Quadrimaera gotoensis, Ariyama, 2019

Ariyama, Hiroyuki, 2019, Species of the Maera - clade collected from Japan. Part 2: genera Austromaera Lowry & Springthorpe, 2005 and Quadrimaera Krapp-Schickel & Ruffo, 2000 (Crustacea: Amphipoda: Maeridae), Zootaxa 4554 (2), pp. 460-496 : 469-473

Quadrimaera gotoensis sp. nov.

[Japanese name: Gotō-sunnariyokoebi, new]

( Figs 6–9 )

Type material. Holotype: male, 11.6 mm (OMNH-Ar-10597), Nama Bay , Nakadōri Island in Gotō Islands, Nagasaki Prefecture, 33°01'28"N 129°05'15"E ( Fig. 1I ), intertidal, under stones, 2007 (date unknown), coll. T. Shiraiwa. Paratype: male, 11.2 mm (OMNH-Ar-10598), same data as holotype.

Type locality. Nama Bay , Nakadōri Island in the Gotō Islands, Nagasaki Prefecture, Japan .

Etymology. Referring to the type locality.

Diagnosis. Gnathopod 1, coxa anteroventral corner rounded. Male gnathopod 2, anterior margin of basis with several robust setae, anterodistal corners of basis and ischium lobate on lateral and medial surfaces, propodus subrectangular, palm transverse, defined by large tooth, palmar margin with small quadrate excavation in middle, posterior excavation absent. Pereopods 5–7, bases subovate, gradually wider in order, posterior margins not setose. Uropod 3, rami subequal, about twice length of peduncle. Telson longer than wide, tips of both lobes incised, each with 3–4 robust setae, longest robust seta about half length of telson.

Description. Based on holotype, male, 11.6 mm (OMNH-Ar-10597) and paratype, male, 11.2 mm (OMNH- Ar-10598) for uropod 1 peduncle.

Head ( Figs 6–7 ). Anteroventral corner produced acutely, eyes subrounded, about 0.2 times as long as head. Antenna 1 about 0.4 times body length, setose; peduncle with ratio of lengths of articles 1–3 1:1.2:0.3, article 1 with 4 (2 lost) robust setae posteromedially, anterodistal corner with bundle of setae; accessory flagellum with 9 articles, terminal article minute, length about half of primary flagellum; primary flagellum with 18 articles. Antenna 2 about 0.8 times length of antenna 1, setose; peduncle with ratio of lengths of articles 3–5 1:3.5:2.8; flagellum with 13 articles, terminal article short. Upper lip, ventral margin rounded, with short setae. Mandible, incisor bearing 3 and 6? cusps in left and right, respectively, left lacinia mobilis 4-dentate, right lacinia mobilis 3- dentate, number of accessory setae 8 on left side and 7 on right side; palp article length ratio in right 1:2.0:1.8, articles 2 – 3 heavily setose. Lower lip with inner lobes, distal margins of inner and outer lobes densely setose, mandibular processes small. Maxilla 1, inner plate bullet-shaped, with 3 long and 1 tiny apical setae, medial margin with several short feeble setae; distal margin of outer plate with 9 robust setae; palp article 1 bearing 3 short setae distolaterally, article 2 with many apical setae. Maxilla 2, outer plate larger than inner plate; medial margin of inner plate with several distal setae and many feeble setae. Maxilliped, distomedial corner of inner plate with 2 robust setae ventrally; outer plate with 25 long-to-short robust setae on distomedial margin; palp with 4 articles, article 4 with large apical robust seta.

Pereon ( Fig. 8 ). Gnathopod 1, coxa roundish trapezoidal, anteroventral corner rounded; basis with posterior margin bearing many long setae, medioproximal surface with several setae; carpus with shallow excavation on anterior margin; propodus palm defined by short robust seta. Gnathopod 2, coxa subtrapezoidal; basis short, anterodistal corners on lateral and medial surfaces lobate, anterior margin with 6 robust setae, posterior margin bearing several long setae; ischium, anterodistal corners on lateral and medial surfaces lobate; merus with acute posterodistal spine; propodus subrectangular, slightly widened distally, length about 1.3 times width; palm transverse, defined by large tooth with robust seta, margin with small quadrate excavation in middle, posterior excavation absent, anterior lobe slightly hollowed in middle, with 3 lateral and 3 medial robust setae, posterior lobe bearing 7 lateral and 6 medial robust setae; dactylus, inner margin swollen in middle.

Pereopods 3–4 subequal in shape, pereopod 3 about 105% length of pereopod 4; coxae subrectangular; bases with posterior margins bearing several long setae. Pereopod 5 about 1.3 times length of pereopod 4; coxa with posterior lobe bearing robust seta; basis subovate, length about 1.8 times width, anterior margin with 7 short robust setae. Pereopod 6 about 1.2 times length of pereopod 5; coxa with 2 and 1 ventral robust setae on anterior and posterior lobes, respectively; basis subovate, length about 1.7 times width, anterior margin with 11 short robust setae, posterior margin minutely serrate. Pereopod 7 slightly shorter than pereopod 6; coxa subtrapezoidal, anteroventral corner with robust seta; basis subovate, length about 1.5 times width, anterior margin with 7 short robust setae, posterior margin serrate.

Pleon ( Fig. 9 ). Epimera 1–3 slightly projected posteroventrally, with minute seta posteriorly; epimera 1–2 each with oblique lateral ridge, ventral margins of epimera 1–3 with 1, 3, 4 robust setae, respectively. Pleopods 1–3, inner rami longer than outer rami, inner rami with 18, 18, 15 articles and outer rami with 17, 18, 17 articles respectively; pleopod 3 shortest, peduncle bearing short seta. Uropod 1, peduncle with 1 basofacial, 9 – 10 dorsolateral, 5 dorsomedial and 1 distolateral robust setae; outer ramus slightly shorter than inner ramus, about 85% length of peduncle, with 4 lateral, 5 medial and 5 terminal robust setae; inner ramus with 4 lateral, 4 medial and 5 terminal robust setae. Uropod 2 about 0.7 times length of uropod 1; peduncle bearing 5 dorsolateral and 2 dorsomedial robust setae; outer ramus about 75% length of inner ramus, about 105% length of peduncle, with 4 lateral, 3 medial and 5 terminal robust setae; inner ramus with 3 lateral, 4 medial and 5 terminal robust setae. Uropod 3 about 85% length of uropod 2; distolateral and distomedial corners of peduncle with 3 and 4 robust setae, respectively; rami subequal, about 1.9 times length of peduncle; outer ramus with single and 2 groups of robust setae laterally and 5 robust setae medially, distal margin with minute second article and 9 setae, longest distal seta about 0.3 times length of rami; inner ramus with 1+1+2 robust setae laterally and 4 robust setae medially, distal margin with 9 setae. Telson longer than wide, each lateral margin with robust seta (lost in left) and 2 sensory setae subdistally; distal margins of lobes each with 2 processes and 2–3 robust setae between processes, longest robust seta about half length of telson, inner processes wider than outer, each outer process with sensory seta.

Coloration. Unknown.

Remarks. The small quadrate excavation on the middle palmar margin of the male gnathopod 2 is a distinctive character in the genus. Only one species, Q. mirandella from Mauritius, has such an excavation other than this new species. But Q. gotoensis sp. nov. can be distinguished from Q. mirandella by the longer article 2 of the mandible, the larger posterodistal tooth of the male gnathopod 2 propodus, the wider bases of the pereopods 5–7, and the distally incised lobes of the telson each bearing a few robust setae. In addition, this is one of the large species in the genus Quadrimaera together with Q. setibasis sp. nov.

Habitat. Under stones, intertidal.

Distribution. Japan: Goto Islands in Nagasaki Prefecture (present study).

Figures

FIGURE 1. Map showing collecting sites of the examined specimens. A, Otsuchi Town in Iwate Prefecture; B, Miura City in Kanagawa Prefecture; C, Maizuru City in Kyoto Prefecture; D, Misaki Town in Osaka Prefecture and Wakayama City in Wakayama Prefecture; E, Kushimoto Town in Wakayama Prefecture; F–H, Ariake Sea; I, Nakadōri Island in the Gotō Islands, Nagasaki Prefecture; J, south of Yakushima Island in Kagoshima Prefecture.

FIGURE 6. Quadrimaera gotoensis sp. nov. Holotype, male, 11.6 mm (OMNH-Ar-10597). Habitus.

FIGURE 7. Quadrimaera gotoensis sp. nov. Holotype, male, 11.6 mm (OMNH-Ar-10597). Scales: 0.1 mm.

FIGURE 8. Quadrimaera gotoensis sp. nov. Holotype, male, 11.6 mm (OMNH-Ar-10597). Scales: 0.2 mm.

FIGURE 9. Quadrimaera gotoensis sp. nov. All except for M, holotype, male, 11.6 mm (OMNH-Ar-10597); M, paratype, male, 11.2 mm (OMNH-Ar-10598). Scales: 0.2 mm.