External Anatomy of Anomura

External Anatomy of Anomura
The image shows the external anatomy of the hermit crab. It constantly cleans the antenna 1 by the third maxillipeds. The compound eyes are supported by eyestalks which detect movement of an object from a distance.

Each pereopod consists of five articles: Coxa, Basis-ischium, Merus, Carpus, Propodus, and Dactyl. In case of emergency, it autotomizes pereopods between basis and ischium.
 


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Arthropoda < Crustacea < Decapoda < Anomura < Paguridae
Hermit crab (Pagurus lanuginosus) is an omnivorous marine animal that utilizes shells for the protection of its abdomen. When it is attacked by predators, it withdraws its body in the shell and defends itself by firmly clinging to the shell by fourth and fifth pereopods, and blocks the hands of predators by the right cheliped.

Pagurus lanuginsus
Hermit Crab
March 2003, Tokyo Bay, Japan
The photo shows the lateral view of a hermit crab (Pagurus lanuginosus). The body structure of Anomura is somewhat asymmetrical. The abdomen, which is normally protected by the shell, winds clockwise where pleopods are attached on one sidef. The right cheliped is larger than the left cheliped. The cheliped carries a pair of movable and immovable fingers. It runs sideways and forward by second and third pereopods. Its cephalothorax is covered with anterior and posterior carapaces. The anterior carapace is hard whereas the posterior carapace is soft and covers the gills underneath.

Lateral View of Pagurus lanuginsus
The photo shows the dorsal view of the hermit crab. The five pairs of legs are shown in the photo (Decapoda, ten legs). The red-orange second antenna is characteristic feature of this species (Pagurus lanuginosus).

Dorsal View of Pagurus lanuginsus
The photo shows the ventral view of the hermit crab (male). The abdomen is soft and covered by thin membrane. At the end of the abdomen, a pair of uropods function as an anchor that hangs on the shell.

Ventral View of Pagurus lanuginsus
The mouth is located between the pairs of maxillipeds. There are three pairs of maxillipeds.

Pagurus lanuginsus Eating Dried Fish January 2004, Chiba, Japan
External Anatomy of Anomura
The image shows the external anatomy of the hermit crab. It constantly cleans the antenna 1 by the third maxillipeds. The compound eyes are supported by eyestalks which detect movement of an object from a distance.

Each pereopod consists of five articles: Coxa, Basis-ischium, Merus, Carpus, Propodus, and Dactyl. In case of emergency, it autotomizes pereopods between basis and ischium.

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Erica Asai
Last Modified: Tue Dec 14 01:44:09 2004
 

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BBC NEWS | Science/Nature | Pilfering crab has insect's nose

BBC NEWS | Science/Nature | Pilfering crab has insect's nose: "Pilfering crab has insect's nose
Robber crab (birgus latro), Current Biology
The robber crab climbs trees to pinch coconuts Image: Current Biology
A land crab re-invented key features of the insect nose over millions of years - a striking example of convergent evolution, Current Biology reports.

An animal's sense of smell needs to operate under very different conditions in air compared with water.

The crab has achieved this in the same way as the ancestors of insects did.

The robber crab, which is descended from marine crabs, had to develop a new way of smelling things when it moved out of the sea and on to land.

Insects evolved some 438-408 million years ago, from an ancestor that also crawled out of water into an air-filled terrestrial environment.

Aggressive opportunist

Convergent evolution describes the situation when animals that are distantly related - like the robber crab and an insect - can evolve similar adaptations in response to natural selection.

Robber crab (birgus latro), Current Biology
They are strong, aggressive opportunists
Marcus Stensmyr, of the Swedish University of Agricultural Science, and colleagues observe that the crab's insect nose 'nicely illustrates how similar selection pressures result in similar adaptation'.

Robber crabs (Birgus latro) are the world's largest land-dwelling arthropods, reaching a length of more than half a metre and a weight of 4kg.

Found on islands from the Indian Ocean to the central Pacific, these aggressive, nocturnal scavengers are known for their ability to climb tall palm trees in search of coconuts - which they later crack open with their massive claws.

The crabs are fully adapted to life on land and will actually drown if submerged in water.

Long-distance attraction

The team studied robber crabs from Christmas Island in Australia. Islanders describe the crabs as 'highly inquisitive' and say they will steal"

Volume 76, No. 5, pp. 513--640, 2003

Volume 76, No. 5, pp. 513--640, 2003: "Annual migrations and spawning of Coenobita clypeatus (Herbst) on Mona Island (Puerto Rico) and notes on inland crustaceans
Ángel M. Nieves-Rivera & Ernest H. Williams, Jr. 547"

Ocean City sitting pretty with Miss Crustacean

Cape May County News: The Press of Atlantic City: "June 23, 2005

Ocean City sitting pretty with Miss Crustacean
By MICHAEL MILLER Staff Writer, (609) 463-6712, E-Mail

OCEAN CITY - While Miss America's TV ratings have never been worse, the star is rising for an Ocean City spoof of the famous pageant.

The Miss Crustacean Pageant - scheduled for Aug. 3 - was featured this month in Newsweek's summer calendar. City spokesman Mark Soifer said he has fielded phone calls so far from Spin Magazine, ESPN the Magazine and Ripley's Believe it or Not! about this uniquely Ocean City contest in which children show off the hermit-crab dioramas they build.

The winner's crab is crowned 'Miss Crustacean' and is paraded in front of a large crowd at the Sixth Street beach to the tune, 'There she is, Miss Crustacean.' The winner gets the Cucumber Rind Cup - a trophy with an actual cucumber, a preferred food of hermit crabs.

The Miss America Organization still has no TV contract for this year's pageant. The show's ratings have steadily declined despite efforts to make the contest more relevant and appealing to viewers.

Meanwhile, Ocean City's gentle satire has become an August hit - at least among media looking to liven up dreary summer news packages, Soifer said.

'Miss Crustacean is getting more publicity than ever. It's listed in the mag azines that go out to radio stations for filler. That's what it is, filler,' Soifer said unapologetically.

Soifer is the publicity mastermind behind both the contest and the city's crab mascot, Martin Z. Mollusk. The hermit crab presides over the pageant, a 30-year tradition in Ocean City.

The children's displays have spoofed TV shows such as 'Survivor' and national politics. Some local businesses compete in the commercial division.

Old Salt is a perennial winner. This Boardwalk gift store displays its Cucumber Rind Cups near the hermit crabs it sells for $2 to $6.

'If you have a really good idea and your"

Respiration in Coenobita

The Crab Street Journal: "Respiration


'The land hermit crabs (genus Coenobita) have been the focus of several respiratory studies but remain difficult to categorize. These crabs may be found some kilometers from the sea (De Wilde, 1973; see also Chapter 3 and the Appendix). At first sight they appear highly terrestrial. A closer look at the level of respiratory adaptation, however, creates confusion, revealing some features clearly similar to the more terrestrial crabs and some similar to less terrestrial forms. Morphologically, the gills are substantially reduced, indicating a low dependence on water. However, the branchial chambers are not enlarged, nor are the branchiostegal walls particularly modified (section 2). Thus, these crabs are apparently not clearly modified for aerial respiration. Coenobita spp. do not voluntarily immerse themselves in water, but a single report of MO2 in C. scaevola submerged in the laboratory (Achituv and Ziskind, 1985) indicates that acquatic MO2 can beincreased above that recorded for animals resting in air, at least in the short term. While this increase probably results from the increased acctivity seen in immersed animals, it does show that resonable O2 updake can occur in submerged animals despite a severely reduced gill area (Table 8.1)

Hemolymph O2 capacities in this group are among thehighest reported for Crustacea, a feature that could be regarded as highly terrestrial. However, the high O2 capacity is coupled with the lowest O2 pressures recorded (in air) in any land crab (Fig. 8.6; Table 8.5). This observation, coupled with the poor development of aerial-gas exchange surfaces, may indicate that these crabs normally conduct a large part of gaseous exchange across the gills despite their apparatus terrestriality. The extremely high O2 capacity of this hemolymph may thus be an adaptation to a very high diffusion limitation occuring accross a generally reduced gas-exchange surface. An"

Clustering in hermit crabs

Untitled Document: "Clustered arrangements of organisms, created by social interactions, are promoted by the patchy distribution of resources (Molles, 1999). This clustering is a result of social facilitation to increase the efficiency of resource attainment. Clusters are defined as groups of 50-5000 animals resting in physical contact with each other (Gherardi and Vannini, 1993).


Clustering in hermit crabs has been shown to be commonplace among Diogenidae and Paguridae in tropical and temperate environments and in varied habitats (Gherardi and Vannini, 1993). Hermit crabs of the genus Clibanarius have been previously analyzed due to this conspicuous habit. These crabs can be observed moving around the cluster and performing social activities in their intertidal habitat (Gherardi, Zatteri, Vannini, 1994). Indeed, it has been shown that the primary functions of the aggregations of crabs are to facilitate social activities such as the exchange of shells and exploitation of food resources (Gherardi and Vannini, 1993; Barnes and Arnold 2001).


Shells are a limiting resource for which hermit crabs must compete, often becoming so scarce that crabs are often forced to utilize shells that are too small or otherwise (Floeter et al, 2000). The overall adaptive fitness of hermit crabs is decreased when crabs are prevented from obtaining an adequate shell. Not only does having an adequate shell protect the crab from predation and physical stress (Bertness, 1981), it facilitates growth and reproductive activities. Growth is limited by shell adequacy, becoming faster when shells are not a limiting resource (Turra and Leite, 2000). Because inadequate shells retard growth, female crabs that cannot grow in their shells switch energy allocation to immediate reproduction, resulting in smaller clutch sizes (Turra and Leite, 1999).

Hermit crabs are highly selective in their search for adequate shells. This often results in the acquisition"

Ecological Importance of Terrestrial Hermit Crabs in the Galapagos Islands

Ecological Importance of Terrestrial Hermit Crabs in the Galapagos Islands: "Ecological Importance of Terrestrial Hermit Crabs in the Galapagos Islands
SALLY E. WALKER (Dept. of Geology, University of Georgia, Athens, GA 30602)
Terrestrial hermit crabs are ubiquitous on tropical islands; however, their ecology is poorly known. This research was undertaken under the auspices of the Charles Darwin Research Foundation and the Galapagos National Park to determine the species of terrestrial hermit crabs that occur on the Galapagos Islands and their ecology in relation to the human population on Santa Cruz Island. The human impacted sites of Director´s Beach and Tortuga Bay and the protected site of Puerto Nuñez were used in this study. Coenobita compressus was the only species encountered. Thais melones was the most commonly used shell at Director’s Beach (54%) while Nerita scabricosta was used by 65% of the hermits at Tortuga Bay and by 75% at Puerto Nuñez. At the human-affected sites, C. compressus emerged 1 to 1.5 hours after sunset to forage on bananas, corn cobs, bread, and grapefruit which were discarded by tourists. Crabs were afraid of humans at these localities, stopping behavior upon approach. At the protected site, crabs appeared two hours before sunset and were not afraid of humans — continuing with mating, aggressive behavior and food foraging. They consumed the purple flowers of Sesuvium, leaves of Tiquilia galapagoa, and foraged within driftwood and mangrove litter. However, the crabs were attracted to the camp garbage and ate the plastic garbage bag, paper labels off the cans, and 'papeles de higenico'. In summary, these 'Cangrejos de Basura' are indeed important organisms for maintaining the cleanliness of Galapagos beaches with their late night beach-sweeping activities.



Citation:

Walker, S.E. 1999. Ecological importance of terrestrial hermit crabs in the Galapagos Islands. Proceedings of the American Association for the Advancement"

Salt and water balance and antennal gland function

Identification guide - Mangrove literature: "Harris, RR and GA Kormanik, 1981. Salt and water balance and antennal gland function in three Pacific species of terrestrial crab (Gecarcinus lateralis, Cardisoma carnifex, Birgus latro). II. The effects of desiccation. Journal of Experimental Zoology 218: 107-116."

Acid-base responses to changes in CO2 in Coconut Crabs

Identification guide - Mangrove literature: "Cameron, J.N., 1981. 'Acid-base responses to changes in CO2 in two Pacific crabs: the coconut crab Birgus latro, and a mangrove crab, Cardisoma carnifex.' Journal of experimental Zoology 218:65-73."

Assessment of the status of the coconut crab Birgus latro on Niue Island

ASFB Member’s Bibliography: "Schiller, C.B. 1992. Assessment of the status of the coconut crab Birgus latro on Niue Island with recommendations regarding an appropriate resource management strategy. Consultancy report. Food and Agriculture Organisation of the United Nations, Rome. 69pp."

The Coconut Crab: Reproduction, early life-history and recruitment

ASFB Member’s Bibliography: "Schiller, C.B., Fielder, D.R., Brown, I.W. and Obed, A. 1991. Reproduction, early life-history and recruitment. pp. 13-33. In, Brown, I.W. and Fielder, D.R. (eds.). The Coconut Crab: Aspects of the biology and ecology of Birgus latro in the Republic of Vanuatu. ACIAR Monograph 8, Canberra."

population structure and evolutionary history of the coconut crab

HistCite - index: JC Avise: "3932 31 76 4004 1996 AUG [15] MOLECULAR ECOLOGY 5(4):557-570
Lavery S; Moritz C; Fielder DR
Indo-Pacific population structure and evolutionary history of the coconut crab Birgus latro
36 45"

Coconut crab - Iridis Encyclopedia

Coconut crab - Iridis Encyclopedia: "Coconut crab

The Coconut crab (Birgus latro) is the largest terrestrial arthropod, known for its ability to crack coconuts with its strong pincers in order to eat the contents. The crab is sometimes called the Robber Crab or Palm Thief (in German), because some crabs steal shiny items such as pots and silverware from houses and tents. Another name is the terrestrial hermit crab, due to the use of shells by young crabs. The crab also has different local names as for example Ayuyu in Guam, or Unga or Kaveu.

The crab's range includes the Indian and western Pacific ocean. The crabs differ slightly in color among different islands, ranging from light violet to deep purple, to brown.
Species

The coconut crab is the largest terrestrial crab. The body length can grow up to 40 cm (16 inches), with a weight of up to 4kg (9 pounds) and a leg span of 1 meter (3 feet), with males being larger than females. (The largest crab overall is the Japanese spider crab, with a leg span of almost 4 meters (13 feet).) The body of the coconut crab is, like most hermit crabs, roughly divided into a front section and an abdomen. The crab has 10 legs. The front most legs have massive pincers used to open coconuts. These claws have been measured to lift objects up to 29 kg (64 lbs) in weight. The next three pairs have smaller tweezers at the end which allow the crab to move quite easily along terrestrial surfaces. In addition these specially adapted limbs enables them to climb verticaly up trees (often coconut palms) up to 6m high. Crabs face skyward while climbing either up or down. The legs may also be used to handle food. The last pair of legs is very small and serves only to clean the breathing organs. Usually, these legs are held inside the body in the cavity containing the breathing organs. The print below shows these small legs extended to the side.

The crab belongs to the class of Hermit crabs, however, it may be difficult for large adults t"

Zoology Unlimited, Endangered Species Surveys

Zoology Unlimited, Endangered Species Surveys: "Coconut Crab


Found throughout the western Pacific and eastern Indian Oceans, the coconut crab (Birgus latro) appears to be mainly restricted to islands. Closely related to hermit crabs, the adult does not require a mollusk shell for protection and only returns to the ocean to release its larvae (Amesbury 1980 – Tech. Report No. 17, University of Guam). Otherwise it lives a purely terrestrial existence scavenging in the forest. Older crabs usually have an established burrow, and they are quite capable of climbing trees. Coconut crabs can grow quite large, to 4kg, and ages in excess of 50 years have been suggested. Like all crabs it must periodically shed its exoskeleton. This is done underground and can last a month or more (Brown & Fielder (eds.) 1991-ACIAR Monograph No. 8). They have been found to be diurnal on islands with no human occupation and nocturnal on islands with humans.

Coconut crabs are gathered for consumption throughout their range. They are easily caught by hand and require no specialized equipment other then a coconut for bait. These qualities have resulted in adverse impacts on populations that occur on islands with human populations. This has prompted wildlife departments to try various management techniques based on established methods for other species. Good scientific data is lacking on this species and further studies are needed to determine conservation needs. Because of the excellent quality of it taste, many have looked at the feasibility of raising crabs. Unfortunately this seems improbable due to the quarrelous nature of the crabs and the long period required reaching a harvestable size.
Happy crab.jpg (38207 bytes) crab transmitter.jpg (64287 bytes)
Happy Gideon with coconut crab on Anatahan Island Coconut crab with radio transmitter - Saipan


The coconut crab, or ayuyu, is an important food species in the Commonwealth of the Northern Mariana Island"

robber crab and an insect --can evolve similar adaptations in response to natural selection

EVOLUTION & GENETIC NEWS, Gaia Church: "A land crab re-invented key features of the insect nose over millions of years --a striking example of convergent evolution, Current Biology reports. An animal's sense of smell needs to operate under very different conditions in air compared to water. The crab has achieved this in the same way as the ancestors of insects did. Insects evolved some 438-408 million years ago, from an ancestor that also crawled out of water into an air filled-terrestrial environment. The robber crab, which is descended from marine crabs, had to develop a new way of smelling things when it moved out of the sea and on to land.
. . Convergent evolution describes the situation when animals that are distantly related - like the robber crab and an insect --can evolve similar adaptations in response to natural selection.They observe that the crab's insect nose "nicely illustrates how similar selection pressures result in similar adaptation "

Smelling organs of robber crabs (Birgus latro) are called aesthetascs

EVOLUTION & GENETIC NEWS, Gaia Church: "Robber crabs (Birgus latro) are the world's largest land-dwelling arthropods, reaching a length of more than half a metre and a weight of 4kg. The crabs are fully adapted to life on land and will actually drown if submerged in water.
. . The smelling organs of robber crabs are called aesthetascs. These are mounted on paired antennae, or antennules. In the robber crab, these smelling organs share many features with insect olfactory organs called sensilia - including a short, blunt shape. The crab's aesthetascs were very different to those of marine crabs."

Search Results

Search Results: "Ghiradella, H., Case, J., Cronshaw, J. 1968 Fine structure of the aesthetasc hairs of Coenobita compressus Edwards. J. Morphol. 124: 361-385."

Locomotion and hermit crabs

Library H: endnote: "Herreid II, C. F. and Full, R. J. (1986). Energetics of hermit crabs during locomotion: the cost of carrying a shell. J. exp. Biol. 120, 297-308.

Herreid II, C. F. and Full, R. J. (1986). Locomotion of hermit crabs (Coenobita compressus) on beach and treadmill. J. exp. Biol. 120, 283-296.

Herreid II, C. F. and Full, R. J. (1988). Energetics and locomotion. In Biology of the Land Crabs (ed. W. Burggren and B. R. McMahon), pp. 333-377. New York: Cambridge University Press."

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