Grandidierella japonicoides, 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 : 21-27

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/0BDCC837-FC5C-469E-9FEF-198531CC8C9F
taxon LSID	lsid:zoobank.org:act:0BDCC837-FC5C-469E-9FEF-198531CC8C9F
treatment provided by	Plazi
scientific name	Grandidierella japonicoides
status	sp. nov.

Treatment

Grandidierella japonicoides View in CoL sp. nov.

[Japanese name: Nihon-dorosokoebi-modoki, new]

( Figs 18–22 View FIGURE 18 View FIGURE 19 View FIGURE 20 View FIGURE 21 View FIGURE 22 , 24 View FIGURE 24 )

Type material. Holotype: male, 5.3 mm (OMNH-Ar-11535), Nazekō-chō, Amami-ōshima Island , Kagoshima Pre- fecture, 28°22'53.5"N, 129°29'40"E ( Fig. 1B View FIGURE 1 ), 24 May 2012, coll. K. Kakui. GoogleMaps Paratypes: ovigerous female, 4.5 mm (OMNH-Ar-11536), same data as holotype; male, 4.7 mm (OMNH-Ar-11537), Sumiyō, Amami-ōshima Island , Kagoshima Prefecture, 28°15'05"N, 129°24'40"E ( Fig. 1C View FIGURE 1 ), lower intertidal, fine sand bottom, 3 July 2019, coll. H. Ariyama GoogleMaps ; male, 3.6 mm (OMNH-Ar-11538), ovigerous female, 4.1 mm (OMNH-Ar-11539) and female, 3.5 mm (OMNH-Ar-11540), Sashiki, Okinawa Island , Okinawa Prefecture, 26°10'17"N, 127°47'18"E ( Fig. 1E View FIGURE 1 ), uppermiddle intertidal, sandy mud bottom, 4 July 2015, coll. H. Ariyama. GoogleMaps

Material for comparison ( Grandidierella japonica Stephensen, 1938 ). Male, 9.0 mm (OMNH-Ar-3852) and ovigerous female, 9.5 mm (OMNH-Ar-3854), mouth of Higashi River, Misaki Town, Osaka Prefecture, intertidal, mud bottom, brackish, 30 March 1990, coll. H. Ariyama; male, 8.0 mm (OMNH-Ar-3853), same place, 11 April 1990, coll. H. Ariyama ( Ariyama 1996). Three males, 6.2, 5.2, 4.0 mm (OMNH-Ar-11541–11543), ovigerous female, 5.0 mm (OMNH-Ar-11544) and female, 4.1 mm (OMNH-Ar-11545), mouth of Yodo River, Osaka City, 34°41'37"N, 135°26'31"E, lower intertidal, mud bottom, 29 May 2017, coll. H. Ariyama.

Type locality. Nazekō-chō , Amami-ōshima Island in Kagoshima Prefecture, Japan .

Etymology. From japonica (closely related species) + the Greek oides (= resembling).

Diagnosis. Male pereon, ventral process present. Male gnathopod 1, ischium and merus lacking posterodistal projection; carpus with 1 large posterodistal tooth and 2 small posteromedial teeth, anteromedial margin bearing stridulating ridges; propodus widened in middle. Male gnathopod 2, coxa with posteromedial projection; basis straight; carpus longer than propodus; propodus with a few robust setae on posterodistal corner and posterior margin. Uropod 1 peduncle with inter-ramal process.

Description of male. Based on holotype, male, 5.3 mm (OMNH-Ar-11535).

Head ( Figs 18 View FIGURE 18 , 19 View FIGURE 19 ). Eyes medium-sized, about 0.3 times length of head. Antenna 1 slender, about 0.7 times as long as body; length ratio of peduncular articles 1–3 1:1.35:0.45, article 1 with 6 ventral robust setae; accessory flagellum very short, minutely biarticulate; primary flagellum with 20 articles, terminal article minute, distal 13 articles each bearing aesthetasc. Antenna 2 slightly stout, length about 0.45 times as long as body; length ratio of peduncular articles 3–5 1:2.65:2.55, article 3 with 1 ventral and 2 medial robust setae; flagellum short, consisting of 6 normal and 1 minute articles, articles 2–6 with 1, 2, 1, 2, 2 robust setae, respectively. Upper lip slightly hollowed ventrally, bearing many thin setae. Mandibles, length ratio of palp articles 1–3 1:1.35: 1.3 in right, articles 1, 2 with 2–3 and 5–6 setae, respectively, article 3 clavate, densely setose distally; incisor and lacinia mobilis each with 4 cusps in left and 5 cusps in right, 9 and 7 accessory setae present in left and right, respectively. Lower lip, apical parts of outer and inner lobes covered with thin setae. Maxilla 1, outer plate with 11 distal robust setae, palp article 2 bearing 5 robust and 5 slender setae apically. Maxilla 2, inner plate with distal and medial setae and mediofacial row of setae, outer plate setose on distal margin. Maxilliped, distal part of inner plate setose, with 4 triangular robust setae; outer plate bearing 11 long-to-short robust setae mediodistally; palp article 2 long, setose medially, article 3 setose distally.

Pereon ( Fig. 20 View FIGURE 20 ). Ventral surface of pereon 1 with rounded process ( Fig. 18 View FIGURE 18 ). Gnathopod 1, coxa trapezoidal; basis very wide, anterolateral surface with ridge, posterior margin convex; ischium short, posterodistal corner not projected; merus posterodistal corner rounded, posterodistal margin with several setae; carpus long, length about 2.0 times width, with 1 large posterodistal tooth and 2 small posteromedial teeth, anteromedial margin bearing 2 robust setae and many stridulating ridges, posteromedial surface setose; propodus short, posterior margin swollen in middle, anterodistal corner and posterior margin setose; dactylus short, almost straight, posterior margin with 3 denticles. Gnathopod 2, coxa trapezoidal, dorsal half of posterior margin projected, medial surface with triangular process posteriorly; basis slender, straight; merus distal margin setose; carpus posterior margin setose; propodus about 0.8 times as long as carpus, posterodistal corner and posterior margin with 3 and 1 short robust setae, respectively; dactylus short, curved posteriorly, posterior margin with 5 denticles. Pereopods 3 and 4, pereopod 3 slightly longer than pereopod 4; coxae trapezoidal, dorsal halves of posterior margins projected, medial surfaces with rounded process posteriorly; bases long; meri slightly dilated distally; carpi shorter than meri; propodi and dactyli narrow. Pereopod 5 shorter than pereopod 4; coxa bilobed; basis rectangular, posteroproximal corner roundly projected, anterior margin with 10 small robust setae, posterior margin bearing small robust seta and several simple setae; carpus with 3 posterior robust setae and anterodistal thick seta; propodus with 4 lateral and 2 medial robust setae; dactylus short, curved. Pereopod 6 about 1.65 times as long as pereopod 5; coxa short, slightly bilobed; basis rectangular, posteroproximal corner roundly projected, anterior margin with 8 small robust setae, posterior margin bearing many plumose setae; merus anterior margin with 2 short robust setae, posterior margin and posterodistal corner each with 1 thick and 1 robust setae; carpus with 3 lateral robust setae, posterodistal corner bearing 2 robust setae; propodus with 5 anterior, 1 lateral and 3 medial 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 smooth, anterior margin with 7 small robust setae and 4 plumose setae, posterior margin bearing many plumose setae; merus with 1 anterior and 4 lateral robust setae, posterior margin bearing 3 thick setae and robust seta, anterodistal corner with small robust seta, posterodistal corner with 1 robust and 1 thick setae; carpus with 3 lateral and 2 medial robust setae, anterodistal and posterodistal corners each with robust seta; propodus with 5 anterior and 4 posteromedial robust setae, posterodistal corner setose; dactylus curved.

Pleon ( Fig. 21 View FIGURE 21 ). Epimeral plates 1–3 each with thick seta on posteroventral corner, ventral margins bare ( Fig. 18 View FIGURE 18 ). Pleopods, peduncles each bearing many plumose setae and 2 coupling hooks; inner ramus longer than outer, outer rami with 12, 11, 10 articles, inner rami with 11, 11, 10 articles respectively. Uropod 1, dorsal surface of peduncle bearing 3 lateral and 6 medial robust setae, ventrodistal end with inter-ramal process; both rami shorter than peduncle, outer ramus slightly shorter than inner ramus, former with 3 dorsal and 4 terminal robust setae, latter bearing 3 dorsolateral, 4 dorsomedial and 4 terminal robust setae. Uropod 2 about 0.6 times as long as uropod 1; peduncle dorsal surface with 1 laterodistal, 1 medial and 1 mediodistal robust setae; outer ramus shorter than and inner ramus longer than peduncle, outer ramus with 3 dorsal and 4 terminal robust setae, inner ramus bearing 2 dorsolateral, 4 dorsomedial and 5 terminal robust setae. Uropod 3 about half length of uropod 2; peduncle slightly wider than long, swollen medially, with 0–1 medial seta; single ramus longer than peduncle, with tiny second article and 3–4 lateral, 2 medial and 4 terminal setae. Telson wider than long, laterodistal corners each with 3 setae.

Description of female. Based on paratype, ovigerous female, 4.5 mm (OMNH-Ar-11536). Antenna 2 ( Fig. 21 View FIGURE 21 F-A2) similar to that of holotype, male, 5.3 mm (OMNH-Ar-11535), but peduncular article 3 with 1 ventral and 2 medial robust setae, article 4 with 4 medial robust setae, article 5 bearing single robust seta, flagellar articles 3–6 with 2, 1, 1, 2 robust setae, respectively. Gnathopod 1 ( Fig. 21 View FIGURE 21 F-G1), coxa trapezoidal; basis straight, anterolateral surface with ridge; ischium short, posterodistal corner without projection; merus short, posterior margin smooth; carpus slightly wide, posterior margin with single robust seta and many long setae, lacking projection; propodus short, about 0.85 times as long as carpus, posterodistal corner and posterior margin with 2 and 1 robust setae, respectively; dactylus slightly curved posteriorly, posterior margin with 3 denticles. Gnathopod 2 ( Fig. 21 View FIGURE 21 F-G2), coxa roundish trapezoidal, medial surface without process; basis straight; merus distal margin with many long setae; carpus posterior margin setose; propodus about 0.9 times as long as carpus, posterodistal corner and posterior margin with 3 and 1 short robust setae, respectively; dactylus short, curved posteriorly, posterior margin with 4 denticles.

Variation. Paratype, male, 3.6 mm (OMNH-Ar-11538). Gnathopod 1 ( Fig. 21 View FIGURE 21 SM-G1) almost same as that of holotype, male, 5.3 mm (OMNH-Ar-11535), but carpus length about 1.7 times width, posteromedial surface of carpus with single small tooth.

Coloration in recently fixed specimen ( Fig. 22 View FIGURE 22 ). Eyes and anterodorsal surface of head dark brown; other parts of head, pereonites, pleonites, urosomites and peduncles of antennae mottled brown; other appendages whitish, but propodi of pereopods 3 and 4 each with pale orange vermiform spot.

Remarks. Grandidierella japonicoides sp. nov. has stridulating ridges on the carpus of the male gnathopod 1. This character is shared with seven species of Grandidierella : G. japonica from Japan; G. japonica sensu Myers, 1981 from Australia (probably different species); G. perlata Schellenberg, 1938 from Fiji; G. vietnamica Dang, 1968 from Vietnam; G. chaohuensis Hou & Li, 2002 and G. taihuensis Morino & Dai, 1990 both from China; and G. lagamarensis from Brazil. This new species and Grandidierella japonica have three teeth on the male gnathopod 1 carpus, although four species ( G. japonica sensu Myers , G. perlata , G. taihuensis and G. lagamarensis ) have a single tooth and two species ( G. chaohuensis and G. vietnamica ) have two teeth. Grandidierella japonicoides can be distinguished from G. japonica by the smaller size (maximum BL: 5.3 mm in male and 4.5 mm in female) and the presence of a posteromedial projection on the male coxa 2 ( Fig. 20G View FIGURE 20 2 View FIGURE 2 ), which is lacking in G. japonica ( Fig. 23M View FIGURE 23 1-C View FIGURE 1 2 View FIGURE 2 ). In addition, relationship of the body length with “carpus length / carpus width” in the gnathopod 1 is quite different in both species ( Fig. 24 View FIGURE 24 ). The gnathopod 1 carpi of G. japonicoides are slenderer than those of G. japonica ( Fig. 23 View FIGURE 23 ) in both sexes.