Lobatoradarea subinermis Ariyama & Kohtsuka, 2025

Lobatoradarea subinermis Ariyama & Kohtsuka , sp. nov.

[New Japanese name: Togenashi-udenaga-yokoebi-modoki]

( Figs 42–46)

Type material. Holotype: female, 4.2 mm (OMNH-Ar-13252), Sagami Bay, off Miura City , Kanagawa Prefecture, 35°06'53"N, 139°33'51"E ( Fig. 1B), 297–448 m depth, using dredge, 20 January 2015, coll. Hisanori Kohtsuka. GoogleMaps

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

Etymology. From the Latin sub (=close to) + inermis (related species commonly lacking the posterodorsal projections). Adjective.

Description of female. Based on holotype, 4.2 mm (OMNH-Ar-13252).

Head ( Figs 42, 43). Rostrum developed, lateral cephalic lobe rounded, anteroventral corner acutely projected. Eyes medium-sized (diameter: 35% of head height). Antenna 1, peduncular articles 1, 2 with length ratio of 1.0: 0.6; article 3, accessory flagellum and primary flagellum lost. Antenna 2, peduncular articles 3, 4 with length ratio of 1.0: 2.5, article 5 and flagellum lost. Upper lip rounded ventrally, bearing several minute setae. Mandibles, both incisors with 6 cusps, laciniae mobilis 6- and 3-toothed in left and right, respectively, accessory setal rows with 5 and 4 thick setae in left and right, respectively; palp stout, article length ratio 1.0: 3.9: 2.2 in left, article 1 short, bare, article 2 long, with 3+1 setae subdistally, article 3 bearing 1 proximal, 7–9 ventral and 1 thick and 2 slender distal setae, lateral surface with dense thin setae and single slender seta. Lower lip, inner lobes developed, bare; outer lobes with relatively long mandibular lobes, setose mediodistally, lateral margins with sparse fine setae. Maxilla 1, inner plate pear-shaped, medial margin bearing long setae; outer plate distally with 11 denticulate robust setae and 7 thick setae; palp article 1 bare, article 2 apically with 6 triangular and 1 long robust setae and 4 slender setae in left and 1 triangular and 6 narrow robust setae and 4 slender setae in right. Maxilla 2, inner plate slightly wider than outer plate. Maxilliped, inner plate with 3 triangular robust setae distally; outer plate bearing 4 long and 7 short robust setae mediodistally; palp article 3 dorsal surface with 6 thick setae and many fine setae.

Pereon ( Figs 42, 44). Pereonite 7 not projected posterodorsally. Gnathopod 1 short; coxa widened distally, with 2 small notches each on anteroventral and posteroventral margins, medial surface without setae; basis straight, anterior margin with 4 short setae, posterior margin and medial surface bare; merus acutely projected distally, with several thick setae on posterodistal margin; carpus relatively long, posterior margin bearing many thick setae; propodus longer than carpus (ca. 1.2 times), posterior margin with several thick setae, palm weakly oblique, defined by 2 lateral (long and short) and 1 medial (short) robust setae; dactylus short. Gnathopod 2 longer than gnathopod 1; coxa relatively long, with 2 small notches each on anteroventral and posteroventral margins, medial surface lacking setae; basis slender, straight, anterior margin with 2 short setae distally, posterior margin bearing 2 long and 2 short setae, inner margin with a long seta; merus acutely projected distally, posterodistal corner with a single seta; carpus long and narrow, posterior margin bearing several bundles of slender setae; propodus slightly longer than carpus (ca. 1.05 times), narrow, anterior margin with a few short setae, posterior margin bearing many bundles of slender setae, palm weakly oblique, defined by 2 lateral (long and short) and 2 medial (short) robust setae; dactylus short. Pereopod 3, coxa longish trapezoidal, with 3 and 2 small notches on anteroventral and posteroventral margins, respectively, medial surface without setae; basis straight, anterior margin with 3 robust setae, posteroproximal margin with a long seta, posterodistal corner bearing a robust seta; ischium posterodistal corner bearing a short seta; merus slightly widened distally, anterodistal corner with a robust seta; carpus posterior margin and posterodistal corner with 3 and 1 robust setae, respectively; propodus longer than carpus, posterior margin and posterodistal corner with 4 and 2 robust setae, respectively; dactylus slender, smooth. Pereopod 4, coxa ventral margin rounded, with 3 and 2 small notches on anteroventral and posteroventral margins, respectively, medial surface bare; basis straight, anterior margin with 1 long proximal seta and 4 robust setae, posterodistal corner bearing a robust seta; ischium posterodistal corner bearing a short seta; merus slightly widened distally, anterodistal corner lacking a robust seta; carpus posterior margin with 3 robust setae; propodus longer than carpus, posterior margin with 4 robust setae; dactylus slender, smooth. Pereopod 5, coxa posteroventral margin with 2 small notches; basis longish ovoid, with anterolateral ridge, anterior margin with single proximal seta and 5 robust setae, anterodistal corner bearing a robust seta, posterior margin sparsely serrated, medial surface with vertical ridge bearing a robust seta; ischium with a robust seta at anterodistal corner; merus with 1+2 anterior, 2 anterodistal, 3 posterior and 3 posterodistal robust setae; carpus–dactylus lost. Pereopod 6, coxa anterior margin straight, without setae, posteroventral margin with 3 small notches; basis ovoid, with indistinct anterolateral ridge, anterior margin and anterodistal corner with 3 and 1 robust setae, respectively, posterior margin sparsely serrated, medial surface with vertical ridge bearing a robust seta; ischium with a robust seta at anterodistal corner; merus–dactylus lost. Pereopod 7, coxa short, oval, posteroventral margin with 2 small notches; basis longish ovoid, with anterolateral ridge, anterior margin with 5 robust setae, posterior margin sparsely serrated, medial surface with vertical ridge lacking a robust seta; merus–dactylus lost.

Pleon ( Figs 42, 45). Pleonites 1, 2 not projected posterodorsally. Epimeral plates 1–3, posteroventral corners minutely produced in plates 1, 2 and angular in plate 3, lateral surfaces of plates 1, 2 with ridge, ventral margin of plate 2 bearing 2 robust setae. Pleopods, pleopod 2 longest; each peduncle bearing 2 coupling hooks, peduncle of pleopod 2 with several anterior and posterior setae and a long distal seta, peduncle of pleopod 3 bearing several posterior setae and 5 posteromedial and 2 lateral robust setae; outer rami longer than inner rami, outer and inner rami with 9, 10, 10 articles and all 9 articles, respectively. Uropod 1, peduncle long, dorsal surface with 6 lateral, 1 laterodistal, 3 medial and 1 mediodistal robust setae, ventrodistal end slightly produced; both rami damaged, inner ramus with several lateral and medial robust setae. Uropod 2, peduncle short, with 1 laterodistal and 3 (1 lost) robust setae, ventrodistal end roundly produced; both rami damaged. Uropod 3, peduncle very short, longer than wide, ventrodistal end acutely produced, dorsal surface with several short setae; outer ramus with several lateral and medial robust setae, inner ramus lost. Telson narrowed distally, distal end damaged, dorsal surface with 6 sensory setae, lateral margins with a few minute setae.

Male. Unknown.

Coloration in life. Based on holotype, female, 4.2 mm (OMNH-Ar-13252, Fig. 46). Head and pereonites 1–5 faintly orange; pereonite 6, 7, pleonites 2, 3 and urosomites 2, 3 white; pleonite 1 and urosomite 1 orange; eyes light red; coxae 1–7 faintly orange to white, with several orange patches; antennae pale pink; gnathopods, pereopods, pleopods and uropods white, but bases of pereopods 5, 6 each with a bright white mark.

Remarks. Although the antenna 1 is almost lost, the uropod 3 inner ramus is also lost and the telson is damaged distally, this species can be identified as a species of the genus Lobatoradarea because of the presence of inner lobes of the lower lip. Only two Lobatoradarea species lack the posterodorsal projections both on the pereonite 7 and the pleonites 1, 2. Lobatoradarea subinermis sp. nov. is different from L. inermis sp. nov. in the acutely produced anterodistal corner of the head, the smaller eyes, and the coloration. The slender dactyli of the pereopods are distinctive in the genus.

Habitat. Deep bottom with a depth of 297–448 m.

Distribution. Japan: Sagami Bay (present study).