering ridge, lacking posterior apex. Antennule ( Fig. 1E View Fig ) 378 μm long, 21-segmented; each segment bearing 2 setae, except 7 setae on 9th segment, 2 setae + aesthetasc on 18th segment, 4 setae on penultimate segment, and 7 setae on terminal segment; 10th segment short, obscure; many setae on anterior segments pinnate, some of them truncated, tipped with small setule; 3 large setae (one on 5th segment and 2 on 9th segment) bearing segments-like annulations. Antenna ( Fig. 1F View Fig ) consisting of coxa, basis, exopod, and 3-segmented endopod; coxa short, bearing patch of spinules on outer margin; basis bearing longitudinal row of needle-like, fine spinules along distal half; exopod small, 2.80 times longer than wide (14 × 5 μm), bearing 1 middle and 2 unequal, terminal setae, larger one of terminal setae with annulation proximally; endopod with armature formula of 0, 1, and 2+ claw; first endopodal segment 68 μm long, with setules on outer margin; second endopodal segment short; third endopodal segment with setules on outer margin; terminal claw spiniform, straight, 65 μm long, slightly shorter than first endopodal segment.

Oral siphon ( Fig. 1G View Fig ) 191 × 74 μm, attenuated distally, extending to insertions of maxillipeds, tipped with translucent, circular material. Mandible ( Fig. 1H View Fig ) consisting of coxal stylet and palp; stylet 184 μm long, slightly curved, distally attenuated, with truncated tip and 12 minute teeth; palp 2-segmented, 49 and 21 μm long, respectively, tipped with 2 unequal, weakly pinnate setae (192 and 75 μm long, respectively); palp plus longer distal seta 262 μm long, 1.42 times longer than stylet. Maxillule ( Fig. 1I View Fig ) bilobed, bearing patch of small spinules on outer margin near base of outer lobe; inner lobe (precoxal endite) about 67 μm long, tipped with 4 longer setae (106, 102, 100, and 63 μm, respectively) and 1 small seta, and ornamented with thin setules on proximal part of inner margin and several thicker setules subdistally; outer lobe (palp) 24 μm long, bearing 2 naked distal setae (87 and 74 μm long, respectively) and 2 pinnate subdistal setae (62 and 33 μm long, respectively). Maxilla ( Fig. 1J View Fig ) 2-segment- ed; proximal segment (syncoxa) bearing flexible hyaline tube of maxillary gland and row of minute, needle-like spinules at proximal region; distal segment (basis) claw-like, as long as proximal segment, curved in distal region, bearing linguiform process proximally and tuft of setules at 60% region of segment length and row of fine spinules along distal third. Maxilliped ( Fig. 1K View Fig ) consisting of syncoxa, basis, and 4-segmented endopod, with armature formula 1, 1, 2, 1, 1, and 1 + claw; basis with fine spinules along outer margin, seta on inner margin minute, obscure; terminal endopodal segment and terminal claw 41 and 72 μm long, respectively.

Legs 1 ( Fig. 2A View Fig ), 2 ( Fig. 2B View Fig ), 3, and 4 ( Fig. 2D View Fig ) biramous, with 3-segmented rami. Leg 3 similar to leg 2, except bearing different armature on third endopodal segment ( Fig. 2C View Fig ). Intercoxal plate of leg 1-3 bearing spinules on distal surface, that of leg 4 smooth. Outer seta on basis of legs 1-3 large, pinnate along distal region. Inner distal corner of basis of leg 1 with spinules. Second endopodal segment of legs 1-4 with bicuspid outer distal process. Inner coxal seta of leg 4 small and naked. Third endopodal segment of fourth leg 72 μm long, its distal spine 68 μm long, slightly longer than segment. Armature formula for legs 1-4 as follows:

Coxa Basis Exopod Endopod

Leg 1 0-1 1-1 I-1; I-1; III, 2, 2 0-1; 0-2; 1, 2, 3 Leg 2 0-1 1-0 I-1; I-1; III, I, 4 0-1; 0-2; 1, 2, 3 Leg 3 0-1 1-0 I-1; I-1; III, I, 4 0-1; 0-2; 1, 1 + I, 3 Leg 4 0-1 1-0 I-1; I-1; III, I, 4 0-1; 0-2; 1, 1 + I, 2

Leg 5 ( Fig. 1B View Fig ) consisting of protopod and exopod; protopod fused with fifth pedigerous somite, bearing 1 pinnate dorsolateral seta; exopodal segment ( Fig. 2E View Fig ) 2.19 times longer than wide (57 × 26 μm), armed with 3 setae; inner and outer margins convex, each bearing about 10 spinules; outer distal seta longest, 61 μm long, weakly pinnate; inner distal seta naked, 45 μm long; inner subdistal seta 27 μm long, pinnate, annulated proximally. Leg 6 ( Fig. 2F View Fig ) represented by 1 pinnate seta and 1 spinule on genital operculum.

Male. Body ( Fig. 3A View Fig ) narrower and smaller than that of female. Body length 698 μm in described specimen. Prosome 465 μm long. Cephalothorax as long as wide (327 × 327 μm). Urosome ( Fig. 3B View Fig ) 5-segmented. Fifth pedigerous somite 95 μm wide. Genital somite wider than long (106 × 130 μm), with many spinules cover- ing lateral surfaces; genital operculum well-developed. Three free abdominal somite 23 × 60, 23 × 55, and 30 × 45 μm, respectively. Caudal ramus 0.83 times longer than wide (20 × 24 μm).

Rostrum as in female. Antennule ( Fig. 3C View Fig ) 18-segmented, geniculate between 15th and 16th segments and between 16th and 17th segments; each segment bearing 2 setae, except 7 setae on 9th segment, 2 setae+ aesthetasc on 13th segment, 2 setae + aesthetasc on 17th segment, and 10 setae on terminal segment; aesthetasc on 13th segment thin, setiform.

Antenna, oral siphon, mandible, maxillule, and maxilla as in female. Maxilliped ( Fig. 3D View Fig ) segmented as in female; basis with thick proximal process on inner margin, inner seta absent.

Legs 2 and 3 slightly different from those of female. In leg 2 endopod ( Fig. 3E View Fig ), second segment bearing enlarged bicuspid outer distal process; third segment bearing shortened outer distal seta, 1 small nodule on anterior surface of outer distal process, and several spinule on distal margin. In leg 3, third endopodal segment ( Fig. 3F View Fig ) bearing slightly curved outer distal process.

Exopodal segment of leg 5 ( Fig. 3G View Fig ) nearly rectangular, 2.56 times longer than wide (34 × 13.3 μm), with few spinules on inner and outer margins; 3 setae 42, 36, and 18 μm long, respectively, from outer to inner. Leg 6 ( Fig. 3H View Fig ) represented by outer distal part of genital operculum bearing 2 unequal setae, spinules on outer and inner margin, and 4 or 5 setules on inner margin.

Remarks. This is the first known species of Asterocheres in Korea ( Kim, 1998). The newly examined material collected in Korea are identifiable as this species by the characteristic, sexually dimorphic features revealed on the third endopodal segment of male leg 2 and by the characteristic ornamentation on the genital operculum of the male, which Ho (1984) described and figured in the original description. Ho (1984) overlooked the presence of an aesthetasc on the thirteenth segment of the male antennule and a slight sexual dimorphism on leg 3, which are considered as useful characters in the present paper.