Ucides Rathbun, 1897

Shih, Hsi-Te, Ng, Peter K. L., Davie, Peter J. F., Schubart, Christoph D., Türkay, Michael, Naderloo, Reza, Jones, Diana & Liu, Min-Yun, 2016, Systematics of the family Ocypodidae Rafinesque, 1815 (Crustacea: Brachyura), based on phylogenetic relationships, with a reorganization of subfamily rankings and a review of the taxonomic status of Uca Leach, 1814, sensu lato and its subgenera, Raffles Bulletin of Zoology 64, pp. 139-175 : 160-161

Ucides Rathbun, 1897

( Fig. 12C, D )

Uca Latreille, 1819: 96 . Type species Cancer uca Linnaeus, 1767 ;

junior homonym of Uca Leach, 1814 . Gender feminine. Ucea Guérin-Méneville, 1844: 8 , pl. 5(3) (incorrect spelling). Ucides Rathbun, 1897: 154 . Type species Cancer cordatus Linnaeus,

1763, by original designation. Gender masculine. Oedipleura Ortmann, 1897: 334 (replacement name for Uca

Latreille, 1819).

Diagnosis. See Diagnosis for subfamily. Confined to the Atlantic and East Pacific coasts of the Americas.

Species included:

1. Ucides cordatus ( Linnaeus, 1763)

= Cancer uca Linnaeus, 1767

= Ocypode fossor Latreille, 1803

= Uca pilosipes Gill, 1859

2. Ucides occidentalis ( Ortmann, 1897)

= Uca laevis H. Milne Edwards, 1837 (pre-occupied name)

Remarks. The morphology of Ucides is superficially similar to that of the gecarcinids, but Chace & Hobbs (1969) provided a suite of characters (especially relating to the maxillipeds and ambulatory legs) that show Ucides to be closer to ocypodids. Schubart & Cuesta (2010), using 16S, found that Ucides cordatus and Ocypode quadrata formed a separate clade, and concluded that both genera are closely related. The present study, nevertheless, supports the recognition of a separate subfamily Ucidinae , typically placed basally within the Ocypodidae ( Figs. 1–3 ).

Key to the subfamilies and genera of Ocypodidae

1. Fronto-orbital distance 1/2–2/3 of maximum carapace width, front relatively broad; no brush of long setae between bases of second and third ambulatory legs leading to branchial cavity. ..................................................................... Ucides (Ucidinae)

– Fronto-orbital distance> 9/10 of maximum carapace width, front relatively narrow; prominent brush of long setae between bases of second and third ambulatory legs leading to branchial cavity. ......................................................................................2 2. Orbital floor with tubercle at inner corner adjacent to antennule. Males of some species with distal end of cornea of eyestalks possessing ornament (horn, stylus or setal brush). Gastric mill with 1 protrusion or 2 pairs of transverse ridges of median teeth on posterior tooth plate, gaps shallow, prominently separated from central ridge. ........................................ 3 ( Ocypodinae )

– Orbital floor without tubercle at inner corner adjacent to antennule (vestigial in Petruca ). Males never with ornament at distal end of cornea of eyestalks. Gastric mill with 2 or more pairs of transverse ridges of median teeth on posterior tooth plate, gaps deep, reaching or near central ridge. ..................... .........................................................................5 ( Gelasiminae )

3. Eyestalks short, cornea large, ovate. Chelipeds unequal in both sexes but major one never prominently enlarged. ..... Ocypode

– Eyestalks slender, cornea round. Male with major cheliped prominently enlarged; minor male and female chelipeds small.........................................................................................4

4. Front narrow, carapace not covered with tubercles. ......... Uca

– Front wide, carapace covered with prominent tubercles. ....... ........................................................................................ Afruca

5. Front narrow. ..........................................................................6

– Front wide. .............................................................................8

6. Carpus of major cheliped with anterodorsal area not flattened;>90% ratio of males with right major chela. Floor of orbit without any elevations. Gastric mill with setal structure on lateral margins of stem region of urocardiac ossicles.............. .................................................................................. Gelasimus

– Carpus of major cheliped with anterodorsal area flattened; ratio of males with right or left major chela ca. 50%. Floor of orbit often with tubercles, ridge or mound. Gastric mill without setal structure on stem region of urocardiac ossicles. ...................7

7. Major cheliped with forceps-shaped fingers or with straight cutting margins <1/2 length of fingers. Minor cheliped merus with short, stiff setae..................................................... Tubuca

– Major cheliped with deep fingers, with straight cutting margins>1/2 length of fingers. Minor cheliped merus with long, thin setae. .............................................................................. Xeruca

8. Dorsal edge of orbit distinctly broad. Gastric mill with 2 large brownish setae at base of posterior tooth plate......................9

– Dorsal edge of orbit narrow. Gastric mill without large brownish setae at base of posterior tooth plate....................................11

9. Manus of major cheliped with posterior extension. Tips of minor fingers with brush of long setae. Orbital floor with small spinous tubercle near inner corner............................... Petruca

– Manus of major cheliped without posterior extension. Tips of minor fingers without brush of long setae. Orbital floor without spinous tubercle near inner corner........................................10

10. Anterolateral margin short; carapace with 0–2 posterolateral striae. All pleonites free, or somites 4–6 partly or completely fused. Major pollex without ventral carina................. Leptuca

– Anterolateral margin long, curving into dorsolateral surface; carapace with 2 posterolateral striae. All pleonites free. Major pollex may possess ventral carina. ............................... Minuca

11. Dactylus of major cheliped with large subdistal tooth; major manus with some tubercles on outer surface. Without pleonal clasping apparatus. ...................................................... Cranuca

– Dactylus of major cheliped without large subdistal tooth; major manus with outer surface smooth. With pleonal clasping apparatus................................................................................12

12. Outer manus of major cheliped with small round depression near base of pollex; carpal cavity not continued distally. ....... ............................................................................... Paraleptuca

– Outer manus of major cheliped without small round depression near base of pollex; carpal cavity with distal extension.......... .................................................................................... Austruca

Figures

Fig. 12. Photographs of some species of the genera Tubuca, Xeruca and Ucides. A, T. urvillei (Ranong, Thailand); B, X. formosensis (Taiwan); C, D, U. cordatus (Brazil).

Fig. 1. A Bayesian inference (BI) tree of the family Ocypodidae and outgroups, based on the combined 28S rRNA, 16S rRNA and COI markers, showing the three clades (three subfamilies), indicated in different colours. The subfamily Gelasiminae is composed of two groups, one is for all Indo-West Pacific fiddler crabs, the other for the American broad-fronted fiddler crabs.

Fig. 2. A Bayesian inference (BI) tree of the family Ocypodidae and outgroups, based on the combined 28S, 16S and COI markers. The solid circle at the node means it is strongly supported by both BI (≥ 90) and ML (≥ 70); and the open circle means only one method is strongly supported. Name of species or genus quoted means it is suggested as a synonym in this study.

Fig. 3. The simplified phylogenetic tree modified from Figs. 1 & 2, with number of species beside or below the taxa/group. The gray boxes mean the genera are not fiddler crabs.