Aoridae, Stebbing, 1899

Ariyama, Hiroyuki & Kodama, Masafumi, 2024, Three species of the family Aoridae Stebbing, 1899 (Crustacea: Amphipoda) collected from remote islands in southern Japan, with a key to all Japanese species of the family, Zootaxa 5433 (4), pp. 500-528 : 524-526

Key to all species of the family Aoridae in Japan (adult males)

Thirty-four aorid species have been recorded from Japan including the present study. This number suggests a high diversity of the aorid amphipods in Japan, next to Australia with 47 species and 2 subspecies ( Lowry & Stoddart 2003). A key to all the Japanese species is shown below. Incidentally, Lembos clavatus Hirayama, 1984 was transferred to the genus Ledoyerella Myers, 1973 in the family Kamakidae Myers & Lowry, 2003 ( Ariyama & Mori 2023).

1. Gnathopod 1 carpochelate, uropod 3 uniramous............................................................. 2

- Gnathopod 1 not carpochelate, uropod 3 biramous.......................................................... 17

2. Gnathopod 2 simple; telson short, with dorsal swellings...................................... ( Paragrandidierella ) 3

- Gnathopod 2 subchelate; telson large, without dorsal swellings................................... ( Grandidierella ) 5

3. Posterodistal corner of peduncular article 5 of antenna 2 inflated............... Paragrandidierella minima Ariyama, 2002

- Posterodistal corner of peduncular article 5 of antenna 2 not inflated............................................. 4

4. Tooth on gnathopod 1 carpus large (> 0.5 times as long as carpus proper).................. P. urauchiensis Ariyama, 2013

- Tooth on gnathopod 1 carpus small (<0.2 times as long as carpus proper)...................... P. unidentata ( Ren, 2006)

5. Gnathopod 2 with dense plumose setae, merus divergent posteriorly.................. Grandidierella gilesi Chilton, 1921

- Gnathopod 2 without plumose setae, merus not divergent...................................................... 6

6. Gnathopod 1 carpus with stridulating ridges................................................................ 7

- Gnathopod 1 carpus lacking stridulating ridges.............................................................. 9

7. Gnathopod 2 carpus shorter than propodus, pereopod 3 basis very slender (length: ca. 5 times of width)....................................................................................... G. gracilis Ariyama & Kohtsuka, 2022

- Gnathopod 2 carpus longer than propodus, pereopod 3 basis not so slender (length: <4 times of width)................. 8

8. Size large (maximum BL: 9.0 mm), coxa 2 lacking posteromedial projection............... G. japonica Stephensen, 1938

- Size small (maximum BL: 5.3 mm), coxa 2 with posteromedial projection................ G. japonicoides Ariyama, 2020

9. Uropod 1 peduncle with inter-ramal process............................................................... 10

- Uropod 1 peduncle without inter-ramal process............................................................. 11

10. Gnathopod 1 ischium with small posterodistal projection................................ G. osakaensis Ariyama, 1996

- Gnathopod 1 ischium lacking posterodistal projection............................. G. pseudosakaensis Ariyama, 2020

11. Gnathopod 1 merus with posterodistal projection, carpus with 3 teeth on posterodistal margin........................ 12

- Gnathopod 1 merus lacking posterodistal projection......................................................... 14

12. Proximal tooth on gnathopod 1 carpus very close to middle tooth.......................... G. contigua Ariyama, 2020

- Proximal tooth on gnathopod 1 carpus apart from middle tooth................................................ 13

13. Both middle and proximal teeth on carpus large......................................... G. fasciata Ariyama, 1996

- Only middle tooth on carpus large.......................................... G. sanrikuensis Ariyama & Taru, 2017

14. Gnathopod 1 carpus with 3 teeth on posterodistal margin (only middle tooth large), coxa 2 with posteromedial projection......................................................... G. halophila Wongkamhaeng, Pholpunthin & Azman, 2012

- Gnathopod 1 carpus with 2 teeth on posterodistal margin, coxa 2 without posteromedial projection.................... 15

15. Gnathopod 1 carpus wide (length: ca. 1.2 times of width).................................... G. nana Ariyama, 2020

- Gnathopod 1 carpus narrow (length: ca. 1.5 times of width)................................................... 16

16. Eyes small (diameter: ca. 0.2 times of head length), teeth on gnathopod 1 carpus close each other.......................................................................................... G. rubroantennata Ariyama & Taru, 2017

- Eyes large (diameter: ca. 0.35 times of head length), teeth on gnathopod 1 carpus separated each other................................................................................... G. ogasawarensis Ariyama & Kawabe, 2022

17. Gnathopod 1 merochelate.............................................................................. 18

- Gnathopod 1 subchelate............................................................................... 30

18. Accessory flagellum developed................................................................... ( Aora ) 19

- Accessory flagellum vestigial.................................................................. ( Aoroides ) 20

19. Accessory flagellum with 4 articles, basis of gnathopod 1 with anterior process......... Aora pseudotypica Hirayama, 1984

- Accessory flagellum with 2 articles, basis of gnathopod 1 without anterior process..................................................................................................... A. biarticulata Ariyama & Kohtsuka, 2022

20. Lateral margin of gnathopod 1 basis with many long setae (ca. 20–60).......................................... 21

- Lateral margin of gnathopod 1 basis with sparse short setae (≤ 10)............................................. 26

21. Anteromedial margin of gnathopod 1 carpus heavily setose (ca. 50–80 setae)..................................... 22

- Anteromedial margin of gnathopod 1 carpus with <5 setae................................................... 25

22. Anteroventral corner of coxa 1 with several plumose setae.................................................... 23

- Anteroventral corner of coxa 1 lacking plumose setae....................................................... 24

23. Eyes small (diameter: less than 0.3 times of head length), gnathopod 1 carpus long (length/BL: 0.19–0.21).................................................................................. Aoroides longimerus Ren & Zheng, 1996

- Eyes large (diameter: ca. 0.35 times of head length), gnathopod 1 carpus short (length/BL: 0.13–0.16)........................................................................................ A. macropus Ariyama & Kawabe, 2022

24. Pereopods 3, 4 bearing dense plumose setae, outer and inner rami of uropod 3 without marginal robust setae........................................................................................... A. secundus Gurjanova, 1938

- Pereopods 3, 4 without plumose setae, outer and inner rami of uropod 3 with 0–1 and 1–2 marginal robust setae, respectively........................................................................... A. myojinensis Ariyama, 2004b

25. Anterior margin of gnathopod 1 basis bearing ca. 20 plumose setae, pereopod 7 basis elliptical...................................................................................................... A. ellipticus Ariyama, 2004b

- Anterior margin of gnathopod 1 basis with <10 simple setae, pereopod 7 basis slender....... A. punctatus Ariyama, 2004b

26. Gnathopod 2 propodus curved posteriorly................................................................. 27

- Gnathopod 2 propodus straight......................................................................... 28

27. Outer and inner rami of uropod 3 with 1–2 and 2–3 marginal robust setae, respectively......... A. curvipes Ariyama, 2004b

- Uropod 3 outer ramus marginally bare, inner ramus with 1–2 marginal robust setae........ A. semicurvatus Ariyama, 2004b

28. Posterior margin of gnathopod 1 carpus scarcely setose (<5 setae)....................... A. columnaris Ariyama, 2004b

- Posterior margin of gnathopod 1 carpus with many plumose setae (ca. 15–40).................................... 29

29. Outer and inner rami of uropods 1, 2 each with 6–10 marginal robust setae................... A. rubellus Ariyama, 2004b

- Outer and inner rami of uropods 1, 2 each with 1–3 marginal robust setae........ A. sagamiensis Ariyama & Kohtsuka, 2022

30. Gnathopod 1 propodus shorter than 2 times length of carpus, medial surface covered with dense long setae..................................................................................................... ( Tethylembos ) 31

- Gnathopod 1 propodus longer than 2 times length of carpus, posteromedial surface weakly setose (ca. 20–40 setae)...... 32

31. Anteroventral corner of coxa 1 acutely projected, pereopod 5 basis excavated posterodistally....................................................................................................... Tethylembos cavatus sp. nov.

- Anteroventral corner of coxa 1 slightly projected roundly, pereopod 5 basis not excavated...... T. japonicus Ariyama, 2004a

32. Posterior margin of gnathopod 1 propodus with dense plumose setae (> 100), maxilliped basis with laterodistal flange............................................................................... Protolembos ryukyuensis sp. nov.

- Posterior margin of gnathopod 1 propodus weakly setose (ca. 20–30 setae), maxilliped basis without flange............ 33

33. Posterior margin of gnathopod 1 propodus serrate; gnathopod 2, anterior and posterior margins of carpus–propodus weakly setose with short setae.................................................. Pseudobemlos serratus Ariyama, 2004a

- Posterior margin of gnathopod 1 propodus with long acute tooth; gnathopod 2, anterior and posterior margins of carpus– propodus with dense long setae....................................... Bemlos seisuiae Kodama & Kawamura, 2019