Quadrimaera setibasis Ariyama 2019, sp. nov.
Creators: name: Ariyama, Hiroyuki
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Maeridae
Quadrimaera
Quadrimaera setibasis

description: Quadrimaera setibasis sp. nov.
[Japanese name: Taiheiyō-sunnariyokoebi-modoki, new]
(Figs 15H 1–2, 21–25)
Type material. Holotype: male, 12.5 mm (OMNH-Ar-10615), Myojinzaki coast, Misaki Town, Osaka Prefecture, 34°18'55"N 135°05'39"E (Fig. 1D), intertidal, under stones, 23 June 2013, coll. H. Ariyama. Paratypes: 3 males, 5.2–9.2 mm (OMNH-Ar-10616–10618), 3 ovigerous females, 5.4–9.4 mm (OMNH-Ar-10619–10621) and female, 10.2 mm (OMNH-Ar-10622), same data as holotype.
Type locality. Myojinzaki coast, Misaki Town, Osaka Prefecture in Japan.
Etymology. From the Latin seti (= setose) + basis, referring to the character of the pereopod 6.
Diagnosis. Gnathopod 1, coxa anteroventral corner rounded. Gnathopod 2, anterior margin of basis without robust setae, anterodistal corners of basis and ischium lobate on lateral and medial surfaces; propodus subrectangular, palm transverse, defined by large tooth, male palmar margin with small rounded excavation in middle and very small, V-shaped posterior excavation, female palmar margin with very shallow middle excavation, without posterior excavation. Pereopods 5–7, bases subovate, each posterodistal lobe small, posterior margin of pereopod 6 heavily setose. Uropod 3, outer ramus longer than inner ramus, about 1.3 times length of peduncle. Telson slightly wider than long, distal margins truncate, without inner distal teeth, each bearing 6 – 9 robust setae, longest seta about 75% length of telson.
Description. Based on holotype, male, 12.5 mm (OMNH-Ar-10615), and paratype, male, 9.2 mm (OMNH- Ar-10616) for uropod 3.
Head (Figs 21–22). Anteroventral corner produced acutely, eyes oval, about 15% length of head. Antenna 1 about 0.45 times body length, densely setose; peduncle with ratio of lengths of articles 1–3 1:1.1:0.3, article 1 without posteromedial robust setae; accessory flagellum with 12 articles, terminal article minute, length about half of primary flagellum; primary flagellum with 33 articles, terminal article minute. Antenna 2 about 65% length of antenna 1, densely setose; peduncle with ratio of lengths of articles 3–5 1:3.9:3.0; flagellum with 13 articles, terminal article minute. Upper lip, dorsal margin produced, ventral margin rounded, with minute setae. Mandible, incisor bearing 3 cusps, lacinia mobilis 4-dentate, number of accessory setae 8 on left side and 9 on right side; palp article length ratio 1:1.6:1.6, articles 2 – 3 heavily setose. Lower lip with inner lobes, distal margins of inner and outer lobes bearing many short setae, mandibular processes small. Maxilla 1, inner plate bullet-shaped, with 3 long and 1 short apical setae, medial margin bare; distal margin of outer plate with 9 robust setae; palp article 1 bearing 2 long 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 19 long-to-short robust setae on distomedial margin; palp with 4 articles, article 2 densely setose medially, article 4 with large apical robust seta.
Pereon (Fig. 23). Gnathopod 1, coxa roundish trapezoidal, anteroventral corner rounded; basis bearing many long setae on posterior margin and medial surface; carpus with slight excavation on anterior margin; propodus palm defined by short robust seta, palmar margin lined with minute robust setae. Gnathopod 2, coxa subpentagonal; basis short, anterodistal corners on lateral and medial surfaces lobate, anterior margin without robust setae, posterior margin bearing several long setae; ischium, anterodistal corners on lateral and medial surfaces lobate; merus slightly produced posterodistally; propodus subrectangular, widened distally, length about 1.3 times width; palm transverse, defined by large tooth with robust seta, palmar margin with small rounded excavation in middle and very small V-shaped excavation posteriorly, anterior lobe with 4 lateral and 4 medial robust setae, posterior lobe bearing 9 lateral and 10 medial robust setae; dactylus, inner margin slightly swollen in middle.
Pereopods 3–4 subequal in shape, pereopod 3 about 1.1 times length of pereopod 4; coxae subrectangular; bases with 1–2 robust setae and 3–4 long setae on posterior margins. Pereopod 5 about 1.2 times length of pereopod 4; coxa with posterior lobe bearing robust seta; basis subovate, length about 1.4 times width, anterior margin with 3 short robust setae, posterior margin expanded in middle, bearing several short setae, posterodistal lobe small; merus, anterior margin setose. Pereopod 6, about 1.1 times length of pereopod 5; coxa with 2 and 1 ventral robust setae on anterior and posterior lobes, respectively; basis subovate, length about 1.55 times width, anterior and posterior margins almost parallel, posterodistal lobe small, anterior margin with several short robust setae, posterior margin heavily setose; merus, anterior margin densely setose. Pereopod 7 slightly shorter than pereopod 6; coxa subtrapezoidal, anteroventral corner with 2 robust setae; basis subovate, length about 1.45 times width, anterior and posterior margins almost parallel, posterodistal lobe small, anterior margin with several short robust setae, posterior margin bearing several short setae; merus, anterior margin heavily setose.
Pleon (Fig. 24). Epimera 1–3 slightly projected posteroventrally, each with minute seta posteriorly; ventral margins of epimera 1–3 with 2, 4, 8 robust setae, respectively. Pleopods 1–3, inner rami slightly longer than outer rami, inner ramus with 14, 13, 13 articles and outer rami with 15, 15, 14 articles respectively; pleopod 3 shortest, peduncle bearing several short setae and distal robust seta. Uropod 1, peduncle with 1 basofacial, 10 dorsolateral, 5 dorsomedial and 1 distolateral robust setae; outer ramus about 0.9 times length of inner ramus, about 75% length of peduncle, with 4 lateral, 5 medial and 5 terminal robust setae; inner ramus with 2 lateral, 5 medial and 5 terminal robust setae. Uropod 2 about 0.6 times length of uropod 1; peduncle bearing 3 dorsolateral and 2 dorsomedial robust setae; outer ramus about 85% length of inner ramus, about 1.15 times length of peduncle, with 5 dorsolateral, 5 dorsomedial (lost) and 5 (1 lost) terminal robust setae; inner ramus with 4 lateral, 5 medial and 5 terminal robust setae. Uropod 3, medial margin of peduncle bearing 2 groups of robust setae; outer ramus about 1.15 times length of inner ramus, about 1.3 times of peduncle length; outer ramus with 3 groups of robust setae laterally and single and 2 groups of robust setae medially, distal margin with minute second article and many long setae, longest distal seta about 0.7 times length of outer ramus; inner ramus with single lateral and 2+2 medial robust setae, distal margin bearing many long setae. Telson slightly wider than long, each lateral margin with 2 sensory setae; distal margins truncate, without inner distal teeth, each bearing 6–7 long and 1–2 short robust setae, longest robust seta about 75% of telson length.
Variation. Gnathopod 2. Female, 10.2 mm (OMNH-Ar-10622, Fig. 24 F-G2), middle excavation on palm very shallow, posterior excavation absent, anterior lobe with 4 lateral and 5 medial robust setae, posterior lobe bearing 8 lateral and 7 medial robust setae. Male, 9.2 mm (OMNH-Ar-10616, Fig. 24 M-G2) almost same as that of holotype, male, anterior lobe with 5 lateral and 3 medial robust setae, posterior lobe bearing 9 lateral and 8 medial robust setae. Small male, 5.2 mm (OMNH-Ar-10618, Fig. 24 SM-G2), middle excavation on palm indistinct, palmar margin with 10 lateral and 10 medial robust setae. Uropod 3. Small male, 5.2 mm (OMNH-Ar-10618), rami slender, outer ramus about 1.8 times length of peduncle. Small ovigerous female, 5.4 mm (OMNH-Ar-10621), rami slender, outer ramus about 1.9 times length of peduncle. Telson. Male, 9.2 mm (OMNH-Ar-10616, Fig. 24 M-G2), distal margin of each lobe bearing 5 – 6 long and single short robust setae.
Coloration in life (Fig. 25). Eyes dark red, antennae pale pink, gnathopod 2 propodus white, dactylus pale orange, other parts bluish light green.
Remarks. Only two species of Quadrimaera, this new species and Q. schellenbergi from Red Sea (Krapp- Schickel & Ruffo 2006), have the heavily setose basis of the pereopod 6. Quadrimaera setibasis sp. nov. is different from Q. schellenbergi in the narrower anterior lobe of the male gnathopod 2 palm and the non-setose bases of the pereopods 5 and 7 (Ruffo 1938, Krapp-Schickel & Ruffo 2006). In addition, this species is the largest in the genus Quadrimaera (maximum body length: 12.5 mm in male).
Habitat. Under stones, intertidal. This species sometimes occurs together with Orientomaera decipiens Ariyama, 2018 and O. obliquua Ariyama, 2018.
Distribution. Japan: Misaki Town in Osaka Prefecture (present study).
description: Published as part of 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), pp. 460-496 in Zootaxa 4554 (2) on pages 487-493, DOI: 10.11646/zootaxa.4554.2.6, http://zenodo.org/record/2623831