Neopleustes Stebbing, 1906

Labay, Vjacheslav S., 2021, Review of amphipods of the family Pleustidae Buchholz, 1874 (Crustacea Amphipoda) from the coastal waters of Sakhalin Island (Far East of Russia). I. Subfamily Neopleustinae Bousfield & Hendrycks, 1994, Zootaxa 4974 (2), pp. 267-306 : 301

Key to the species of the genus Neopleustes Stebbing, 1906

(based on the characteristics of the dorsal armament and on the structure of coxa 1)

1. Body segments with strong dorsal teeth (fig. 1a,b, d–i)....................................................... 2

- Body segments without strong dorsal teeth (fig. 1c)............................. Neopleustes carinatus Margulis, 1963

2. Pereon segments 1–6 without carination, pereon segment 7 with strong dorsal tooth posteriorly (fig. 1a,b).............. 3

- Pereon with a large number of dorsal teeth (fig. 1d–i)........................................................ 4

3. Pereonal & pleonal segments without aesthetascs dorsally (fig. 1a)............. Neopleustes boecki boecki ( Hansen, 1887)

- Pereonal & pleonal segments with submedial and sublateral groups of plumose aesthetascs dorsally (fig. 1b)................................................................................... Neopleustes boecki pacifica s sp. nov.

4. Pereon segments 1–4 without carination, pereon segments 5–7 with strong dorsal tooth posteriorly (fig. 1g,h,i).......... 5

- Pereon carinated posteriorly from segment 1 to segment 7 (fig. 1d,e,f)........................................... 7

5. Lower margin of coxal plate 1 rounded, without central ventral angle (fig. 4g)..... Neopleustes kussakini ( Budnikova, 1995)

- Lower margin of coxal plate 1 with central ventral angle (fig. 4h,i).............................................. 6

6. Head, pereonal & pleonal segments without setae dorsally, lower margin of coxal plate 1 with acute central ventral angle (figs. 1h, 4h)....................................................... Neopleustes pulchellus pulchellus (Krøyer, 1846)

- Head, pereonal & pleonal segments with submedial and sublateral long pappose single setae dorsally, lower margin of coxal plate 1 with subquadrate central ventral angle (figs. 1i, 4i)................... Neopleustes pulchellus asiaticus s sp. nov.

7. Body, pereon segments 1–3 weak carinations, and strongly carinated from segment 4 to segment 7 (fig. 1d)..................................................................... Neopleustes columbianus Hendrycks & Bousfield, 2004

- Body, pereon strongly carinated from segment 1 to segment 7 (fig. 1e,f).......................................... 8

8. Head with anterodorsal crest, lower margin of coxal plate 1 with acute central ventral angle (figs. 1e, 4e)................................................................................ Neopleustes euacanthoides Gurjanova, 1972

- Head without anterodorsal crest, lower margin of coxal plate 1 without acute central ventral angle (fig. 1f)................................................................................... Neopleustes euacanthus (G. Sars, 1877)