Grandidierella rubroantennata, Ariyama & Taru, 2017

Ariyama, Hiroyuki & Taru, Masanori, 2017, Three Species of Grandidierella (Crustacea: Amphipoda: Aoridae) from Coastal Areas of the Tohoku and Kanto-Tokai Districts, East Japan, with the Description of Two New Species, Species Diversity 22, pp. 187-200 : 193-196

Grandidierella rubroantennata sp. nov. ( Figs 2C , 8 ; Table 1)

[Japanese name: Akahige-dorosokoebi]

Grandidierella insulae (not of Myers 1981): Ariyama 1996: 180, figs 11–15; Ariyama 2016: 111, unnumbered fig.

Material examined. Paratype: female (OMNH- Ar-10296), 7.2 mm, rocky coast at Matsugahana, Uchiura, Kamogawa City , Chiba Prefecture, 35°07′05″N, 140°10′58″E ( Fig. 1D ), marine, intertidal, under stones, 30 July 2016, coll . M . Taru.

Additional material. Holotype: male (OMNH-Ar-3847), 9.0 mm, intertidal zone of Nagasaki coast in Misaki , Osaka Prefecture, under stones, 17 May 1992, coll. H. Ariyama. Paratypes: two males (OMNH-Ar-3848, 3849), 7.6 and 8.4 mm, and two females (OMNH-Ar-3850, 3851), 8.8 and 8.8 mm, intertidal zone of Toyokuni-zaki coast in Misaki , Osaka Prefecture, in muddy sand under stones, 22 April 1989, coll . H . Ariyama; male (OMNH-Ar-10334), 6.2 mm, intertidal zone of Nagasaki coast in Misaki , Osaka Prefecture, under stones, 25 May 2013, coll . H . Ariyama; female (OMNH-Ar-10335), 5.6 mm, intertidal zone of Toyokunizaki coast in Misaki , Osaka Prefecture, under stones, 1 June 2003, coll . H . Ariyama.

Diagnosis. Antenna 1 flagellum with 12–21 articles; antenna 2 not robust, flagellum with 6–9 articles. Male gnathopod 1, basis wide; merus lacking posterodistal projection; carpus with 2 posterodistal teeth, posterior one large; propodus slightly curved posteriorly, anterodistal corner with small projection. Male gnathopod 2, basis anterodistal corner without nipple; carpus very long, about 1.8 times as long as propodus. Uropod 1 peduncle with inter-ramal process.

Description of female [based on paratype (OMNH- Ar-10296), 7.2 mm]. Antenna 1 ( Fig. 8A, A 1 ) slender, about half length of body; length ratio of peduncular articles 1–3 1.0: 1.2: 0.5, article 1 with 4 robust setae ventromedially; flagellum with 14 normal and 1 minute articles. Antenna 2 ( Fig. 8B, B 1 ) slightly stout, length about 0.8 times as long as antenna 1; length ratio of peduncular articles 3–5 1.0: 2.6: 3.1, article 3 with 1 lateral, 5 medial and 1 ventral robust setae, article 4 bearing 9 medial and 1 ventral robust setae, article 5 with 4 medial robust setae; flagellum short, consisting of 6 normal and 1 minute articles, articles 2–6 with 1, 2, 2, 2, 2 robust setae, respectively. Left mandible ( Fig. 8C, C 1 ) with length ratio of palp articles 1–3 1.0: 1.2: 1.5, articles 1 and 2 with 2 and 5 setae, respectively, article 3 clavate, heavily setose distally; incisor with 6 cusps, lacinia mobilis with 4 cusps, 9 accessory blades present.

Gnathopod 1 ( Fig. 8D, D 1 ) slightly stout; coxa trapezoidal; basis slightly broadened, lateral surface with ridge; merus trapezoidal, not projected posterodistally, distal margin setose; carpus relatively broad, posterior margin with many thick and normal setae; propodus relatively wide, slightly longer than carpus, posterodistal corner and posterior margin with 2 and 2 robust setae, respectively, anterodistal corner setose; dactylus gradually curved, posterior margin minutely serrate. Gnathopod 2 ( Fig. 8E, E 1 ) slender; coxa trapezoidal; basis straight; carpus not elongate, widened in middle, posterior margin with many thick and normal setae; propodus about 85% length of carpus, with 3 and 1 robust setae on posterodistal corner and posterior margin, respectively, anterior and distal margins setose; dactylus gradually curved, posterior margin minutely serrate. Pereopods 5–7 bases ( Fig. 8F ) rectangular, anterior and posterior margins each with several robust setae and plumose setae, numbers of plumose setae of pereopods 5–7 0, 1, 1 on anterior margins and 4, 9, 9 on posterior margins, respectively.

Uropod 1 ( Fig. 8G ) relatively long; dorsal surface of peduncle bearing 3 lateral and 5 medial robust setae, ventrodistal end with inter-ramal process; both rami shorter than peduncle, outer ramus subequal to inner ramus, former with 5 dorsolateral, 2 dorsomedial and 4 terminal robust setae, latter bearing 4 dorsolateral, 4 dorsomedial and 5 terminal robust setae. Uropod 2 ( Fig. 8H ) short, about 55% as long as uropod 1; dorsal surface of peduncle with 2 lateral and 1 medial robust setae; outer ramus shorter than peduncle, inner ramus subequal to peduncle, outer ramus with 3 dorsolateral, 1 dorsomedial and 4 terminal robust setae, inner ramus bearing 3 (1 lost) dorsolateral, 3 dorsomedial and 5 terminal robust setae. Uropod 3 ( Fig. 8I ) very short, about half length of uropod 2; peduncle wider than long, medial margin bearing 2 minute setae; single ramus about 1.7 times length of peduncle, tip with tiny second article, lateral and medial margins each bearing 2 setae, terminal end with 5 setae. Telson ( Fig. 8J ) wider than long, laterodistal corners each with 3 setae, each lateral margin bearing 2 sensory setae.

Description of male. See Ariyama (1996).

Variation in numbers of flagellar articles of antennae ( Table 1). Numbers varying from 12 to 21 in antenna 1 and from 6 to 9 in antenna 2 (excluding terminal minute article), with tendency to increase with growth.

Coloration in life ( Fig. 2C ). Eyes black and white; head, pereonites and pleonites brown; antennae mostly bright red and partly white; other appendages faintly orange, but propodi of pereopods 3 and 4 each with red vermiform spot.

Etymology. From the Latin rubro (=red)+ antennatus (=antennate), referring to the coloration of the antennae.

Remarks. The morphological features of this specimen agree well with those of Grandidierella insulae sensu Ariyama (1996) . This occurrence is the first record of the species in addition to Osaka and Wakayama Prefectures. Grandidierella insulae was originally described based on the material from Lord Howe Island in Australia ( Myers 1981), and Ariyama (1996) identified Japanese specimens as G. insulae because of the agreement in most characters. However, reexamining many Japanese specimens, we found that the Japanese species is different from the true G. insulae in the numbers of the flagellar articles of antennae. The numbers in the former are 12–21 articles in the antenna 1 and 6–9 articles in the antenna 2 ( Table 1), while those of the latter are both 5 articles. The former also differs from the latter in the absence of tooth-like process on the peduncular article 1 of antenna 1 and the shorter article 1 of the mandibular palp (about 0.8 times as long as article 2). Herein we establish G. rubroantennata sp. nov. for the Japanese specimens and designate its type specimens as shown in “Material examined” and “Additional material”.

This new species also resembles Grandidierella koa Barnard, 1977 from Hawaii in the male gnathopod 1 with 2 posterodistal teeth on the carpus and with a small projection on the anterodistal corner of propodus. But G. koa can be distinguished from the new species by the slender basis of the male gnathopod 1, the nipple on the anterior apex of the male gnathopod 2 basis and the many long plumose setae on the pereopods 6 and 7 bases ( Barnard 1977; Ariyama 1996).

Habitat. Muddy sand under stones of rocks in the middle-lower intertidal zone; marine, rarely semi-brackish ( Ariyama 1996).

Distribution. Japan: coasts of Osaka and Wakayama Prefectures ( Ariyama 1996), coast of Chiba Prefecture (present study).

Figures

Fig. 2. Photographs of the specimens in life.A, Grandidierella sanrikuensis sp. nov., holotype, male (OMNH-Ar-10195), 7.7mm; B, G. sanrikuensis, paratype, female (OMNH-Ar-10197), 8.5mm; C, G. rubroantennata sp. nov., paratype, female (OMNH-Ar-10296), 7.2mm; D, G. osakaensis Ariyama, 1996, male (OMNH-Ar-10297), 5.8mm; E, G. osakaensis, female (OMNH-Ar-10359), 5.8mm. Scales: 1mm.

Fig. 8. Grandidierella rubroantennata sp. nov. Paratype, female (OMNH-Ar-10296), 7.2mm. A, left antenna 1, lateral view; A1, accessory flagellum of left antenna 1, medial view; B, left antenna 2, lateral view; B1, tip of left antenna 2, lateral view, normal setae omitted; C, left mandible, medial view; C1, incisor, lacinia mobilis and accessory blades of left mandible, medial view; D, left gnathopod 1, lateral view; D1, distal part of left gnathopod 1, lateral view, normal setae omitted; E, left gnathopod 2, lateral view; E1, distal part of left gnathopod 2, lateral view, normal setae omitted; F, basis of left pereopod 7, lateral view; G, left uropod 1, dorsolateral view; H, left uropod 2, dorsolateral view; I, left uropod 3, dorsal view; J, telson, dorsal view. Scales: 0.1mm.

Fig. 1. Map showing the collecting sites. A–C, Grandidierella sanrikuensis sp. nov.; D, G. rubroantennata sp. nov.; E–G, G. osakaensis Ariyama, 1996. In sites C, E and G, G. japonica Stephensen, 1938 was also collected nearby.