Paragrandidierella minima Ariyama, 2002

Ariyama, Hiroyuki, 2013, Reinstatement of Paragrandidierella (Crustacea: Amphipoda: Aoridae) from Japan, with the Description of a New Species, Species Diversity 18, pp. 223-235 : 233-235

Paragrandidierella minima Ariyama, 2002 ( Fig. 9 )

[Japanese name: Himedorosokoebi]

Paragrandidierella minima Ariyama, 2002: 155 , figs 1–6; Miura, 2008: 109, unnumbered figs; Ariyama, 2012: 177, unnumbered fig; Jung and Yoon, 2013: 259, figs 1–5.

Grandidierella minima: Ren 2006: 368 , fig. 156.

Material examined. Holotype: male (OMNH-Ar- 4922), 2.1 mm, sandy bottom off Kamaguchi, Awaji Island , Hyogo Prefecture (34°29′N, 134°58′E), 3 m deep, 22 August 1987, coll. M. Tanda and H. Yokoyama. Paratypes: one male (OMNH-Ar-4924), 2.2 mm, and two females (OMNH- Ar-4923, 4926), 2.1, 1.8 mm, same data as holotype . Five males (OMNH-Ar-9556–9560), 2.8, 2.4, 2.0, 1.8, 1.6 mm, one female (OMNH-Ar-9561), 3.0 mm, and one ovigerous female (OMNH-Ar-9562), 2.9 mm, Funakoshi, Iwagi Island , Ehime Prefecture (34°15.6'N, 133°10.0'E), sandy bottom, 1 m deep, 3 August 2002, coll . H . Ariyama.

Description of male. [based on holotype for mouthparts, and another male (OMNH-Ar-9556) for antennae].

Antenna 1 ( Fig. 9A, A 1 ) relatively long, about 0.6 times as long as body; length ratio of peduncular articles 1–3 1.0: 0.8: 0.3; flagellum with 12 normal and 1 minute articles, articles 8–12 each with aesthetasc on dorsodistal corner. Antenna 2 ( Fig. 9B ) short, about 0.4 times as long as body; length ratio of peduncular articles 3–5 1.0: 1.3: 1.1, article 3 bearing robust seta on medial surface, ventrodistal corner of article 5 inflated; flagellum very short, shorter than peduncular article 5, consisting of 4 normal and 1 minute articles, flagellar articles 2–4 with 1, 2, and 2 robust setae, respectively.

Mandibles ( Fig. 9C, D ) with incisors each with 3 cusps, laciniae mobilis each with 2 cusps. Maxilla 1 ( Fig. 9E, F ) with outer plate bearing 3 robust and 5 normal setae. Maxilliped ( Fig. 9G ) with distal and medial margins of inner plate bearing many plumose setae, medial margin of outer plate with plumose seta and 6 thick, robust setae.

Description of female [based on ovigerous female (OMNH-Ar-9562)]. Antenna 1 ( Fig. 9H ) relatively short, about half as long as body; length ratio of peduncular articles 1–3 1.0: 0.9: 0.3; flagellum with 9 normal and 1 minute articles, articles 6–9 each with aesthetasc on dorsodistal corner. Antenna 2 (Fug. 9I) short, 0.3 times as long as body; length ratio of peduncular articles 3–5 1.0:1.4: 1.2; flagellum short, but slightly longer than peduncular article 5, consisting of 3 normal and 1 minute articles, flagellar articles 2 and 3 each with 2 robust setae.

Variation in male antenna 2 and gnathopod 1 (7 males examined). Small male [1.6 mm (OMNH-Ar-9560), Fig. 9J, L ]: ventrodistal corner of antenna 2 article 5 not inflated; tooth of gnathopod 1 carpus shorter than that of holotype (ca. 15% as long as carpus proper), posterior margin of propodus slightly swollen, with robust seta. Medium-sized male [2.0 mm (OMNH-Ar-9558), Fig. 9K, M ]: ventrodistal corner of antenna 2 article 5 slightly inflated; tooth of gnathopod 1 carpus of medium length (ca. 25% as long as carpus proper), posterior margin of propodus swollen, without robust setae. Large male [2.8 mm (OMNH-Ar-9556), Fig. 9N ]: tooth of gnathopod 1 carpus longer than that of holotype (ca. 40% as long as carpus proper); posterior margin of propodus swollen, without robust setae.

Remarks. The morphological features of the specimens collected from Iwagi Island are quite similar to those of the type specimens from Osaka Bay (e.g., inflated ventrodistal corner of peduncular article 5 of male antenna 2), and closely resemble those in the description of Ren (2006) and Jung and Yoon (2013) except for the accessory flagellum.

Distribution. Japan: Tokyo Bay, Seto Inland Sea (Wakayama, Hyogo, Hiroshima, and Ehime Prefectures), and Oita and Miyazaki Prefectures ( Ariyama 2012). China: Meixia, Hainan Province ( Ren 2006). Korea: Bija-ri, Soanmyeon, Wando-gun, Jeollanam-do ( Jung and Yoon 2013).

Habitat. Sandy tidal flats and sandy beaches with high current speed, from middle intertidal zone to upper subtidal zone ( Ariyama 2012); among floating seaweed ( Ren 2006); among algae in muddy intertidal zone ( Jung and Yoon 2013). The habitat reported in China seems dubious, because it is quite different from the Japanese habitat and species of Paragrandidierella and Grandidierella generally inhabit sandy or muddy bottoms.

Figures

Fig. 9. Paragrandidierella minima Ariyama, 2002. A, B, N, male (OMNH-Ar-9556), 2.8mm; C–G, holotype male (OMNH-Ar-4922), 2.1mm; H, I, ovigerous female (OMNH-Ar-9562), 2.9mm; J, L, male (OMNH-Ar-9560), 1.6mm; K, M, male (OMNH-Ar-9558), 2.0mm. A, left antenna 1, lateral view; A1, accessory flagellum of left antenna 1, lateral view; B, left antenna 2, lateral view; C, incisor, lacinia mobilis, and accessory blades of right mandible, ventral view; D, incisor, lacinia mobilis, and accessory blades of left mandible, ventral view; E, distal part of outer plate of right maxilla 1, dorsal view; F, distal part of outer plate of left maxilla 1, ventral view; G, outer and inner plates of right maxilliped, dorsal view, normal setae omitted; H, I, antennae 1 and 2, lateral views; J, K, distal parts of antennae 2, lateral views, normal setae omitted; L–N, carpi–dactyli of gnathopods 1, lateral views, normal setae omitted. Scales: 0.1mm.

Fig. 1. Paragrandidierella urauchiensis sp. nov. Holotype male (OMNH-Ar-9543), 3.1mm. Habitus, right lateral view.