Aoroides macrops, Ariyama & Kawabe, 2022

Ariyama, Hiroyuki & Kawabe, Katsutoshi, 2022, Two New Species of Aoridae from Chichijima Island, the Ogasawara Islands in Japan (Crustacea: Amphipoda), Species Diversity 27 (1), pp. 113-128 : 114-120

publication ID	https://doi.org/ 10.12782/specdiv.27.113
publication LSID	lsid:zoobank.org:pub:EAA93134-A1D0-4959-BFF3-E1ADADD958D2
persistent identifier	https://treatment.plazi.org/id/3314BF54-6FD7-4ED1-A2F8-D9C3C4259ADD
taxon LSID	lsid:zoobank.org:act:3314BF54-6FD7-4ED1-A2F8-D9C3C4259ADD
treatment provided by	Felipe
scientific name	Aoroides macrops
status	sp. nov.

Treatment

Aoroides macrops View in CoL sp. nov.

[New Japanese name: Ōme-burabura-sokoebi] ( Figs 2–5 View Fig View Fig View Fig View Fig , 6A View Fig ; Table 1)

Material examined. Holotype: male (OMNH-Ar-12315), 2.7mm, Futami Fishing Port , Chichijima Island, Ogasawara Islands, Tokyo Prefecture ( Fig. 1A View Fig ), Japan, 27°05′48″N, 142°11′55″E, 1–1.5 m depth, attached to fish cage, 11 July 2020, coll. K. Kawabe. GoogleMaps Paratypes: 6 males (OMNH- Ar-12316–12321), 3.2, 2.9, 2.8, 2.7, 2.4, and 2.3 mm, respectively (OMNH-Ar-12318 not dissected), and 2 ovigerous females (OMNH-Ar-12322, 12323), 2.9 and 2.8 mm, respectively, same data as holotype.

Material for comparison. Aoroides longimerus Ren and Zheng, 1996 : three males (OMNH-Ar-4235, 4237, 4241), 4.2, 3.6, and 3.1 mm, respectively, examined in Ariyama (2004a).

Type locality. Futami Fishing Port, Chichijima Island , Ogasawara Islands, Tokyo Prefecture, Japan .

Etymology. A compound noun in apposition from the Ancient Greek macro (=large)+ ops (=eye), referring to the size of eyes.

Description of male. Based on holotype (OMNH- Ar-12315, 2.7 mm).

Head ( Figs 2 View Fig , 3 View Fig ). Eyes large (diameter: 35% of head length). Antenna 1, peduncular articles 1–3 with length ratio of 1.0: 1.0: 0.4, article 1 stout, ventral margin with 4 long robust setae; accessory flagellum vestigial, 1-articulate, with 3 setae on tip; flagellum with 13 articles, last article short, articles 4–11 each bearing aesthetasc at posterodistal end. Antenna 2 shorter than antenna 1 (about 0.85 times), stout, setose posteriorly; peduncular articles 3–5 with length ratio of 1.0: 2.4: 2.3; flagellum with 3 articles, article 1 with 1 thick and 2 robust setae, articles 2, 3 each bearing 2 robust setae posteriorly. Upper lip, ventral margin rounded, with many short thin setae. Mandibles with left and right incisors bearing 6 cusps; left lacinia mobilis 4-toothed and right one bifid, left accessory blades 3 in number and right ones 2; article length ratio of palp 1.0: 1.55: 2.2, articles 1, 2 bare, article 3 with 1 or 2 long distal setae. Lower lip with short mandibular process, medial margin of outer lobe with several apical setae and many short thin setae, distal margin of inner lobe bearing short thin setae. Maxilla 1 with small inner plate bearing single long seta; outer plate with 10 stout robust setae apically; tip of palp article 2 with 6 distal robust setae and 3 simple setae. Maxilla 2, outer plate setose distally, inner plate with many setae on distal to medial margins. Maxilliped with inner plate bearing 4 small robust setae and several plumose setae; outer plate broad, distomedial margin with 7 robust setae; palp stout, weakly setose, dorsodistal end of article 3 projected, article 4 with nail on tip.

Pereon ( Fig. 4 View Fig ). Gnathopod 1 large; coxa depressed triangular, bearing 6 plumose and 1 thick setae on anterior margin; basis long, anterior and lateral margins with dense plumose setae, posterior margin bare; ischium short, anterior and lateral margins with several plumose setae distally; merus lanceolate, distal 3/4 surfaces (lateral–posterior–medial) covered with dense plumose setae; carpus roundish rectangular, anterior and posterior margins and medial surface bearing dense plumose setae; propodus almost straight, about 0.8 times as long as carpus, posterodistal corner notched, anterior margin and anterodistal corner with 1 and 2 simple setae, respectively, posterior margin with several simple setae, medial surface bearing dense plumose setae; dactylus long, strongly curved, posterior margin smooth, with several simple setae. Gnathopod 2 small; coxa roundish square, ventral margin with a few setae; basis long, anterior margin with many long simple setae, posterior margin with a few short setae; meus setose posterodistally; carpus longish triangular, posterior margin setose; propodus almost same length as carpus, palm slightly oblique, defined by long robust seta, posterior margin and medial surface setose; dactylus curved, posterior margin with 6 denticles. Pereopods 3, 4 slightly shorter than gnathopod 2; coxae roundish square; bases anterior and posterior margins bearing several and a few setae, respectively; meri and carpi short (length/width ca. 1.7 in carpi), posterior margins without robust setae; propodi long; dactyli short. Pereopod 5 longer than pereopod 4; coxa bilobed; basis wide, posteroproximal corner a little projected roundly, anterior margin with 4 short robust setae, posterior margin with several setae; carpus with 1 posterolateral and 3 posterodistal robust setae; propodus anterior margin bearing 1, 2, 1, 4 robust setae, posterodistal corner setose. Pereopod 6 about 5/4 times as long as pereopod 5; coxa bilobed; basis wide, posteroproximal corner slightly projected roundly, anterior margin with 5 short robust setae, posterior margin with several setae; carpus with 1 posterolateral and 2 posterodistal robust setae; propodus anterior margin bearing 1, 2, 3, 3, 2 robust setae, posterodistal corner setose. Pereopod 7 about 5/4 times length of pereopod 6; coxa roundish; basis wide, posteroproximal corner angularly projected, anterior margin with 2 short robust setae, posterior margin with 5 setae; carpus medial surface with 1, 2, 3 robust setae; propodus anterior margin bearing 1, 1, 1, 2, 1 robust setae, posterodistal corner setose.

Pleon ( Fig. 5 View Fig ). Epimeral plates 1–3 each with small projection and short seta on posteroventral corner, ventral margins bare ( Fig. 2 View Fig ). Pleopods length 2>1>3; peduncles with 4, 4, 3 plumose setae in pleopods 1–3, respectively; outer rami shorter than inner rami, both rami with 7, 6, 6 articles, respectively. Uropod 1, peduncle with 1 basofacial, 3 dorsolateral and 2 dorsomedial robust setae, inter-ramal process long, 42% length of peduncle; outer ramus same length as peduncle, inner ramus about 1.1 times as long as peduncle, former with 2 dorsolateral, 1 dorsomedial and 4 terminal robust setae, latter bearing 3 dorsomedial and 4 terminal robust setae. Uropod 2, peduncle with 2 dorsolateral and 1 dorsomedial robust setae, inter-ramal process short, 7% length of inner ramus; outer ramus almost same length as peduncle, inner ramus ca. 1.35 times as long as peduncle, former with 1 dorsolateral, 1 dorsomedial and 4 terminal robust setae, latter bearing 1 dorsolateral, 3 dorsomedial and 4 terminal robust setae. Uropod 3, peduncle with 1 medioproximal and 2 laterodiatal robust setae, inter-ramal process short, 10% length of peduncle; both rami almost same length as peduncle, outer ramus with marginal robust seta in middle, tip bearing 1 robust seta, 2 long thick setae and several simple setae, inner ramus bearing marginal robust seta and long thick apical seta. Telson roundish pentagonal, distal margin with pair of 2 simple and 1 sensory setae, lateral margins each with 2 sensory setae.

Description of female [based on paratype (OMNH- Ar-12322, 2.9 mm)]. Generally similar to male holotype except for gnathopods and oostegites. Gnathopod 1 ( Fig. 5 View Fig F-G1) weakly setose; coxa trapezoidal, without plumose setae; basis relatively short, stout, anterior margin with a few short setae; merus and carpus, posterior margins setose; propodus about 1.1 times length of carpus, posterior margin and medial surface setose, palm oblique, defined by long robust seta; dactylus weakly curved, posterior margin with 4 denticles. Gnathopod 2 ( Fig. 5 View Fig F-G2), coxa large, roundish square, ventral margin with a few setae; basis relatively long, anterior and posterior margins each with a few short setae; meus setose posterodistally; carpus triangular, posterior margin setose; propodus ca. 1.1 times length of carpus, palm slightly oblique, defined by long robust seta, posterior margin and medial surface setose; dactylus curved, posterior margin with 4 denticles.

Variation. Gnathopod 1: large male (paratype, OMNH- Ar-12316, 3.2 mm; Fig. 5 View Fig LgM-G1), carpus more slender than that of holotype ( Fig. 4G View Fig 1 View Fig ); small male (paratype, OMNH-Ar-12321, 2.3 mm; Fig. 5 View Fig SM-G1), propodus roundish, posterior margin of dactylus with 3 denticles. Numbers of robust setae on uropod 3 rami ( Table 1): outer ramus usually with 1 marginal and 1 terminal robust setae in large males and females; inner ramus with 1 marginal robust seta in large males and with 1–2 marginal and 1 terminal robust setae in large females.

Coloration of specimen 3 days after fixation [based on paratype, male (OMNH-Ar-12318, 2.8 mm) ( Fig. 6A View Fig )]. Eyes dark red; anterior part of pereonite 1 and posterior parts of pereonites 1–7 and pleonites 1, 2 each with reddish brown line, anterior surface of upper lip and anterodorsal and posteroventral margins of coxa 1 also reddish brown; other body and appendages translucent or white.

Remarks. The present specimens are similar only to Aoroides longimerus in the heavily setose male gnathopod 1, the coxa of which bears several plumose setae anteriorly, and the uropod 2 with a short inter-ramal process. This species was originally described from China ( Ren and Zheng 1996), recorded from Osaka and Wakayama Prefectures in Japan ( Ariyama 2004a), and introduced to the western and northern coasts of France ( Gouillieux et al. 2016; Dauvin et al. 2020). However, A. macrops sp. nov. can be distinguished from the Japanese specimens of A. longimerus by (1) larger eyes (diameter less than 30% of head length in A. longimerus ), (2) shorter peduncular article 4 of the antenna 2 (length/BL 0.11–0.12, but ca. 0.14 in A. longimerus ), (3) shorter carpus of the male gnathopod 1 (length/BL 0.13– 0.16, but 0.19–0.21 in A. longimerus ), (4) shorter carpi of the pereopods 3 and 4 (length/width 1.9–2.3 in A. longimerus ), and (5) single marginal robust seta each on the uropod 3 rami (usually 2 or 3 in A. longimerus ). The body coloration is also different (color paler, reddish brown line on pereonite 6 absent in A. longimerus ). The original description of A. longimerus shares (2)–(4) with the Japanese specimens ( Ren and Zheng 1996). But regarding (1) and (5), although there are no descriptions in the text, large eyes and a single marginal robust seta on the uropod 3 rami are shown in their fig. 2-1 and fig. 2-9, respectively. Chinese specimens should be investigated in detail for comparison with this new species.

Habitat. Shallow subtidal, attached to fish cage.

Distribution. Japan: Chichijima Island, the Ogasawara Islands in Tokyo Prefecture (present study).