Grandidierella Coutière, 1904

Ariyama, Hiroyuki & Kohtsuka, Hisanori, 2022, Three new species of the family Aoridae collected from Sagami Bay, central Japan (Crustacea: Amphipoda), Zootaxa 5159 (3), pp. 393-413 : 405-411

Grandidierella Coutière, 1904

[Japanese name: Dorosokoebi-zoku]

Grandidierella Coutière, 1904: 166 .—J.L. Barnard & Karaman, 1991: 194.— Myers & Lowry, 2003: 465.

Neomicrodeutopus Schellenberg, 1925: 168 .

Grandidierella (Bigrandidierella) Karaman, 1985: 37 .

Propejanice Myers & Desiderato, 2019: 288 .

Type species. Grandidierella mahafalensis Coutière, 1904 , fixed by monotypy.

Diagnostic description. See Ariyama & Kawabe (2022).

Grandidierella gracilis sp. nov.

[Japanese name: Hosonaga-dorosokoebi, new]

( Figs 9–13 )

Type material. Holotype: male, 3.9 mm (OMNH-Ar-12442), west of Jōgashima Island in Miura City , Kanagawa Prefecture, 35°08′15″N 139°34′44″E –35°08′58″N 139°34′45″E, 87–89 m depth, sand bottom, 31 October 2013 . Paratypes: ovigerous female, 6.4 mm (OMNH-Ar-12443), west of Jōgashima Island in Miura City , Kanagawa Prefecture, 35°08′06″N 139°34′03″E –35°08′23″N 139°33′46″E, 95–97 m depth, 16 April 2014 ; male, 2.6 mm (OMNH-Ar-12444), west of Miura City , Kanagawa Prefecture, 35°09′09″N 139°34′50″E –35°08′57″N 139°34′00″E, 76–80 m depth, 27 April 2016 ; male, 4.0 mm and ovigerous female, 4.9 mm (OMNH-Ar-12445, 12446), off Shimoda City , Shizuoka Prefecture, 34°38′18″N 138°56′30″E –34°38′13″N 138°56′18″E, 42–47 m depth, gravel bottom, 27 November 2014 .

Type locality. Sagami Bay , west of Jōgashima Island in Miura City, Kanagawa Prefecture, Japan .

Etymology. The Latin gracilis , - is, - e (= slender) refers to the body shape.

Description of male. Based on holotype (OMNH-Ar-12442, 3.9 mm) and paratype (OMNH-Ar-12445, 4.0 mm) only for lower lip, coxa 1, and pereopods 6, 7.

Body ( Fig. 9 ) slender; eyes medium-sized, about 0.3 times length of head.

Head ( Fig. 10 ). Antenna 1 slender, ca. 0.4 times as long as body; length ratio of peduncular articles 1–3 1:1.4:0.6, article 1 with 3 ventromedial robust setae; accessory flagellum short, minutely biarticulate, tip with 5 setae; primary flagellum with 16 articles, terminal article minute, articles 3, 5, 7–14 each with aesthetasc. Antenna 2 also slender, length about 3/4 length of antenna 1; length ratio of peduncular articles 3–5 1:1.85:1.9, article 3 with 2 lateral and 2 ventral robust setae; flagellum short, consisting of 6 normal and 1 minute articles, article 3 with 2 robust and 1 thick setae, articles 4–6 each bearing 2 robust setae. Upper lip rounded ventrally, bearing many thin setae. Mandibles, incisor with 4 cusps, lacinia mobilis with 3 and 4 cusps in left and right, respectively, accessory setae 9 in left and 7 in right; palp stout, article 3 rectolinear, article length ratio 1:0.95–1.0:1.05–1.1, articles 1, 2 with 2 and 3 setae, respectively, article 3 bearing many long thick setae distally and subdistally. Lower lip with short mandibular process, mediodistal corner of outer lobe setose, distal 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 4 slender setae apically. Maxilla 2, inner plate bearing distal and medial setae, outer plate setose on distal margin. Maxilliped, distal part of inner plate setose, mediodistal corner with curved robust seta and plumose seta; outer plate bearing 9 long-to-short robust setae mediodistally; palp article 2 long, articles 2, 3 weakly setose, article 4 with nail apically.

Pereon ( Fig. 11 ). Ventral surface lacking process. Gnathopod 1 not so large, carpochelate; coxa trapezoidal; basis wide, clavate; ischium short, posterodistal corner not projected; merus posterodistal corner lacking projection, distal margin setose; carpus rectangular, length except posterodistal tooth about 1.6 times width, posterodistal corner with acute tooth, medial surface without tooth, anterior margin bearing 37 stridulating ridges and 2 short robust setae medially, posterior margin setose; propodus ovoid, about 0.7 times as long as carpus, posterior margin lacking robust setae, weakly setose; dactylus slightly curved posteriorly, posterior margin with 7 denticles. Gnathopod 2 subchelate; coxa trapezoidal; basis very long, slender, anterior and posterior margins each with a few setae; merus posterodistal corner setose; carpus trapezoidal, posterior margin and posteromedial surface heavily setose; propodus ca. 1.15 times as long as carpus, posterodistal corner and posterior margin with 3 and 1 short robust setae, respectively; dactylus short, slightly curved posteriorly, posterior margin with 4 denticles. Pereopods 3, 4 slender, pereopod 3 longer than gnathopod 2 and pereopod 4, weakly setose; coxae trapezoidal; bases elongate; meri slightly wide, straight; propodi longer than carpi; dactyli narrow. Pereopod 5 shorter than pereopod 4; coxa bilobed; basis rectangular, posteroproximal corner triangularly projected, anterior and posterior margins with several simple setae; merus with thick seta each on anterodistal and posterodistal corners; carpus bearing anterodistal thick seta and 3 posterior robust setae; propodus with 3 anterior robust setae and 1 posterior and 2 posterodistal thick setae; dactylus short, slightly curved, with plumose seta. Pereopod 6 long; coxa short, bilobed; basis rectangular, posteroproximal corner roundly projected, anterior margin with 5 short robust and 3 simple setae, posterior margin bearing 9 plumose, 2 robust and 5 simple setae; merus with 1 anterodistal, 2 posterior and 1 posterodistal thick setae; carpus with 3 lateral robust setae, posterodistal corner bearing 1 robust and 1 thick setae; propodus with 4 anterior robust setae, posterodistal corner setose; dactylus slightly curved, with plumose seta. Pereopod 7 about 1.2 times as long as pereopod 6; coxa short, not bilobed; basis rectangular, posteroproximal corner slightly projected, anterior margin with 3 short robust setae, anterodistal corner bearing thick seta, posterior margin with 9 plumose setae; merus anterior margin with robust seta, posterodistal corner with thick seta; carpus with 3 lateral and 1 medial robust setae, mediodistal margin and posterodistal corner each with thick seta; propodus with 4 anterior robust setae and 2 posterior thick setae, posterodistal corner setose; dactylus slightly curved, bearing plumose seta.

Pleon ( Figs 9 , 12 ). Epimeral plates 1–3 rounded posteroventrally, each with short seta, ventral margins bare. Pleopods, peduncles of pleopods 1–3 bearing 2, 2, 4 plumose setae, respectively; outer rami shorter than inner rami, outer rami with 10, 9, 9 articles and inner rami with 9, 9, 8 articles in pleopods 1–3, respectively. Uropod 1 long; dorsal surface of peduncle bearing 2 lateral and 5 medial robust setae, ventrodistal end with short inter-ramal process (18% length of peduncle); both rami shorter than peduncle, outer ramus slightly longer than inner ramus, former with 3 dorsolateral, 2 dorsomedial and 4 terminal robust setae, latter bearing 1 ventrolateral, 1 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 and 1 mediodistal robust setae; outer ramus shorter and inner ramus longer than peduncle, outer ramus 3/4 length of inner ramus, former with 1 dorsolateral, 1 dorsomedial and 4 terminal robust setae, latter bearing 2 dorsolateral, 3 dorsomedial and 5 terminal robust setae. Uropod 3 ca. 0.55 times length of uropod 2; peduncle slightly longer than wide, swollen medially, dorsal and ventral surfaces each with seta; single ramus about 2.6 times as long as peduncle, with 2 lateral, 2 dorsal and 2 medial setae, tip bearing tiny second article and 4 setae. Telson fleshy, laterodistal corners each with 2 simple and 1 sensory setae, lateral margins each bearing 2 sensory setae.

Description of female. Based on paratype, ovigerous female (OMNH-Ar-12443, 6.4 mm). Generally similar to male holotype except for gnathopods and oostegites. Gnathopod 1 ( Fig. 12 F-G1) subchelate; coxa roundish trapezoidal; basis almost straight; ischium and merus short, both lacking projection; carpus wide, posterior margin heavily setose; propodus about 0.9 times as long as carpus, palm almost transverse, posterior margin with 2 robust setae; dactylus slightly curved posteriorly, posterior margin with 4 denticles. Gnathopod 2 ( Fig. 12 F-RG2) almost same as that of male, but basis wider, propodus with 3 posterodistal and 2 posterior robust setae.

Variation. Paratype, male (OMNH-Ar-12445, 4.0 mm). Gnathopod 1 ( Fig. 12 M-G1) almost same as that of holotype, but carpus posteromedial surface with small tooth, anterior margin bearing 4 small robust setae and 45 stridulating ridges. Paratype, juvenile male (OMNH-Ar-12444, 2.6 mm). Gnathopod 1 ( Fig. 12 JM-RG1), carpus short like female, posterodistal tooth very small; propodus posterior margin with long robust seta.

Coloration in life ( Fig. 13 ). Based on paratype, ovigerous female (OMNH-Ar-12443, 6.4 mm). Eyes brown, whole body yellowish light brown.

Remarks. Grandidierella gracilis sp. nov. has stridulating ridges on the carpus of the male gnathopod 1.This character is shared with eight species of Grandidierella : G. chaohuensis Hou & Li, 2002 ; G. japonica Stephensen, 1938 ; G. japonica sensu Myers, 1981 (probably different species); G. japonicoides Ariyama, 2020 ; G. lagamarensis ( Myers & Desiderato, 2019) ; G. perlata Schellenberg, 1938 ; G. taihuensis Morino & Dai, 1990 ; and G. vietnamica Dang, 1968 . Among these species, G. japonica sensu Myers, 1981 , G. japonicoides , G. lagamarensis , and G. perlata resemble G. gracilis in the teeth arrangement on the male gnathopod 1 carpus ( Table 1 ); however, this new species can be distinguished from G. japonica sensu Myers, 1981 by the poorly setose antennae, from G. japonicoides by the sparsely setose posterior margins of the pereopods 6, 7 bases, and from G. lagamarensis and G. perlata by the ordinary form of the male gnathopod 2. In addition, the habitat of G. gracilis is quite different from those of the eight species which inhabit freshwater areas, brackish waters or shallow seas ( Table 1 ).

Habitat. Sand or gravel bottom, 42–97 m depth.

Distribution. Japan: Sagami Bay (present study).

Figures

FIGURE 9. Grandidierella gracilis sp. nov. Holotype, male, 3.9 mm (OMNH-Ar-12442). Habitus.

FIGURE 10. Grandidierella gracilis sp. nov. All but M: holotype, male, 3.9 mm (OMNH-Ar-12442); M: paratype, male, 4.0 mm (OMNH-Ar-12445). Scales: 0.05 mm.

FIGURE 11. Grandidierella gracilis sp. nov. All but M: holotype, male, 3.9 mm (OMNH-Ar-12442); M: paratype, male, 4.0 mm (OMNH-Ar-12445). Scales: 0.1 mm.

FIGURE 12. Grandidierella gracilis sp. nov. All except for F, JM and M: holotype, male, 3.9 mm (OMNH-Ar-12442); F: paratype, ovigerous female, 6.4 mm (OMNH-Ar-12443); JM: paratype, juvenile male, 2.6 mm (OMNH-Ar-12444), slender setae omitted; M: paratype, male, 4.0 mm (OMNH-Ar-12445), slender setae omitted. Scales: 0.1 mm.

FIGURE 13. Grandidierella gracilis sp. nov. Photograph of paratype, ovigerous female, 6.4 mm (OMNH-Ar-12443) by H. Kohtsuka, live specimen.