Grandidierella halophila Wongkamhaeng, Pholpunthin & Azman, 2012

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 : 16-21

Grandidierella halophila Wongkamhaeng, Pholpunthin & Azman, 2012

[Japanese name: Munetoge-dorosokoebi, new]

( Figs 13–17 )

Grandidierella halophilus Wongkamhaeng, Pholpunthin & Azman, 2012: 434 , figs 2–10.— Wongkamhaeng, Dumrongrojwattana & Boonyanusith, 2017: 148, figs 2, 3.

Material examined. Two males, 4.0, 3.8 mm (OMNH-Ar-11530, 11531) and female, 3.6 mm (OMNH-Ar-11532), mouth of Urauchi River, Iriomote Island , Okinawa Prefecture, 24°25'09"N, 123°46'30"E ( Fig. 1F ), uppermost subtidal, fine sand bottom, 17 July 2015, coll. H. Ariyama ; male, 3.5 mm (OMNH-Ar-11533) and ovigerous female, 4.4 mm (OMNH-Ar-11534), mouth of Gesashi River, Higashi Village, Okinawa Island , Okinawa Prefecture, 26°36'05"N, 128°08'30"E ( Fig. 1D ), lower intertidal, fine sand bottom, 2 July 2015, coll. H. Ariyama.

Type locality. Samur Sakorn in Thailand ( Wongkamhaeng et al. 2012) .

Diagnosis. Male pereon, ventral process present. Male gnathopod 1, ischium and merus without posterodistal projection; carpus with 3 teeth, middle tooth large; propodus widened distally. Male gnathopod 2, coxa with posteromedial projection; basis straight; carpus longer than propodus; propodus with several robust setae on posterodistal corner and posterior margin. Uropod 1 peduncle with inter-ramal process.

Description of male. Based on male, 4.0 mm (OMNH-Ar-11530), and male, 3.8 mm (OMNH-Ar-11531) for pereonal ventral process, coxa 2 and uropod 2.

Head ( Figs 13 , 14 ). Eyes medium-sized, about quarter length of head. Antenna 1 slender, about 0.6 times as long as body; length ratio of peduncular articles 1–3 1:1.3:0.5, article 1 with 5 ventral robust setae; accessory flagellum minute, with 1 article; primary flagellum with 14 articles, terminal article minute, posterodistal corners of articles 4, 7, 9–13 each bearing aesthetasc. Antenna 2 short, length about 0.35 times as long as body, slightly stout; length ratio of peduncular articles 3–5 1:3.1:3.1, article 3 with 3 medial and 2 ventrodistal robust setae, article 4 bearing 4 medial and 2 ventral robust setae; flagellum short, consisting of 4 normal and 1 minute articles, articles 3–5 with 2, 2, 1 robust setae, respectively. Upper lip slightly hollowed ventrally, bearing many thin setae. Mandibles with length ratio of palp articles 1–3 1:1.15:1.15, articles 1, 2 each with seta, article 3 rectolinear, setose distally; incisor with 4 and 5 cusps in left and right, respectively, lacinia mobilis with 4 cusps, 7 accessory setae present. Lower lip, mediodistal margin of outer lobe bearing bundle of setae, 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 several slender setae apically. Maxilla 2 with inner plate bearing distal and medial setae and mediofacial row of setae, outer plate setose on distal margin. Maxilliped, inner plate setose on distal and medial margins, distal end bearing 3 robust setae (mediodistal setae quadrate); outer plate broad, mediodistal margin with 11 long-to-short robust setae; palp article 2 long, article 2 setose medially, article 3 setose distally.

Pereon ( Fig. 15 ). Ventral surfaces of pereonites 1–3 with triangular, minute and curved processes, respectively. Gnathopod 1, coxa roundish triangular; basis wide, lateral surface with ridge, posterior margin convex; ischium short; merus posterodistal margin bearing several setae, without projection; carpus relatively wide, length about 1.6 times width, distal margin with minute tooth, posterodistal corner with large tooth, posteromedial margin bearing small tooth in middle, setose moderately; propodus ovoid, widened distally, posterior margin setose; dactylus short, almost straight, posterior margin with 3 denticles. Gnathopod 2, coxa trapezoidal, with blunt (damaged?) or acute projection posteromedially; basis straight; merus posterodistal margin setose; carpus elongate, relatively wide, posterior margin heavily setose; propodus 0.6 times as long as carpus, posterodistal corner and posterior margin each with 2 short robust setae; dactylus short, curved posteriorly, posterior margin with 3 denticles. Pereopods 3 and 4, pereopod 3 longer than pereopod 4; coxae trapezoidal; bases long; meri wide, a little dilated distally; carpi shorter than meri; propodi and dactyli narrow. Pereopod 5 shorter than pereopod 4; coxa bilobed; basis rectangular, posteroproximal corner projected, anterior margin with several robust setae, posterior margin bearing several short setae; merus with long thick seta each on anterodistal and posterodiatal corners; carpus bearing 2 lateral and 1 posterodistal robust setae; propodus with 2 anterodistal thick setae and 4 posterolateral robust setae; dactylus short, strongly curved. Pereopod 6 about 1.7 times as long as pereopod 5; coxa short, bilobed; basis rectangular, posteroproximal corner projected, anterior margin with several robust setae, posterior margin with 2 plumose setae and several short setae; merus anterior margin with 2 robust and several slender setae, posterior margin bearing 2 long thick setae and 2 robust setae; carpus with 1 anterior and 3 lateral robust setae; propodus with 6 anterior robust setae, medial surface bearing 2 robust and 1 thick setae, posterodistal corner setose; dactylus curved. Pereopod 7 about 1.2 times as long as pereopod 6; coxa short, slightly bilobed; basis roundish rectangular, posteroproximal corner not projected, anterior margin with several short robust setae and plumose seta, posterior margin bearing many plumose setae and short robust seta in middle; merus anterior margin with several short setae (robust in part), posterior margin bearing several thick setae; carpus with 3 lateral and 2 medial robust setae; propodus with 10 anterior and 5 posteromedial robust setae, posterodistal corner setose; dactylus curved.

Pleon ( Fig. 16 ). Epimeral plates 1–3 each with thick seta on posteroventral corner, ventral margins bare ( Fig. 13 ). Pleopods, each peduncle bearing several plumose setae and 2 coupling hooks; inner ramus longer than outer, outer rami each with 10 articles, inner rami with 9–10 articles. Uropod 1, dorsal surface of peduncle bearing 4 lateral and 5 medial robust setae, lateral surface with 3 robust setae ventrally, ventrodistal end with inter-ramal process; both rami shorter than peduncle, outer ramus subequal to inner ramus, former with 3 dorsolateral and 4 terminal robust setae, latter bearing 3 dorsolateral (2 minute), 3 dorsomedial and 5 terminal robust setae. Uropod 2, laterodistal and mediodistal corners of peduncle slightly projected, dorsal surface with 1 medial, 1 laterodistal and 1 mediodistal robust setae; both rami longer than peduncle, outer ramus shorter than inner ramus, former with 2 dorsolateral, 1 dorsomedial and 4 terminal robust setae, latter bearing 1 dorsolateral, 3 dorsomedial and 5 terminal robust setae. Uropod 3, peduncle wider than long, swollen medially, laterodistal corner with seta; single ramus about 2.5–2.6 times length of peduncle, tip with tiny second article, bearing 2 lateral, 1–2 medial and 5 terminal setae. Telson wider than long, laterodistal corners each with 2 setae.

Description of female. Based on female, 3.6 mm (OMNH-Ar-11532). Gnathopod 1 ( Fig. 16 F-G1), coxa roundish trapezoidal; basis widened distally; ischium and merus short, both lacking projection; carpus slightly wide, posterior margin without projection; propodus about 0.8 times as long as carpus, posterior margin with 2 robust setae; dactylus slightly curved posteriorly, posterior margin with 3 denticles. Gnathopod 2 ( Fig. 16 F-G2) almost same as that of male, 4.0 mm (OMNH-Ar-11530) except for oostegite, but posteromedial projection of coxa 2 absent and carpus shorter and narrower.

Variation. Male, 3.5 mm (OMNH-Ar-11533). Gnathopod 1 ( Fig. 16M 2-G 1 ) almost same as that of male, 4.0 mm (OMNH-Ar-11530), but distal tooth on carpus distinct. Gnathopod 2, coxa with acute posterior projection.

Coloration in recently fixed specimen ( Fig. 17 ). Eyes dark brown; head, pereonites, pleonites and urosomites light brown, but lateroventral parts of them partly dark brown, dorsal parts of head and pereonite 6 dark brown. Antennae right brown. Gnathopods and pereopods whitish, but coxae dark brown.

Remarks. Most distinct character of this species is the male coxa 2 bearing a long posteromedial projection. No other Grandidierella species possesses such a projection ( G. japonicoides sp. nov. has a short projection as stated below). Morphological characters of the examined specimens agree with the original description and figures by Wongkamhaeng et al. (2012) except for the slender antenna 2 and the wider carpus of the gnathopod 1. These differences are probably due to size of the specimens, i.e. body lengths of my specimens are 3.5–4.4 mm, whereas that of the holotype is 6.9 mm. Wongkamhaeng et al. (2012) also described a female specimen, 3.9 mm; however, this specimen is a young male, because the carpus of the gnathopod 1 has a posterodistal tooth. In addition, the specific name should be corrected to halophila , as the gender of the genus is feminine.

Habitat in Japan. Fine sand bottom in the lower intertidal to uppermost subtidal zone, brackish.

Distribution. Thailand: Samut Sakorn ( Wongkamhaeng et al. 2012), Rayong Province ( Wongkamhaeng et al. 2017). Japan: Okinawa Island and Iriomote Island (present study).

Figures

FIGURE 1. Map showing collecting sites of the examined specimens in the Ryukyu Archipelago.

FIGURE 2. Grandidierella contigua sp. nov. Holotype, male, 9.1 mm (OMNH-Ar-11513). Habitus.

FIGURE 13. Grandidierella halophila Wongkamhaeng, Pholpunthin & Azman, 2012. Male, 4.0 mm (OMNH-Ar-11530). Habitus.

FIGURE 14. Grandidierella halophila Wongkamhaeng, Pholpunthin & Azman, 2012. Male, 4.0 mm (OMNH-Ar-11530). Scales: 0.05 mm.

FIGURE 15. Grandidierella halophila Wongkamhaeng, Pholpunthin & Azman, 2012. All but M1, male, 4.0 mm (OMNH-Ar- 11530); M1, male, 3.8 mm (OMNH-Ar-11531). Scales: 0.1 mm.

FIGURE 16. Grandidierella halophila Wongkamhaeng, Pholpunthin & Azman, 2012. All except for F, M1 and M2, male, 4.0 mm (OMNH-Ar-11530); F, female, 3.6 mm (OMNH-Ar-11532); M1, male, 3.8 mm (OMNH-Ar-11531); M2, male, 3.5 mm (OMNH-Ar-11533). Scales: 0.1 mm.

FIGURE 17. Grandidierella halophila Wongkamhaeng, Pholpunthin & Azman, 2012. Photograph of male, 4.0 mm (OMNH- Ar-11530), fixed specimen (7.5 hours after fixation).