Petrolisthes marginatus Stimpson 1859

Petrolisthes marginatus Stimpson, 1859

(Fig. 5 E, F)

Petrolisthes marginatus Stimpson 1858: 227 [nomen nudum].

Petrolisthes marginatus Stimpson 1859: 74 [type locality Florida, United States]. Porcellana cessacii A. Milne-Edwards 1878: 229 [type locality Cape Verde]. Petrolisthes cessacii.— A. Milne-Edwards and Bouvier 1900: 346.— Melo 1999: 250.

Material examined. Caribbean Sea, 1956: 1 ovigerous female (USNM 270426). Guadeloupe: Rat Island, Pointre a Pitre, WL Schmitt coll., 30 March 1956: 1 ovigerous female (USNM 270427); Ibidem, 30 March 1956: 1 male (USNM 270428). Trinidad and Tobago: Tobago: 1 male, 1 ovigerous female (USNM 268887); Buccoo Reef, middle portion off high ground, 0 6 April 1959: 1 ovigerous female (USNM 270429); Ibidem, 0 9 April 1959: 1 female (USNM 270430). Panama: Golfo de San Blás, Pico Feo, 0 7 April 1973, 1 m: 1 male, 1 ovigerous female (USNM 184919). Curaçao: Vista Alegre, Allan Hancock Pacific Expedition, R /V “ Velero III”, 23 April 1939, shore: 3 males, 2 females (USNM 1163337). Venezuela: Isla Aves, 15°40’N, 63°36’W, S Raney coll., 14 September 1975: 1 female (USNM 155663). Brazil: Pernambuco, Fernando de Noronha, Praia do Atalaia, 31 December 1963: 1 male (MZUSP 24795); Espírito Santo, Trindade Island, B Prazeres coll., 1976: 1 male (MZUSP 29825); Praia das Tartarugas, 20°30’54.1’S, 29°18’18.2”W, tidepool and rocky shore, JB Mendonça coll., 0 5 July 2013: 2 males, 3 female (MZUSP 34648); Praia do Lixo, 20°31’29.8’S, 29°19’43.9”W, JB Mendonça coll., 25 October 2014, 13.7 m: 1 ovigerous female (MZUSP 34747); Ibidem, left wall, JB Mendonça coll., 0 4 November 2014, 15.4 m: 1 male (MZUSP 34753). Ascension Island: 26 November 1985, 4 m: 1 male (USNM 256566); Georgetown, Fort Hayes, Rocky Point, RB Manning and Rogers coll., 22 May 1971: 2 juveniles (USNM 1292596); Collyer Point, K Jourdan coll., 15 July 1976: 1 female (USNM 1277841); McArthur Point, 11 July 1976: 8 males, 4 females, 1 ovigerous female (USNM 1292595); Ibidem, associated with rocks, RB Manning et al. coll., 11 July 1976: 1 male, 1 ovigerous female (USNM 1295570); Ibidem, Southwest Bay, in sandy bottom, tidepool, S Olson coll., 12 July 1970: 1 male (USNM 1277811); Ibidem, northern edge of South West Bay, Turtle Shell Beach, tide pool with sand bottom in lava flow, May 1971: 1 juvenile (USNM 1277843). Annobon Island: 01°25’S, 05°38’E, st. 271, Pillsbury coll., 19 May 1965, shore: 4 males, 2 females, 1 ovigerous female (USNM 121055); 01°24’S, 05°37’E, st. 273, Pillsbury coll., 19 May 1965, 2 m: 1 ovigerous female (USNM 121056). Senegal: Th Monod coll., 30 November 1947: 2 males (USNM 98961).

Size. Largest male, cl 8.4, cw 8.6 (MZUSP 34648). Largest female, cl 9.4, cw 9.8 (MZUSP 34747).

Coloration (Figs. 5 E, F). Carapace dorsal surface, Mxp3 lateral surface, P1–5 ischia and meri, and dorsal surface of the abdomen covered with numerous magenta dots of different sizes over a light pinkish background. P2–4 carpi, propodi and dactyli are entirely dark magenta (Fig. 5 E). Ventral surface regularly magenta, except for one large, white, rounded spot on the Mxp3 coxa.

Habitat. Petrolisthes marginatus has been found in crevices on reefs and other rough substrates, under rocks, from the littoral down to depths of 3 m (Veloso & Melo 1993; Ferreira & Melo 2016). In Trindade Island P. marginatus was caught in tide pools and from depths down to 15.4 m.

Distribution. Western Atlantic—United States, Florida; Gulf of Mexico; Puerto Rico; Virgin Islands, Saint Thomas; Barbados; Curaçao and Bonaire; Trinidad and Tobago; Nicaragua; Panama, Gulf of San Blás; Colombia, Providencia, Rosario and Santa Marta Islands; Venezuela, Blanquilla, Los Roques, Aves, Margarita and Cubagua Islands; and Brazil (Fernando de Noronha and Trindade Islands). Eastern Atlantic – Africa: Senegal to Ghana and oceanic islands of Cape Verde, Annobon and Ascension (Werding 1977; Ferreira 2009; Ferreira & Melo 2016).

Remarks. Petrolisthes marginatus is amphi-atlantic in distribution (see also Gore 1983). However, all previous records of P. marginatus str. s. from the Brazilian continental shelf are probably erroneous as either there is no voucher specimen for them or the species has been mistaken for other species of Petrolisthes occurring in the area with more than 3 teeth in the P1 carpus, such as P. amoenus, P. galathinus (Bosc, 1802) and P. rosariensis Werding, 1978. Actually, the only confident records of P. marginatus to the southwestern Atlantic are from the oceanic islands of Fernando de Noronha and Trindade.

Indeed, Melo (1999) first included Maranhão, Brazil, as part of the geographic range of P. marginatus (as P. cessacii), but referred to no voucher specimen for it; all subsequent records of P. marginatus from Maranhão (Coelho et al. 2007; Ferreira 2009; Ferreira & Melo 2016) were in fact based upon Melo (1999). The Santos et al. (2012) record of P. marginatus from Bahia, Brazil, proved to be referable to P. amoenus and P. rosariensis (see under comparative material examined).

Stimpson's (1859) too brief description of Petrolisthes marginatus lead others astray: A. Milne-Edwards' (1878) Petrolisthes cessacii actually proved to be but a synonym of P. marginatus, while Benedict's (1901) P. marginatus was shown to belong to a new species, namely Petrolisthes dissimulatus Gore, 1983. Petrolisthes marginatus differs from P. dissimulatus in having: (1) one epibranchial spine (versus two epibranchial spines in P. dissimulatus); (2) the carapace oblong, longer than broad (versus carapace subcircular, as broad as long in P. dissimulatus); (3) the front and the median frontal lobe prominent (versus front and median frontal lobe broader and less prominent in P. dissimulatus); (4) P1 slender (versus P1 more robust in P. dissimulatus); and (5) P1 merus with a single, distal spine in ventral view (versus P1 with two meral distal spines in ventral view in P. dissimulatus). Additionally, P. marginatus is a larger species (cw 7.0–15.5) while, in contrast, P. dissimulatus is much smaller (cw 3–4.5).

Petrolisthes marginatus has been erroneously recorded from several areas in the tropical eastern Pacific (Haig 1960). Pacific specimens were re-examined by Chace (1962) and assigned to a new species, Petrolisthes haigae Chace, 1962, referred to as a trans-Panamanian congener of P. marginatus. Petrolisthes marginatus differs from P. haigae in the: (1) front narrower and oblong (versus front broader and round in P. haigae); (2) median frontal lobe more prominent and narrower (versus median frontal lobe shorter and broader in P. haigae); and (3) P1 slender, with the lateral margin of propodus not so round, nearly straight versus P1 more robust, with the lateral margin of propodus rounded in P. haigae).