Overview

Brief Summary

Overview

The Sally Lightfoot crab, sometimes called the red rock crab,(1) is a common sight on rocky beaches on the Atlantic and Pacific coastlines of the Americas, from Florida down to Brazil and Mexico down to Chile,(1,2,3,4) as well as on nearby islands such as the Galápagos (1,2,3,4,5) and along the Atlantic coast of Africa.(2,6) Adults, which have carapace widths of around 5-8 centimeters, are generally bright red, brown, or orange with various patterns, while young Sally Lightfoot crabs are darker-colored.(2,4) Sally Lightfoot crabs spend most of their time hiding away in rock crevices,(4,7) but when they come out to feed—primarily during low tide(4,5,7) and during less sunny parts of the day (3)—they move with the remarkable agility and speed that give them their common name.(2,4) While they feed, powerful waves often crash over them, but they are able to withstand these by flattening themselves against rocks and holding on tightly.(2,4) Although these crabs mainly eat red and green algae,(2,4,5) they will eat practically anything they can get,(4) including mussels, barnacles, other crabs, young sea turtles, dead fish, and the young of seabirds such as boobies.(3,4) They also clean the beach of other material such as broken eggs and bird and bat droppings.(3,4) Through their role as predators, grazers, and cleaners, and also through their role as prey for many animals including large birds, octopuses, Kemp’s Ridley sea turtles, and chain moray eels,(4) Sally Lightfoot crabs can play an important part in coastal ecosystems.(3,5)

  • 1. Johnson, Markes E., Paul M. Karabinos, and Victor Mendia. “Quaternary Intertidal Deposits Intercalated with Volcanic Rocks on Isla Sombrero Chino in the Galápagos Islands (Ecuador).” Journal of Coastal Research 26.4 (2010): 762-768.
  • 2. Davis, Christopher. “Marine Invertebrates of Bermuda: Sally Lightfoot Crab (Grapsus grapsus).” The Cephalopod Page. 6 Jul. 2011. http://www.thecephalopodpage.org/MarineInvertebrateZoology/Grapsusgrapsus.html
  • 3. Gianuca, Dimas and Carolus Maria Vooren. “Abundance and Behavior of the Sally Lightfoot Crab (Grapsus grapsus) in the Colony of the Brown Booby (Sula leucogaster) in the São Pedro and São Paulo Archipelago.” Investigaciones Marinas 35.2 (2007): 121-125.
  • 4. Shapiro, Leo. “Grapsus grapsus (Linnaeus, 1758).” EOL Species Rapid Response. 6 Jul. 2011. http://eolspecies.lifedesks.org/pages/15872
  • 5. Vinueza, L. R., G. M. Branch, M. L. Branch, and R. H. Bustamante. “Top-Down Herbivory and Bottom-Up El Niño Effects on Galápagos Rocky-Shore Communities.” Ecological Monographs 76.1 (2006): 111-131.
  • 6. Kensley, B. F. “The Occurrence of Grapsus grapsus tenuicruistatus (Herbst) at the Tsitsikama Coastal National Park (Decapoda, Brachyura, Grapsidae.” Koedoe 13 (1970): 127-130.
  • 7. Johnson, Garland E. “An Ethological Study of the Rock Crab, Grapsus grapsus (Family Grapsidae) with Emphasis on Behavior Variations during Ontogeny and with Habitat.” American Zoologist 5.4 (1965): 632.
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Introduction

Sally Lightfoot is the name of a type of crab that lives on the Atlantic and Pacific coastlines of the Americas, from Florida down to Brazil and Mexico down to Chile,(1,2,3,4) as well as on nearby islands such as the Galápagos (1,2,3,4,5) and along the Atlantic coast of Africa.(2,6) Their backs can measures about 5-8 centimeters across, and their body is bright red with various patterns (though their bodies are darker-colored when they are young), and have ten legs.(2,4) Sally Lightfoot crabs, also known as red rock crabs(1) (although the adults can really be many colors from red to orange to brown(4)), spend most of their time hiding away in rock crevices.(4,7) But when they come out to feed—mainly during low tide (4,5,7) and less sunny parts of the day (3)—they move with the remarkable agility and speed that give them their name, “Sally Lightfoot.”(2,4) While they eat, powerful waves often crash over them, but they survive this by flattening themselves against rocks and holding on tightly.(2,4) These crabs mainly eat red and green algae,(2,4,5) but will gobble down practically anything they can get,(4) including mussels, barnacles, other crabs, young sea turtles, dead fish, and the young of seabirds such as boobies.(3,4) Their big appetite means that they also help clean the beach of material such as broken eggs and dried bird and bat droppings.(3,4) Through their role as predators, grazers, and cleaners, and also through their role as prey for many animals including large birds, octopuses, Kemp’s Ridley sea turtles, and chain moray eels,(4) Sally Lightfoot crabs can be an important part of their environment.(3,5)

  • 1. Johnson, Markes E., Paul M. Karabinos, and Victor Mendia. “Quaternary Intertidal Deposits Intercalated with Volcanic Rocks on Isla Sombrero Chino in the Galápagos Islands (Ecuador).” Journal of Coastal Research 26.4 (2010): 762-768.
  • 2. Davis, Christopher. “Marine Invertebrates of Bermuda: Sally Lightfoot Crab (Grapsus grapsus).” The Cephalopod Page. 6 Jul. 2011. http://www.thecephalopodpage.org/MarineInvertebrateZoology/Grapsusgrapsus.html
  • 3. Gianuca, Dimas and Carolus Maria Vooren. “Abundance and Behavior of the Sally Lightfoot Crab (Grapsus grapsus) in the Colony of the Brown Booby (Sula leucogaster) in the São Pedro and São Paulo Archipelago.” Investigaciones Marinas 35.2 (2007): 121-125.
  • 4. Shapiro, Leo. “Grapsus grapsus (Linnaeus, 1758).” EOL Species Rapid Response. 6 Jul. 2011. http://eolspecies.lifedesks.org/pages/15872
  • 5. Vinueza, L. R., G. M. Branch, M. L. Branch, and R. H. Bustamante. “Top-Down Herbivory and Bottom-Up El Niño Effects on Galápagos Rocky-Shore Communities.” Ecological Monographs 76.1 (2006): 111-131.
  • 6. Kensley, B. F. “The Occurrence of Grapsus grapsus tenuicruistatus (Herbst) at the Tsitsikama Coastal National Park (Decapoda, Brachyura, Grapsidae.” Koedoe 13 (1970): 127-130.
  • 7. Johnson, Garland E. “An Ethological Study of the Rock Crab, Grapsus grapsus (Family Grapsidae) with Emphasis on Behavior Variations during Ontogeny and with Habitat.” American Zoologist 5.4 (1965): 632.
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Distribution

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

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Physical Description

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.

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Ecology

Habitat

St. Peter and St. Paul Archipelago Habitat

Among other ecoregions, this taxon occurs in St. Peter and St. Paul Rocks, a set of small rocky islands far out in the Atlantic Ocean between Brazil and the coast of West Africa. In particular, there are five islets, five very large rocks and a series of smaller skerries that comprise this formation.The rock type of this formation is ultramafic and not volcanic.

This is one of the few places on Earth where an underwater oceanic ridge breaks through the surface of the sea. This formation, also known as St. Peter and St. Paul Archipelago, is the second tallest deep sea mountain or megamullion. These isolated rocks function as a biogeographic oasis in the deep ocean, providing a prime niche for marine life to prosper nearer the ocean’s surface. While the islands are virtually devoid of terrestrial vegetation, the rich marine flora and fauna provides a food source to seabirds that reside and breed here.

Isolation from the mainland provides a habitat of significant ecological and biogeographical interest. More than 800 kilometers from South America, St. Peter and St. Paul Rocks (0°56’N, 29°21’W) land area is estimated to be only 15,000 square metres. Composed of mylonitic peridotite, the submarine mountain of which these rocks are the pinnacles extends 4000 metres into the ocean depths. St. Peter and St. Paul Rocks were  visited by Charles Darwin in 1832 on the first Beagle expedition.

The structure of the islets is a rugged serpentine surface, consisting of numerous fissures, pinnacles and ridgelines. The meager terrestrial vegetation that does occur includes simplistic marine grasses, mosses, fungus and algae. A filamentous blue-green algae, Lyngbya spp, and a minute green algae as Stichococcus bacillaris are example flora.The ocean floor structure in the vicinity of the formation is very irregular as well as steep and rocky; silt bottoms do not occur to the north and south until attaining a depth of approximately three km.

While terrestrial flora is scarce, the isolated islands provide habitat for a rich benthic and littoral marine biota. This food source supports many seabirds, which are the only vertebrate wildlife found on the islands. Breeding seabirds found on the Rocks during the 1971 survey included Brown booby (Sula leucogaster), Brown noddy (Anous stolidus), and Black noddy (Anous minutus). All life-cycle stages of the booby were found during this survey, suggesting that their breeding was aseasonal. The bird eggs often fall prey to Sally Lightfoot Crabs (Grapsus grapsus), a marine invertebrate that is present in large numbers on the islets. The invertebrate element of the Rocks’ food chain primarily consists of microbial feeders. These include protozoa, nematodes (Acrobeloides, Diploscapter and Panagrolaimus genera), bdellodes rotifers, and certain mites (Scheloribates spp.).

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Depth range based on 5 specimens in 1 taxon.

Environmental ranges
  Depth range (m): 1 - 1
 
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Rocky shorelines and beaches at and above the sprayline (Henderson 2002).

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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.

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Known predators

Grapsus grapsus is prey of:
Actinopterygii

Based on studies in:
Barbados (Littoral, Rocky shore)

This list may not be complete but is based on published studies.
  • F. Briand, unpublished observations
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Known prey organisms

Grapsus grapsus preys on:
detritus
Porifera
Spirobranchus giganteus
Ectoprocta

Based on studies in:
Barbados (Littoral, Rocky shore)

This list may not be complete but is based on published studies.
  • F. Briand, unpublished observations
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Life History and Behavior

Behavior

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.

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Growth

Development

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

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Physiology and Cell Biology

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.

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Grapsus grapsus

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 5
Species With Barcodes: 1
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Wikipedia

Grapsus grapsus

Grapsus grapsus is one of the most common crabs along the western coast of the Americas. It is known variously as, "red rock crab", "abuete negro", and along with crabs such as Percnon gibbesi as, "Sally Lightfoot".

Distribution[edit]

Grapsus grapsus is found along the Pacific coast of Mexico, Central America, South America (as far south as northern Peru), and on nearby islands, including the Galápagos Islands. It is also found along the Atlantic coast of South America, but is replaced in the eastern Atlantic Ocean (Ascension Island and West Africa) by its congener Grapsus adscensionis.[2]

Description[edit]

Grapsus grapsus is a typically shaped crab, with five pairs of legs, the front two bearing small, blocky, symmetrical chelae. The other legs are broad and flat, with only the tips touching the substrate. The crab's round, flat carapace is slightly longer than 8 centimetres (3.1 in). Young G. grapsus are black or dark brown in colour and are camouflaged well on the black lava coasts of volcanic islands. Adults are quite variable in colour; some are muted brownish-red, some mottled or spotted brown, pink, or yellow.

Taxonomy[edit]

Grapsus grapsus was first described by Carl Linnaeus in the 1758 10th edition of Systema Naturae as "Cancer grapsus".[1]

The species Grapsus grapsus and G. adscensionis were not separated until 1990. The latter is found in the eastern Atlantic, while the former is not.[3] While the validity of the separation into two species has been questioned, there are constant morphological differences in the colouration of the pereiopods and the form of the first zoea larva, and no evidence for any genetic connection between the two populations, and they are generally treated as separate species.[4]

Santa Cruz Island, Galapagos Islands

Ecology and behaviour[edit]

Two juveniles in the Galápagos Islands


Adult in the Galápagos Islands

This crab lives amongst the rocks at the often turbulent, windy shore, just above the limit of the sea spray. It feeds on algae primarily, sometimes sampling other plant matter and dead animals. It is a quick-moving and agile crab, and hard to catch. Not considered very edible by humans, it is used as bait by fishermen.

G. grapsus has been observed in an apparent cleaning symbiosis taking ticks from marine iguanas on the Galápagos Islands.[5]

Grapsus grapsus was collected by Charles Darwin during his voyages on HMS Beagle,[6] and also by the first comprehensive study of the fauna of the Gulf of California, carried out by Ed Ricketts, together with John Steinbeck and others. Steinbeck records:[7]

Many people have spoken at length of the Sally Lightfoots. In fact, everyone who has seen them has been delighted with them. The very name they are called by reflects the delight of the name. These little crabs, with brilliant cloisonné carapaces, walk on their tiptoes, They have remarkable eyes and an extremely fast reaction time. In spite of the fact that they swarm on the rocks at the Cape [San Lucas], and to a less degree inside the Gulf [of California], they are exceedingly hard to catch. They seem to be able to run in any of four directions; but more than this, perhaps because of their rapid reaction time, they appear to read the mind of their hunter. They escape the long-handled net, anticipating from what direction it is coming. If you walk slowly, they move slowly ahead of you in droves. If you hurry, they hurry. When you plunge at them, they seem to disappear in a puff of blue smoke—at any rate, they disappear. It is impossible to creep up on them. They are very beautiful, with clear brilliant colors, red and blues and warm browns.



Man reacts peculiarly but consistently in his relationship with Sally Lightfoot. His tendency eventually is to scream curses, to hurl himself at them, and to come up foaming with rage and bruised all over his chest. Thus, Tiny, leaping forward, slipped and fell and hurt his arm. He never forgot nor forgave his enemy. From then on he attacked Lightfoots by every foul means he could contrive and a training in Monterey street fighting has equipped him well for this kind of battle). He hurled rocks at them; he smashed at them with boards; and he even considered poisoning them. Eventually we did catch a few Sallys, but we think they were the halt and the blind, the simpletons of their species. With reasonably well-balanced and non-neurotic Lightfoots we stood no chance.

References[edit]

  1. ^ a b c Peter Davie (2012). "Grapsus grapsus (Linnaeus, 1758)". World Register of Marine Species. Retrieved October 21, 2012. 
  2. ^ G. Guerao, C. D. Schubart & J. D. Cuesta (2001). "The first zoeal stages of Grapsus grapsus (Linnaeus) and Geograpsus lividus (H. Milne Edwards) (Decapoda, Brachyura, Grapsidae) from the western Atlantic" (PDF). Nauplius 9 (2): 111–121. 
  3. ^ Raymond B. Manning & Fenner A. Chace, Jr. (1990). "Decapod and Stomatopod Crustacea from Ascension Island, South Atlantic Ocean". Smithsonian Contributions to Zoology 503. 
  4. ^ A. S. Freire, M. A. A. Pinheiro, H. Karam-Silva & M. M. Teschima (2010). "Biology of Grapsus grapsus (Linnaeus, 1758) (Brachyura, Grapsidae) in the Saint Peter and Saint Paul Archipelago, Equatorial Atlantic Ocean" (PDF). Helgoland Marine Research 65 (3): 263–273. doi:10.1007/s10152-010-0220-5. 
  5. ^ Craig G. Macfarland & W. G. Reeder (1974). "Cleaning symbiosis involving Galápagos tortoises and two species of Darwin's finches". Zeitschrift für Tierpsychologie 34 (5): 464–483. doi:10.1111/j.1439-0310.1974.tb01816.x. 
  6. ^ "Darwin at the Museum" (PDF). Oxford University Museum of Natural History. Retrieved March 23, 2011. 
  7. ^ John Steinbeck. The Log from the Sea of Cortez. Pan Books. 
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