Grandidierella gilesi Chilton, 1921

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 : 10-15

Grandidierella gilesi Chilton, 1921

[Japanese name: Keashi-dorosokoebi, new]

( Figs 8–12 )

Grandidierella gilesi Chilton, 1921: 552 , fig. 2.— Chilton, 1925: 537.—K.H. Barnard, 1935: 300, fig. 12a.— Schellenberg, 1938: 93.— Nayar, 1959: 40, pl. 14, fig. 6.— Sivaprakasam, 1970: 157.— Ledoyer, 1979: 152, fig. 8II.— Myers, 1981: 222, fig. 6.— Asari & Myers, 1982: 248, figs 7, 8.— Ledoyer, 1982: 249, fig. 9I.— Ortiz & Lalana, 1999: 194 (list).— Myers, 2002: 220.— Lowry & Stoddart, 2003: 70 (list).— Ren, 2006: 370, fig. 157.— Wongkamhaeng, Hongpadharakiree & Chotikarn, 2016: 54, figs 2–5.

Grandidierella gilesi?: Imbach, 1967: 90 , pl. 35.

Material examined. Two males, 4.3, 3.4 mm (OMNH-Ar-11527, 11528) and ovigerous female, 4.6 mm (OMNH- Ar-11529), mouth of Nakama River, Iriomote Island , Okinawa Prefecture, 24°16'43"N, 123°52'57"E ( Fig. 1I ), mid-dle–lower intertidal, sandy mud under stones, 15 July 2015, coll. H. Ariyama.

Type locality. Chilka Lake in India ( Chilton 1921) .

Diagnosis. Male pereon, ventral process absent. Male gnathopod 1, ischium and merus lacking posterodistal projection; merus to propodus heavily setose posteromedially; carpus with 2 posterodistal teeth; propodus straight. Male gnathopod 2, coxa without posteromedial projection; basis straight; merus divergent posteriorly, posterodistal margin with many long setae; carpus and propodus almost same length, elongate, heavily setose posteromedially, propodus posterodistal corner with 2 short robust setae; dactylus very short. Uropod 1 peduncle with inter-ramal process.

Description of male. Based on male, 4.3 mm (OMNH-Ar-11527).

Head ( Figs 8 , 9 ). Eyes medium-sized, about quarter length of head. Antenna 1, peduncular article 1 with 5 robust setae ventrally; peduncular articles 2, 3 and flagellum lost. Antenna 2, peduncular article 3 short, with robust seta dorsodistally, peduncular articles 4, 5 and flagellum lost. Upper lip rounded ventrally, bearing many thin setae. Mandibles with length ratio of palp articles 1–3 1:1.2:1.2, articles 1, 2 with 1–2 and 8–9 setae, respectively, article 3 clavate, setose distally; incisor and lacinia mobilis each with 4 cusps, 8 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 5 robust and 5 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 narrowed distally, setose on distal and medial margins, distal end bearing 3 straight and 1 curved robust setae; outer plate long, mediodistal margin with 10 long-to-short robust setae; palp article 2 long, medial margin densely setose, article 3 with many setae medially and distally.

Pereon ( Fig. 10 ). Ventral surface lacking process. Gnathopod 1, coxa trapezoidal; basis wide, lateral surface with ridge, posterior margin slightly convex; ischium short; merus without posterodistal projection, posterior margin with many setae; carpus wide, length about 1.55 times width, posterodistal corner with 2 teeth (proximal one large), posterior margin and postertomedial surface bearing dense plumose setae; propodus almost straight, posterior margin and medial surface setose; dactylus short, slightly curved posteriorly, posterior margin with 2 denticles. Gnathopod 2 slender; coxa trapezoidal; basis straight; merus strongly divergent posteriorly, posterodistal margin bearing many long plumose setae; carpus elongate, almost same length as propodus, slender, posterior margin and medial surface with many long plumose setae; propodus very narrow, posterodistal corner with 2 short robust setae, posterior margin with long and short setae, medial surface bearing many long plumose setae; dactylus very short, slightly curved posteriorly, posterior margin with 2 denticles. Pereopod 3 slender, coxa slightly produced posteriorly, basis long, merus a little dilated distally, carpus shorter than merus, propodus and dactylus narrow. Pereopod 4 lost except for coxa and gill. Pereopod 5 shorter than pereopod 3; coxa bilobed; basis rectangular, anterior margin with several short robust setae, posterior margin bearing several short setae; merus with long thick seta each on anterodistal and posterodistal corners; carpus with long thick seta on anterodistal corner and 3 robust setae on posterior margin; propodus with 2 anterodistal thick setae and 4 posterior robust setae; dactylus short, strongly curved. Pereopod 6 about 1.6 times as long as pereopod 5; coxa short, bilobed; basis rectangular, anterior margin with several short setae (robust in part), posterior margin with several long plumose setae and short setae; merus with marginal thick or short setae; carpus with 4 lateral and 2 posterodistal robust setae; propodus with 6 anterior and 3 medial robust setae, posterodistal corner with many long setae; dactylus curved. Pereopod 7 about 1.25 times as long as pereopod 6; coxa short, slightly bilobed; basis roundish rectangular, anterior and posterior margins with many long plumose setae; merus with marginal thick or short setae; carpus with 5 lateral, 2 posterior and 2 posterodistal robust setae; propodus with 7 anterior and 4 posteromedial robust setae; dactylus curved.

Pleon ( Fig. 11 ). Epimeral plates 1–3 each with long thick seta on posteroventral corner, ventral margins bare ( Fig. 8 ). Pleopods, each peduncle short, bearing several plumose setae and 2 coupling hooks; inner ramus longer than outer, outer rami with 11–12 articles, inner rami each with 11 articles. Uropod 1, dorsal surface of peduncle bearing 4 lateral and 6 medial robust setae, ventrodistal end with inter-ramal process; both rami shorter than peduncle, outer ramus subequal to inner ramus, former with 2 dorsolateral, 2 dorsomedial and 4 terminal robust setae, latter bearing 1 dorsolateral, 3 dorsomedial and 5 terminal robust setae. Uropod 2 about 0.6 times 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, 3 dorsomedial and 5 terminal robust setae. Uropod 3 about half length of uropod 2; peduncle longer than wide, mediodistal corner projected; single ramus about 1.8 times length of peduncle, tip with tiny second article, bearing 2 lateral, 1 medial and 4 terminal setae. Telson wider than long, laterodistal corners each with 2 sensory and 1 simple setae.

Description of female. Based on ovigerous female, 4.6 mm (OMNH-Ar-11529). Gnathopod 1 ( Fig. 11 F-G1), coxa trapezoidal; basis relatively wide; ischium short, posterodistal corner setose; merus short; carpus trapezoidal, posterior margin without projection; propodus almost straight, slightly longer than carpus; merus to propodus heavily setose postertomedially, posterior margin with long robust seta distally; dactylus short, slightly curved posteriorly, posterior margin with 3 denticles. Gnathopod 2 ( Fig. 11 F-G2) almost same as that of male, 4.3 mm (OMNH- Ar-11527) except for oostegite.

Coloration in recently fixed specimen ( Fig. 12 ). Eyes dark brown; head, pereonites, pleonites and urosomites brown. Antenna 1 peduncular article 1 light brown, peduncular articles 2, 3 and flagellum pale red and partly white; antenna 2 reddish light brown and white. Proximal parts of gnathopods and pereopods light brown, other parts white.

Remarks. This species is characterized by the densely setose gnathopods 1 and 2 and the divergent merus of the gnathopod 2 in both sexes. Morphological characters of the present specimens almost agree with those of Grandidierella gilesi in the literature. However, in the propodus of the female gnathopod 1, its width varies in different literature from narrow to broad (narrow in the present specimen) and number of the robust setae on the posterior margin varies from 0 to 3 (1 in the present specimen) ( Chilton 1921, Imbach 1967, Ledoyer 1979, Myers 1981, Asari & Myers 1982, Ledoyer 1982, Ren 2006).

Habitat in Japan. Sandy mud bottom under stones in the middle–lower intertidal zone, brackish.

Distribution. Madagascar ( Ledoyer 1982). India: Chilka Lake ( Chilton 1921), Vizagapatam and Travancore (K.H. Barnard 1935), Adyar ( Nayar 1959), Pinnakayal and Tuticorin ( Sivaprakasam 1970), Killai ( Asari & Myers 1982). Australia: New South Wales ( Myers 1981). Thailand: Talé Sap ( Chilton 1925), Phuket ( Myers 2002), Phetchaburi Province ( Yokoyama et al. 2002), Bangkok ( Wongkamhaeng et al. 2016). Indonesia: Surabaya ( Ledoyer 1979), Maros ( Ortiz & Lalana 1999). Viet Nam: Bay of Nhatrang ( Imbach 1967). Philippines: Cebu ( Schellenberg 1938). China: Hainan Island ( Ren 2006). Japan: Iriomote Island (present study).

Figures

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

FIGURE 8. Grandidierella gilesi Chilton, 1921. Male, 4.3 mm (OMNH-Ar-11527). Habitus.

FIGURE 9. Grandidierella gilesi Chilton, 1921. Male, 4.3 mm (OMNH-Ar-11527). Scales: 0.05 mm.

FIGURE 10. Grandidierella gilesi Chilton, 1921. Male, 4.3 mm (OMNH-Ar-11527). Scales: 0.1 mm.

FIGURE 11. Grandidierella gilesi Chilton, 1921. All but F, male, 4.3 mm (OMNH-Ar-11527); F, ovigerous female, 4.6 mm (OMNH-Ar-11529). Scales: 0.1 mm.

FIGURE 12. Grandidierella gilesi Chilton, 1921. Photograph of male, 4.3 mm (OMNH-Ar-11527), fixed specimen (5 hours after fixation).Antennae and left pereopods 3–7 lost after photographing.