Neopisosoma mexicanum ( Streets, 1871 )

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 : 43-44

Neopisosoma mexicanum ( Streets, 1871)

( Fig. 20 )

Pachycheles mexicanus Streets 1871: 225 , pl. 2, fig. 1; Haig 1957: 3.

Neopisosoma mexicanum .— Haig 1960: 127, pl. 30, fig. 2; Moran 1984: 79; Lazarus-Agudelo & Cantera-Kintz 2007: 229; Miranda & Mantelatto 2016: 511.

Material examined. Panama [Pacific]: 1 male, cl 6.0, cw 6.0, 1 ov. female, cl 4.9, cw 5.1 ( FLMNH UF 57709 ), Azuero Peninsula, Búcaro de Tonosí , near “Casa Iguana”, 7°20’08.4”N, 80°21’12.8”W, rocky plateau with rocks, low tide, leg. M. Leray & P.P.G. Pachelle, 14.02.2019 (fcn PAN-001). Extra-limital material . Costa Rica [Pacific]: 1?male, cl cw indet. ( MZUCR 5027-04 ), Area de Conservación Guanacaste, Junquillal, Islote Junquillal, intertidal, polychaete reefs, leg. G. Ampie & Y. Vega, 19.05.2016 [examined and identified by R. Vargas Castillo] .

Previous records from Panama. Haig (1957, 1960).

Distribution. East Pacific: Mexico, El Salvador, Nicaragua, Panama (Búcaro de Tonosí on Azuero Peninsula, Punta Guayabo Chiquito in Darién), Costa Rica, Colombia and Ecuador (including Galápagos) ( Haig 1960; Moran 1984; Miranda & Mantelatto 2016; present study).

Ecology. Largely and very shallow subtidal, rocky and mixed rocky-sandy beaches, probable depth range: 0–3 m; typically under rocks and in rock crevices ( Haig 1960; present study), also in intertidal “arenaceous worm tubes” ( Moran 1984).

Remarks. Prior to Haig’s (1957) record of N. mexicanum from Panama and Colombia (as Pachycheles mexicanus ), the species was known only from the holotype. Neopisosoma mexicanum is characterised by the P1 carpus with three slender teeth on mesial surface; the pubescence present on the minor P1 palm only; the presence of pleopods in males; and the telson composed of seven plates. The colouration of N. mexicanum ( Fig. 20 , showing a specimen from Costa Rica) is not particularly bright or diagnostic, consisting of a brown-yellowish mottled and spotted carapace, chelipeds (P1) and ambulatory legs (P2–4).

According to the results of a molecular analysis of the genera Pachycheles and Neopisosoma (based largely on sequences of the 16S mitochondrial gene), N. mexicanum forms a small clade together with the south-eastern Pacific Petrolisthes violaceus ( Guérin-Méneville, 1829) ; this clade is not closely related to the remaining species of Neopisosoma ( Miranda & Mantelatto 2016). In another molecular analysis, focusing mainly on the porcellanid crabs of Chile ( Baeza 2016), P. violaceus formed a sister clade to Liopetrolisthes within a polyphyletic Petrolisthes ; however, N. mexicanum was not included in that study. Importantly, Neopisosoma was also shown to be paraphyletic in an earlier study by Werding et al. (2001), based on COI sequences. These studies strongly indicate that some porcellanid species, such as N. mexicanum , may be assigned to the wrong genus, possibly as a result of remarkable adaptive convergence.

Genus Orthochela Glassell, 1936

Figures

FIGURE 20. Neopisosoma mexicanum (Streets, 1871): extra-limital specimen, possibly male (cl cw indet.) from Guanacaste, Costa Rica (MZUCR 5027-04), dorsal view [photograph courtesy of Gilberth Ampie Cruz (Proyecto Biomar-ACG) and Rita Vargas Castillo].