Morinoia japonica (Tattersall, 1922)

(Fig. 19)

Talorchestia japonica Tattersall, 1922: 452, pl. 21, figs 1–10.

Orchestia japonica . — Stephensen, 1935: 6.

Platorchestia japonica .— Bousfield, 1982: 27.— Morino & Dai, 1990: 21 figs 9–11.― Morino, 1991: 65, fig. 206 (key), 212– 2.—1999: 629 (key), 635, fig. 2, 643.— Miyamoto & Morino, 2004: 70, key.— Hou & Li, 2005: 3260.— Tomikawa, 2017: 254, table 1.

Morinoia japonica Lowry & Myers, 2019: 61, fig. 27.

Not Orchestia platensis japonica .— Iwasa, 1939: 261, pl. 10, figs 4–6 (= P. pachypus (Derzhavin, 1937) .

Not Platorchestia japonica .— Morino & Dai, 1990: 21, figs 9–11 [not P. japonica, but Platorchestia group 3].— Hou & Li, 2003: 2442, figs 1–4 [not P. japonica, but Platorchestia group 3].— Miyamoto & Morino, 2004: 83, figs 8–10, 15 (= Platorchestia paludosus Cheng, Nakazono, Lin & Chan, 2011).

Non-Taxonomic Citations

Platorchestia japonica .— Tsubokura, Kikuchi & Nakao, 1998: 626, 627, table 1, 628, fig. 3, 630, fig. 4, 631, fig. 5, table 2, 632, fig. 6, table 3, 633, table 4, 636, fig. 11c (gill morphology).— Wildish & Radulovici, 2019: 2422, table 4, 2426, table 6).

Types. Syntypes, 30 specimens (not found in the Manchester Museum (Dmitri Logunov, pers. comm., 11/06/2021). Not in the Cardiff Museum (pers. comm. Teresa Darbyshire).

Type locality. Lake Biwa at Zézé, Japan .

Ecological type. Marsh-hoppers or riparian-hoppers.

Habitat. S hores of Lake Biwa among damp weeds.

Size. Male, 7–9 mm, female, 6–9 mm.

Diagnosis Based on Tattersall (1922) and Morino & Dai (1990).

Pleopods rami about 0.9 × length of peduncle. Uropod 3 ramus about 0.6 × length of peduncle. Telson apically incised, with 6–7 robust setae per lobe.

Remarks. According to Cheng et al. (2011) Morinoia paludosus is morphologically very close to M. japonica (Tattersall, 1922) . “The distribution pattern of setae in the lateral margin of the telson and sharpness of ramus tip of uropod 3, however, are diagnostic differences between the two species.” Citing sequence divergence in COI, “ Morinoia paludosus differed from M. japonica 13.3% on average, values that are comparable to inter-specific differences in other amphipod taxa”.

Distribution. Japan: Lake Biwa (Tattersall 1922); China: Yanqing County; Yuanmingyuan Park; Jingmiyingshuiqu River (Hou & Li 2005); Yangtze River, Jingmiyingshuiqu River (Hou & Li 2003).