Orientomaera incisa Ariyama 2020, sp. nov.
Creators: name: Ariyama, Hiroyuki
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Maeridae
Orientomaera
Orientomaera incisa

description: Orientomaera incisa sp. nov.
[Japanese name: Kirekomi-sunnariyokoebi, new]
(Figs 16–20)
Type material. Holotype: male, 8.5 mm (OMNH-Ar-10737), Tagurazaki coast, Wakayama City, Wakayama Prefecture, 34°16ʹ00ʹʹN, 135°03ʹ39ʹE (Fig. 1B), intertidal, under stones, 17 June 2018, coll. H. Ariyama. Paratypes: 2 males, 6.4 and 5.6 mm (OMNH-Ar-10739–10740); ovigerous female, 7.5 mm (OMNH-Ar-10738), same data as holotype.
Type locality. Tagurazaki coast, Wakayama City, Wakayama Prefecture.
Etymology. From the Latin incisus, -a, -um (=incised), referring to the shape of palm.
Diagnosis. Antennae, peduncles slender. Gnathopod 1, coxa anteroventral corner produced acutely. Gnathopod 2, propodus subrectangular, palm slightly oblique, palmar margin with 2 large triangular teeth anteriorly and many robust setae. Pereopods 5–7, bases subovate, posterior margins convex. Telson wider than long, robust seta about 0.25 times length of telson.
Description. Based on holotype, male, 8.5 mm (OMNH-Ar-10736) and paratype, male, 6.4 mm (OMNH-Ar- 10739) for lower lip and maxilla 1.
Head (Figs 16–17). Antenna 1 about 45% body length, setose; peduncle slender, article 2 about 8.5 times as long as wide, ratio of lengths of articles 1–3 1:1.1:0.35, article 1 with 4 robust setae posteriorly; accessory flagellum with 8 articles, terminal article minute, length about half of primary flagellum; primary flagellum with 19 articles, terminal article minute. Antenna 2 about 0.65 times length of antenna 1, slender, setose; peduncle with ratio of lengths of articles 3–5 1:2.2:1.65; flagellum with 8 articles, terminal article minute. Mandible, left incisor bearing 5 cusps, right incisor with 4 cusps, left lacinia mobilis 5-dentate, right lacinia mobilis 4-dentate, number of accessory setae 9 on each side; palp article length ratio 1:2.5 – 2.6:1.7, articles 2–3 setose. Maxilla 1, inner plate with 3 plumose setae on tip, medial margin with several feeble setae; distal margin of outer plate with 8 robust setae; palp article 1 bearing many long feeble setae distolaterally. Maxilla 2, medial margin of inner plate with a few long and short setae distally. Maxilliped, distomedial corner of inner plate with 3 robust setae; outer plate with 17 long-to-short robust setae on distomedial margin.
Pereon (Fig. 18). Gnathopod 1, coxa subquadrate, anteroventral corner produced acutely; basis with posterior margin bearing 5 long setae, proximomedial surface with 2 long setae; propodus palm defined by 3 short robust setae. Gnathopod 2, coxa subtrapezoidal; basis short, anterodistal corner acutely projected, anteroproximal and posterior margins with 1 and 4 long setae, respectively; propodus subrectangular, slightly widened distally, length 1.36 times width; palm slightly oblique (angle of palmar corner: 92°), palmar margin with 2 large triangular teeth anteriorly (making incision) and 2 small teeth at posterior end, and with 4 lateral and 4 medial robust setae on anterior side of incision and 8 lateral and 6 medial robust setae on posterior side of incision; dactylus curved. Right gnathopod 2 similar to left one, but slightly smaller (ratio of propodus length: 96%).
Pereopods 3–4 subequal in shape, pereopod 3 about 1.1 times length of pereopod 4; coxae subquadrate; bases posterior margins each bearing 3 long setae. Pereopod 5 about 1.15 times length of pereopod 4; coxa with posterior lobe bearing robust seta; basis subovate, length about 1.9 times width, anterior margin with 7 short robust setae, posterior margin weakly convex. Pereopod 6 slightly longer than pereopod 5; coxa with 3 ventral robust setae on anterior lobe; basis subovate, length about 1.7 times width, anterior margin with 7 short robust setae, posterior margin weakly convex, bearing sparse short setae. Pereopod 7 about 1.2 times length of pereopod 6; coxa subtrapezoidal, anterior margin with robust seta; basis subovate, length about 1.6 times width, anterior margin with 9 short robust setae, posterior margin convex, with sparse short setae.
Pleon (Fig. 19). Epimera 1–3, each posteroventral corner slightly projected (indistinct in epimeron 1), ventral margins with 2, 3 and 4 robust setae respectively; epimera 1–2 each with oblique lateral ridge. Pleopods 1–3, inner rami with 7, 7, 6 articles and outer rami with 10, 9, 9 articles respectively; pleopod 3 shortest, peduncle bearing 4 and 2 setae on lateral margin and at posterodistal corner, respectively. Uropod 1, peduncle with 8 dorsolateral and 6 dorsomedial robust setae; outer ramus slightly shorter than inner ramus, about 0.65 times length of peduncle, with 2 lateral, 3 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 2 dorsolateral and 2 dorsomedial robust setae, distolateral corner with robust seta; rami subequal, outer ramus almost same length as peduncle, with 5 lateral and 5 terminal robust setae; inner ramus with 2 lateral, 5 medial and 5 terminal robust setae. Uropod 3 about 0.75 times length of uropod 2; distolateral corner of peduncle with 3 robust setae; rami subequal, about 1.3 times length of peduncle; outer ramus bearing 3 groups of robust setae laterally and 2 single robust setae medially, inner ramus with 2 medial robust setae, longest distal seta about 1.15 times length of rami. Telson wider than long, lateral margins convex, each with 2 sensory setae, distal margins of lobes each with 2 processes, inner process larger than outer, bearing single robust seta and sensory seta between processes, robust seta short, about 0.25 times as long as telson.
Description of female. Ovigerous female, paratype, 7.5 mm (OMNH-Ar-10738). Gnathopod 2 (Fig. 19 F-G2) subsimilar to that of holotype, male, palm with 4 lateral and 3 medial robust setae on anterior side of incision and 8 lateral and 5 medial robust setae on posterior side of incision; left gnathopod 2 slightly smaller than right one (ratio of propodus length: 97%).
Variation. Male paratype, 5.6 mm (OMNH-Ar-10740). Gnathopod 2 (Fig. 19 SM-G2) almost same as that of holotype, palm with 3 lateral and 2 medial robust setae on anterior side and 7 lateral and 6 medial robust setae on posterior side.
Coloration in life (Fig. 20). Eyes dark red, other parts pale pink.
Remarks. This new species apparently has the character of Orientomaera except for the shape of the gnathopod 2 palm. Orientomaera incisa is different from its congeners in the incised palm of the gnathopod 2.
Habitat. Under stones, intertidal. This species is collected from similar habitat of Orientomaera decipiens Ariyama, 2018 and O. obliquua Ariyama, 2018.
Distribution. Japan: Wakayama Prefecture (present study).
description: Published as part of Ariyama, Hiroyuki, 2020, Species of the Maera - clade collected from Japan. Part 3: genera Maera Leach, 1814, Meximaera Barnard, 1969 and Orientomaera Ariyama, 2018 (addendum), with a key to Japanese species of the clade (Crustacea: Amphipoda: Maeridae), pp. 451-479 in Zootaxa 4743 (4) on pages 471-472, DOI: 10.11646/zootaxa.4743.4.1, http://zenodo.org/record/3690502