Zootaxa 4034(3): 471-494 (2015)

Hsi-Te Shih, Peter K. L. Ng & John H. Christy

Among the fiddler crabs from the Americas, Uca panamensis (Stimpson, 1859) (Crustacea: Decapoda: Ocypodidae) is unusual in its behavior and ecology, living in stony habitats rather than sandy or muddy substrates. This species also has several unusual morphological characters of the carapace and major and minor chelae, and had been placed in either the subgenera Minuca Bott, 1954, or Leptuca Bott, 1973. The armature at the inner corner of the orbital floor, as well as the morphology of the urocardiac ossicles of the gastric mill of U. panamensis, are, however, plesiomorphic characters, and are closer to the condition in species belonging the subgenera Uca and Afruca. Phylogenetic relationships, based on mitochondrial 16S rDNA and cytochrome oxidase subunit I, and nuclear 28S rDNA, supported by its unusual morphological features indicate that this species belongs to its own subgenus. A new subgenus Uca (Petruca) subgen. nov. is herein established for U. panamensis. In addition, the status of Uca thayeri Rathbun, 1900, U. umbratila Crane, 1941, U. virens Salmon & Atsaides, 1968, and U. longisignalis Salmon & Atsaides, 1968, are revised and discussed based on a reappraisal of their phylogenetic relationships.

Key words: Crustacea, Brachyura, systematics, new subgenus, Uca panamensis, molecular evidence, 28S rDNA, 16S rDNA, cytochrome oxidase subunit I

FIGURE 1. Uca panamensis (neotype, USNM 1294205, CW 16.8 mm). A, dorsal view; B, boss on carapace behind right dorsolateral margin (arrowed); C, ventral view. Scale, B = 2 mm.

FIGURE 2. Uca panamensis (neotype, USNM 1294205, CW 16.8 mm). A, orbital region; B, inner side of orbital region, showing the tubercle of orbital armature (arrowed); C, frontal view; D, front; E, third maxillipeds. Scale, A, E = 2 mm; B = 1 mm; C = 10 mm; D = 5 mm.

FIGURE 3. Major and minor chelipeds of Uca panamensis (neotype, USNM 1294205, CW 16.8 mm). A, B, outer and inner views of major cheliped; C, D, outer and inner views of minor cheliped. Scale, C, D = 2 mm.

FIGURE 4. Uca panamensis, right G1 (neotype, USNM 1294205, CW 16.8 mm). A, dorsal view; B, dorsal view of terminal segment; C, D, ventral view of terminal segment. Scale, A = 2 mm; B, C = 0.5 mm.

FIGURE 5. Urocardiac ossicle of Uca panamensis. A, B, neotype, USNM 1294205 (16.8 mm); C, ZRC (CW 12.6 mm, ♂); D, ZRC (CW 13.7 mm, ♀). A, C, D, ventral view; B, lateroventral view. Scale, A, B = 1 mm; C, D = 0.5 mm.

FIGURE 6. Urocardiac ossicle of the subgenus Minuca species. A, Uca brevifrons (ZRC 2012.0126, CW 22.1, ♂); B, U. cf. virens (NCHUZOOL 13946, CW 17.0 mm, ♂); C, U. victoriana (NCHUZOOL 13945, CW 12.2 mm, ♀); D, U. pugnax (NCHUZOOL 13941, CW 15.2 mm, ♂); E, U. burgersi (NCHUZOOL 13956, CW 13.0 mm); F, U. rapax (NCHUZOOL 13942, CW 23.4 mm, ♂); G, U. mordax (NCHUZOOL 13940, CW 18.0 mm, ♀); H, U. minax (NCHUZOOL 13957, CW 23.2 mm, ♂); I, U. vocator (NCHUZOOL 13948, CW 21.9 mm, ♀). Scale = 1 mm.

FIGURE 7. Urocardiac ossicle of the subgenus Leptuca species. A, Uca subcylindrica (NCHUZOOL 13952, CW 15.2 mm, ♂); B, U. terpsichores (NCHUZOOL 13582, CW 9.9 mm, ♂); C, U. uruguayensis (NCHUZOOL 13577, CW 14.1 mm, ♂); D, U. spinicarpa (NCHUZOOL 13947, CW 13.3 mm, ♀); E, U. panacea (NCHUZOOL 13950, CW 14.8 mm, ♂); F, U. pugilator (NCHUZOOL 13586, CW 15.9 mm, ♂); G, U. speciosa (NCHUZOOL 13951, CW 12.6 mm, ♂); H, U. umbratila (NCHUZOOL 13579, CW 16.2 mm, ♂); I, U. thayeri (NCHUZOOL 13953, CW 19.0 mm, ♂). Scale = 1 mm.

FIGURE 8. Uca panamensis ♂ (A, B) and its habitat (C). Photographs taken in Panamá. B, courtesy of P. Backwell.

Copyright © 2016 Hsi-Te SHIH