Janiralata kwangsooi sp. nov.

urn:lsid:zoobank.org:act: C97BC4EA-4FCC-40F2-87A8-FBBC0DCB78B4

Figs 2‒7, Table 1

Materials examined. Holotype: 1 male NIBRIV0000911351, Dongyeo islet, Dokdori 53, Ulleung-eup, Ulleunggun, Gyeongsangbuk-do, Korea, 37°243872N 131°861251E, 23m depth, 17℃, 20 June 2023, collected by Taekjun Lee.

Paratypes: 1 male NIBRIV0000911352, 1 male NIBRIV0000911353, 1 male NIBRIV0000911354, 1 male NIBRIV0000911355, 1 female NIBRIV0000911356, same data as holotype.

Diagnosis (male): Antennular article 1 with two broom and two UB setae; mandibular palp article 1 with three simple setae; maxillula medial lobe with four serrate apical setae; maxillipedal basis with five simple setae, palp article 1 with two simple setae; pereopod I ischium with eight UB and 12 simple setae; pleopod 1 with ten simple setae on distodorsal margin; exopod article 2 of pleopod 3 with nine simple setae distally; uropodal protopod with 21 UB setae.

Description (male): Body (Fig. 2A) total length measured in holotype 4.2 mm, length 2.2 times longer than wide, preserved specimens white in color.

Cephalothrax (Fig. 2A) 0.5 times longer than wide and 0.3 times of whole body (1.3 mm), without rostrum; anterolateral margin concave, with anterior projections; lateral UB setae present, dorsal margin covered with numerous setae; eyes globular, vertical length of 0.3 mm, ommatidia on eyelobe dorsally.

Pereon (Fig. 2A) 0.5 times of whole body (2.1 mm), maximal body width in pereonite 6 1.5 times of width of cephalothorax (2.0 mm); dorsal margin and lateral protrusion of each pereonite armed with simple setae.

Pleonite (Fig. 2A) 0.1 times longer than wide, no setae present. Pleotelson (Fig. 2A) ovoid; 0.8 times longer than wide, 0.3 times of whole body (1.2 mm), posteromedial apex convex, bluntly rounded; posterolateral margin curved, anal opening subterminal, dorsal and lateral margin covered with numerous simple setae.

Antennula (Fig. 2B) peduncular article 1 0.9 times longer than wide, with two broom and two UB setae; article 2 1.6 times longer than wide, with three broom, seven UB, and three simple setae; peduncular article 3 1.5 times longer than wide, with one UB and two simple setae on distal corner and four short simple setae along lateral margin; flagellar article 1 0.8 times longer than wide, with on broom, one UB, and four simple setae distally; ornamentation including setae and aesthetascs of following articles: 2:2:3:3:3:4:3:2:3:2:4:1:2:2:4.

Antenna (Fig. 2C) article 1 0.9 times longer than wide, with one UB distal seta; article 2 0.5 longer than wide, with one UB seta distally; article 3 1.4 times longer than wide, with three UB setae distolaterally, scale with one simple seta along lateral edge, five UB and three fine setae on distal region; article 4 0.7 times longer than wide, with two UB and three simple setae distolaterally.

Mandibles (Fig. 3) pars molaris truncate, distal margin of grinding surface stepped, with four short simple setae, palp inserted on cuticular projection; article 1 (Fig. 3A) 2.4 times longer than wide, with three simple setae distally; article 2 2.3 times longer than wide, with two robust serrate setae and four simple setae on distolateral margin; article 3 2.3 times longer than wide, with one robust apical seta and numerous simple setae along lateral margin; right mandible (Fig. 3A) pars incisiva with five cusps; lacinia mobilis absent, with 12 robust serrate setae; left mandible (Fig. 3B) pars incisiva with five cusps, lacinia mobilis and eight serrate setae below pars incisiva.

Labium (Fig. 3C) body divided into two lobes by deep medial incision, distal margin of each lobe with simple setae and many hairs.

Maxillula (Fig. 3D) lateral lobe with 12 robust serrate setae distally and numerous fine setae along inner margin, one simple seta present on distal margin; medial lobe with four serrate apical setae and fine setae along outer margin.

Maxilla (Fig. 3E) lateral two lobes each with three long simple and one serrate seta distally; medial lobe with ten robust serrate and numerous fine setae distally.

Maxilliped (Fig. 3F) basis 2.2 times longer than wide with four simple setae medially and one short simple seta on distolateral corner; endite 1.7 times longer than wide, with five fan-like, nine serrate, and one simple setae on distodorsal margin, five simple setae on distoventral margin, three coupling hooks proximomedially; epipodite 2.6 times longer than wide, distal end with one short seta, reaching to palp article 3; palp article 1 0.9 times longer than wide, with two simple setae on distomedial and distolateral corners; article 2 1.1 times longer than wide, with 18 simple setae on medial margin; article 3 0.8 times longer than wide, with 25 simple setae along medial and distomedial margin; article 4 3 times longer than wide, with six simple setae along lateral margin and 15 setae on distal margin; article 5 2.2 times longer than wide, with 16 simple setae distally.

Pereopods (Figs 4–5) all coxae visible in dorsal view, each coxa with simple setae, ranging from one to two or three; pereopod I subchelate, carpus broadened at center; articular plate projected from distal margin of propodus partly covered dactylus of all pereopods.

Pereopod I (Fig. 4A) article L/W ratios 2.3:2.5:0.9:2.1:3.9:0.9; basis with two UB and ten simple setae; ischium with eight UB and 12 simple setae; merus with five UB and seven simple setae; carpus with seven UB and 19 simple setae, 19 robust setae along posterior margin; propodus with one UB and four simple setae distally, 22 short simple setae along anterior and posterior margins, proximoventral border serrated; dactylus armed with four simple setae.

Pereopod II (Fig. 4B) article L/W ratios 2.7:3.4:1.4:3.8:4.6:1.4; basis with four broom, seven UB, and 13 simple setae; ischium with six UB and 12 simple setae; merus with seven UB and nine simple; carpus with one broom, 15 UB, and 22 simple setae; propodus with one broom, 14 UB, and 39 simple setae; dactylus with three claws and four simple setae.

Pereopod III (Fig. 4C) article L/W ratios 2.6:2.8:1.3:3.2:4.1:1.4; basis with two broom, three UB, and nine simple setae; ischium with eight UB and seven simple setae; merus with five UB and eleven simple setae; carpus with one broom, nine UB, and 13 simple setae, distal edge covered with fine hairs; propodus with one broom, 11 UB, and 27 simple setae; dactylus with four simple setae.

Pereopod IV (Fig. 4D) article L/W ratios 2.8:1.8:1.4:2.5:3.9:1.3; basis with six broom, two UB, and seven simple setae; ischium with eight UB and three simple setae; merus with seven UB and seven simple setae; carpus with 19 UB and three simple setae, numerous fine hairs present along distal margin; propodus with one broom, seven UB, and 26 simple setae; dactylus with four simple setae.

Pereopod V (Fig. 5A) article L/W ratios 2.6:2.3:1.2:2.9:3.6:1.3; basis with three broom, three UB, and ten simple setae; ischium with nine UB and seven simple setae; merus four UB and 11 simple setae; carpus with seven UB and ten simple setae, distal margin covered with hairs; propodus with four UB setae; dactylus with four simple setae.

Pereopod VI (Fig. 5B) article L/W ratios 2.7:2.7:1.2:2.9:4.2:1.3; basis with one broom, one UB, and 11 simple setae; ischium with seven UB and five simple setae; merus with six UB and four simple setae; carpus with five UB and eight simple setae, hairs present along distal edge; propodus with one broom, six UB, and 14 simple setae; dactylus with four setae.

Pereopod VII (Fig. 5C) article L/W ratios 2.6:2.8:1.2:3.5:4.8:1.5; basis with two broom, three UB, and eight simple setae; ischium with four UB and five simple setae; merus with six UB and five simple setae; carpus with five UB and nine simple setae; propodus with one broom, six UB, and six simple setae; dactylus with four simple setae.

Pleopod I (Fig. 6A, B) 1.4 times longer than maximum wide (measured at broadest section of distal part); separated in half by medial stylet-guiding groove running from proximal end; proximolateral part rounded; distolateral edge of hyaline lamella angular, projecting laterally; each half of pleopod I with five simple setae on distoventral quarter, distomesial part with pair of small protrusions, several short setae along distal apex.

Pleopod II (Fig. 6C) protopod oval, 1.5 times longer than wide, 12 simple setae along distal apex; endopodal stylet, elongate, medially swollen, becoming narrower until distal tip without any ornamentation; exopod distal apex round, located below stylet distomedially in protopod.

Pleopod III (Fig. 6D) protopod 0.8 times longer than wide; endopod, suboval, 1.4 times longer than wide, with three plumose apical setae; exopod with two articles, article 1 4.9 times longer than wide, numerous hairs covering lateral margin, article 2 2.2 times longer than wide with nine apical setae.

Pleopod IV (Fig. 7A) protopod 0.6 times longer than wide; endopod 1.5 times longer than wide, distomesial tip protruded; exopod 3.1 times longer than wide, with lateral margin covered by hairs.

Pleopod V (Fig. 7B) ellipse, 1.7 times longer than wide, with distomesial protrusion.

Uropod (Fig. 7C) protopod 1.5 times longer than wide, with 21 UB setae; endopod 4.2 times longer than wide, slightly longer than exopod, with six broom, 13 UB, and 23 simple setae; exopod 4.6 times longer than wide, with 19 UB and 12 simple setae.

Sexual dimorphism of female: Pereonites 2–4 distinctly expanded than other pereonites, maximal body width in pereonite 3; antenna (Fig. 2D) article 1 same as in male; article 2 0.6 longer than wide, with one UB seta distally; article 3 1.3 times longer than wide, with three UB and one simple setae distolaterally, scale with one simple seta on lateral edge and seven simple setae on distal end; article 4 0.9 times longer than wide, with two UB and two simple setae distolaterally; article 5 4.2 times longer than wide, with one broom, nine UB, and 20 simple setae; article 6 6.2 times longer than wide, with three broom, four UB, and 41 simple setae; flagellum with 88 articles, article 1 longer than following articles, 1.4 times longer than wide; following articles rectangular, with 0–3 short simple setae; Pereopods longer; Operculum semi-circular, length 0.8 times longer than width, outer margin with numerous short setae.

Variability: No significant variability was observed among paratypes in the armature of any appendages except that segmentation of antennular flagellum showed subtle difference in L/W ratio among body segments.

Etymology: The new species is named after Dr. Kwang-Soo Kim, a polychaete researcher who contributed to this study by providing academic advice.

Identification key. This updated identification key to East Asian Janiralata species is derived from previous studies of Kim & Yoon (2021) and Kim et al. (2022). It has modifications with new species added.