Aoroides sagamiensis, Ariyama & Kohtsuka, 2022

Ariyama, Hiroyuki & Kohtsuka, Hisanori, 2022, Three new species of the family Aoridae collected from Sagami Bay, central Japan (Crustacea: Amphipoda), Zootaxa 5159 (3), pp. 393-413 : 400-405

Aoroides sagamiensis sp. nov.

[Japanese name: Sagami-burabura-sokoebi, new]

( Figs 5–8 )

Type material. Holotype: male, 3.1 mm (OMNH-Ar-12435), west of Jōgashima Island in Miura City , Kanagawa Prefecture, 35°08′22″N 139°34′38″E –35°08′17″N 139°34′28″E, 87–90 m depth, gravel and sand bottom, 25 March 2015 . Paratypes: female, 3.7 mm (OMNH-Ar-12436), same data as holotype; male, 3.1 mm and female, 4.5 mm (OMNH-Ar-12437, 12438), west of Jōgashima Island in Miura City , Kanagawa Prefecture, 35°08′06″N 139°34′03″E –35°08′23″N 139°33′46″E, 95–97 m depth, 16 April 2014 ; male, 2.3 mm and female, 3.0 mm (OMNH-Ar-12439, 12440), west of Jōgashima Island in Miura City , Kanagawa Prefecture, 35°08′15″N 139°34′44″E – 35°08′58″N 139°34′45″E, 87–89 m depth, sand bottom, 31 October 2013 ; female, 3.0 mm (OMNH-Ar-12441), west of Jôgashima Island in Miura City , Kanagawa Prefecture, 35°08′25″N 139°34′25″E –35°08′07″N 139°33′32″E, 100–103 m depth, 20 January 2015 .

Type locality. Sagami Bay , west of Jōgashima Island in Miura City, Kanagawa Prefecture, Japan .

Etymology. The Latin sagamiensis , - is, - e refers to the type locality.

Description of male. Based on holotype (OMNH-Ar-12435, 3.1 mm) and paratype (OMNH-Ar-12437, 3.1 mm) only for pereopods 5, 7.

Head ( Figs 5 , 6 ). Eyes medium-sized, about quarter of head length. Antenna 1 very long, ca. 0.95 times of BL, slender, poorly setose; peduncular articles 1–3 with length ratio of 1:1.75:0.55, article 1 with 4 robust setae ventrally; accessory flagellum vestigial, tip bearing 2 setae; primary flagellum with 14 articles, last article minute, articles 10, 11 each with aesthetasc. Antenna 2 about 0.6 times as long as antenna 1, slender, weakly setose; peduncular articles 3–5 with length ratio of 1:3.5:3.3; flagellum with 3 articles, with 4, 2, 2 long robust setae, respectively. Upper lip with ventral margin rounded, bearing short thin setae. Mandibles, incisor with 5 and 7 cusps in left and right, respectively, lacinia mobilis 4-toothed in left and 3-toothed in right, accessory blades bifid, 3 in left and 2 in right; palp rod-shaped, article length ratio 1:1.9–2.0:2.8, articles 1, 2 bare, article 3 with 2 long setae on tip. Lower lip with acute-tipped mandibular process, distal margin of outer lobe with 3 thick setae; distal margin of inner lobe bearing short thin setae. Maxilla 1 with small inner plate bearing long plumose seta; outer plate with 10 robust setae apically; tip of palp article 2 with 6 distal robust setae. Maxilla 2, outer plate setose mediodistally, inner plate with mediofacial row of setae and distal setae. Maxilliped with inner plate bearing 2 quadrate and 1 short robust setae and several thick setae; outer plate broad, barely not reaching apex of palp article 2, distomedial margin with 10 long-to-short robust setae; palp weakly setose, dorsodistal end of article 3 projected, article 4 bearing nail on tip.

Pereon ( Fig. 7 ). Sternal process absent. Gnathopod 1 large, merochelate; coxa roundish trapezoidal, anteroventral corner roundly projected, with robust seta; basis stout, anterior margin with a few short simple setae, lateral margin bearing several long and short simple setae; ischium with simple seta posterodistally; merus long, abruptly narrowed distally, distal 2/3 bearing dense plumose setae; carpus bullet-shaped, anterior margin with simple seta near distal corner, posterior margin with dense plumose setae; propodus straight, almost same length as carpus, anterior margin with a few simple setae, posterior margin and medial surface bearing many simple setae; dactylus slightly curved, posterior margin with 4 small denticles. Gnathopod 2 smaller than gnathopod 1, subchelate; coxa oval, ventral margin with 4 short setae; basis almost straight, anterior margin with several short setae, posterior margin bearing 3 robust setae; meus short, setose distally; carpus longish triangular, posterior margin heavily setose; propodus slightly longer than carpus, palm oblique, defined by robust seta, anterodistal corner, posterior and distal margins setose; dactylus short, slightly curved, posterior margin with 4 denticles. Pereopods 3, 4 slender, pereopod 3 slightly longer than gnathopod 2, pereopod 4 almost same length as gnathopod 2; coxae roundish trapezoidal; bases narrow, anterior and posterior margins each with a few setae; meri and carpi lacking robust setae on posterior margins; propodi and dactyli narrow. Pereopod 5, coxa bilobed; basis wide, posteroproximal corner rounded, anterior margin with a few short setae (1 robust); carpus with thick seta at posterodistal corner; propodus anterior margin bearing 3 robust setae, posterodistal corner weakly setose. Pereopod 6 longer than pereopod 5; coxa bilobed; basis wide, posteroproximal corner rounded, anterior margin bare, posterior margin with a few short setae; merus with thick seta each on posterodistal corner, posterior margin and posterodistal corner; carpus with 1 posterolateral and 3 (1 lost) posterodistal robust setae; propodus anterior margin with 4 robust setae, posterodistal corner setose. Pereopod 7 probably longer than pereopod 6; coxa semicircular; basis wide, posteroproximal corner slightly projected, anterior margin with a few short setae (1 robust), posterior margin bearing several short setae, posterodistal corner with thick seta; merus with 1, 3, 2 thick setae on anterodistal corner, posterior margin and posterodistal corner, respectively; carpus–dactylus lost.

Pleon ( Figs 5 , 8 ). Epimeral plates 1–3 each with minute projection and short seta on posteroventral corner, ventral margins bare. Pleopods, pleopod 2>1> 3 in length; peduncles with 3, 4, 1 plumose setae in pleopods 1–3, respectively; outer rami shorter than inner rami, both rami with 6 articles in pleopods 1, 2, and with 5 articles in pleopod 3. Uropod 1, peduncle with 3 dorsolateral and 2 dorsomedial robust setae, inter-ramal process medium, 34% length of peduncle; outer and inner rami ca. 0.85 and 0.9 times as long as peduncle, respectively, outer ramus with 1 dorsolateral and 4 terminal robust setae, inner ramus bearing 2 dorsolateral and 4 terminal robust setae. Uropod 2 about 0.7 times length of uropod 1, peduncle with 2 dorsolateral and 1 dorsomedial robust setae, inter-ramal process vestigial; outer ramus almost same length as peduncle, inner ramus ca. 1.15 times of peduncle, outer ramus with 1 dorsal and 4 terminal robust setae, inner ramus bearing 3 dorsal and 4 terminal robust setae. Uropod 3 short, about half length of uropod 2, peduncle with 2 laterodistal robust setae, inter-ramal process vestigial; outer and inner rami ca. 1.05 and 1.15 times of peduncle, respectively, outer ramus without marginal robust seta, tip with tiny second article and 1 robust and 3 long setae, inner ramus with 1 marginal and 1 terminal robust setae and long apical seta. Telson roundish pentagonal, distal margin with pair of 1 long, 1 short and 1 sensory setae.

Description of female. Based on paratype (OMNH-Ar-12438, 4.5 mm). Generally similar to male holotype except for gnathopods and oostegites. Gnathopod 1 ( Fig. 8 F-G1) subchelate; coxa roundish trapezoidal, anteroventral corner not projected; basis slightly stout, poorly setose; ischium setose posterodistally; merus short, posterodistal margin setose; carpus longish triangular, posterior margin setose; propodus slightly longer than carpus, posterior margin and medial surface setose, palm oblique, defined by long robust seta; dactylus weakly curved, posterior margin with 5 denticles. Gnathopod 2 ( Fig. 8 F-G2) subchelate; coxa large, roundish trapezoidal; basis narrow, straight, anterior and posterior margins with several short setae; meus short, setose distally; carpus longish triangular, posterior margin heavily setose; propodus long, ca. 1.2 times length of carpus, palm oblique, defined by robust seta, anterodistal corner and distal margin setose; dactylus short, slightly curved, posterior margin with 3 denticles.

Variation. Paratype, male (OMNH-Ar-12437, 3.1 mm). Gnathopod 1 ( Fig. 8 M-RG1) larger than that of holotype ( Fig. 7 RG1) in spite of same body length; coxa long, acutely projected anteriorly; basis, carpus and propodus more slender and merus shorter than those of holotype. Paratype, small male (OMNH-Ar-12439, 2.3 mm). Gnathopod 1 almost same as that of holotype. Paratype, female (OMNH-Ar-12438, 4.5 mm). Uropod 3, outer ramus with 1 marginal and 1 terminal robust setae, inner ramus with 2 marginal and 1 terminal robust setae.

Coloration in life. Unknown.

Remarks. Aoroides sagamiensis sp. nov. has a distinctive male gnathopod 1 with poorly setose basis and heavily setose merus. Only Aoroides rubellus Ariyama, 2004 from Japan shares such a gnathopod 1 in the genus. However, this new species can be distinguished from A. rubellus in the fewer robust setae on the uropods 1–3.

Habitat. Gravel and sand bottom, 87–103 m depth.

Distribution. Japan: Sagami Bay (present study).

Figures

FIGURE 5. Aoroides sagamiensis sp. nov. Holotype, male, 3.1 mm (OMNH-Ar-12435). Habitus.

FIGURE 6. Aoroides sagamiensis sp. nov. Holotype, male, 3.1 mm (OMNH-Ar-12435). Scales: 0.05 mm.

FIGURE 7. Aoroides sagamiensis sp. nov. All but M: holotype, male, 3.1 mm (OMNH-Ar-12435); M: paratype, male, 3.1 mm (OMNH-Ar-12437). Scales: 0.1 mm.

FIGURE 8. Aoroides sagamiensis sp. nov. All except for F and M: holotype, male, 3.1 mm (OMNH-Ar-12435); F: paratype, female, 4.5 mm (OMNH-Ar-12438); M: paratype, 3.1 mm (OMNH-Ar-12437), slender setae omitted. Scales: 0.1 mm.