Grandidierella sanrikuensis, Ariyama & Taru, 2017

Ariyama, Hiroyuki & Taru, Masanori, 2017, Three Species of Grandidierella (Crustacea: Amphipoda: Aoridae) from Coastal Areas of the Tohoku and Kanto-Tokai Districts, East Japan, with the Description of Two New Species, Species Diversity 22, pp. 187-200 : 188-193

publication ID	https://doi.org/ 10.12782/sd.22_187
publication LSID	lsid:zoobank.org:pub:07D72FEB-42BC-4D79-A5A6-3F0D9C9C430A
persistent identifier	https://treatment.plazi.org/id/B57368E1-F3EB-4B86-8DC6-A5E0212318FF
taxon LSID	lsid:zoobank.org:act:B57368E1-F3EB-4B86-8DC6-A5E0212318FF
treatment provided by	Felipe
scientific name	Grandidierella sanrikuensis
status	sp. nov.

Treatment

Grandidierella sanrikuensis View in CoL sp. nov.

( Figs 2A, B View Fig , 3–7 View Fig View Fig View Fig View Fig View Fig ) [Japanese name: Sanriku-dorosokoebi]

Grandidierella sp. Fujita et al., 2017: 66, fig. 1a.

Material examined. Holotype: male (OMNH- Ar-10195), 7.7 mm, mouth of Higashi-moune River in Higashi-moune, Karakuwa-cho, Kesennuma City , Miyagi Prefecture, 38°54′00″N, 141°37′29″E ( Fig. 1A View Fig ), brackish, intertidal, sandy mud bottom under stones, 21 May 2015, coll. M. Taru. GoogleMaps Paratypes: male (OMNH-Ar-10196), 6.5 mm, and female (OMNH-Ar-10197), 8.5 mm, same data as holotype; male (OMNH-Ar-10198), 3.8 mm, mouth of Nishimoune River in Nishi-moune, Karakuwa-cho, Kesennuma City , Miyagi Prefecture, 38°53′42″N, 141°37′33″E ( Fig. 1A View Fig ), brackish, intertidal, among small gravel, 25 May 2016, coll GoogleMaps . M GoogleMaps . Taru; male (OMNH-Ar-10199), 8.4 mm, and ovigerous female (OMNH-Ar-10200), 9.0 mm, mouth of Jaou River in Hosoura, Shizugawa , Minami-sanriku Town , Miyagi Prefecture, 38°41′43″N, 141°29′57″E ( Fig. 1B View Fig ), brackish, intertidal, sand and gravel bottom under stones, 26 May 2016, coll GoogleMaps . M GoogleMaps . Taru; male (OMNH-Ar-10201), 7.0 mm, and female (OMNH-Ar-10202), 6.6 mm, Ohama-Setoshima, Mangoku-ura , Watanoha , Ishinomaki City , Miyagi Prefecture, 38°24′56″N, 141°24′18″E ( Fig. 1C View Fig ), brackish, intertidal, sandy mud bottom under stones, 7 June 2016, coll GoogleMaps . T. Suzuki.

Diagnosis. Antenna 2 not robust. Male gnathopod 1, merus bearing single distal projection; carpus with 3 posterodistal teeth, middle tooth large; propodus slightly curved posteriorly, anterodistal corner without small projection. Male gnathopod 2, carpus long, about 1.4 times as long as propodus. Uropod 1 peduncle with inter-ramal process.

Description of male [based mostly on holotype (OMNH-Ar-10195), 7.7 mm, supplemented by paratype (OMNH-Ar-10199), 8.4 mm for lower lip, pereopods 5–7 and pleopods]. Body ( Fig. 3 View Fig ) slender, pereon segments lacking ventral process. Eyes medium-sized, about quarter length of head.

Antenna 1 ( Fig. 4A, A View Fig 1 View Fig ) slender; length ratio of peduncular articles 1–3 1.0: 1.3: 0.6, article 1 with 5 robust setae ventromedially; flagellum with 12 normal articles (tip lost). Antenna 2 ( Fig. 4B, B View Fig 1 View Fig ) slightly stout, length (peduncular articles 3–5 and flagellum) about 0.6 times as long as body; length ratio of peduncular articles 3–5 1.0: 2.5: 3.0, article 3 with 1 medial and 3 ventral robust setae, article 4 bearing 2 medial and 1 ventral robust setae; flagellum short, consisting of 9 normal and 1 minute articles, articles 3, 4, 6, 8, 9 with 1, 1, 1, 1, 2 robust setae, respectively.

Upper lip ( Fig. 4C View Fig ) subrounded ventrally, bearing many thin setae. Mandibles ( Fig. 4D, D View Fig 1, E, E1 View Fig ) with length ratio of palp articles 1–3 1.0: 1.5–1.6: 1.5, articles 1 and 2 with 2 and 6–7 setae, respectively, article 3 clavate, heavily setose distally; incisor with 5 cusps, lacinia mobilis with 3–4 cusps, 9–10 accessory blades present; blunt process present on mediodistal surface of body. Lower lip ( Fig. 4F View Fig ) covered with thin setae on apical parts of outer and inner lobes. Maxilla 1 ( Fig. 4G, G View Fig 1 View Fig ) with 10 and 5 robust setae on outer plate and palp article 2, respectively. Maxilla 2 ( Fig. 4H View Fig ) with inner plate setose on distal and medial margins, outer plate setose on distal margin. Maxilliped ( Fig. 4I, I View Fig 1 View Fig ) with inner plate setose on distal and medial margins, distal end bearing 1 rectangular and 1 triangular robust setae; outer plate broad, mediodistal margin with 7 triangular robust setae and distal margin bearing 4 long robust setae; laterodistal end with robust seta; palp article 2 long, article 3 setose distally.

Gnathopod 1 ( Fig. 5A View Fig ) large; coxa trapezoidal; basis wide, lateral surface with ridge, posterior margin convex; ischium short; merus projected posterodistally, distal margin with several setae; carpus extremely wide, posterodistal corner with 3 teeth (middle one large, others small); propodus slightly curved posteriorly, posterodistal corner swollen; dactylus relatively long triangular, posterior margin smooth. Gnathopod 2 ( Fig. 5B, B View Fig 1 View Fig ) slender; coxa trapezoidal; basis slightly curved anteriorly; merus setose on posterodistal margin; carpus elongate, about 1.4 times as long as propodus, widened in middle, posterior margin with many thick and normal setae; propodus with 2 and 2 robust setae on posterodistal corner and posterior margin, respectively, anterodistal corner and distal margin setose; dactylus slightly curved posteriorly, posterior margin minutely serrate.

Pereopods 3 and 4 ( Fig. 5C, D View Fig ), pereopod 3 longer than pereopod 4; coxae trapezoidal, bases long, meri long, a little dilated distally, carpi shorter than meri, propodi and dactyli narrow. Pereopod 5 ( Figs 5E View Fig , 6I View Fig ) with coxa bilobed, posterior half narrower than anterior half; basis rectangular, anterior margin with several short robust setae, posterior margin with several short robust setae and a few distal plumose setae; merus with 3 long thick setae on posterior margin; carpus with 2 long thick setae on anterodistal margin and robust seta on posterodistal corner; propodus with 2 anterior thick setae, anterodistal corner setose, posterior margin lined with 6 robust setae; dactylus short. Pereopod 6 ( Figs 5F View Fig , 6J View Fig ) about 1.5 times as long as pereopod 5; coxa short, bilobed; basis rectangular, anterior margin with several short robust setae, posterior margin with many plumose setae; merus with anterodistal robust seta and 5 posterior long thick setae; carpus with 2 anterior and 5 posterior robust setae; propodus with 1 anterior and 7 posterior robust setae. Pereopod 7 ( Figs 5G View Fig , 6K View Fig ) about 1.1 times as long as pereopod 6; coxa short, slightly bilobed; basis rectangular, anteri- or margin with several short robust setae, posterior margin with many plumose setae; merus with anterodistal robust seta and 7 posterior long thick setae; carpus with 3 anterior and 4 posterior robust setae; propodus with 6 anterior and 4 posterior robust setae.

Epimeral plates 1–3 ( Fig. 6A View Fig ) each with long thick seta on posteroventral corner, ventral margins bare. Pleopods ( Fig. 6B–D View Fig ) with peduncles bearing several plumose setae and 2 coupling hooks; inner ramus longer than outer, outer rami with 10–11 articles, inner rami with 9–11 articles. Uropod 1 ( Fig. 6E View Fig ) relatively long; dorsal surface of peduncle bearing 2 lateral and 4 medial robust setae, ventrodistal end with inter-ramal process; both rami shorter than peduncle, outer ramus subequal to inner ramus, former with 4 dorsal and 4 terminal robust setae, latter bearing 2 dorsolateral, 3 dorsomedial and 5 terminal robust setae. Uropod 2 ( Fig. 6F View Fig ) short, about 55% as long as uropod 1; dorsal surface of peduncle with 2 lateral and 3 medial robust setae; outer ramus shorter than peduncle, inner ramus subequal to peduncle, outer ramus with 1 dorsal and 4 terminal robust setae, inner ramus bearing 2 dorsolateral, 2 dorsomedial and 4 terminal robust setae. Uropod 3 ( Fig. 6G View Fig ) very short, about 0.6 times as long as uropod 2; peduncle wider than long, medial margin bearing 3 minute setae; single ramus about 1.5 times length of peduncle, tip with tiny second article, lateral margin bearing 5 setae. Telson ( Fig. 6H View Fig ) wider than long, laterodistal corners each with 4 setae.

Description of female [based on paratype (OMNH- Ar-10197), 8.5 mm]. Generally similar to male holotype except for gnathopods and oostegites. Gnathopod 1 ( Fig. 7A, A View Fig 1 View Fig ) slightly stout; coxa trapezoidal; basis slightly broadened, lateral surface with ridge; merus trapezoidal, not projected posterodistally, distal margin setose; carpus relatively broad, posterior margin with many thick and normal setae; propodus wide, about 1.1 times as long as carpus, posterodistal corner and posterior margin with 3 and 2 robust setae, respectively, anterior margin setose; dactylus gradually curved, posterior margin minutely serrate. Gnathopod 2 ( Fig. 7B, B View Fig 1 View Fig ) slender; coxa trapezoidal; basis straight; merus setose on posterodistal margin; carpus not elongate, widened in middle, posterior margin with many thick and normal setae; propodus about 0.9 times as long as carpus, with 5 and 2 robust setae on posterodistal corner and posterior margin, respectively, anterior and distal margins setose; dactylus almost straight, posterior margin minutely serrate.

Variation in male gnathopod 1. Middle-sized male [paratype (OMNH-Ar-10196), 6.5 mm; Fig. 7C View Fig ]: posterior tooth on posterodistal margin of carpus smaller than that of holotype, posterior margin of dactylus minutely serrate. Small male [paratype (OMNH-Ar-10198), 3.8 mm; Fig. 7D View Fig ]: posterodistal corner of merus not projected, posterior and anterior teeth on posterodistal margin of carpus indistinct, posterior margin of propodus smoothly rounded, posterior margin of dactylus minutely serrate.

Coloration in life ( Fig. 2A, B View Fig ). Eyes black and white; head, pereonites and pleonites brown; antennae pale red and partly white; propodus of male gnathopod 1 faintly red; other appendages whitish.

Etymology. From Sanriku, another name of Aomori – Miyagi Prefectures, including the collecting sites.

Remarks. This new species has the male gnathopod 1 with the posterodistally projected merus and the carpus bearing 3 distinct teeth on the posterodistal margin. This character is shared with the following three species: Grandidierella dentimera Myers, 1970 from Hawaii, G. fasciata and G. osakaensis from Japan. However, Grandidierella sanrikuensis sp. nov. can be clearly distinguished from the latter three species by the smaller posterior tooth on the carpus of the male gnathopod 1. Only the middle tooth is large in G. sanrikuensis , whereas both the middle and posterior teeth are large in G. dentimera , G. fasciata and G. osakaensis ( Myers 1970; Ariyama 1996).

Habitat. Sandy mud bottom under stones or among gravel in brackish intertidal zone.

Distribution. Known only from the coasts of northern Miyagi Prefecture. All the collecting sites of this new species are under reconstruction of shore protection after a tsunami disaster on 11 March 2011; therefore, the habitat of the species is feared to be endangered ( Fujita et al. 2017).