Grandidierella ogasawarensis, 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 : 121-127

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/3512EBC0-3325-482D-87C6-413E3684F3EB
taxon LSID	lsid:zoobank.org:act:3512EBC0-3325-482D-87C6-413E3684F3EB
treatment provided by	Felipe
scientific name	Grandidierella ogasawarensis
status	sp. nov.

Treatment

Grandidierella ogasawarensis View in CoL sp. nov.

[New Japanese name: Ogasawara-dorosokoebi] ( Figs 6B View Fig , 7–10 View Fig View Fig View Fig View Fig ; Tables 2, 3)

Aoridae View in CoL sp.: Hamabe 2017: 63, fig. 3B.

Material examined. Holotype: male (OMNH-Ar-12324), 5.0 mm, mouth of Kiyose River , Chichijima Island, Ogasawara Islands, Tokyo Prefecture ( Fig. 1B View Fig ), Japan, 27°05′55″N, 142°11′53″E, intertidal, under stones, 11 July 2020, coll. K. Kawabe. GoogleMaps Paratypes: 2 males (OMNH- Ar-12325, 12326), 4.5 and 3.6 mm, respectively, and 2 females (OMNH-Ar-12327, 12328), 5.4 and 5.1 mm, respectively, same data as holotype GoogleMaps . Non-type: male (OMNH- Ar-12329, ASAO-A.17002), ca. 5.5 mm (damaged), same locality and habitat, 5 January 2017, coll GoogleMaps . K GoogleMaps . Hamabe.

Material for comparison. Grandidierella rubroantennata Ariyama and Taru, 2017 : holotype, male (OMNH- Ar-3847), 9.0 mm, and paratypes, 2 males (OMNH- Ar-3848, 3849), 7.6 and 8.4 mm, respectively, and 2 females (OMNH-Ar-3850, 3851), both 8.8 mm, examined in Ariyama (1996); paratypes, 1 male (OMNH-Ar-10334), 6.2 mm, and 2 females (OMNH-Ar-10335, 10296), 5.6 and 7.2 mm, respectively, examined in Ariyama and Taru (2017); nontypes: 1 male (OMNH-Ar-12330), 5.4 mm, and 1 female (OMNH-Ar-12331), 5.5 mm, intertidal zone of Toyokunizaki coast in Misaki, Osaka Prefecture, 34°19′21″N, 135°07′00″E, under stones, 5 June 2005, coll. H . Ariyama; 1 male (OMNH-Ar-12332), 5.2 mm, same locality and habitat, 12 June 2012, coll . H . Ariyama.

Type locality. Mouth of Kiyose River , Chichijima Island, Ogasawara Islands, Tokyo Prefecture, Japan .

Etymology. Referring to the type locality.

Description of male. Based on holotype (OMNH- Ar-12324, 5.0 mm) and paratype (OMNH-Ar-12325, 4.5 mm) only for pereopod 7.

Head ( Figs 7 View Fig , 8 View Fig ). Eyes large (diameter: 33% of head length). Antenna 1 slender, peduncular articles 1–3 with length ratio of 1.0: 1.25: 0.55, article 1 stout, ventral margin with 5 robust setae; accessory flagellum short, 1-articulate, with 4 setae apically; flagellum with 9+ articles (tip lost), articles 2, 4, 6–8 each bearing aesthetasc at posterodistal end. Antenna 2 slightly stouter than antenna 1; peduncular articles 3–5 with length ratio of 1.0: 2.5: 2.8, article 3 with 3 medial and 1 ventral robust setae, article 4 bearing 4 medial and 2 ventral robust setae; flagellum with 7 articles, terminal article minute, article 3–6 with 1, 1, 1, 2 robust setae, respectively. Upper lip subrounded ventrally, ventral margin bearing many thin setae. Mandibles, left and right incisors with 4 and 5 cusps, respectively; left lacinia mobilis 4-toothed and right one 3-toothed, left accessory blades 9 in number and right ones 8; palp stout, article length ratio 1.0: 1.1: 1.35, article 1 with 2 short setae, article 2 with 7 setae, article 3 clavate, bearing many slender setae and 1 thick seta. Lower lip with short mandibular process, outer lobe with 2 bundle of setae, 1 thick seta and many thin setae, inner lobe bearing many short thin setae on apical margin. Maxilla 1 with bare, rounded inner plate; outer plate with 9 distal robust setae; palp article 2 bearing 6 robust and 4 slender setae apically. Maxilla 2, inner plate with distal and medial setae and mediofacial row of setae, outer plate setose on distal margin. Maxilliped with inner plate bearing 3 quadrate, 1 curved and 1 slender robust setae; outer plate with 11 long-to-short robust setae mediodistally; palp slender, article 2 long, with many medial setae, article 3 setose distally, article 4 bearing dorsal thick seta and apical nail.

Pereon ( Fig. 9 View Fig ). Ventral surface lacking process. Gnathopod 1 very large; coxa trapezoidal, with short seta ventrally; basis wide, lateral surface with ridge, posterior margin convex, posterodistal corner with 2 setae; ischium short, posterodistal corner not projected, with short seta; merus posterodistal corner lacking projection, with several setae; carpus ovoid, length excluding teeth ca. 1.45 times width, distal margin with triangular tooth, posterodistal corner with long acute tooth, distance between teeth relatively broad, anterior margin bearing sparse short setae, posterior margin and posteromedial surface weakly setose; propodus curved, about 0.8 times as long as carpus, anterodistal corner with small projection, posterodistal corner a little swollen roundly, with several setae; dactylus short, triangular, posterior margin with 2 denticles. Gnathopod 2 slender; coxa trapezoidal; basis slender, slightly curved anteriorly, anterodistal corner without “nipple” sensu Barnard (1977), posterior margin with a few short setae; merus short, distal margin setose; carpus long, posterior margin heavily setose; propodus short, about half length of carpus, posterodistal corner with single robust seta; dactylus short, curved posteriorly, posterior margin with 2 denticles. Pereopods 3, 4 slightly shorter than gnathopod 2; coxae trapezoidal; bases long; meri rectangular, weakly setose; carpi short; propodi and dactyli narrow. Pereopod 5 shorter than pereopod 4; coxa bilobed, with 2 simple setae; basis roundish rectangular, posteroproximal corner roundly projected, anterior margin with several setae (robust in part), posterior margin with 4 medial plumose setae and 3 robust and 2 simple setae; merus with 2 long thick setae posteriorly; carpus bearing 2 posterolateral and 1 posterodistal robust setae; propodus anterior margin bearing 5 robust setae, posterodistal corner with 2 long thick setae; dactylus short. Pereopod 6 ca. 1.45 times as long as pereopod 5; coxa short, bilobed, with 2 plumose, 2 robust and 1 simple setae; basis rectangular, posteroproximal corner roundly projected, anterior margin with lateral plumose seta and 4 robust setae, anterodistal corner bearing 1 thick and 1 simple setae, posterior margin with 11 plumose setae (2 lateral and 9 medial) and 3 robust and 2 simple setae; merus posterior margin with 5 long thick setae, posterodistal corner bearing 1 thick (damaged) and 1 robust setae; carpus with 5 lateral robust setae; propodus with 8 anterior robust setae, posterodistal corner setose. Pereopod 7 a little longer than pereopod 6 in paratype (OMNH-Ar-12325, 4.5 mm); coxa short, slightly bilobed, with 1 plumose and 2 robust setae; basis rectangular, posteroproximal corner a little projected, anterior margin with 5 robust setae, anterodistal corner with 1 robust and 1 simple setae, posterior margin bearing 10 plumose setae (3 lateral and 7 medial) and 7 robust and 1 simple setae; merus posterior margin with 4 long thick setae, posterodistal corner bearing 1 robust and 1 long thick setae; carpus posterolateral surface with 3 robust setae, posterodistal corner bearing 1 robust and 1 long thick setae; propodus anterior margin with 5 robust setae, posterior margin bearing long thick seta, posterodistal corner setose.

Pleon ( Fig. 10 View Fig ). Epimeral plates 1–3 rounded posteroventrally, each with robust seta, ventral margins bare ( Fig. 7 View Fig ). Pleopods length 2>1>3; peduncles with 12, 5, 10 plumose setae in pleopods 1–3, respectively; outer rami shorter than inner rami, outer rami with 9, 9, 8 articles, respectively, inner rami with 8 articles. Uropod 1 stout; peduncle with 3 dorsolateral and 5 dorsomedial robust setae, ventrodistal end with short inter-ramal process (15% length of peduncle); both rami shorter than peduncle, outer ramus a little shorter than inner ramus, former with 4 dorsolateral, 1 dorsomedial and 4 terminal robust setae, latter bearing 3 dorsolateral, 3 dorsomedial and 5 terminal robust setae. Uropod 2 short, about 0.6 times as long as uropod 1; peduncle dorsal surface with 1 lateral, 1 laterodistal, 1 medial and 1 mediodistal robust setae; inner ramus almost same length as peduncle, outer ramus shorter than inner ramus, former with 2 dorsolateral, 2 dorsomedial and 4 terminal robust setae, latter bearing 2 dorsolateral and 4 terminal robust setae. Uropod 3 about half length of uropod 2; peduncle slightly wider than long, swollen medially, with 2 dorsal setae; single ramus ca. 1.75 times length of peduncle, with tiny second article and 2 lateral, 2 medial and 5 terminal setae. Telson wider than long, laterodistal corners each with 3 setae, lateral margins each with 2 sensory setae.

Description of female [based on paratype (OMNH- Ar-12327, 5.4 mm)]. Generally similar to male holotype except for gnathopods and oostegites. Gnathopod 1 ( Fig. 10 View Fig F-G1), coxa trapezoidal; basis relatively stout, posterodistal corner with a few setae; ischium and merus short, both lacking projection, distal margin of merus setose; carpus wide, posterior margin heavily setose; propodus a little shorter than carpus, posterior margin with 4 robust setae; dactylus slightly curved posteriorly, posterior margin with 4 denticles. Gnathopod 2 ( Fig. 10 View Fig F-G2), coxa trapezoidal; basis straight; merus short, distal margin setose; carpus shorter than that of male, posterior margin heavily setose; propodus short, about 0.9 times as long as carpus, posterodistal corner and posterior margin each with 2 robust setae; dactylus short, curved posteriorly, posterior margin with 4 denticles.

Variation. Antenna 1: medium-sized male (paratype, OMNH-Ar-12325, 4.5 mm), flagellum with 16 articles, terminal article minute; small male (paratype, OMNH- Ar-12326, 3.6 mm), flagellum with 12 articles, terminal article minute. Antenna 2: medium-sized male, flagellum with 8 articles, terminal article minute; small male, flagellum with 6 articles, terminal article minute. Gnathopod 1: large male (paratype, OMNH-Ar-12329, ca. 5.5 mm) and mediumsized male, almost same as that of holotype ( Fig. 9G View Fig 1 View Fig ); small male ( Fig. 10 View Fig SM-G1), teeth on carpus closer each other, propodus wider than that of holotype, dactylus with 2 posterior denticles. Gnathopod 2: medium-sized male, almost same as that of holotype, but posterodistal corner and posterior margin of propodus with 2 and 1 robust setae, respectively, dactylus with 3 posterior denticles; small male ( Fig. 10 View Fig SM-G2), almost similar to paratype female ( Fig. 10 View Fig F-G2), but posterodistal corner and posterior margin of propodus with 2 and 1 robust setae, respectively, dactylus with 3 posterior denticles. Numbers of plumose setae on pereopods 5–7 ( Table 2, upper part): plumose setae on coxae present in female pereopod 5 and pereopods 6, 7 of both sexes; those on basis anterior margins present in pereopods 6 of both sexes and female pereopod 7; those on basis posterior margins present in pereopods 5–7 of both sexes.

Coloration of specimen 3 days after fixation [based on paratype, male (OMNH-Ar-12325, 4.5 mm) ( Fig. 6B View Fig )]. Eyes brown; head, pereonites and pleonites light brown; peduncular articles 2, 3 and flagellum of antenna 1 and flagellum of antenna 2 pale red, peduncular articles 4, 5 of antenna 2 pale orange proximally and white distally; other appendages whitish.

Remarks. The present specimens are characterized by (1) male gnathopod 1 with 2 teeth on the carpus and an anterodistal projection on the propodus, (2) male gnathopod 2 with an elongate carpus, and (3) uropod 1 bearing an inter-ramal process. Only three species in the genus Grandidierella possess all of these characters: G. koa Barnard, 1977 from Hawaii; G. insulae Myers, 1981 from Lord Howe Island in Australia; and G. rubroantennata from Osaka, Wakayama and Chiba Prefectures in Japan ( Barnard 1977; Myers 1981; Ariyama and Taru 2017). However, the present specimens are apparently different from these species in several characters ( Table 3); therefore, we establish G. ogasawarensis as a new species herein. This species can be clearly distinguished by the male gnathopod 1 carpus with two teeth separated each other, whereas the teeth are close each other in the related species. Grandidierella ogasawarensis sp. nov. is most similar to G. rubroantennata from Japan; however, the former differs from the latter in the smaller body, the larger eyes (diameter: about 0.2 times of head length in G. rubroantennata ), and the setation of the pereopods 5–7. On the setation of G. rubroantennata , reexamination of the specimens examined in Ariyama (1996) and Ariyama and Taru (2017) reveals that several plumose setae were overlooked in the previous studies, so the setation of them is described correctly in this study ( Table 2, lower part). According to the table, lateral plumose setae occur on the both margins of the pereopod 6 basis and the posterior margin of the pereopod 7 basis in males of G. ogasawarensis , while they never occur in males of G. rubroantennata .