Grapsus grapsus ( Linnaeus, 1758 )

TAVARES, MARCOS & MENDONÇA, JOEL BRAGA DE JR., 2022, Brachyuran crabs (Crustacea, Decapoda) from the remote oceanic Archipelago Trindade and Martin Vaz, South Atlantic Ocean, Zootaxa 5146 (1), pp. 1-129 : 92-93

Grapsus grapsus ( Linnaeus, 1758)

( Figs. 49A–D )

Cancer grapsus Linnaeus, 1758: 630 [pro parte– only material from “America”]

Trindade specimens. 1 male, 2 females (1 ovigerous) ( MZUSP 16135 ) , Trindade Island, Enseada dos Portugueses, M. Tavares and F. Kurtz coll., 13.viii.1986, low tide . 1 male, 1 ovigerous female ( MZUSP 27941 ) , ibidem, Praia dos Andradas, 20°30’45.7’’S, 29°18’21.9”W, J.B. Mendonça coll., 28.vi.2012, rocky tide pool . 3 juvenile males, 1 juvenile female, 1 juvenile ( MZUSP 40333 ) , ibidem, J.B. Mendonça coll., 21.vii.2013, rocky tide pool. 1 male juvenile ( MZUSP 41057 ) , 1 juvenile ( MZUSP 40325 ) , ibidem, 20°30’37.6’’S, 29°18’28.1”W, J.B. Mendonça coll., 20.xi.2017, rocky tide pool. 1 male ( MZUSP 32608 ) , 1 female ( MZUSP 32607 ) , 1 ovigerous female ( MZUSP 32605 ) , ibidem, Praia das Tartarugas, 20°31’01.5’’S, 29°18’11.8’’W, J.B. Mendonça coll., 25.v.2014, low tide . 2 juvenile males ( MNZUSP 40238 ) , 20°31’03.8’’S, 29°18’08.4’’W, J.B. Mendonça coll., 10.vi.2012, low tide at night. 2 juveniles ( MZUSP 41261 ) , ibidem, Ponta Norte, Crista do Galo , 20°29’22.1’’S, 29°20’03.1”W, J.B. Mendonça coll., 16.vi.2016, rocky tide pool, 1.5 m .

Size of largest male: cl 58 mm, cw 66 mm; largest female: cl 58 mm, cw 64 mm.

Comparative material examined. Grapsus grapsus : Brazil: Central Atlantic : 1 male, 1 ovigerous female ( MZUSP 41258 ), São Pedro and São Paulo Archipelago, 00°55’02’’N, 29°20’44’’W, 1146 km off the coast of northeastern Brazil, M. Tavares coll., 4–5.iii.2018, rocky tide pool. Rocas Atoll: 1 male ( MZUSP 5306 ), C. Jesus coll., 6.vii.1981. Fernando de Noronha Archipelago: 1 male ( MZUSP 7248 ), S. Rodrigues coll., 1.xi.1985. Grapsus tenuicrustatus (Herbst, 1783) : Society Islands : 1 male ( MZUSP 41259 ), Tupai Atoll, near Bora Bora, stn 13, 16°15’S, 15°148’ W, J. Poupin coll., 13.v.1991, on the reefs, JP leg. Grapsus albolineatus Lamarck, 1818 : New Caledonia: 1 male ( MZUSP 41260 ), Noumea, Baie des Citrons , M. Tavares coll., 21.ix.1993, low tide .

Distribution. Western Atlantic: Bermuda, Florida, Gulf of Mexico, Antilles, Colombia, Venezuela and Brazil (Insular: São Pedro and São Paulo Archipelago, Rocas Atoll, Fernando de Noronha and Trindade ( Moreira 1901; Rathbun, 1918; Oliveira 1945; 1951; Chace & Hobbs 1969; Holthuis et al. 1980; Rodriguez 1980; Lemaitre 1981; Felder et al. 2009). Of note, Moreira (1901: 39) clearly stated that his material of Grapsus grapsus came from the oceanic archipelago of Fernando de Noronha. This record should not be confused with coastal Penambuco, under whose jurisdiction the archipelago falls into ( Chace & Hobbs 1969). It is true, however, that this species occasionally make it to the Brazilian coast, as exemplified by one female caught in 10 September 1965, in Mucuripe, Ceará ( Fausto Filho 1966). Eastern Pacific: from Baja California to Central Chile (including Clipperton, Malpelo the Galapagos islands, and Juan Fernández) ( Garth 1946; Poupin et al. 2009).

Ecological notes. In the small and arid São Pedro and São Paulo Archipelago (SPSP) the nearshore colony of the brown booby, Sula leucogaster (Boddaert) , share a small space with a dense population of Grapsus grapsus (M. Tavares pers. obs. 2018). The crab population in Belmont, the largest islet in SPSP, has been estimated in as much as 5,600 individuals ( Freire et al. 2009) for which S. leucogaster is an important food source. Gianuca & Vooren (2007) observed G. grapsus feeding on detritus and dry excrement, feathers, regurgitated fish, dead birds, material adhered to egg shells, and preying upon live nestlings of S. leucogaster .

In contrast, in Trindade (this study) the seabirds’colonies are generally established far from the shore, hence out of reach for species depending upon nearshore habitats (see above under the land crab Johngarthia lagostoma ).

Grapsus grapsus feeds on pink algal encrustations in the splash zone and preys upon cirripeds and mytilid mussels when available (SPSP, Holthuis et al. 1980; Peru, Romero 2003). In Trindade, it occasionally visit freshwater streams, some times along with Johngarthia lagostoma (see Arai et al. 2017). Smaller crabs walk away from large ones. Fully red crabs were observed preying upon younger green individuals. Cannibalism was much higher (24%) in SPSP ( Freire et al. 2011) than in Peru (5%) ( Romero 2003), apparently as a result of the high density of crabs on the small SPSP. In Trindade (this study), G. grapsus feeds upon algal films exposed during the low tide (Fig. 49A, D), fish carcasses, and newborn sea turtles (Fig. 49B, C). Grapsus grapsus has been reported preying upon baby sea turtles in Ascension and Fernando de Noronha as well (Manning & Holthuis 1990; Bellini 1996, respectively).

During the mating, the male is under the female (sternum to sternum), which is held tightly by the male’s chelipeds. Females attained functional sexual maturity at a smaller size (cw 31 mm) than males (cw 51 mm) and males had at least some red color in the carapace and were larger than females in all mating pairs observed by Freire et al. (2009; 2011), whereas coloration apparently is not specific to sexual maturity in females. Females carry about 23,000 eggs in average and approach the swash zone to hydrate the eggs. The prevalence of ovigerous females was greater during the summer and spring in SPSP ( Freire et al. 2009).

Hartnoll (2009) found indications that molting occurs in air (not in water) in G. adscensionis .

Grapsus grapsus is notorious for its leaping behavior. Araújo (2014) reported on both adults and juveniles males and females jumping from a rock to another rather than entering the water. The leaping behavior has been observed in other species as well (e.g. Deudero et al. 2005); the tree crab Aratus pisonii (H. Milne Edwards, 1837) for instance jumps from the tree to the water to escape from threats (M. Tavares pers. obs.).

Remarks. Nicoll (1908: 3), on Grapsus grapsus from the São Pedro and São Paulo Archipelago made an early reference to the green color of younger crabs, while noting that the larger ones were “bright vermilion” ( Fig. 49A–D ). Morphologically, juveniles (e.g. cl 6 mm, cw 7mm) markedly differ from adults in that the carapace is subquadrate and the orbital, antennal and antennular cavities are continuous with one another. In contrast, developed specimens have rather discoidal carapaces and larger epistomes, so much that it obliterates most of the antennal fossa and hence the first antennular article is no longer visible externally. The antennal fossa shows as a wide slitlike, oblique cavity separated from the antennal cavity. The antenna is almost excluded from the orbit. The interantennular septum is a wide inverted U in juveniles, whereas it is almost entirely sunken into the front, hence poorly visible, in full grown specimens. Juveniles have the cheliped carpus provided with an ordinary spine on the mesial margin instead of a broad, flattened sharp-tipped spine of the adults ( Fig. 49A ). Juveniles have the globular urinary article with a remarkably large orifice through which the antennary gland opens, so typical of the species, already at cl 6 mm and cw 7 mm. This characteristic remains in full grown specimens.

Lobo (1919: 147) and Moreira (1920) mistook G. grapsus for Goniopsis cruentatus [sic], which according to Lobo’s report was found in great numbers on the beaches and rocks [sic] near the water. Likewise, Moreira’s (1920) record of Geograpsus lividus (H. Milne Edwards) probably refers to a young specimen of G. grapsus . Oliveira (1951) listed G. grapsus from Trindade (but not G. cruentata or G. lividus ) ( Table 5 ).

Türkay (1982) and Manning & Chace (1990) considered G. grapsus and G. adcensionis distinct species (Türkay actually used the name Grapsus webbi H. Milne Edwards, 1853 , instead of G. adscensionis ), a decision later supported by larval morphology ( Guerao et al. 2001).

Figures

FIGURE 49. A–D, Grapsus grapsus (Linnaeus, 1758), Trindade Island.A, C, D, May 2012. B, June 2016. Note in (A) flattened sharp-tipped spine of the adults (arrow). Photographs by J.B. Mendonça.