Lobatoradarea angulata Ariyama & Kodama, 2025

Lobatoradarea angulata Ariyama & Kodama , sp. nov.

[New Japanese name: Kado-udenaga-yokoebi]

( Figs 31–35)

Type material. Holotype: ovigerous female, 8.3 mm (OMNH-Ar-13234), south of Tanegashima Island , Kagoshima Prefecture, 30°12'27"N, 130°59'09"E ( Fig. 1L), 104–194 m depth, using beam-trawl, TR/ V Toyoshio-maru ( Hiroshima University), 22 May 2024, coll. Masafumi Kodama. GoogleMaps Paratypes: 2 ovigerous females, 8.8, 7.7 mm (OMNH-Ar-13235, 13236), female with juveniles, 7.7 mm (OMNH-Ar-13237), 2 females, 5.6, 5.4 mm (OMNH- Ar-13238, 13239), 2 males, 5.1, 4.4 mm (OMNH-Ar-13240, 13241), same data as holotype GoogleMaps .

Type locality. South of Tanegashima Island , Kagoshima Prefecture, Japan .

Etymology. From the Latin angulatus, -a, -um (=angular), referring to the shape of the coxa 4. Adjective.

Description of female. Based on holotype, ovigerous female, 8.3 mm (OMNH-Ar-13234).

Head ( Figs 31, 32). Rostrum developed, lateral cephalic lobe angular, anteroventral corner moderately projected. Eyes large (diameter: 47% of head height), bulging laterally. Antenna 1, peduncular articles 1–3 with length ratio of 1.0: 0.7: 0.2; accessory flagellum very short, rod-shaped, with 4 setae; primary flagellum with 19+ articles, tip lost, article 1 long, 7 articles with aesthetasc. Antenna 2, peduncular articles 3–5 with length ratio of 1.0: 2.4: 3.1, each article bearing several robust setae; flagellum very long, with 58+ articles, article 1 long, tip lost. Upper lip relatively long, produced ventrally, ventral margin with many short and minute setae, anteroproximal surface bearing minute setae. Mandibles, both incisors with 8 cusps, laciniae mobilis 7- and 3-toothed in left and right, respectively, both accessory setal rows with 6 thick and 6 slender setae; palp stout, article length ratio 1.0: 3.4: 2.7, article 1 short, bare, article 2 long, with 5–6 setae subdistally, article 3 bearing 1 proximal, 8–9 ventral and 2 thick and 2 slender distal setae, lateral and medial surfaces covered with dense thin setae. Lower lip, inner lobes developed, bare; outer lobes with mandibular lobes setose distally, mediodistal margins with many setae, ventrodistal surfaces and lateral margins with sparse fine setae. Maxilla 1, inner plate pear-shaped, medial margin bearing long plumose setae, tip with a long thick seta; outer plate distally with 11 denticulate robust setae and many slender 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 10 short robust setae mediodistally; palp article 3 dorsal surface with 5 thick setae and many fine setae.

Pereon ( Figs 31, 33). Pereonite 7 strongly projected posterodorsally. Gnathopod 1 small; coxa roundish rectangular, with a small notch on posteroventral margin, lateral surface with a long seta posteroproximally, medial surface bearing many setae; basis slender, straight, anterior margin lined with robust setae, posterior margin bearing 4 long proximal setae and several short setae, medial surface setose proximally; ischium with a robust seta posterodistally; merus acutely projected distally, with several thick setae on posterodistal margin; carpus relatively short, anterior margin with 3 robust setae, posterior margin bearing many thick setae; propodus longer than carpus (ca. 1.15 times), posterior margin setose, palm weakly oblique, defined by 6 (3 lateral and 3 medial) short robust setae; dactylus short. Gnathopod 2 much longer than gnathopod 1; coxa roundish trapezoidal, with 2 small notches on posteroventral margin, medial surface bearing several setae distally; basis slender, straight, anterior margin lined with several robust setae, posterior margin lined with long and short slender setae; ischium with a robust seta anteriorly; merus acutely projected distally, posterior margin with several setae; carpus long and narrow, posterior margin bearing several bundles of slender setae; propodus longer than carpus (ca. 1.3 times), narrow, anterior margin lined with short setae, posterior margin bearing many bundles of slender setae, palm weakly oblique, defined by 7 (4 lateral and 3 medial) short robust setae; dactylus short. Pereopod 3 shorter than gnathopod 2; coxa roundish square, with 1 and 3 small notches on anteroventral and posteroventral margins, respectively, medial surface bearing many slender setae and 2 short robust setae; basis slightly curved anteriorly, anterior margin with several slender setae proximally and 8 robust setae distally, posterior margin with several slender setae and 7 robust setae; merus anterior margin with 2 robust setae, anterodistal and posterodistal corners bearing 3 and 1 robust setae, respectively; carpus anterior margin with a robust seta in middle, posterior margin and posterodistal corner bearing 4 and 2 robust setae, respectively; propodus longer than carpus, anterior and posterior margins with 3 and 1+2+2+1+1+2 robust setae, respectively; dactylus smooth. Pereopod 4 almost same length as pereopod 3; coxa ventral margin strongly angular in middle, with 2 small notches on posteroventral margin, medial surface bearing many setae; basis slightly curved anteriorly, anterior margin with several slender setae proximally and 6 robust setae distally, posterior margin with several slender setae proximally and 1+1+1+2+2 robust setae distally; ischium–dactylus almost similar to those of pereopod 3. Pereopod 5, coxa anteroventral, posteroventral and posterior margins with 1, 1 and 2 small notches, respectively; basis oval, lateral surface with anterior and median ridges, anterior margin with many proximal setae and 1+1+1+2+1 robust setae, anterodistal corner bearing 2 robust setae, posterior margin serrated, medial surface with vertical ridge bearing a robust seta; ischium with 2 robust setae at anterodistal corner; merus with 2+1+2 anterior, 2 anterodistal, 1+2+1 posterior and 5 posterodistal robust setae; carpus with 1+3+1 anterior, 4 anterodistal, 1+2+1 posterior and 3 posterodistal robust setae; propodus with 1+2+2+1+1+2 anterior, 2 anterodistal and 1+2+2+1 posterior robust setae; dactylus smooth. Pereopod 6, coxa anterior margin slightly excavate, with several setae, posteroventral margin with 2+3 small notches; basis ovoid, lateral surface with anterior and median ridges, anterior margin with many proximal setae and 5 robust setae, anterodistal corner bearing 3 robust setae, posterior margin serrated, medial surface with several proximal setae, median robust seta and vertical ridge bearing a robust seta; ischium with 2 robust setae at anterodistal corner; merus with 1+2+2+2 anterior, 3 anterodistal, 1+1+2+1+2 posterior and 6 posterodistal robust setae; carpus–dactylus lost. Pereopod 7, coxa short, semicircular, anterior margin setose, posterior margin with 3 small notches; basis wide, roundish rectangular, lateral surface with anterolateral and median ridges, anterior margin with many proximal setae and 7 robust setae, anterodistal corner bearing 2 robust setae, posterior margin serrated, medial surface with short vertical ridge bearing a robust seta; merus with 1+3+2+2+2 anterior, 3 anterodistal, 1+1+1+2+2 posterior and 8 posterodistal robust setae; carpus with 3+3+3+3 anterior, 7 anterodistal, 1+1+2+1+2+1 posterior and 5 posterodistal robust setae; propodus with 2+2+3+2+3+2+2 anterior, 3 anterodistal and 1+1+2+2+2+1 posterior robust setae; dactylus smooth.

Pleon ( Figs 31, 34). Pleonites 1, 2 acutely projected posterodorsally. Epimeral plates 1–3, posteroventral corners minutely produced, lateral surfaces with ridge in plates 1, 2, ventral margins bearing 3, 4 and 4 robust setae, respectively. Pleopods, pleopod 2 longest; each peduncle bearing many or several setae and 2 coupling hooks, peduncle of pleopods with 1, 1 and 6 robust setae posteromedially, respectively, peduncle of pleopod 3 also bearing 2 lateral robust setae; outer rami almost same length as inner rami, both rami with 17–19 articles. Uropod 1, peduncle long, dorsal surface with 8 lateral, 1 laterodistal, 7 medial and 1 mediodistal robust setae, ventrodistal end roundly produced; outer ramus ca. 0.7 times length of peduncle, with 6 lateral and 4 terminal robust setae; inner ramus ca.1.6 times as long as outer ramus, with 11 (1 lost) lateral, 8 medial and 4 terminal robust setae. Uropod 2 about 0.85 times as long as uropod 1; peduncle short, with 5 lateral, 1 laterodistal, 2 medial and 1 mediodistal robust setae, ventrodistal end triangularly produced; outer ramus ca. 0.8 times length of peduncle, with 4 lateral and 4 (1 lost) terminal robust setae; inner ramus ca. 2.25 times as long as outer ramus, with 11 lateral, 9 medial and 4 terminal robust setae. Uropod 3 about 0.9 times length of uropod 2; peduncle very short, slightly longer than wide, ventrodistal end acutely produced, lateral margin with several minute setae; outer ramus ca. 1.85 times length of peduncle, with 8 lateral and 8 medial robust setae, tip bearing minute seta; inner ramus about 1.45 times as long as outer ramus, with 13 lateral, 16 medial and 1 dorsoproximal robust setae, tip bearing minute seta. Telson small, subtrapezoidal, dorsal surface with pair of 2+1 sensory setae, each lateral margin bearing 2 short setae, distal margin rounded, with 4 small notches, mediodistal margin bearing several denticles and many minute setae.

Description of male. Based on paratype, male, 5.1 mm (OMNH-Ar-13240). Almost similar to holotype, ovigerous female, 8.3 mm (OMNH-Ar-13234) except for size and oostegites. Gnathopods resembling those of female; but gnathopod 1 larger, coxa longer, lacking many inner setae, basis wider, posterior margin without long setae, propodus posterodistal corner bearing 5 (3 lateral and 2 medial) short robust setae ( Fig. 34 M-G1); gnathopod 2 coxa longer, lacking medial setae and bearing a small notch each on anteroventral and posteroventral corners, basis with a long seta posteriorly, propodus ca. 1.15 times as long as carpus, posterodistal corner with 4 (2 lateral and 2 medial) short robust setae ( Fig. 34 M-G2).

Coloration in life ( Fig. 35). Type A (most of specimens), based on paratype, ovigerous female, 7.7 mm (OMNH- Ar-13236). Head, pereonites and pleonites dark orange, urosomites light orange, eyes bright orange; antennae peduncles dark orange, flagella faintly-orangish white; coxae and bases of all pereopods dark orange partly with indistinct whitish points, ischia–dactyli of gnathopods 1, 2 light orange, those of pereopods 3–7 reddish orange and white, pleopods and uropods pale pink. Type B (part of large females), based on paratype, ovigerous female, 8.8 mm (OMNH-Ar-13235). Mid-lateral surfaces from posterior head to pleonite 3 with bright white band, other parts almost same as Type A.

Remarks. Lobatoradarea angulata sp. nov. has the angular ventral margin of the coxa 4. Although L. thermicola sp. nov. has a similar coxa 4, the other Lobatoradarea species have a coxa 4 with rounded or slightly angular ventral margin. This new species is different from L. thermicola in having larger eyes and in the smooth dactyli of the pereopods 3–7.

Habitat. On the bottom between the depth of 104–194 m.

Distribution. Japan: south of Tanegashima Island, Kagoshima Prefecture (present study).