Planes minutus

Planes minutus (Linnaeus, 1758)

(Fig. 51C, D)

Cancer minutus Linnaeus, 1758: 625 [Type locality: “in Pelagi Fuco natante”].

Nautilograpsus major MacLeay, 1838: 66 [Type locality: Cape of Good Hope].

Planes cyaneus Dana, 1851b: 250 [Type locality: “in mare Pacifico”, i.e. Pacific Ocean, 28°N, 174°E ”].

Trindade specimens. 1 ovigerous female (MZUSP 40350), Trindade Island, Praia da Calheta, J.B. Mendonça coll., 2.xii.2014, on drifting roape. 1 ovigerous female (MZUSP 40257), ibidem, 20°30’28.89’’S, 29°18’37.76”W, J.B. Mendonça coll., 11.xii.2017, on washed log, low tide. 1 male, 5 females (adult and juveniles) (MZUSP 40347), ibidem, Praia das Tartarugas, 20°31’03.8’’S, 29°18’20.7”W, J.B. Mendonça coll., 12.vii.2012, on washed buoy. 1 male, 2 females, 2 juveniles (MZUSP 40341), 2 males, 5 juveniles (MZUSP 33828), ibidem, Praia dos Andradas, 20°30’45.7’’S, 29°18’21.9”W, J.B. Mendonça coll., 28.iii.2014, washed ashore. 2 males, 1 juvenile (MZUSP 40331), ibidem, C.H. Guimarães coll., 29.i.2012, stranded shoe.

Size of largest male: cl 19 mm, cw 20 mm; largest female: cl 20 mm, cw 21 mm.

Comparative material examined. Planes minutus: United States: 2 males, 1 female (USNM 4558), off Martha’s Vineyard, 39°49’25”N, 69°49’W, United States Fish Commission stn 937 coll., 4.viii.1881, surface [F.A. Chace det.]. Europe: 2 males (MZUSP 42001), Saint Tropez, Pampelonne, iv. 2009. Central Atlantic: 2 males, 2 females (USNM 112487), St. Helena, off Rupert’s Bay, A. Loveridge coll., 11.ii.1963, from buoy [F.A. Chace det. as P. major]. Brazil: São Paulo: 1 male (MZUSP 913), São Sebastião, E. Garbe coll., 1915. 1 male (MZUSP 8334), São Sebastião, Praia do Araçá, A. Fransozo coll., 25.ix.1981. 1 male (MZUSP 9084), ibidem, Baraqueçaba, S. A. Rodrigues coll., 3.x.1987. 1 male (MZUSP 4174), Bertioga, Praia de Guaratuba, F. Val, coll., 1971. 1 male, 1 ovigerous female (MZUSP 1413), Itanhaém. R. Sptiz coll., viii.1927. 1 female (MZUSP 914), Iguape, R. Krone coll., 1900 [M.J. Rathbun id., 1918, as P. cyaneus]. 1 male, 1 ovigerous female (MZUSP 24677), Juréia-Itatins, R. B. Pettan coll., 17.ix.2011, stranded.

Distribution. Several authors recorded Planes minutus as P. cyaneus or P. major. Western Atlantic: Gulf of Mexico, Brazil (Piauí, Rio Grande do Norte to Rio Grande do Sul), Uruguay and northern Argentina. Brazilian oceanic islands (Rocas Atoll and Trindade) (Chace 1951; 1966; Shirley 1974; Juanic 1976; Manning & Holthuis 1981; Melo 1996; Spivak & Bas 1999; Prado & Melo 2002; Lima et al. 2010; Pons et al. 2011; Spivak et al. 2019). This is the first record of P. minutus from Trindade. Central Atlantic: Saint Helena (Chace 1966). Mediterranean Sea (Manning & Holthuis 1981). Eastern Atlantic: recorded from Gabon by Crosnier (1967) (see also Pfaller et al. 2019b and comments from Manning & Holthuis 1981, as P. cyaneus). Eastern Pacific and Indian Ocean (Chace 1951; Manning

& Holthuis 1981; Vanini & Valmori 1981; Pfaller et al. 2019b). chelys imbricata (Linnaeus), Chelonia mydas (Linnaeus) and Lepidocheles olivacea (Chace 1951; Carranza et al. 2003; Bugoni et al. 2007; Pons et al. 2011). One single loggerhead turtle was found to carry up to five crabs (Pons et al. 2011), usually above the tail and beneath the carapace, more rarely among the epibionts on the host’s carapace. Heterosexual pairs and megalopae, juveniles singletons associated or not with adult crabs occur on turtles (Frick et al. 2004; Frick et al. 2011). Crabs are infrequently found associated with nesting sea turtles (Pfaller et al. 2019b). Planes minutus also colonizes plant material (Sargassum) and a large variety of flotsam including buoys (Pons et al. 2011), drifting roape, washed materials such as log, buoy and shoe (this study). Fishing buoys colonized by crabs after being left in the water for only approximately 12 hours were taken as an indication that crabs rapidly move between substrates and colonize whatever substrates are available (Pons et al. 2011). Planes minutus feeds upon the turtles’ epibiotic community composed primarily of neustonic invertebrates and algae (Davenport 1994; Frick et al. 2004). Ovigerous females obtained from turtles were carrying 8,934 eggs in average (Frick et al. 2004); only the first zoeal stage is known to date (Cuesta et al. 1997).

Remarks. The species of Planes are easily confused with one another. Chace (1951) carried out an in-depth revision of the genus and provided a synopsis of the characters that best differentiate the species in this genus. Planes minutus (Fig. 51C, D) and P. marinus are both provided with setae on the upper anterior margin of the propodi of P2–P5 forming a natatory fringe (Chace 1966) (natatory fringe worn away in the specimen P. marinus MZUSP 40330 from Trindade, Fig. 51A, B). Planes minutus and P. marinus can be differentiated from each other by a combination of characters which includes (characters for in P. marinus between brackets): 1) carapace about as wide as long (longer than wide in the Trindade specimens) (vs carapace distinctly wider than long) and 2) carapace laterally

The juveniles of P. minutus recovered at Trindade have nearly square carapaces and natatory fringes on P2–P5 already at cl 3.9 mm and cw 4.1 mm (e.g. MZUSP 40341).

The specimens from Brazil previously identified by Prado & Melo (2002) with P. cyaneus were reassessed and reidentified as P. minutus (see above under comparative material).