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Grapsus grapsus

Grapsus grapsus (Linnaeus, 1758)

Common Names

Sally Lightfoot crab (English)

Languages: English

Description

Behaviour

Johnson (1965) studied Grapsus grapsus on Oahu, Hawaii, and found that crabs in the study area spent nearly two thirds of their time inactive and hiding in crevices and nearly 20% of their time feeding. They were most active during low tide.

Graspus graspus often feed among rocks swept by surf, flattening themselves against the rock just before each wave hits. These crabs have complex intraspecific visual displays and displaying individuals are the last to prepare for each wave and the first to rise up again after each wave (Wright et al. 1968). When moving about, G. grapsus is strikingly fast and agile.

Author(s): Shapiro, Leo
Rights holder(s): Shapiro, Leo

Development

Guerao et al. (2001) describe the first zoeal larval stage of G. graspus and discuss implications regarding relationships with close relatives.

Author(s): Shapiro, Leo
Rights holder(s): Shapiro, Leo

Morphology

Grapsus grapsus has a carapace up to ~8 cm. It is highly variable in color and pattern, but often bright red, orange, and brown; young individuals are dark brown or black.

Author(s): Shapiro, Leo
Rights holder(s): Shapiro, Leo

Physiology

Grapsus grapsus is an excellent osmoregulator: it can maintain the water balance of its haemolymph (internal body fluid) within narrow limits in the face of external salinity ranging from 50% to 125% (Evans 2009) or 150% (Little 1990) seawater. This allows it to function well in a wide range of microhabitats along the shoreline.

Beninger and Larocque (1998) describe an accessory sex gland that in Grapsus grapsus produces a neutral mucopolysaccharide which they suggest may function (1) as a lubricant to reduce mechanical wear of the ejaculatory canal by the second gonopod during copulation, and (2) to reduce the viscosity of the ejaculate from the vas deferens as it enters the narrow ejaculatory canal.

Author(s): Shapiro, Leo
Rights holder(s): Shapiro, Leo

Ecology

Habitat

Rocky shorelines and beaches at and above the sprayline (Henderson 2002).

Author(s): Shapiro, Leo
Rights holder(s): Shapiro, Leo

Distribution

Florida to Brazil and Mexico to Peru; Galapagos Islands (Henderson 2002).

Author(s): Shapiro, Leo
Rights holder(s): Shapiro, Leo

Associations

Grapsus grapsus has been reported as prey of a variety of animals including the Galapagos Lava Heron (Butorides striata sundevalli) (Kushlan 2009) and other large birds, the chain moray (Echidna catenata) (Sazima and Sazima 2004), octopus (Octopus sp.) (Sazima and de Almeida 2009), and Kemp's Ridley sea turtle (Lepidochelys kempii)  (Ernst and Lovich 2009).

Food consists largely of grazed algae (see, e.g., Vinueza et al. 2006), but G. grapsus is an omnivorous and opportunistic feeder, consuming items as diverse as bat guano and probably dead bats (Lopez-Foment 1981, cited in Arroyo-Cabrales and Jones 1988), green sea turtle hatchlings (Chelonia mydas) (Ernst and Lovich 2009), masked booby chicks (Sula dactylatra) (Anderson 1989), and food remains, broken eggs, and dead birds in Brown Booby (Sula leucogaster) colonies (Gianuca and Vooren 2007).

Beebe (1924) reported G. grapsus removing (and presumably consuming) ticks (Amblyomma darwini) from a Marine Iguana (Amblyrhynchus cristatus). This may indicate a symbiotic relationship benefiting both crab and lizard.

Author(s): Shapiro, Leo
Rights holder(s): Shapiro, Leo

References

Anderson, D. L. (1989).  The role of hatching asynchrony in siblicidal brood reduction of two booby species. Behavioral Ecology and Sociobiology. 25, 363-368.
Arroyo-Cabrales, J., & Jones J. K. (1988).  Balantiopteryx plicata. Mammalian Species. 1-4.
Beebe, W. (1924).  Galapagos: World's End. New York: G.P. Putnam's Sons.
Beninger, P. G., & Larocque R. (1998).  Gonopod tegumental glands: a new accessory sex gland in the Brachyura. Marine Biology. 132, 435-444.
Ernst, C. H., & Lovich J. E. (2009).  Turtles of the United States and Canada. Baltimore, Maryland: Johns Hopkins University Press .
Evans, D. H. (2009).  Osmotic and Ionic Regulation: Cells and Animals. Boca Raton, FL: CRC Press, Taylor & Francis Group.
Gianuca, D., & Vooren C. M. (2007).  Abundance and behavior of the sally lightfoot crab (Grapsus grapsus) in the colony of the brown booby (Sula leucogaster) in the Sao Pedro and Sao Paulo Archipelago. Invest. Mar. Valparaiso. 35, 121-125.
Guerao, G., Schubert C. D., & Cuesta J. A. (2001).  The first zoeal stage of Grapsus grapsus L. and Geograpsus lividus (H. Milne Edwards) (Decapoda, Grapsidae) from the western Atlantic. Nauplius. 9, 111-121.
Henderson, C. L. (2002).  Field Guide to the Wildlife of Costa Rica. Austin, Texas: University of Texas Press.
Johnson, G. E. (1965).  An ethological study of the rock crab, Grapsus grapsus (family Grapsidae) with emphasis on behavior variations during ontogeny and with habitat. American Zoologist. 5, 632.
Kushlan, J. A. (2009).  Foraging and plumage coloration of the Galapagos Lava Heron (Butorides striata sundevalli). Waterbirds. 32, 415-422.
Little, C. (1990).  The Terrestrial Invasion: an Ecophysiological Approach to the Origin of Land Animals. Cambridge, UK: Cambridge University Press.
Lopez-Forment, W. (1981).  Algunos aspectos ecologicos del mur cielago Balantiopteryx plicata plicata Peters, 1867 (Chiroptera: Emballonuridae) en Mexico. An. Inst. Biol., Univ. Nac. Auton., Mexico, Ser. Zool. . 50, 673-699.
Sazima, I., & deAlmeida L. B. (2008).  The bird kraken: octopus preys on a seabird at an oceanic island in the tropical West Atlantic. Marine Biodiversity Records. 1,
Sazima, I., & Sazima C. (2004).  Daytime hunting behaviour of Echidna catenata (Muraenidae): why chain morays foraging at ebb tide have no followers. Aqua Journal of Ichthyology and Aquatic Biology. 8, 1-8.
Vinueza, L. R., Branch G. M., Branch M. L., & Bustamente R. H. (2006).  Top-down herbivory and bottom-up El Nino effects on Galapagos rocky-shore communities. Ecological Monographs. 76, 111-131.
Wright, H. O. (1968).  Visual displays in brachyuran crabs: field and laboratory studies. American Zoologist. 8, 655-665.