Lobatoradarea inermis Ariyama, Kohtsuka & Kodama, 2025

Lobatoradarea inermis Ariyama, Kohtsuka & Kodama , sp. nov.

[New Japanese name: Togenashi-udenaga-yokoebi]

( Figs 22–26)

Type material. Holotype: male, 5.0 mm (OMNH-Ar-13230), Sagami Bay, off Miura City , Kanagawa Prefecture, 35°09'07"N, 139°34'29"E ( Fig. 1A), 84–91 m depth, using dredge, 9 May 2016, coll. Hisanori Kohtsuka. GoogleMaps Paratype: female, 4.6 mm (OMNH-Ar-13231), same data as holotype; male, 4.8 mm (OMNH-Ar-13232), mouth of Kagoshima Bay , between Ibusuki City and Minami-ōsumi Town, Kagoshima Prefecture, 31°12'47"N, 130°42'21"E ( Fig. 1J), 108–109 m depth, muddy bottom, using dredge, T / V Nansei-maru ( Kagoshima University), 2 October 2024, coll. Masafumi Kodama. GoogleMaps

Type locality. Sagami Bay , off Miura City in Kanagawa Prefecture Japan .

Etymology. From the Latin inermis , -is, -e (=unarmed), referring to the body lacking posterodorsal projections. Adjective.

Description of male. Based on holotype, 5.0 mm (OMNH-Ar-13230).

Head ( Figs 22, 23, 25A 2). Rostrum developed, lateral cephalic lobe roundish triangular, anteroventral corner slightly projected. Eyes large (diameter: 51% of head height), bulging laterally. Antenna 1, peduncular articles 1–3 with length ratio of 1.0: 0.8: 0.3, articles 1, 2 with a few robust setae; accessory flagellum short, cylindrical, tip with 4 setae; primary flagellum with 29+ articles, tip lost, article 1 relatively long, 1 article with aesthetasc. Antenna 2, peduncular articles 3–5 with length ratio of 1.0: 2.5: 3.1, each article bearing several robust setae; flagellum long, with 32+ articles, tip lost, article 1 long. Upper lip weakly produced ventrally, bearing many thin setae ventrally. Mandibles, both incisors with 8 cusps, laciniae mobilis 7- and 3-toothed in left and right, respectively, both accessory setal rows with 6 thick setae; palp stout, article length ratio 1.0: 3.2: 2.9 in right, article 1 short, bare, article 2 long, with 6–7 setae ventrally, article 3 bearing 1 proximal, 11 ventral and 1 long and 2 short distal setae, lateral surface covered with dense thin setae. Lower lip, inner lobes developed, bare; outer lobes with relatively short mandibular lobes, setose mediodistally. Maxilla 1, inner plate pear-shaped, medial margin bearing long plumose setae; outer plate distally with 11 denticulate robust setae and 8 thick setae; palp article 1 bare, article 2 apically with 7 triangular and 1 long robust setae and 4 slender setae in left and 9 narrow robust setae and 5 slender setae in right. Maxilla 2, inner plate ca. 1.4 times width of outer plate. Maxilliped, inner plate with 3 triangular robust setae distally; outer plate bearing 5 long and 7 short robust setae mediodistally; palp article 3 dorsal surface with 3 thick setae and many fine setae.

Pereon ( Figs 22, 24). Pereonite 7 not projected posterodorsally. Gnathopod 1 short; coxa subrectangular, with a small notch each on anteroventral and posteroventral margins, medial surface bearing several setae; basis slender, straight, anterior margin with 6 robust setae and a few slender setae, posterior margin bearing 1 long and several short setae, medial surface with 3 long setae; merus projected distally, with several thick setae on posterodistal margin; carpus relatively short, posterior margin bearing many thick setae; propodus longer than carpus (ca. 1.25 times), posterior margin setose, palm weakly oblique, defined by 1 long and 3 short robust setae (2 lateral and 2 medial); dactylus short. Gnathopod 2 longer than gnathopod 1; coxa roundish rectangular, with a small notch on anteroventral margin and a small notch and robust seta on posteroventral margin; basis slender, straight, anterior margin with 8 robust setae, posterior margin bearing 3 long and several short setae; merus projected distally, posterior margin with a few setae; carpus long and narrow, posterior margin bearing several bundles of slender setae; propodus longer than carpus (ca. 1.1 times), narrow, anterior margin lined with short setae, posterior margin bearing many bundles of slender setae, palm weakly oblique, defined by 4 (2 lateral and 2 medial) short robust setae; dactylus short. Pereopod 3, coxa roundish rectangular, with a small notch each on anteroventral and posteroventral margins, medial surface bearing 5 thick and 1 slender setae; basis almost straight, anterior margin with 6 robust setae, posterior margin lined with short setae, lateral surface bearing 2 thick setae proximally; merus slightly widened distally, anterior margin with 3 robust setae, anterodistal corner with 3 robust setae; carpus–dactylus lost. Pereopod 4, coxa ventral margin rounded, with 2 small notches each on anteroventral and posteroventral margins, medial surface bearing a few setae; basis almost straight, anterior and posterior margins with 4 and 3 robust setae, respectively; ischium and merus similar to those of pereopod 3, carpus–dactylus lost. Pereopod 5, coxa anterodistal corner and posterior margin with 1 and 5 small notches, respectively; basis ovoid, anterolateral ridge indistinct, anterior margin with 3 proximal setae and 1+1+2+3+2 robust setae, anterodistal corner bearing 3 robust setae, posterior margin sparsely serrated, medial surface with vertical ridge bearing a small robust seta; ischium with 2 robust setae at anterodistal corner; merus with 2+2 anterior, 2 anterodistal, 4 posterior and 2 posterodistal robust setae; carpus–dactylus lost. Pereopod 6, coxa anterior margin straight, without setae, posteroventral margin with 3 small notches; basis ovoid, with anterolateral ridge, anterior margin with several proximal setae and 1+1+2 robust setae, anterodistal corner bearing 2 robust setae, posterior margin sparsely serrated, medial surface with vertical ridge bearing a seta; ischium with 2 robust setae at anterodistal corner; merus with 2+2+2 anterior, 2 anterodistal, 2+2+2+2 posterior and 1? posterodistal robust setae; carpus with 2 anterior and 2 anterodistal robust setae; propodus with 4 anterior, 1 anterodistal and 4 posterior robust setae; dactylus smooth. Pereopod 7, coxa short, trapezoidal, posteroventral margin with a small notch; basis ovoid, with anterolateral ridge, anterior margin with 2 proximal setae and 1+1+2 robust setae, posterior margin sparsely serrated, medial surface with short vertical ridge bearing 2 short setae; merus with 1+2+2 anterior, 3 anterodistal, 1+2+1+1+1 posterior and 7 posterodistal robust setae; carpus–dactylus lost.

Pleon ( Figs 22, 25). Pleonites 1, 2 lacking posterodorsal projections. Epimeral plates 1–3, posteroventral corners minutely produced, lateral surfaces with ridge in plates 1, 2, ventral margins with 2, 3, 2 robust setae in plates 1–3, respectively. Pleopods, pleopod 2 longest; each peduncle bearing a few or several setae and 2 coupling hooks, peduncle of pleopod 1 with a robust seta posteromedially, peduncle of pleopod 2 with a long distal seta, peduncle of pleopod 3 bearing 3 posteromedial and 1 lateral robust setae; both rami almost same lengths, outer rami with 11, 12, 13 articles and inner rami with 10, 11, 5+ articles in pleopods 1–3, respectively. Uropod 1, peduncle long, dorsal surface with 8 (1 lost) lateral, 1 laterodistal, 5 (1 lost) medial and 1 mediodistal robust setae, ventrodistal end slightly produced; outer ramus short, tip lost, with 3 lateral robust setae; inner ramus ca.1.15 times as long as peduncle, with 5 lateral, 4 (1 lost) medial and 4 terminal robust setae. Uropod 2 shorter than uropod 1; peduncle short, with 2 lateral and 1 laterodistal robust setae, ventrodistal end slightly produced; outer ramus ca. 0.75 times length of peduncle, with 3 (1 lost) lateral and 4 (1 lost) terminal robust setae; inner ramus longer than outer ramus (tip lost), with 5 lateral and 5 medial robust setae. Uropod 3 relatively long, about 0.75 times length of uropod 1; peduncle very short, longer than wide, ventrodistal end slightly produced, medial margin with several short setae; outer ramus short (tip lost), with 2 lateral and 3 medial robust setae; inner ramus very long, ca. 2.65 times length of peduncle, with 6 lateral and 9 medial robust setae. Telson small, trapezoidal, distal margin truncated, both laterodistal corners with a small notch, dorsal surface bearing 6 sensory setae and 6 short setae.

Description of female. Based on paratype, female, 4.6 mm (OMNH-Ar-13231). Almost similar to holotype, male, 5.0 mm (OMNH-Ar-13230) except for oostegites. Gnathopods almost similar to those of male; but gnathopod 1 coxa lacking anteroventral notch, basis with 2 long setae on posteroproximal margin, and carpus anterior margin with several robust setae ( Fig. 25 F-G1), and gnathopod 2 basis bearing single long seta posteroproximally ( Fig. 25 F-G2).

Coloration in life. Based on holotype, male, 5.0 mm (OMNH-Ar-13230, Fig. 26). Eyes light red, other parts faintly-orangish white, but lateral surface of pereonite 7 with dark red mark mid-posteriorly and posterolateral margin of pleonite 3 dark red.

Remarks. Lobatoradarea inermis sp. nov. shares the bare dorsal margins of the pereonite 7 and pleonites 1, 2 with L. subinermis sp. nov. However, this new species can be distinguished from L. subinermis by the slightly produced anteroventral corner of the head and the larger eyes.

Habitat. Deep bottom with a depth of 84–109 m.

Distribution. Japan: Sagami Bay and Kagoshima Bay (present study).