Lobatoradarea coccina Ariyama, Kohtsuka & Hoshino, 2025

Lobatoradarea coccina Ariyama, Kohtsuka & Hoshino , sp. nov.

[New Japanese name: Beni-udenaga-yokoebi]

( Figs 7–11)

Type material. Holotype: female, 6.4 mm (OMNH-Ar-13211), mouth of Koajiro Bay, Miura City , Kanagawa Prefecture, 35°09'55"N, 139°36'43"E ( Fig. 1C), 10–12 m depth, mud bottom, using dredge, 26 February 2015, coll. Hisanori Kohtsuka. GoogleMaps Paratypes: ovigerous female, 4.6 mm (OMNH-Ar-13212) and male, 4.0 mm (OMNH- Ar-13213), Akinohama Beach, Izu Ōshima Island , Tokyo, 34°47'14"N, 139°24'31"E ( Fig. 1D), 15–20 m depth, accumulated red algae, using SCUBA diving, 2 April 2024, coll. Osamu Hoshino; 2 ovigerous females, 6.3, 5.3 mm (OMNH-Ar-13214, 13215) and male, 3.7 mm (OMNH-Ar-13216), 13 March 2025, other data same as paratypes (OMNH-Ar-13212, 13213) GoogleMaps .

Type locality. Mouth of Koajiro Bay , Miura City in Kanagawa Prefecture, Japan .

Etymology. From the Latin coccineus, -a, -um (=scarlet), referring to the body color. Adjective.

Description of female. Based on holotype, 6.4 mm (OMNH-Ar-13211).

Head ( Figs 7, 8). Rostrum strongly developed, lateral cephalic lobe roundish-angular, anteroventral corner acutely projected. Eyes medium-sized (diameter: 38% 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 4 setae; primary flagellum with 42+ articles, tip lost, article 1 relatively long, 11 articles with aesthetasc. Antenna 2, peduncular articles 3–5 with length ratio of 1.0: 2.1: 2.7, each article bearing several robust setae; flagellum with 15+ articles, distal part lost, article 1 long. Upper lip weakly produced ventrally, bearing many thin setae. Mandibles, both incisors with 9 cusps, laciniae mobilis 7- 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: 3.2: 2.0 in right, article 1 short, bare, article 2 long, with 3 setae subdistally, article 3 bearing 1 proximal, 10 ventral 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 long mandibular lobes, setose mediodistally, ventral surfaces and lateral margins with sparse fine setae. Maxilla 1, inner plate pear-shaped, medial margin bearing long plumose setae; outer plate distally with 11 denticulate robust setae and several thick setae; palp article 1 bare, article 2 apically with 6 triangular and 2 long robust setae and 5 slender setae in left and 7 narrow robust setae and 4 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 4 long and 9 short robust setae mediodistally; palp article 3 dorsal surface with 5 thick setae and many fine setae.

Pereon ( Figs 7, 9). Pereonite 7 with strong projection posterodorsally. Gnathopod 1 short; coxa subrectangular, with a small notch on posteroventral margin, medial surface bearing many setae; basis slender, straight, proximal part with many setae anteromedially and posterolaterally; merus acutely projected posterodistally, with several thick setae on mid-posterior margin; carpus relatively long, posterior margin bearing many thick setae; propodus slightly shorter than carpus (ca. 0.95 times), posterior margin with several bundles of thick setae, palm weakly oblique, defined by 4 (2 lateral and 2 medial) short robust setae; dactylus short. Gnathopod 2 much longer than gnathopod 1; coxa rectangular, with 1 and 2 small notches on anteroventral and posteroventral margins, respectively, medial surface bearing several setae; basis slender, straight, anterior margin lined with short setae, posterior and posterolateral margins bearing several long setae; merus acutely projected posterodistally, 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 shorter than gnathopod 2; coxa roundish trapezoidal, with 5 small notches each on anteroventral and posteroventral margins, medial surface bearing many setae; basis slightly curved anteriorly, anterior margin lacking robust setae, posteroproximal margin with several slender setae; merus anterodistal corner with a robust seta; carpus posterior margin with 4 robust setae; propodus longer than carpus, posterior margin with 1+1+1+1+2+1 robust setae; dactylus with a minute projection on inner margin. Pereopod 4 almost same length as pereopod 3; coxa ventral margin slightly angular, with 3 and 9 small notches on anteroventral and posteroventral margins, respectively, medial surface bearing many setae; basis slightly curved anteriorly, anterior margin lacking robust setae, anterodistal corner with a robust seta, anteroproximal and posteroproximal margins with several slender setae; ischium–dactylus similar to those of pereopod 3. Pereopod 5 longer than pereopod 4; coxa anteroventral and posterior margins with 2 and 7 small notches, respectively, medial surface setose anteriorly; basis ovoid, with anterolateral ridge, anteroproximal part setose laterally and medially, anterior margin and anterodistal corner with 5 and 2 robust setae, respectively, posterior margin minutely serrated, medial surface with vertical ridge bearing a robust seta; ischium lacking a robust seta; merus with 1+1+2 anterior, 3 anterodistal, 1+1+2+1 posterior and 3 posterodistal robust setae; carpus with 1+3+2+2 anterior, 1 anterodistal, 1+1+2+1 posterior and 3 posterodistal robust setae; propodus with 2+2+2+2+2 anterior, 3 anterodistal and 1+1+1+2+1 posterior robust setae; dactylus with a minute projection. Pereopod 6 longer than pereopod 5; coxa anterior margin straight, with many setae, posteroventral margin with 8 small notches; basis ovoid, with anterolateral ridge, anteroproximal part with several lateral setae and 2 medial thick setae, anterior margin and anterodistal corner with 5 and 1 robust setae, respectively, posterior margin minutely serrated, medial surface with vertical ridge bearing a robust seta; ischium without a robust seta; merus with 3 anterior, 1 anterodistal, 1+1+1+1+2+1+1 posterior and 3 posterodistal robust setae; carpus with 2+2+2+1+2 anterior, 4 anterodistal, 1+1+2+3+1 posterior and 5 posterodistal robust setae; propodus with 1+2+2+2+2+2 anterior, 3 anterodistal and 1+1+1+1+1+3 posterior robust setae; dactylus with a minute projection. Pereopod 7 slightly longer than pereopod 6; coxa short, anterior margin straight, with many setae, posteroventral margin with 3 small notches; basis ovoid, with anterolateral ridge, anteroproximal part with several setae laterally and medially, anterior margin and anterodistal corner with 4 and 2 robust setae, respectively, posterior margin minutely serrated, medial surface with short vertical ridge bearing a robust seta; merus with 1+2+2+2 anterior, 3 anterodistal, 1+1+2+1 posterior and 5 posterodistal robust setae; carpus with 1+2+2+1 anterior, 4 anterodistal, 1+2+1+1+1 posterior and 5 posterodistal robust setae; propodus with 2+2+2+2+2+1 anterior, 2 anterodistal and 1+1+1+2+1 posterior robust setae; dactylus with a minute projection.

Pleon ( Figs 7, 10). Pleonites 1, 2 strongly projected posterodorsally. Epimeral plates 1–3, posteroventral corners minutely produced, lateral surfaces with ridge, ventral margins of plates 2, 3 bearing 1 and 3 robust setae, respectively. Pleopods, each peduncle bearing several or many setae and 2 coupling hooks, peduncle of pleopods 1, 2 with 3–4 posterior robust setae, peduncle of pleopod 3 bearing 5 posterior and 1 lateral robust setae; all rami damaged. Uropod 1, peduncle long, dorsal surface with 6 lateral, 1 laterodistal, 5 medial and 1 mediodistal robust setae, ventrodistal end slightly produced; outer ramus ca. 0.8 times length of peduncle, with 4 (1 lost) lateral and 4 (1 lost) terminal robust setae; inner ramus damaged, with lateral and medial robust setae. Uropod 2 shorter than uropod 1; peduncle short, with 3 (2 lost) lateral, 1 laterodistal, 2 medial and 1 mediodistal robust setae, ventrodistal end slightly produced; outer ramus ca. 0.9 times length of peduncle, with 3 (1 lost) lateral and 4 (2 lost) terminal robust setae; inner ramus damaged, with lateral and medial robust setae. Uropod 3 relatively long; peduncle very short, longer than wide, ventrodistal end produced, lateral and ventral margins each with 3 short setae; outer ramus ca. 2.05 times length of peduncle, with 4 lateral and 3 medial robust setae; inner ramus about 1.55 times as long as outer ramus, with 7 lateral and 13 medial robust setae. Telson small, trapezoidal, distal margin rounded, with a small notch in right, dorsal surface with 6 sensory setae, lateral margins with several minute setae.

Description of male. Based on paratype, male, 4.0 mm (OMNH-Ar-13213). Almost similar to holotype, ovigerous female, 6.4 mm (OMNH-Ar-13211) except for oostegites. Gnathopods resembling those of female; but coxae with a small notch each on anteroventral and posteroventral margins, both coxae and bases less setose, gnathopod 1 propodus slightly longer than carpus (ca. 1.05 times, Fig. 10 M-G1), and gnathopod 2 palm defined by 3 (2 lateral and 1 medial) short robust setae ( Fig. 10 M-G2).

Coloration in life. Based on holotype, female, 6.4 mm (OMNH-Ar-13211, Fig. 11). Head light red, but translucent around eyes, eyes pink; pereonites, pleonite 1, ventral parts of pleonites 2, 3, coxae and bases of pereonites 5–7 bright red with sparse white spots; dorsal parts of pleonites 2, 3 white, urosomites and uropods pale pink; peduncles of antennae light red, flagellum white; gnathopods pale pink, pereopods except for pereopods 5–7 bases red and white.

Remarks. Lobatoradarea coccina sp. nov. is characterized by a combination of the acutely projected anteroventral corner of the head and the strong projection on the pereonite 7. All other known species of the new genus Lobatoradarea do not exhibit this combination. The scarlet coloration is also distinctive.

Habitat. On mud bottom or among algae in the shallow subtidal zone ( 10–20 m depth).

Distribution. Japan: mouth of Koajiro Bay, Miura City in Kanagawa Prefecture, and Izu Ōshima Island in Tokyo (present study).