Ceradocus, Costa, 1853

Krapp-Schickel, Traudl & Vader, Wim, 2009, On some Maerid genera (Crustacea, Amphipoda, Maeridae) collected by the Hourglass Cruises (Florida). Part 1: Genera Anamaera, Ceradocus, Clessidra gen. nov., Jerbarnia, Maera, Meximaera, with a key to world Ceradocus, Journal of Natural History 43 (33 - 34), pp. 2057-2086 : 2061-2065

Genus Ceradocus Costa

Diagnostic characters

Eyes oval. Accessory flagellum long or short (in the studied region 4–8 arts). Md palp art1 acutely lengthened, the last article very short, not falcate. Maxillae with medial setae on the inner plates. Mx1 inner plate triangularly widened, left and right side symmetrical. Mx2 inner plate with dense oblique row of facial setae. Peraeon segment 7 without coxal gills. Cx1 produced anteroventrally, posteroventral margin without teeth or processes. Gn2 slightly or not sexually dimorphic, in males symmetrical or asymmetrical, dactylus outer margin with 0–1 seta. P7 basis weakly expanded, posterior margin weakly serrate. Peraeon and pleon can be with dorsal teeth or smooth. Ep3 is usually serrated. Urosome segments with teeth or processes usually present. U3 rami truncated, long, foliaceous, subequal in length, extending well beyond tips of U1,2, distally with robust setae never exceeding telson length, tips subacute, outer ramus 1-articulate. Telson deeply cleft, lateral margins straight to slightly convex, without apical spination, one distal tip on outer side of the lobes with subdistal robust setae shorter or longer than telson length.

Identification key to world Ceradocus (adult males)

This key is based on literature, not on material. We were unable to include Ceradocus capensis Sheard, 1939 ; C. cotonensis is included twice because the urosome segments 1–2 have not been described. All mention of Gn2 concerns the larger of the two gnathopods in asymmetric species.

1. Urosome segments 1,2 dorsally smooth............................ 2 Urosome segments 1, usually also 2, dorsally with teeth............... 5 (NB not described for C. cotonensis so surmised to be smooth)

2. Metasome dorsally smooth...................................... 3 Metasome dorsally serrate....................................... 4

3. Ep3 with posterodistal margin smooth...................................................... Ceradocus woorree (Queensland, 6–7 mm) Ep3 distal half of posterior margin with four or five serrations.......................................... Ceradocus laevis ( Philippines, 9 mm)

4. Gn2 symmetric, palm oblique, regularly convex............................................ Ceradocus cotonensis (Rodrigues Island, 7.5 mm) Gn2 asymmetric, palm almost transverse, irregularly convex...................................... Ceradocus shoalsi (Rodrigues Island, 4mm)

5. A1 accessory flagellum with more than 10 articles.................... 6 A1 accessory flagellum with less than 10 articles..................... 8

6. Gn2 with palm almost transverse, with U-shaped excavations......................................... Ceradocus ramsayi ( Australia, 8.5 mm) Gn2 palm oblique.............................................. 7

7. Gn2 palm irregularly convex, without clear humps or indentations. Urosome segments 1,2 with up to three teeth on each side............................................ Ceradocus koreanus (S. Korea, 21 mm) Gn2 palm with two flat-topped humps. Urosome segments 1,2 with seven or more teeth on each side.............. Ceradocus circe ( Australia, 23 mm)

8. Ep3 smooth or with only very few serrations........................ 9 Ep3 serrated at least in distal half.................................11

9. Ep3 with posterodistal corner strongly produced, otherwise smooth................................ Ceradocus oliveri (Rodrigues Island, 4 mm) Ep3 distally with serrations in addition to posterodistal tooth..........10

10. Urosome segment 2 with two dorsal teeth. Telson with two robust setae on each lobe...... Ceradocus hawaiiensis sensu Barnard, 1955 (Hawaii, 5 mm) Urosome segment 2 with four dorsal teeth. Telson with four or more robust setae on each lobe.... Ceradocus hawaiiensis s. Ledoyer, 1972 ( Madagascar, 10 mm)

11. Metasome segments 1–3 dorsally smooth...........................12 Metasome segments 1–3 dorsally with teeth or serrations..............14

12. Gn2 palm almost transverse, with medial flat-topped hump and large distal indentation............... Ceradocus paucidentatus (California, 7–8 mm) Gn2 palm oblique.............................................13

13. Eyes round. Ep1,2 with distal half of posterior margin serrate, Ep3 whole posterior margin coarsely serrate..... Ceradocus shoemakeri ( Bahamas, 7 mm) Eyes oval. Ep1 rounded, Ep2,3 with distal half of posterior margin serrate................................ Ceradocus breweri ( Bermuda, 8 mm)

14. Gn2 symmetrical, i.e. left and right gnathopods identical..............15 Gn2 asymmetrical, i.e. one clearly larger than the other, often also different...20

Gn2 symmetrical

15. Gn2 palm transverse, almost smooth... Ceradocus sellickensis ( Australia, ?? mm) Gn2 palm oblique.............................................16

16. Urosome segments 1,2 with more than five dorsal teeth each...........17 Urosome segments 1,2 with five, fewer or no teeth....................18

17. Gn2 palm sinuous, without median notch. Urosome segments 1,2 dorsally with 9–10 teeth.................... Ceradocus sheardi ( Cuba, 6–16 mm) Gn2 palm oblique, convex, almost smooth. Urosome segments 1,2 dorsally with 18 and 8 teeth, respectively... Ceradocus oxyodus (Queensland, 9 mm)

18. Urosome segments 1,2 with 0 to one tooth each......................19 Urosome segments 1,2 with three to five dorsal teeth each. Gn2 palm straight, with median notch....................................... Ceradocus sp. B (sensu S. LeCroy 2000), = “ C. orchestiipes ” sensu Kunkel, 1910 = Meximaera briani Krapp-Schickel, 2008a (Dry Tortugas, 5–8 mm)

19. Ep1,2 with serrate posterior margins. Gn2 with palm oblique, with small medial notch........... Ceradocus cotonensis (Rodrigues Island, 7.5 mm) Ep1,2 with posterior margins smooth (except posterodistal tooth). Gn2 with palm oblique, very irregular, with large flat-topped hump...................................... Ceradocus orchestiipes (Mediterranean, 16 mm)

Gn2 asymmetrical

20. Gn2 palm almost or completely transverse......................... 21 Gn2 palm oblique to very oblique................................ 26

Gn2 palm transverse:

21. Urosome segment 2 dorsally smooth. Gn2 palm with narrow medial sinus.... 22 Urosome segment 2 dorsally with teeth (may be small). Gn2 palm different... 23

22. Telson with five robust setae on each lobe................................................... Ceradocus chevreuxi (Gambier Islands, 6 mm) Telson with two robust setae on each lobe........................................................ Ceradocus yandala (Queensland, 4 mm)

23. Ep1–3 all quite coarsely serrate.................................. 24 Ep1 smooth (except posterodistal tooth).......................... 25

24. Gn2 palm regularly convex, with very small medial notch and strongly defined palmar corner......................................................... Ceradocus chevreuxi s. Ledoyer, 1979 ( Madagascar, 6 mm) Gn2 palm with broad medial indentation, with flat-topped hump inside................. Ceradocus spinifer s. Ledoyer, 1979 ( Madagascar, 10 mm) [NB. May not be the same as C. “ spinifera ” Ledoyer, 1973, based on females]

25. Urosome segment 2 dorsally with six teeth. A1 accessory flagellum with nine articles........................ Ceradocus natalensis (S. Africa, 10 mm) Urosome segment 2 dorsally with three small teeth. A1 accessory flagellum with six articles............. Ceradocus crenatipalma ( Madagascar, 5 mm)

Gn2 palm oblique

26. Metasome segments 1–3 with few dorsal teeth (<3 per segment)....... 27 Metasome segments 1,2 with many dorsal teeth..................... 28

27. Metasome segments 1–3 with tooth formula 1-3-3. Gn2 with palm very oblique, irregular, with two flat-topped humps................................ Ceradocus orchestiipes s. Stebbing (Cap Verde Islands, c. 10 mm) Metasome segments 1–3 with tooth formula 1-1-1. Gn2 with palm very oblique, with one triangular hump............................................................. Ceradocus spinicauda (California, 9 mm) (but cf. C. chiltoni from New Zealand)

28. Urosome segments 1,2 with many (six or more) dorsal teeth........... 29 Urosome segments 1,2 with fewer than six dorsal teeth............... 33

Us1,2 with six or more teeth

29. Urosome segment 1 with more than 10 dorsal teeth.................. 30 Urosome segment 1 with six to eight dorsal teeth.................... 31

30. Ep1–3 all serrate, Ep3 very coarsely. Gn2 palm oblique, smooth................................. Ceradocus rubromaculatus ( Australia, 12 mm) (NB We have been unable to include the Madagascar material identified as this species) Ep1,2 with only very few serrations, Ep3 serrate. Gn2 palm very oblique, smooth, but with triangular hump close to dactyl. Urosome segments 1,2 with 10 and two to five dorsal teeth, respectively................................................. Ceradocus tattersalli ( Madagascar, 6 mm)

31. Gn2 palm oblique, smooth, regularly convex. Urosome segments 1,2 with eight and three dorsal teeth. Ep1,2 with serrations in distal third................................ Ceradocus rubromaculatus s. Myers ( Fiji, 8 mm) Gn2 palm oblique, very irregular. Urosome segments 1,2 with seven or eight and five to seven dorsal teeth, respectively..........................32

32. Gn2 palm irregular, with deep median notch. Ep1,2 with four or five serrations near posterodistal corner................................................ Ceradocus serratus s. Ledoyer ( Madagascar, 10–15 mm) (NB Australian material probably same species) Gn2 palm sinuous, with strong hump beset with robust setae medially. Ep1 smooth, Ep2 with a few light serrations........................................................ Ceradocus greeni ( Mauritius, 5.2–6.2 mm)

Us1,2 with fewer than six dorsal teeth

33. Gn2 oblique, palmar margin more or less regular....................34 Gn2 oblique, palmar margin irregular.............................36

34. Urosome 1 with no dorsal teeth middorsally, but large teeth laterally.................................... Ceradocus dooliba ( Australia, 23 mm) Urosome segment 1 with dorsal teeth present middorsally.............35

35. Ep1,2 without any serrations on posterior margin. Urosome segments 1,2 with about five dorsal teeth. Gn2 with palm oblique, sinuous, palmar corner not well developed...................................................... Ceradocus cf rubromaculatus s. Krapp (Great Barrier Reef, 6 mm) Ep1,2 with distal half of posterior margin serrate. Urosome segments 1,2 with five and four dorsal teeth. Gn2 with palm oblique, regularly convex, palmar corner clear........ Ceradocus r. haumuri ( New Zealand, 9.5 mm)

36. Gn2 palm shorter than hind margin of propodus.....................37 Gn2 palm subequal with hind margin of propodus...................38

37. Gn2 palm sinuous, without median notch.................................................... Ceradocus mahafalensis ( Madagascar, 6 mm) Gn2 palm sinuous, with deep narrow median notch................................................ Ceradocus m. incisa ( Mauritius, 5.5 mm)

38. Gn2 palm very oblique, sinuous, with large median hump. Ep1,2 rounded, with smooth margins........... Ceradocus chiltoni ( New Zealand, ??mm) (but cf. C. spinicauda from California) Gn2 palm very oblique, sinuous, with large median indentation. Ep1 rounded, Ep2 with two serrations on posterodistal corner................................................ Ceradocus inermis ( Japan, 6.5 mm)

For using the characters independently from our key, we built a more detailed character matrix for all Ceradocus species ( Figure 2 ; C. capensis Sheard, 1939 was not included because it is too poorly described, it must remain species dubium). We tried to use exclusively the described typical material, and not the different and often not matching descriptions of later authors. As in many described species parts are missing or not well described, this composition is a very first attempt and will need corrections and additions. It is meant as a stimulus for further more detailed descriptions as well as checking, completing and correcting the descriptions here. It is not ready for a cladistic analysis because of incomplete descriptions and small morphological differences, which can change within the same species as the result of allometric growth.

The characters used in the matrix are listed in Table 1.

Figures

Figure 2. Character matrix for all known species of Ceradocus. Explanation of characters is supplied in Table 1.