Lobatoradarea obliquua Ariyama & Kodama, 2025

Lobatoradarea obliquua Ariyama & Kodama , sp. nov.

[New Japanese name: Naname-udenaga-yokoebi]

( Figs 27–30)

Type material. Holotype: male, 2.9 mm (OMNH-Ar-13233), Ōsumi Strait, off Cape Sata, Minami-ōsumi Town , Kagoshima Prefecture, 30°52'54"N, 130°40'48" ( Fig. 1K), 121–123 m depth, rock and gravel bottom, using dredge, T / V Nansei-maru ( Kagoshima University), 1 October 2024, coll. Masafumi Kodama.

Type locality. Ōsumi Strait in Kagoshima Prefecture, Japan .

Etymology. From the Latin obliquus, - a, - um (= oblique), referring to the strongly oblique palms of the gnathopods. Adjective.

Description of male. Based on holotype, male, 2.9 mm (OMNH-Ar-13233).

Head ( Fig. 27). Rostrum strongly developed, lateral cephalic lobe roundish-angular, anteroventral corner acutely projected. Eyes large (diameter: 43% of head height). Antenna 1, peduncular articles 1–3 with length ratio of 1.0: 0.6: 0.3; accessory flagellum very short, bullet-shaped, with 5 setae; primary flagellum with 18+ articles, tip lost, article 1 long, 3 articles with aesthetasc. Antenna 2, peduncular articles 3–5 with length ratio of 1.0: 3.0: 4.7, each article bearing several robust setae; flagellum with 28+ articles, tip lost, article 1 very long. Upper lip relatively short, ventral margin rounded, anterior surface and ventral margin with many minute setae. Mandibles, both incisors with 7 cusps, laciniae mobilis 5- and 3-toothed in left and right, respectively, accessory setal rows with 5 and 4 thick setae, respectively; palp stout, article length ratio 1.0: 3.9: 2.8 in left, article 1 short, bare, article 2 long, with 1–2 setae subdistally, article 3 bearing 1 proximal, 1 median and 8 ventral setae and 1 thick and 2 slender distal setae, lateral surface covered with dense thin setae. Lower lip, inner lobes developed, bare; outer lobes with relatively short mandibular lobes, mediodistal surfaces with fine setae. Maxilla 1 (left), inner plate narrowed distally, medial margin bearing 12 long plumose setae, tip with 1 long and 2 short setae; outer plate distally with 11 denticulate robust setae and 4 thick setae; palp article 1 bare, article 2 apically with 6 triangular and 1 long robust and 4 slender setae. Maxilla 2, inner plate ca. 1.3 times width of outer plate. Maxilliped, inner plate with 3 triangular robust setae distally; outer plate bearing 4 long and 6 short robust setae mediodistally; palp article 3 dorsal surface with 4 thick setae and many fine setae.

Pereon ( Figs 28, 29). Pereonite 7 not projected posterodorsally. Gnathopod 1 small; coxa roundish rectangular, with 1 and 3 small notches on anteroventral and posteroventral margins, respectively, medial surface bearing several setae; basis slender, slightly curved anteriorly, anterior margin with 4 robust setae, medial surface bearing a long seta posteroproximally; merus projected distally, with several thick setae on posterodistal margin; carpus longish triangular, posterior margin bearing many thick setae; propodus longer than carpus (ca. 1.15 times), posterior margin with many thick setae, palm strongly oblique, defined by 2 (1 lateral and 1 medial) long robust setae; dactylus short. Gnathopod 2 longer than gnathopod 1; coxa roundish rectangular, with 1 and 2 small notches on anteroventral and posteroventral margins, respectively, medial surface lacking setae; basis slender, straight, anterior and posterior margins with a few short setae; merus projected distally, posterodistal corner with 2 setae; carpus long and narrow, posterior margin bearing several bundles of thick setae; propodus longer than carpus (ca. 1.1 times), narrow, anterior margin with a few short setae, posterior margin bearing many bundles of thick setae, palm strongly oblique, defined by 2 (1 lateral and 1 medial) long robust setae; dactylus short. Pereopod 3 longer than gnathopod 2; coxa roundish rectangular, with 3 and 2 small notches on anteroventral and posteroventral margins, respectively, medial surface bearing several setae; basis straight, anterior margin with 3 robust setae, posterior margin with a few short setae, posterodistal corner bearing a robust seta; merus anterodistal corner with a robust seta, posterodistal corner bearing a long seta; carpus posterior margin and posterodistal corner with 3 and 2 robust setae, respectively; propodus longer than carpus, posterior margin and posterodistal corner with 4 and 2 robust setae, respectively; dactylus with a minute projection on inner margin. Pereopod 4 almost same length as pereopod 3; coxa ventral margin rounded, with 2 and 3 small notches on anteroventral and posteroventral margins, respectively, medial surface bearing several setae; basis straight, anterior and posterior margins with several slender setae, posterodistal corner bearing a robust seta; ischium–dactylus similar to those of pereopod 3. Pereopod 5, coxa anteroventral and posterior margins with 1 and 3 small notches, respectively; basis ovoid, with anterolateral ridge, anterior margin with a few slender setae and 3 robust setae, anterodistal corner bearing 2 robust setae, posterior margin serrated, medial surface with vertical ridge bearing a robust seta; ischium with a long seta at anterodistal corner; merus anterior margin with 2+3 robust setae, anterodistal corner bearing 3 robust setae, posterior margin with 2 (1 lost) robust setae, posterodistal corner bearing 4 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 3 robust setae, anterodistal corner bearing a robust seta, posterior margin serrated, medial surface with short vertical ridge bearing a robust seta (damaged); ischium with a long seta at anterodistal corner; merus–dactylus lost. Pereopod 7, coxa short, oval, posteroventral margin with a small notch, gill unknown; basis large, ovoid, posteroproximal corner roundly projected, lateral surface with anteroproximal ridge, anterior margin with a proximal seta and 5 robust setae, anterodistal corner bearing a robust seta, posterior margin serrated, medial surface with short vertical ridge bearing a robust seta; ischium with a long seta at anterodistal corner; merus with 3 anterior, 2 anterodistal, 4 posterior and 4 posterodistal robust setae; carpus–dactylus lost.

Pleon ( Fig. 29). Pleonites 1, 2 projected posterodorsally. Epimeral plates 1–3, posteroventral corners minutely produced, lateral surfaces with ridge in plates 1, 2, ventral margins bearing 2, 2 and 1 robust setae in plates 1–3, respectively. Pleopods, pleopod 2 longest, each peduncle with 2 coupling hooks; pleopod 1 peduncle lacking setae, but with a robust seta posteromedially, both rami with 11 articles; pleopod 2 peduncle bearing several slender setae, 1 long anterodistal seta and 2 posteromedial robust setae, outer and inner rami with 12 and 11 articles, respectively; pleopod 3 peduncle with 3 lateral and 6 posteromedial robust setae, both rami damaged. Uropod 1, peduncle long, dorsal surface with 4 lateral, 1 laterodistal, 3 medial and 1 mediodistal robust setae, ventrodistal end with long inter-ramal process; outer ramus short, ca. 0.65 times length of peduncle, with 4 terminal robust setae; inner ramus damaged, with 2+ medial robust setae. Uropod 2 damaged; peduncle with 1+ lateral, 1 laterodistal and 1 mediodistal robust setae, ventrodistal end weakly produced; outer ramus short, with 1 lateral and 3 (1 long and 2 short) terminal robust setae; inner ramus with 1+ lateral and 2+ medial robust setae. Uropod 3, peduncle slightly longer than wide, ventrodistal end acutely produced, dorsal and ventral surfaces with a few setae; outer ramus ca. 1.25 times length of peduncle, distinctly narrowed distally, with 2 lateral and 1 medial robust setae and apical minute seta; inner ramus lost. Telson small, triangular, distal margin pointed, with 5 minute setae, each lateral margins bearing 3–4 short setae proximally, dorsal surface with couple of 2+1 sensory setae.

Female. Unknown.

Coloration in life. Based on holotype, male, 2.9 mm (OMNH-Ar-13233, Fig. 30). Head light brown, eyes whitish pink; pereonites 1–4 light brown, pereonites 5–7 and pleonites 1, 2 pale brown, lateral surfaces of pereonite 7 and pleonites 1, 2 each with distinct orange mark mid-posteriorly, pleonite 3 and urosomites white; antenna 1 peduncular article 1 white, articles 2, 3 dark red, flagellum pale pink, antenna 2 peduncular articles 1–3 white, article 4 dark red, article 5 and flagellum pale pink; upper part of mouth parts pale orange, other appendages white and partly pale orange.

Remarks. Lobatoradarea obliquua sp. nov. is characterized by the strongly oblique palms of the gnathopods 1, 2 and the long inter-ramal process of the uropod 1 peduncle. These characters are unique in the genus.

Habitat. Rock and gravel bottom with a depth of 121– 123 m.

Distribution. Japan: Ōsumi Strait in Kagoshima Prefecture (present study).