Riukiaria koreana sp. nov.

urn:lsid:zoobank.org:act: B67C0886-6A00-4C4D-B69C-0733D70DBDDC

Figs 6–7, 10D, 11B, 13, 15–16

Rhysodesmus semicircularis – Takakuwa 1941b: 413–414, fig. 1 (partim), “ Kagosima, Sihusi, Itihata, Miyasima, Kyoto, Hieisan, Yamanaka, Siramine” (= all in Japan), and “Husan (Korea)” (= Busan, South Korea).

Riukiaria semicircularis – Shinohara 1977: 118. — Lim 2001: 126–128, fig. 141.

Diagnosis

Typical species of Riukiaria in size, colouration and basic form of gonopods. Riukiaria koreana sp. nov. differs from Riukiaria semicircularis (Takakuwa, 1941b) by its completely smooth metazonites (vs with coarse row of tubercles in R. semicircularis), lacking a row of sawteeth on male tarsus of rings 3–13 (vs present in R. semicircularis), having a pair of cone-shaped coxal processes on legpair 2, by a shorter and straight prefemoral process (vs long and flagellum-like, undulating in R. semicircularis), and by a curved acropodite not reaching the prefemoral process (vs forming an almost complete circle in R. semicircularis).

Etymology

Emphasizing its occurrence in the Korean Peninsula, and its separation from all other species of Riukiaria. Adjective, feminine.

Type material

Holotype SOUTH KOREA • ♂; Jellanam Prov., Jindo Town, Gogun-myeon, Jindo-daero 1320; 34°26′18.6″ N, 126°21′4.3″ E; 10 Jul. 2024; G. Kim leg.; LEGOA030054 JD07.

Paratypes SOUTH KOREA • 1 ♀; same locality and date as holotype; HNHM diplo-4561 JD03 • 1 ♀; same locality and date as holotype; HNHM diplo-4561 JD04 • 1 ♂; same locality and date as holotype; HNHM diplo-4560 JD06 • 1 ♂; same locality and date as holotype; HNHM diplo-4560 JD08 • 1 ♂; same locality and date as holotype; HNIBRIV12831 JD01 • 1 ♂; same locality and date as holotype; LEGOA030052 JD02 • 1 ♂; same locality and date as holotype; LEGOA030056 JD10 • 1 ♂; same locality and date as holotype; LEGOA030057 JD11 • 1 ♀; same locality and date as holotype; LEGOA030053 JD05 • 1 ♀; same locality and date as holotype; LEGOA030055 JD09 • 1 ♀; same locality and date as holotype; LEGOA030058 JD12 • 1 ♂; Jellanam Prov., Hwasun Town, Baega-myeon, Songdan-gil 479-55; 35°10′22.1″ N, 127°11′0.6″ E; 6 Jul. 2024; G. Kim leg.; LEGOA030059 HS01 24 • 1 ♂; Jellanam Prov., Hwasun Town, Baega-myeon, Songdan-gil 479-55; 35°10′04.8″ N, 127°11′10.3″ E; 25 Sep. 2023; D. Kim leg.; LEGOA030061 HS02 • 1 ♂; same data as for preceding; LEGOA030062 HS03 • 1 ♂; same data as for preceding; LEGOA030063 HS04 • 1 ♂; same data as for preceding; LEGOA030065 HS06 • 1 ♂; same data as for preceding; LEGOA030066 HS07 • 1 ♂; same data as for preceding; LEGOA030066 HS09 • 1 ♀; same data as for preceding; LEGOA030060 HS01 • 1 ♀; same data as for preceding; LEGOA030064 HS05 • 1 ♀; same data as for preceding; LEGOA030067 HS08 • 1 ♀; same data as for preceding; LEGOA030069 HS10 • 1 ♂; Jellanam Prov., Wando Town, Gunoe-myeon, Samdu 1-gil; 34°20′50.7″ N, 126°40′07.7″ E; 27 Jul. 2024; G. Kim leg.; LEGOA030070 WD01 • 1 ♀; same data as for preceding; LEGOA030071 WD02 • 1 ♂; Jellanam Prov., Gurye Town, Sandong-myeon, Jwasa-ri. Nogodan; 35°18′08.0″ N, 127°30′48.8″ E; 25 May 2024; 1160 m a.s.l.; D. Kim leg.; LEGOA030072 GR02 • 1 ♂; same data as for preceding; LEGOA030073 GR03 • 1 ♂; Gyeongsangbuk Prov., Yecheon Town, Hyoja-myeon, Gohang-ri, near Mt. Sobaek-san; 36°50′14.0″ N, 128°27′39.1″ E; 750 m a.s.l.; 24 Jul. 2023; D. Kim leg.; LEGOA030074 YC02 • 1 ♂; same data as for preceding; LEGOA030075 YC03 • 1 ♂; same data as for preceding; LEGOA030076 YC04 • 1 ♂; same data as for preceding; GenBank nos: PV446411 (COI), PV544276 (EF1-α); LEGOA030077 YC05 • 1 ♂; same data as for preceding; LEGOA030078 YC06 • 1 ♂; same data as for preceding; GenBank nos: PV446412 (COI), PV544277 (EF1-α); LEGOA030079 YC07 • 1 ♀; same data as for preceding; LEGOA030080 YC10 • 1 ♀; same data as for preceding; LEGOA030081 YC11 • 1 ♂; Gangwon Prov., Wonju Town, Seowon-myeon, Uhyeon-ri, Mt. Baeggun-san; 37°15′40.5″ N, 127°57′48.2″ E; 640 m a.s.l.; 4 Jun. 2023; D. Kim leg.; LEGOA030082 WJ01 • 1 ♀; same data as for preceding; LEGOA030083 WJ02 • 1 ♂; Gyeongsangnam Prov., Sancheong Town, Sicheon-myeon, Dongdang-ri, Mt. Gugok-san; 35°17′49.9″ N, 127°46′58.9″ E; 640 m a.s.l.; 2 Oct. 2023; D. Kim leg.; HNHM diplo-04562 SC13 • 1 ♀; same data as for preceding; HNHM diplo-04562 SC01 • 1 ♂; same data as for preceding; LEGOA030084 SC02 • 1 ♂; same data as for preceding; LEGOA030085 SC03 • 1 ♂; same data as for preceding; LEGOA030086 SC04 • 1 ♂; same data as for preceding; LEGOA030087 SC05 • 1 ♂; same data as for preceding; LEGOA030088 SC06 • 1 ♂; same data as for preceding; LEGOA030089 SC07 • 1 ♂; same data as for preceding; LEGOA030091 SC09 • 1 ♂; same data as for preceding; LEGOA030092 SC10 • 1 ♂; same data as for preceding; LEGOA030095 SC14 • 1 ♂; same data as for preceding; LEGOA030096 SC15 • 1 ♂; same data as for preceding; LEGOA030097 SC16 • 1 ♀; same data as for preceding; LEGOA030090 SC08 • 1 ♀; same data as for preceding; LEGOA030093 SC11 • 1 ♀; same data as for preceding; LEGOA030094 SC12 • 1 ♀; same data as for preceding; LEGOA030098 SC17 • 1 ♀; same data as for preceding; LEGOA030099 SC18 • 1 ♀; same data as for preceding; LEGOA030100 SC19.

Description

HEAD. Smooth, with 2+2 large frontal setae and several smaller ones on clypeus and around antennal sockets; epicranial suture distinct. Antennae straight; article 1 globose; articles 2–6 long, subequal in length, increasingly setose; article 7 small, globose, length equal to width, with 4 apical sensory cones hidden among dense setae.

COLLUM. Parallelogram-shaped, only slightly convex, its length 2.5 times as large as that of metatergite 2, posterolateral corners directed caudad, anterior margin nearly semicircular, without ridge.

BODY. Collum and first two rings narrow, body sides between rings 4–12 parallel, then gradually tapering towards telson. Proterga and metaterga completely smooth, metaterga with weak transverse depression in middle from ring 5 onwards. Posterolateral edge of paranota 2–4 rectangular, from 5 onwards slightly pointed triangular shape, from 12 triangular, with weak excavation on posterior edge of each of the metaterga. Pore formula mostly typical for Polydesmida, pores on rings 5, 7, 9–10, 12–13, and 15–19, in lateral position on swollen paranota. Rings 13–19 gradually tapering, posterolateral projections becoming more pointed.

TELSON. Epiproct protruding, in dorsal view triangular, in lateral view slightly curved, with 4+4 setae on sides, and with 1+1 setae apically; paraprocts (anal valves) smooth, with 2+2 setae on median ridges; hypoproct semicircular, with 1+1 setae on small tubercles.

LEGS. Bases of midbody legpairs well separated in males by 1.6–2.2 mm, in females by 1.9–2.5 mm, sterna smooth and wide, pro- and metasterna well separated. Prefemur of legs beginning at ring 7 with well-developed ventral spine (Fig. 11B: ps) increasing in size from midbody onwards; femur about twice as long as prefemur, slightly clavate; postfemur short, half as long as femur; tibia slender, setose, as long as postfemur; tarsus densely setose, about 1.5 times as long as tibia; all legs with curved claws.

MEASUREMENTS. Males (based on 36 specimens): total body length 29–42 mm, midbody width (including paranota) 5.4–7.7 mm, metatergal length 1.3–2.3 mm, midbody prozonite width 3.8–4.9 mm, collum width 4.6–6.5 mm, median collum length 1.8–2.8 mm. Females (based on 20 specimens): total body length 31–40 mm, midbody width (including paranota) 6.6–7.8 mm, metatergal length 1.6–2.2 mm, midbody prozonite width 4.3–5.6 mm, collum width 5.4–6.6 mm, median collum length 2.0– 2.9 mm.

COLOURATION (Figs 7A, 13). Preserved specimens in ethanol: dorsum, prozonites, metazonite, and proximal part of epiproct dark grey, almost blackish, distal part of epiproct lighter. Posterior portion of paranota with bright yellow spots on all rings, including collum. Posterior part of head and proximal part of antennal articles dark grey; clypeus, cheeks and distal end of antennal articles, femur, postfemur and tibia from legs 2 onwards light grey or whitish; legpair 1, other articles of other legs, and ventral side white.

MALE CHARACTERS. Coxae of legpair 2 with pair of protruding, cone-shaped processes, remaining legs and sterna without modifications. Posterior margin of rings 5–13 medially with minute serrated edge (Fig. 7B). Gonopods (Fig. 6A–D): two forceps-like processes as typical of Riukiaria; one prefemoral process (pfp), and the other acropodite (a) (after Korsós et al. 2011: 57, fig. 1). Coxa stout, as long as wide, without coxal apophysis, with single apophyseal macroseta (ms) on dorsal side. Cannula on mesal side, starting near macroseta, then connected to prefemur and continuing in prostatic groove. Prefemur short, densely setose, prefemoral process straight, directed dorsad, about ⅔ in length compared to acropodite, gradually tapering to pointed tip. Acropodite (a) straight at base, subparallel with prefemoral process (pfp), about 1.5 times as thick as prefemoral process, gradually bending dorsally at midpoint, tip curving, directed towards but not reaching end of prefemoral process. Prostatic groove (pg) running along dorsal side of acropodite, (a) opening at tip.

FEMALE CHARACTERS. Body of females wider than that of males, subequal in length; other somatic characters, including colouration and strong prefemoral ventral spines, similar. Posterior margin of rings 5–13 medially without serrated edge. Coxae of legpair 2 without projection (Fig. 10D), further legs also without any sternal or coxal modifications. Cyphopods in situ closely behind legpair 2, in common ovalshaped opening; valves of equal size, pentagon-shaped, ventral edges each with a small peak (Fig. 10D), operculum laterally closely overlaying, receptacles deeply embedded under valves.

Distribution

Riukiaria koreana occurs scattered across the entire South Korean Peninsula (Fig. 15).

Remarks

In the original description of Rhysodesmus (= Riukiaria) semicircularis, Takakuwa (1941b) mentioned a single Korean locality, “Husan” (= Busan, South Korea). This record was mentioned by some authors (Miyosi 1952, 1959; Shinohara 1977), based on literature and without examining specimens from Korea. Lim (2001) translated the original description, while mentioning “it is necessary to make a better description based on fresh material” (Lim 2001: 126). Lim Kil-Young (2024 pers. comm.) admitted that his concept of Riukiaria in Korea needs re-evaluation. Here, with fresh Korean material of Riukiaria at hand, we can clearly establish the differences from the Japanese R. semicircularis (see Diagnosis).