Aora Krøyer, 1845

Ariyama, Hiroyuki & Kohtsuka, Hisanori, 2022, Three new species of the family Aoridae collected from Sagami Bay, central Japan (Crustacea: Amphipoda), Zootaxa 5159 (3), pp. 393-413 : 394

Aora Krøyer, 1845

[Japanese name: Himeyumbo-sokoebi-zoku]

Aora Krøyer, 1845: 335 .— Myers & Moore, 1983: 167 (key).— Myers, 1988: 187.—J.L. Barnard & Karaman, 1991: 161.— Myers & Lowry, 2003: 465.

Type species. Aora typica Krøyer, 1845 , fixed by monotypy.

Diagnostic description [emended from J.L. Barnard & Karaman (1991)]. Body laterally compressed, smooth. Head, rostrum short, ocular lobes short, anterodistal corner slightly or not projected; eyes small to large. Urosomites free. Antenna 1 very long, slender; peduncular article 3 usually shorter than article 1; accessory flagellum 2- to 6- articulate. Antenna 2 shorter than antenna 1, flagellum short, with 4–9 articles. Mandible, palp strong, slender, with 3 articles, article 3 longest, parallel-sided or semi-falciform, well setose; left molar traversed with parallel channels. Maxilla 1, inner plate triangular or conical, with apical seta; outer plate with 9–10 apical robust setae; palp biarticulate, with several robust setae distally. Maxilla 2 broad, inner plate with mediofacial row of setae. Maxilliped, inner plate with several robust setae distally; outer plate with several marginal robust setae; palp consisting of 4 articles, article 4 bearing robust seta (nail) on tip. Coxae, male coxa 1 dilated, produced forward, male coxae 2–7 and all coxae in female ordinary to short, weakly overlapping; gills present on coxae 2–6; oostegites of female broad, present on coxae 2–5. Male gnathopod 1 greatly enlarged, merochelate; merus produced into long distal tooth; carpus long, linear, propodus usually shorter than carpus. Female gnathopod 1 smaller than that of male, subchelate; carpus shorter than propodus, palm oblique. Gnathopod 2 of both sexes smaller than gnathopod 1, subchelate; propodus shorter than or as long as carpus in male, length variable in female, palm oblique. Pereopods 3, 4 similar to each other; bases slender. Pereopods 5–7 similar to each other, progressively longer; bases broad. Epimeral plates 1–3 usually each with notch on ventroposterior corner. Uropods biramous; uropod 1 peduncle shorter than or same length as rami, distal end of peduncle with long inter-ramal process, both rami subequal in length; uropod 2 shorter than uropod l, peduncle shorter than rami, distal end of peduncle with short or vestigial inter-ramal process, outer ramus slightly shorter than inner ramus; uropod 3 shortest, peduncle slightly elongate, shorter than rami, both rami subequal in length, outer ramus often with tiny second article. Telson entire, fleshy, usually with pair of hooked cusps.

Remarks. This genus contains twenty species to date (Horton et. al. 2022). But Aora inermis Appadoo & Myers, 2004 from Mauritius should be included in another genus (possibly Tethylembos ), because this species has an acute anterodistal corner of the head, the non-merochelate (subchelate) male gnathopod 1, and the uropod 2 with a long inter-ramal process. The Aora species share the merochelate gnathopod 1 and the smaller subchelate gnathopod 2 both in male with the Aoroides species; however, the former can be distinguished from the latter by the 2–6 articulated accessory flagellum (rudimentary or absent in Aoroides ) and the parallel-sided or semi-falciform article 3 of the maxillipedal palp (rod-shaped in Aoroides ).