Petrolisthes robsonae Glassell, 1945

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 : 115-116

Petrolisthes robsonae Glassell, 1945

Petrolisthes robsonae Glassell 1945: 227 , fig. 3; Haig 1957b: 10; Haig 1960: 57, pl. 18, fig. 2; Gore & Abele 1976: 24; Gore 1982: 19; Abele & Kim 1989: 22; Rodríguez et al. 2005: 565; García-Madrigal & Andréu-Sánchez 2009: 39, fig. 5A.

Material examined. None.Material listed on STRI collections website [https://stricollections.org/portal/collections]. Panama [Pacific]: 45 specimens, cl cw indet. ( USNM 270276 ), Darién, Río Tuira , slightly downstream topping bank from La Palma, leg. R.W. Bouchard, 14.02.1985 (det. B. Werding, 2004) .

Previous records from Panama. Hildebrand (1939, as P. armatus ( Gibbes, 1850)) ; Glassell (1945); Haig (1957b, 1960); Gore & Abele (1976); Gore (1982); Abele & Kim (1989).

Distribution. East Pacific: Mexico, El Salvador, Panama (Ciudad de Panamá, Panama Canal area, La Palma in Darién) and Ecuador (Haig 1957; Abele & Kim 1989; present study). West Atlantic: Panama ( Panama Canal area) ( Abele & Kim 1989; Rodríguez et al. 2005; see below).

Ecology. Intertidal and shallow subtidal, known depth range: 0–6 m; on muddy bottoms, under mangrove leaves, corals, rocks, etc., able to withstand great changes in salinity ( Haig 1960; 1968; García-Madrigal & Andréu- Sánchez 2009).

Remarks. Petrolisthes robsonae is allied to P. armatus , but can be distinguished from it by the presence of two teeth on the mesial side of the P1 carpus (vs. three teeth in P. armatus ); the reduced number of teeth on the dorsal surface of P2–P3 meri; and the presence of a distinct distoanterior spine on the P2–P4 carpi ( Haig 1960).

Although P. robsonae is currently considered as a transisthmian species, its distribution in the western Atlantic seems to be extremely limited and it is not clear whether the Caribbean population is well established. Haig (1960) reported a single specimen of P. robsonae from the lowest channel of Gatun Locks on the Caribbean entrance to the Panama Canal. According to the author, this single record was probably due to accidental introduction (since the species has not been reported elsewhere in the Atlantic) as its resistance to changes in salinity could enable some individuals to cross the Panama Canal. Abele and Kim (1989) reported four additional juvenile specimens of P. robsonae from the same area. More material of P. robsonae from the Panama Canal area is needed to confirm Haig’s hypothesis of P. robsonae being only an occasional migrant through the Panama Canal and not spreading out much further.