Asterocheres geminus, 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 : 198-202

publication ID	https://doi.org/ 10.12651/JSR.2024.13.2.185
persistent identifier	https://treatment.plazi.org/id/ED1887CB-FFF3-FFFA-FF41-B777B1B3655F
treatment provided by	Felipe
scientific name	Asterocheres geminus
status	sp. nov.

Treatment

Asterocheres geminus n. sp. ( Figs. 6-8 View Fig View Fig View Fig )

https://zoobank.org/urn:lsid:zoobank.org:act:24487F34-

4F05-4D99-AD6A-0AB6936FCDC4

Type material. Holotype (intact ♀, MABIK CR00254 664), intact paratypes (2♀♀, MABIK CR00254665 ), and dissected paratypes (1♀, 1♂) from washings of unidentified sponges, Seogwipo, Jeju Island (33°13 ʹ 39.6 ʺ N, 126°35 ʹ 58.9 ʺ E), trimix diving, depth 50.1 m, coll. T. Lee , 25 May 2022 GoogleMaps . Holotype and intact paratypes have been deposited in the Marine Biodiversity Institute of Korea ( MABIK), Seocheon. Dissected paratypes are retained in the collection of I.-H. Kim .

Etymology. The name is derived from the Latin gemin (= twin), referring to the similarity between the new species and A. boeckii ( Brady, 1880) .

Female. Body ( Fig. 6A View Fig ) moderately narrow. Body length 749 μm in dissected and described specimen. Oth- er 3 females 727, 715, and 715 μm long, respectively. Prosome 520 μm long. Cephalothorax slightly wider than long. All prosomal somites with rounded lateral corners. Urosome ( Fig. 6B View Fig ) 4-segmented. Fifth pedigerous somite bearing few spinules on lateral margin. Genital double-somite 1.07 times longer than wide, widest across proximal third, narrowing along distal two-thirds; genital apertures positioned dorsolaterally at 45% region of double-somite length; postgenital lateral margin with about 20 subequal setules (or spinules). Two free abdominal somite 33 × 53 and 34 × 47 μm, respectively. Anal somite with fine spinules arranged along posteroventral margin ( Fig. 6C View Fig ). Caudal ramus ( Fig. 6C View Fig ) slightly wider than long (24 × 25 μm), bearing fine spinules along posteroventral margin.

Rostrum ( Fig. 6D View Fig ) as tapering ridge, without distal apex. Antennule ( Fig. 6E View Fig ) 264 μm long, 21-segmented but articulation indistinct between 2 terminal segments; 18th, 20th, and terminal segments with 2 setae+ aesthetasc, 4 setae, and 7 setae, respectively; all other segments each with 2 setae; some of setae on proximal segments pinnate, bearing minute setule at truncated tip. Antenna ( Fig. 6F View Fig ) similar to that of A. aesthetes ; exopodal segment 9 × 4 μm; first endopodal segment 55 μm long, bearing spinules at proximal third and on inner margin; terminal claw spiniform, 60 μm long, slightly longer than first endopodal segment.

Oral siphon ( Fig. 6G View Fig ) 173 × 54 μm, reaching between maxilliped and leg 1. Mandible ( Fig. 6H View Fig ) consisting of coxal stylet and palp; coxal stylet 160 μm long, bearing 12 teeth (excluding pointed distal tip) on distal part ( Fig. 6I View Fig ); palp indistinctly 2-segmented, proximal segment 32 μm long, distal segment 11 μm long, bearing 2 unequal pinnate setae of 118 and 44 μm long, respectively; palp plus longer terminal seta 161 μm long, almost same in length as coxal stylet. Maxillule ( Fig. 6J View Fig ) as usual for genus; inner lobe about 64 μm long, distally bearing 4 large and 1 small setae (lengths of 4 large setae 95, 90, 86, and 55 μm, respectively); outer lobe 23 μm long, bearing 4 setae (lengths of 2 naked terminal setae 69 and 55 μm, respectively; lengths of 2 pinnate subdistal setae 51 and 29 μm, respectively). Maxilla ( Fig. 6K View Fig ) bearing row of needle-like spinules on proximal region of proximal segment (syncoxa); distal segment (basis) distinctly longer than proximal segment, bearing 1 tubercle at 40% region of outer margin and setules and spinule row along distal half. Maxilliped ( Fig. 6L View Fig ) as in A. aesthetes , but with 1 transverse row of small spinules on third endopodal segment; last endopodal segment 33 μm long; terminal claw 70 μm long.

Legs 1 ( Fig. 7A View Fig ), 2 ( Fig. 7 B View Fig ), 3, and 4 ( Fig. 7D View Fig ) similar to those of A. aesthetes , but outer seta on basis of these legs smaller than those of latter species. Leg 3 similar to leg 2, except bearing 1 spine and 5 setae on third endopodal segment ( Fig. 7C View Fig ). Third endopodal segment of leg 4 46 μm long; its distal spine 35 μm long, shorter than segment. Armature formula for legs 1-4 as in A. aesthetes .

Leg 5 ( Fig. 7E View Fig ) consisting of 1 naked dorsolateral seta on fifth pedigerous somite and free exopod; exopodal segment 1.89 times longer than wide (36 × 19 μm); outer and inner margins coves, each with several small spinules; 2 distal setae pinnate, subequal (outer and inner setae 35 and 36 μm long, respectively); inner subdistal setae naked 28 μm long, annulated proximally. Leg 6 ( Fig. 7F View Fig ) as 1 pinnate seta and 1 spinule on genital operculum.

Male. Body ( Fig. 8A View Fig ) smaller than that of female, 536 μm long. Prosome 367 μm long. Cephalothorax 264 × 260 μm, Urosome ( Fig. 8B View Fig ) 5-segmented. Fifth pedigerous somite 70 μm wide. Genital somite ( Fig. 8A, B View Fig ) nearly circular, 95 × 107 μm, with few minute spinules on lateral margin. First and second abdominal somites characteristically short, each less than half as long as anal somite. Caudal ramus wider than long.

Rostrum as in female. Antennule ( Fig. 8C View Fig ) 18-segment- ed, geniculate between 16th and 17th segments; 9th segment with 7 setae; 13th and penultimate segments each with 2 setae+ aesthetasc; terminal segment with 10 setae; all other segments each with 2 setae; anterodistal corner of penultimate segment produced, pointed.

Antenna, oral siphon, mandible, maxillule, and maxilla as in female. Maxilliped with 1 proximal process on inner margin, but bearing no seta ( Fig. 8D View Fig ).

Legs 1, 2, and 4 as in female. Outer distal process of third endopodal segment of leg 3 ( Fig. 8E View Fig ) curved as in A. aesthetes (endopod of leg 2 same as that of female, unlike in latter species).

Leg 5 exopodal segment of leg 5 ( Fig. 8F View Fig ) 1.69 times longer than wide (22× 13 μm); its 3 setae 27, 30, and 15 μm long, respectively, from outer to inner. Leg 6 ( Fig. 8G View Fig ) represented by outer distal corner of genital operculum bearing 2 unequal setae at apical region, several spinules on inner and outer margins and 6 or 7 stiff setules on inner margin.

Remarks. A comparison of characters between the new species and its congeners reveals that the new species appears to be most close to A. boeckii ( Brady, 1880) which was redescribed by Bandera & Conradi (2016). The male is unknown in A. boeckii . Based on female characters 1-14 in Table 1, the two species exhibit 86% similarity value, sharing 12 identical character states in 14 characters. As revealed two differences, the genital double-somite of the female is shorter than wide in A. boeckii but slightly longer than wide in A. geminus n. sp., and the oral siphon extends to the insertions of leg 1 in A. boeckii but to the midway between the maxilliped and leg 1 in A. geminus n. sp. As additional differences, the new species has (1) a tubercle-like process on the distal segment of the maxilla (vs. the tubercles absent in A. boeckii according to the figure of Bandera & Conradi, 2016), (2) the mandibular palp (including the longer distal seta) which is as long as the coxal stylet (vs. the palp is shorter than the stylet in A. boeckii ), and (3) the setules on the postgenital lateral margins of the genital double-somite are subequal in the shape and length (vs. the setules of A. boeckii are grouped into longer anterior and shorter posterior groups, as illustrated by Bandera & Conradi, 2016).

It is noticed that the third endopodal segment of male leg 3 of the new species exhibits the same sexual dimorphism as in A. aesthetes and leg 6 of the male is also very similar between the two species. However, unlike A. aesthetes , the new species bears no sexual dimorphism in leg 2 and shows other minor differences in the mandible, maxilla, and leg 5.