Grandidierella contigua, Ariyama, 2020

Ariyama, Hiroyuki, 2020, Six species of Grandidierella collected from the Ryukyu Archipelago in Japan with descriptions of four new species (Crustacea: Amphipoda: Aoridae), Zootaxa 4810 (1), pp. 1-44 : 3-10

publication ID	https://doi.org/ 10.11646/zootaxa.4810.1.1
publication LSID	lsid:zoobank.org:pub:BBD6D565-039A-47C7-9110-653DD75EBDBF
persistent identifier	https://treatment.plazi.org/id/0387413C-4C7A-FFB9-FF2E-62083474FE4F
treatment provided by	Plazi
scientific name	Grandidierella contigua
status	sp. nov.

Treatment

Grandidierella contigua View in CoL sp. nov.

[Japanese name: Rinsetsu-dorosokoebi, new]

( Figs 2–7 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 )

Type material. Holotype: male, 9.1 mm (OMNH-Ar-11513), Harutahama, Yakushima Island , Kagoshima Prefec-

ture, 30°18'25.9"N, 130°39'24.0"E ( Fig. 1A View FIGURE 1 ), coarse sand bottom in stream, brackish, 27 March 2017, coll. K. Kan. Paratypes: ovigerous female, 8.4 mm (OMNH-Ar-11514), same data as holotype; 2 males, 8.8, 6.7 mm (OMNH- Ar-11515, 11516) and female, 6.5 mm (OMNH-Ar-11517), Harutahama, Yakushima Island , Kagoshima Prefecture, 30°18'12.4"N, 130°39'16.7"E ( Fig. 1A View FIGURE 1 ), coarse sand bottom in stream, brackish, 27 March 2017, coll. K. Kan GoogleMaps ; 3 males, ca. 3.7 (damaged), 3.5, 2.9 mm (OMNH-Ar-11518–11520), ovigerous female, 3.5 mm (OMNH-Ar-11521) and female, 3.4 mm (OMNH-Ar-11522), mouth of Nakara River, Iriomote Island , Okinawa Prefecture, 24°21'11"N, 123°45'12"E ( Fig. 1H View FIGURE 1 ), upper–middle intertidal, sandy mud bottom under stones and soft sandstone, 16 July 2015, coll. H. Ariyama. GoogleMaps

Material for comparison ( Grandidierella fasciata Ariyama, 1996 ). Holotype, male, 8.4 mm (OMNH-Ar- 3840), mouth of Higashi River, Misaki Town , Osaka Prefecture, 34°19'N, 135°07'E, intertidal, sandy mud bottom mixed with gravel, brackish, 20 February 1992, coll. H. Ariyama. GoogleMaps Allotype, female, 6.5 mm (OMNH-Ar-3841), same data as holotype. Paratypes: male, 7.4 mm (OMNH-Ar-3842) and female, 6.7 mm (OMNH-Ar-3843), 6 February 1989, same place as holotype, coll. H. Ariyama; male, 7.7 mm (OMNH-Ar-3844) and ovigerous female, 10.1 mm (OMNH-Ar-3845), 7 June 1990, same place as holotype, coll. H. Ariyama; male, 8.2 mm (OMNH-Ar-3846), 4 May 1991, same place as holotype, coll. H. Ariyama ( Ariyama 1996). Three males, 5.3, 4.6, 4.1 mm (OMNH-Ar- 11523–11525) and female, 5.1 mm (OMNH-Ar-11526), same data as holotype GoogleMaps .

Type locality. Harutahama in Yakushima Island , Kagoshima Prefecture, Japan .

Etymology. From the Latin contiguus, - a, - um (= contiguous), referring to the middle and proximal teeth on the gnathopod 1 carpus.

Diagnosis. Male pereon, ventral process absent. Male gnathopod 1, ischium lacking posterodistal projection, merus posterodistal corner projected, posterior surface densely rugose; carpus with 1 small posterodistal tooth and 2 contiguous posterior teeth (large and small); propodus almost straight, posterodistal corner slightly swollen. Male gnathopod 2, coxa without posteromedial projection; basis straight; carpus longer than propodus, posterior margin and medial surface heavily setose; propodus with several robust setae on posterodistal corner and posterior margin. Uropod 1 peduncle with short inter-ramal process.

Description of male. Based on holotype, male, 9.1 mm (OMNH-Ar-11513).

Head ( Figs 2 View FIGURE 2 , 3 View FIGURE 3 ). Eyes small, about 0.2 times length of head. Antenna 1 slender, about 0.7 times as long as body; length ratio of peduncular articles 1–3 1:1.2:0.45, article 1 with 4 ventromedial robust setae; accessory flagellum very short, minutely biarticulate, tip with 5 setae; primary flagellum with 25 articles, terminal article minute. Antenna 2 stout, length (peduncular articles 3–5 and flagellum) about 0.65 times as long as body; length ratio of peduncular articles 3–5 1:3.25:3.2, article 3 with 2 posterior and 1 medial robust setae; flagellum short, consisting of 7 normal and 1 minute articles, articles 2, 3, 5–7 with 1, 1, 1, 1, 2 robust setae, respectively. Upper lip rounded ventrally, bearing many thin setae. Mandibles with length ratio of palp articles 1–3 1:1.4:1.4, article 1 with 5 short setae, article 2 bearing 6–8 setae, article 3 clavate, densely setose distally; incisor with 5 cusps, lacinia mobilis with 5 and 6 cusps in left and right, respectively, 9 accessory setae present. Lower lip, apical parts of outer and inner lobes covered with thin setae. Maxilla 1, outer plate with 10 distal robust setae, palp article 2 bearing 6 robust and 5 slender setae apically. Maxilla 2, inner plate bearing distal and medial setae and mediofacial row of setae, outer plate setose on distal margin. Maxilliped, distal part of inner plate setose, with 3 quadrate and 1 triangular robust setae; outer plate bearing 14 long-to-short robust setae mediodistally; palp article 2 long, with many medial setae, article 3 setose distally.

Pereon ( Fig. 4 View FIGURE 4 ). Ventral surface lacking process. Gnathopod 1, coxa trapezoidal; basis wide, lateral surface with ridge, posterior margin convex; ischium short, posterodistal corner not projected; merus posterodistal corner with projection, posterolateral and posteromedial surfaces densely rugose; carpus longish ovoid, length about 1.8 times width, posterodistal corner with small triangular tooth, posterior margin bearing 2 contiguous teeth (long and very short) in middle, sparsely setose; propodus almost straight, posterodistal corner a little swollen roundly, setose; dactylus short, curved posteriorly, posterior margin with 4 denticles. Gnathopod 2, coxa trapezoidal; basis slender, straight, anterior margin lined with setae; merus posterodistal margin densely setose; carpus long, relatively wide, posterior margin and medial surface heavily setose; propodus about 0.65 times as long as carpus, posterodistal corner and posterior margin with 2 and 3 short robust setae, respectively; dactylus short, curved posteriorly, posterior margin with many denticles. Pereopods 3 and 4, pereopod 3 slightly longer than pereopod 4; coxae trapezoidal; bases long; meri slightly wide, straight, densely setose posteriorly and anterodistally; carpi shorter than meri; propodi and dactyli narrow. Pereopod 5 shorter than pereopod 4; coxa bilobed; basis roundish rectangular, posteroproximal corner roundly projected, anterior and posterior margins with several simple setae; merus with 4 long thick setae; carpus bearing 2 anterodistal thick setae and 3 posterior robust setae; propodus with 5 posterior robust setae; dactylus short, straight. Pereopod 6 about 1.7 times as long as pereopod 5; coxa short, bilobed; basis rectangular, posteroproximal corner roundly projected, anterior margin with 1 plumose, 4 robust and several simple setae, posterior margin with many plumose and several simple setae; merus anterodistal corner with 2 thick setae, posterior margin bearing 3 thick setae, posterodistal corner with 2 robust setae; carpus with 5 lateral robust setae, posterodistal corner bearing 1 robust and 1 thick setae; propodus with 5 anterior robust setae, posterodistal corner setose; dactylus curved. Pereopod 7 about 1.15 times as long as pereopod 6; coxa short, slightly bilobed; basis rectangular, posteroproximal corner not projected, anterior margin with 2 distal plumose setae and 2 robust and several simple setae, posterior margin bearing many plumose and several simple setae; merus posterior margin bearing 3 thick setae, posterodistal corner with 2 robust setae; carpus with 5 lateral robust setae, posterodistal corner bearing robust seta; propodus with 5 anterior robust setae, posterodistal corner setose; dactylus curved.

Pleon ( Fig. 5 View FIGURE 5 ). Epimeral plates 1–3 rounded posteroventrally, each with long seta, ventral margins bare ( Fig. 2 View FIGURE 2 ). Pleopods, each peduncle bearing many plumose setae and 2 coupling hooks; inner ramus longer than outer, outer rami with 15–16 articles, inner rami with 14–16 articles. Uropod 1 stout; dorsal surface of peduncle bearing 2 lateral and 4 medial robust setae, ventrodistal end with short inter-ramal process (about 9% length of peduncle); 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 about 0.6 times as long as uropod 1; peduncle dorsal surface with 2 lateral and 1 mediodistal robust setae; inner ramus almost same length as peduncle, outer ramus shorter than inner ramus, former with 2 lateral and 4 terminal robust setae, latter bearing 2 dorsolateral, 3 dorsomedial and 5 terminal robust setae. Uropod 3 about half length of uropod 2; peduncle slightly wider than long, swollen mediodistally, lateral margin bare; single ramus slightly longer than peduncle, with tiny second article and 5 lateral, 2 medial and 5 terminal setae. Telson wider than long, laterodistal corners each with 3 setae.

Description of female. Based on paratype, ovigerous female, 8.4 mm (OMNH-Ar-11514). Gnathopod 1 ( Fig. 5 View FIGURE 5 F-G1), coxa trapezoidal; basis almost straight; ischium and merus short, both lacking projection; carpus wide, posterior margin with robust seta and many simple setae; propodus about 0.85 times as long as carpus, posterior margin with 5 robust setae; dactylus slightly curved posteriorly, posterior margin with 6 denticles. Gnathopod 2 ( Fig. 5 View FIGURE 5 F-G2) almost same as that of holotype, male, 9.1 mm (OMNH-Ar-11513) except for oostegite, but basis wider, carpus shorter.

Variation. Paratype, middle-sized male, 6.7 mm (OMNH-Ar-11516). Gnathopod 1 ( Fig. 5M View FIGURE 5 1-G1 View FIGURE 1 ) almost same as that of holotype, male, 9.1 mm (OMNH-Ar-11513), but middle tooth on carpus posterior margin situated distally, separated from proximal short tooth, propodus short and wide, posterior margin of dactylus with 3 denticles. Paratype, small male, ca. 3.7 mm (OMNH-Ar-11518). Gnathopod 1 ( Fig. 5M View FIGURE 5 2-G View FIGURE 2 1 View FIGURE 1 ), middle tooth on carpus posterior margin situated more distally, posterior tooth minute, propodus shorter and wider than paratype, middle-sized male, 6.7 mm (OMNH-Ar-11516).

Coloration. Recently fixed small specimen ( Fig. 6 View FIGURE 6 ): eyes dark brown; dorsal surface of head mottled dark brown, dorsal parts of pereonites 4 and 7 dark brown; other body parts yellowish white with indistinct brown speckles; antennae white and partly pale brown; gnathopods and pereopods white. Preserved large specimens ( Fig. 7 View FIGURE 7 ): eyes dark brown; dorsal surface of head mottled dark brown, pereonites 4 and 7 dark brown, other pereonites, pleonites and urosomites in male brown, pereonites 3, 5 and 6, pleonites and urosomites in female pale brown; antenna 2 peduncle white and partly dark brown; other appendages white.

Remarks. Grandidierella contigua sp. nov. has a male gnathopod 1 with a posterodistally projected merus and a carpus bearing three distinct teeth on the posterodistal margin, the proximal tooth of which is very small and contiguous with the large middle tooth ( Fig. 4G View FIGURE 4 1 View FIGURE 1 ). Such a gnathopod 1 is unique in the genus Grandidierella . The rugose merus of the male gnathopod 1 is also characteristic; however, G. fasciata , G. osakaensis and G. sanrikuensis (reexamination of the type specimens) and G. pseudosakaensis sp. nov. share this character with this new species.

The gnathopod 1 of the middle-sized male ( Fig. 5M View FIGURE 5 1-G1 View FIGURE 1 ) is similar to that of G. sanrikuensis which has a small proximal tooth on the carpus, but G. contigua is different from G. sanrikuensis in the densely setose meri of the male pereopods 3 and 4 ( Fig. 4P View FIGURE 4 3 View FIGURE 3 , P 4 View FIGURE 4 ) and the coloration ( Figs 6 View FIGURE 6 , 7 View FIGURE 7 ). The small specimens of this species collected from Irimomote Island resemble G. fasciata in the shape of the male gnathopod 1 ( Fig. 5M View FIGURE 5 2-G View FIGURE 2 1 View FIGURE 1 ) and the coloration. But G. fasciata has a posterodistal projection on the male gnathopod 1 ischium and a longer inter-ramal process on the uropod 1 peduncle. The length of the inter-ramal process is 7–9% (average: 8%) of the peduncle length in G. contigua , whereas 14–22% (average: 18%) in G. fasciata .