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Coenobita perlatus

By Noelle M. McKenzie

Geographic Range

Coenobita perlatus is found in the Indo-Pacific from the Islands of Aldabra, Mauritius, and Seychelles through Samoa. These areas are located in the south central Pacific Ocean about 1,600 miles northeast of New Zealand, north of Madagascar and directly above the 10 degree latitude line. (Ingle, 1993)

Habitat

Coenobita perlatus are found living near coastal shorelines. Coenobita perlatus require regular access to the sea or water of high salinity. They are never far from shore or adjacent dunes, and have been found in tidal pools, sandy areas, and humid areas with dune vegetation. Migration occurs from the dune areas to the sea when C. perlatus need to release their eggs into the water or are in need of water to maintain their body moisture. (Hazlett, 1998, Burggren, 1988, Veltman, 1997)

Physical Description

Coenobita perlatus are approximately 80mm long and 80g in body mass. They occupy the multicolored discarded shells of gastropods in order to protect their soft, coiled abdomen and inner organs such as the liver and gonads. These land hermit crabs are decapods, which means they have 10 legs (5 pairs): The first pair is modified as the claws or chelipeds (pinchers), and two pairs of legs are used for walking. The next pair, the claws, are used for defense and transporting food and water to the their mouth. The last two pairs are highly modified but are used more for cleaning than holding on to the shell. When walking, these crabs drag their shells along, but despite this burden, they can run quickly. Each C. perlatus has a loosely fitting carapace that covers the forepart of the body. Coenobita perlatus prefer shells that fit snugly in order to prevent evaporation of moisture and to protect their soft abdomens. Coenobita perlatus have four antennae that help them to sense their surroundings. They have shown some geographic physical variation, but this variations have not been studied in depth.

Male and female C. perlatus can only be distinguished when they are out of their shells. Both the female and male genital pores are located on the coxal ventral surface of each pereiopod (on an appendage of one of the first five abdominal segments), and a long coxal tube (an extension of a pereiopod which is joined broadly to lateral margins of tergites) is present in the male.

(Hazlett, 1998, Burggren, 1988, Veltman, 1997)

  • Sexual Dimorphism
  • sexes shaped differently
  • Average mass
    80 g
    2.82 oz
  • Average length
    80 mm
    3.15 in

Reproduction

These creatures reproduce sexually and will not reproduce in captivity. Reproduction occurs while both individuals are in intermolt (hard-shelled stage), often in or near the burrows of males, or on land near the sea. Male C. perlatus place a spermatophore on the female (externally) which is then dissolved by secretions as the eggs are released. The eggs (about 10,000-50,000 per fertilization) are attached to the pleopods (appendages used for swimming) on the female's abdomen and remain there for some time. Female C. perlatus moisten the eggs with water that is held in the gastropod shell. After the eggs develop, females carry them on their abdomens to the sea, where they leave them on wet sand or a wet rock for the tide to carry them out to sea. The eggs are hatched and the larvae undergo planktonic development. Young C. perlatus are small, molting several times while still at sea in order to reach adult size. They then move to land, where they are vulnerable to their predators until they find a shell. Once C. perlatus have found shells, they live on land the rest of their lives. (Hazlett, 1998, Burggren, 1988, Ingle, 1993, Veltman, 1997)

Lifespan/Longevity

Coenobita perlatus can live up to 25-30 years in the wild, but once in captivity they typically live from 1-4 years.

  • Range lifespan
    Status: wild
    25-30 (high) years
  • Typical lifespan
    Status: captivity
    1 to 4 years

Behavior

Despite the common name hermit crab, which alludes to a solitary lifestyle, these are very social creatures. They travel in groups of about 25 and are found, in the wild, living in colonies of up to 100 or more. Coenobita perlatus are nocturnal. During the day, when it is hot, they bury themselves in the damp sand or take shelter under ledges of logs to keep cool and reduce moisture loss. Afternoon tropical sun is a danger to these crabs because they require a certain amount of moisture for their gills to operate properly. If they become too dry, they can suffocate. In addition to taking cover from the sun, they also have gills on their big claw in order to conserve moisture. These gills must be kept wet to maintain good health.

When C. perlatus no longer fit their shells they look for bigger ones. The original occupant of the shell, if still present, is quickly removed, and the aggressor moves into its new home. If frightened, land hermit crabs may grasp things tightly with their claws. Even the smallest C. perlatus can draw blood if scared. (Hazlett 1988, Ingle 1993)

Communication and Perception

Coenobita perlatus have been observed communicating to one another by making sounds referred to as chirping. They use their antennae to sense smells and have excellent vision. They are also sensitive to vibrations.

Food Habits

Known as "garbage collectors of the seashore," Coenobita perlatus individuals are scavengers, eating a variety of dead and rotting material found along the seashore. These crabs, in general, do not fight over food and can often go long periods of time without food or water. Most C. perlatus carry water in their shells, which the use for breathing and as a water source when they are far from the sea. (Ingle, 1993)

Economic Importance for Humans: Positive

Coenobita perlatus can be used as a source of food for humans, but are most commonly found as household pets. They also play a vital role in seashore clean-up because they are scavengers. By ridding the shoreline of dead sea matter and other material that collects on the shore, hermit crabs are beneficial in keeping the shoreline clean and creating a healthier environment for humans and other aquatic and coastal organisms. (Veltman, 1997)

Conservation Status

Humans are currently the greatest danger to Coenobita perlatus. Though these creatures are not going extinct and are not yet endangered, we humans are destroying their habitats, collecting the crabs for food, over- collecting for pet shops, and polluting the environment. There are many conservation actions currently taking place that affect C. perlatus indirectly. These include shoreline clean-up of human pollution, and prevention of pollution by factories and barges. Pollution is a great threat to C. perlatus because they need a healthy environment to reproduce properly, a safe place to grow their eggs, and clean land and water to live on and drink from.

Other Comments

Growth on land is accomplished by the shedding of their exoskeleton. It takes about ten days for their skin to harden after molting, and as they grow larger, they search out roomier shells to more comfortably accommodate thier bodies. (Hazlett, 1998, Veltman, 1997)

Contributors

Noelle M. McKenzie (author), University of Michigan-Ann Arbor.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

detritivore

an animal that mainly eats decomposed plants and/or animals

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

food

A substance that provides both nutrients and energy to a living thing.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

scavenger

an animal that mainly eats dead animals

scrub forest

scrub forests develop in areas that experience dry seasons.

sedentary

remains in the same area

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

References

Dr. Brian Hazlett, Professor of Biology Department, University of Michigan

Burggren, W. and McMahon, B. 1988. Biology of the Land Crabs. Cambridge University Press, Cambridge.

Ingle, R.1993. Hermit Crabs of the Northeastern Atlantic Ocean and the Mediterranean Sea. Chapman & Hall: Natural History Museum Publications, London.

Lloyd Center Research Program. 1996. http://www.ultranet.com/~lloydctr/hermit.html

http://www.pathfinder.com/PetPath/Exotic/Breeds/AQUATIC/HERMITC/HERMITC.html

http://dino.slsa.sa.gov.au/sagov/agencies/museum/hermit.htm

Veltman, T. 1997. http://www.xs4all.nl/~pal/hermit.htm

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