Cardisoma guanhumi communicates in various ways, but mainly with visual, auditory, and chemical signals. To attract mates, females release pheromones. To orient itself, C. guanhumi depends on polarized light or the light from the horizon at dawn or dusk. It also uses the setae on its appendages for tactile purposes. It is heavily sensitive to vibrations.
Communication Channels: visual ; tactile ; acoustic ; chemical
Other Communication Modes: pheromones
Perception Channels: visual ; polarized light ; tactile ; acoustic ; vibrations ; chemical
Due to their size, C. guanhumi is not heavily preyed on. However, it sometimes falls prey to large birds, mammals, and other C. guanhumi. Humans are the largest threat with respect to predation, harvesting giant land crabs in massive quantities for food. Fortunately, it is fairly safe in its burrow from predation. Hence, burrowing not only provides C. guanhumi with shelter, but also protects it from predation. In fact, the absence of a burrow, in addition to physical vulnerability and other factors, explains the high mortality rates of C. guanhumi during the larval stage.
Known Predators:
Cardisoma guanhumi grows roughly 127 mm wide and 102 mm long, weighing 400 g on average, though males are generally larger than females. As a juvenile, it is typically tan or brown in color with orange legs. As an adult, its coloring ranges from blue to violet, though some females are white or ashy gray. Its body, protected by a smooth carapace, consists of a cephalothorax and abdomen. Connected to its cephalothorax are five pairs of biramous appendages covered with tactile setae, each of which are sturdy and longer than the width of the cephalothorax. At its front are two pairs of antennae and two pincers, one larger than the other. The larger pincer in males can reach 300 mm in length. The difference in pincer size notwithstanding, C. guanhumi is bilaterally symmetric.
Average mass: 400 g.
Range length: 90 to 110 mm.
Average length: 102 mm.
Range wingspan: N/A to N/A mm.
Average wingspan: N/A mm.
Range basal metabolic rate: 330.307 micromole oxygen/hour to 388.171 micromole oxygen/hour. Note: could not find information expressed in cm3.O2/g/hr.
Average basal metabolic rate: 359.239 micromole oxygen/hour. Note: could not find information expressed in cm3.O2/g/hr.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; polymorphic
Sexual Dimorphism: male larger; sexes colored or patterned differently; male more colorful
Many giant land crabs do not survive the larval stage. Those who reach adulthood achieve sexual maturity in approximately four years. Unfortunately, there is not much further data available regarding the lifespan of C. guanhumi. However, biologists hypothesize that the lifespan of a species of land crab is inversely proportional to its growth rate. In other words, the faster they grow, the shorter they live, and vice versa. From this, it is probable that C. guanhumi has a relatively longer lifespan than other land crabs, as it grows more slowly and molts three times as much (averaging 60 molts per lifetime as opposed to 20). In fact, the largest female C. guanhumi kept in captivity lived 13 years. Albeit biologists admonish against extrapolating laboratory findings to a species' actual environment, I have given some rough estimates of lifespan below based on given data regarding the lifespans of C. guanhumi and other land crabs.
Range lifespan
Status: captivity: 13 (high) years.
Average lifespan
Status: wild: 11 years.
Average lifespan
Status: captivity: 11 years.
Cardisoma guanhumi lives within several hundred meters of the shore, particularly along estuaries and river banks. It burrows in dense shrubbery, mud, or coastal sand above the tide line. Burrows can extend up to six feet underground, and contain small pools of water at the bottom. Cardisoma guanhumi shares its burrow with insects and other small arthropods. The atmospheres within such burrows typically have very high carbon dioxide concentrations because they are often sealed with mud.
Range elevation: N/A to N/A m.
Average elevation: Generally remains at sea level. m.
Range depth: N/A to N/A m.
Average depth: Generally remains at sea level. m.
Habitat Regions: terrestrial ; saltwater or marine
Terrestrial Biomes: forest ; rainforest
Aquatic Biomes: rivers and streams; temporary pools; coastal
Other Habitat Features: estuarine
Cardisoma guanhumi is found along the Gulf of Mexico and Caribbean Sea throughout the southeastern United States, Central America, the northern tip of South America, and parts of the Caribbean Islands.
Biogeographic Regions: nearctic ; neotropical ; atlantic ocean
Cardisoma guanhumi is an omnivore. Although it prefers leaves, fruits, and grasses, C. guanhumi also feeds on insects, carrion, and feces. To forage it typically does not stray far from its burrow and uses light and sound to find food. After foraging, it carries its food in its claws back to its burrow, eats, and saves whatever it does not finish for later.
Animal Foods: carrion ; insects; terrestrial non-insect arthropods
Plant Foods: leaves; fruit
Other Foods: detritus ; dung
Foraging Behavior: stores or caches food
Primary Diet: omnivore
Due to the moist atmosphere within its burrow, C. guanhumi provides a myriad of arthropods with habitats. These arthropods live on its body, but do not seem to harm it, primarily feeding off of left over debris from previous C. guanhumi meals. Because the food habits of C. guanhumi are so eclectic, its effect on its prey populations are, if anything, trivial. However, through preferential feeding, C. guanhumi can alter the compositions of various species of plants by choosing to eat certain plants and seeds over others.
Ecosystem Impact: disperses seeds; creates habitat
Species Used as Host:
Mutualist Species:
Commensal/Parasitic Species:
Cardisoma guanhumi is a significant source of food in various parts of the Caribbean, particularly in Puerto Rico and the Bahamas. Harvesters have been known in Venezuela to catch as many as 400 giant land crabs per night. Sold at $30.00 (US) per dozen, this amounts to $1,000.00 per day per harvester in giant land crab revenues.
Positive Impacts: food
While the adverse affects on humans of C. guanhumi are minimal, it is sometimes deemed a garden pest for digging burrows in lawns and crop fields. In addition, it can occasionally cause ulcers and lesions to those who eat it when it has previously consumed poisonous fruit. Lastly, the pool at the bottom of the burrow provides a breeding ground for mosquitos that may potentially vector diseases such as malaria and subperiodic filariasis.
Negative Impacts: crop pest
Cardisoma guanhumi has a complex life cycle that begins during the rainy season (which varies by latitude) when females spawn their eggs into the ocean, strictly coinciding with the lunar cycle. Once hatched C. guanhumi molts through five larval periods before it undergoes metamorphosis into a megalops, the stage when the appendages first appear. The nest metamorphosis produces the juvenile crab, which closely resembles the adult form. Each metamorphosis is accompanied by a molting of the cuticle. The following molt, named the puberty molt, precedes full sexual maturation. Molting regulates the life cycle of C. guanhumi. Generally, C.guanhumi molts 60 times during its lifespan, compared to 20 times, which is typical of other crab species. After achieving sexual maturation, C. guanhumi becomes primarily terrestrial, returning to the ocean only to spawn and begin the life cycle once again.
Development - Life Cycle: metamorphosis
Although C. guanhumi is not endangered, there is concern regarding its harvesting. It has been exploited excessively in the Caribbean for food. To combat this, Puerto Rico enacted strict regulations and Florida is currently considering similar legislation.
US Federal List: no special status
CITES: no special status
Cardisoma guanhumi is fundamental to the cuisine of many Caribbean nations as well as Florida and Venezuela; however, there is much concern regarding its excessive harvesting.
The reproductive cycle of C. guanhumi is heavily dependent on weather and the lunar cycle. At the beginning of the rainy season (typically late spring, but varies by latitude), females begin to actively search for a mate while migrating from their burrow to the shore. Major migrations take place prior to full moons; minor ones precede new moons. While males can copulate as much as they wish between molts, females can only copulate several times.
Mating System: polygynandrous (promiscuous)
Cardisoma guanhumi reaches sexual maturity at roughly four years of age. Mating begins during the rainy season when females migrate to the shore--particularly before a full moon and (to a far lesser extent) before a new moon. In preparation for their migrations, females gain substantial weight. Males actively court females and in response, females emit pheromones as well as tactile and auditory signals. Copulation typically takes place outside of burrows, and fertilization is internal. Following copulation, females carry their eggs (which can number anywhere between 20,000 and 1,200,000) for approximately two weeks before spawning them into the ocean.
Breeding interval: Cardisoma guanhumi breeds once a year.
Breeding season: Spring to late summer, though varies by latitude.
Range number of offspring: 20000 to 1200000.
Average number of offspring: 525000.
Average gestation period: 2 weeks.
Average time to independence: 2 weeks.
Average age at sexual or reproductive maturity (female): 4 years.
Average age at sexual or reproductive maturity (male): 4 years.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
After fertilization, females carry their eggs on their backs for approximately two weeks. At this point, the eggs begin to hatch, and she shakes them off into the ocean. In spite of its evolution toward terrestriality, C. guanhumi is still heavily dependent on the ocean for at least part of the life.
Parental Investment: pre-fertilization (Provisioning); pre-hatching/birth (Protecting: Female)
Cardisoma guanhumi, also known as the blue land crab, is a species of land crab found in tropical and subtopical estuaries and other maritime areas of land along the Atlantic coast of the Americas from Brazil[2] and Colombia, through the Caribbean and Gulf of Mexico, to the Bahamas, and north to Ponce Inlet, Florida[3] Princess Place Preserve on the Palm Coast, and Bermuda.[4] The species varies in colour from dark blue to brown or pale grey, and may grow to 15 centimetres (6 in) in carapace width and weigh over 500 grams (18 oz).[3][5]
The carapace of C. guanhumi can reach a width up to 15 cm (6 in).[5] As with many crab species, males possess dimorphic claws: the larger claw can grow up to around 15 cm (6 in) in length, eventually becoming larger than the carapace itself. The eyes are stalked and their colour ranges from a deep blue to a pale grey. Juveniles generally have a brown carapace with orange coloured legs. Females usually appear light gray or white. Adult colours are usually present between 80 g (2.8 oz) and 180 g (6.3 oz). Individuals of the species can weigh over 500 g (18 oz).[3]
Cardisoma guanhumi is found throughout estuarine and other coastal regions of the Caribbean, and along the Atlantic coast of Central and South America (south to Brazil).[2] In the United States it can be found in coastal areas of the Gulf of Mexico and Florida north to Vero Beach.[3] Relatively cold water temperatures in the winter, less than 20 °C (68 °F), affect the larval survival and restricts the species' possibility of spreading further north.[3]
Cardisoma guanhumi is omnivorous, collecting and eating leaves and fruits close to its burrow whilst also eating insects and carrion. Like many crabs, this species is cannibalistic. They move in the shade during the day and will eschew moving in prolonged direct sunlight to feed at night instead.[3] According to a fisherman who's been catching them for 50 years, once captured, the smaller ones take two weeks to filter (clean) before they are consumable and the larger ones take a month.[6]
Cardisoma guanhumi finds its food using light and sound detectors. Experiments show that crabs can be drawn out of their burrows to investigate the sound of falling fruit, once out they initiate a search for food. Predatory behavior is released in these crabs by detection of small moving objects. Crabs in the genus Cardisoma are able to detect small vibrations on the ground within the range of 10–1500 Hz and 70 dB. Visual acuity increases with body size due to an increase in both the number and diameter of ommatidia.[3]
The reproductive cycle is closely linked to seasonal weather patterns and lunar phase. Heavy rains in the spring initiate migrations. When this occurs, C. guanhumi begins to gain weight, as more food is consumed and gathered for the first few weeks of the migratory period. Males mate with mature females during this time. Fertilization is internal, and throughout July and August most females carry the eggs externally. After approximately 2 weeks the eggs will hatch and must be released into saltwater for the larvae to survive. Several spawns per year may occur with spawning season varying with location within the range. In Florida, spawning season lasts from June to December and reaches its peak in October and November. In the Bahamas the season extends from July to September, while in Venezuela spawning lasts from July to November. Eggs hatch into free swimming larvae with 5 zoeal stages and 1 postlarval or megalopa stage. Typical development time from hatching to the first crabs stage is 42 days under laboratory conditions; however, this time may be much shorter in wild specimens.[3]
C. guanhumi is a slow-growing species compared to most other crabs. It requires more than 60 molts – roughly three times more than other species of crab – to reach its full size. The crab will generally seal the exit to its burrow using mud, 6–10 days before it molts, in order to protect itself from predators. (After molting, crabs are more vulnerable to attack as their shell has not yet hardened.)[3]
Cardisoma guanhumi, also known as the blue land crab, is a species of land crab found in tropical and subtopical estuaries and other maritime areas of land along the Atlantic coast of the Americas from Brazil and Colombia, through the Caribbean and Gulf of Mexico, to the Bahamas, and north to Ponce Inlet, Florida Princess Place Preserve on the Palm Coast, and Bermuda. The species varies in colour from dark blue to brown or pale grey, and may grow to 15 centimetres (6 in) in carapace width and weigh over 500 grams (18 oz).
A group of blue land crabs
