Polyonyx nitidus Lockington, 1878

Ferreira, Luciane Augusto De Azevedo & Anker, Arthur, 2021, An annotated and illustrated checklist of the porcelain crabs of Panama (Decapoda: Anomura), Zootaxa 5045 (1), pp. 1-154 : 128

Polyonyx nitidus Lockington, 1878

( Figs. 80 , 81 )

Polyonyx nitidus Lockington 1878: 396 , 405; Haig 1960: 239, fig. 12(2); Haig 1962: 192; Werding & Haig 1982: 69; Hickman &

Zimmeran 2000: 68, unnumbered colour photograph; Werding 2001: 115; Hiller et al. 2004: 132; Moscoso 2012: 82, fig. 5H. Polyonyx quadriungulatus Glassell 1935: 93 , pl. 9; Haig 1960: 236, fig. 12(1), pl. 41, fig. 2.

Material examined. Panama [Pacific]: 1 ov. female, cl 9.2, cw 13.2, 1 male, cl 7.5, cw 10.0 ( MZUSP 33661 ) , Panama, Las Perlas Is ., Isla Bartolomé, depth 0–1 m at low tide, under large rocks in coarse sand, in tube of Chaetopterus sp. , leg. A. Anker, 19.04.2015; 1 ov. female, cl 3.0, cw 4.0, 1 male, cl 2.8, cw 3.9 ( MZUSP 33664 ), Las Perlas Is., small rocky island off north-eastern coast of Isla Saboga, depth 0–1.5 m at low tide, under rocks in coarse sand, in tube of Chaetopterus sp. , leg. A. Anker, 22.04.2015 .

Previous records from Panama. Haig (1962).

Distribution. East Pacific: USA (California), Mexico, Panama (Las Perlas Is., Taboga Is.), Colombia and Ecuador (including Galápagos) ( Haig 1960, as P. quadriungulatus and P. nitidus ; Hickman & Zimmerman 2000; Hiller et al. 2004; present study).

Ecology. Intertidal and (more common) subtidal, known depth range: 0–47 m; on sandy or sandy-muddy bottoms, often with rocks and rubble; obligate symbiont of large parchment worms, Chaetopterus sp. cf. variopedatus , usually in male-female pairs in each tube ( Haig 1962; present study, see Fig. 81 ).

Remarks. Haig (1960) treated P. quadriungulatus Glassell, 1935 from the warm-temperate outer Baja California as a species morphologically distinct from P. nitidus , supposed to occur in the Gulf of California and further south along the Pacific coast to Ecuador, including the Galápagos Islands. She was aware that the differences between these two presumed species were rather slight, suggesting that they may also be considered as subspecies of a single species. Werding (2001) concluded that the characters used by Haig (1960) to distinguish P. quadriangulatus and P. nitidus (number and configuration of movable spinules on the propodi and number of fixed spines on the dactyli of P2–P4) are not consistent, and that therefore P. quadriungulatus should be treated as a junior synonym of P. nitidus (see also Hiller et al. 2004). Indeed, in the present Panamanian material, the number of spinules on the ventral surface of the P2–P4 propodi varied from four to six: two to four medially aligned spinules and two spinules on the distal corner, near the propodo-dactylar articulation. The uniform pale orange-brown colouration of the Panamanian specimens of P. nitidus ( Figs. 80 , 81 ) corresponds well to that of the Galápagos specimens in Hickman & Zimmerman (2000).

Genus Porcellana Lamarck, 1801

Figures

FIGURE 80. Polyonyx nitidus Lockington, 1878: A–C, male (cl 7.5 mm, cw 10.0 mm) from Las Perlas Islands, Panama (MZUSP 33661), dorsal (A), ventral (B) and frontal (C) views [photographs by AA].

FIGURE 81. Polyonyx nitidus Lockington, 1878: A, male (cl 7.5 mm, cw 10.0 mm) from Las Perlas Islands, Panama (MZUSP 33661), in chaetopterid worm tube (host removed); B, ovigerous female (cl 9.2 mm, cw 13.2 mm) from the same locality (MZUSP 33661), dorsal view [photographs by AA].