Johngarthia lagostoma
Encyclopedia
Johngarthia lagostoma is a species of terrestrial crab
that lives on Ascension Island
and three other islands in the South Atlantic. It grows to a carapace
width of 110 mm (4.3 in) on Ascension Island, where it is the largest native land animal. It exists in two distinct colour morphs, one yellow and one purple, with few intermediates. The yellow morph dominates on Ascension Island, while the purple morph is more frequent on Atol das Rocas. The species differs from other Johngarthia
species by the form of the third maxilliped.
Johngarthia lagostoma lives in burrows among vegetation, at altitudes of up to 400 m (1,312.3 ft), emerging at night to feed on plant matter and occasionally on animals. From January to March there is an annual migration to the sea to release the plankton
ic larvae
. The species was first described (as Gecarcinus lagostoma) by Henri Milne-Edwards
in 1837 from material sent to him by the naturalists Jean René Constant Quoy
and Joseph Paul Gaimard
, collected by the French ship Astrolabe.
, , and . On Ascension Island, J. lagostoma is restricted outside the breeding season
to the slopes of Green Mountain
, where there is sufficient moisture and vegetation, the rest of the island being too arid for the crab to survive. All the land above 400 metres (1,312.3 ft) is suitable habitat for the crabs, as is much of the land above 200 m (656.2 ft). They are occasionally found at lower altitudes, including the well-watered gardens of Georgetown
, and the sooty tern
breeding colony in the south-west of the island (known as the Wideawake Fairs). On , J. lagostoma is abundant wherever plants grow, included the highest parts of the island.
The geographic distribution of J. lagostoma across a small number of islands in the southern Atlantic Ocean
is very unusual, and difficult to explain by planktonic dispersal. Its nearest relatives are the other species of Johngarthia
, two of which (J. malpilensis and J. planata) inhabit islands in the Pacific Ocean
off Central America
, and one (J. weileri
) is found on islands in the Gulf of Guinea
. Some authors have suggested the existence of former islands, now submerged, which could have acted as "stepping stone
s" for the colonisation of Ascension Island; the isolation of Ascension Island from any other land mass makes transportation of either larvae or adults difficult.
on Ascension Island; individuals from are somewhat smaller. In the family Gecarcinidae, species are normally separated by the form of the first pleopod (gonopod), which is used by males during mating, but there is no difference in the gonopod between J. lagostoma and J. planata. Instead, J. lagostoma differs from other species in the genus by the form of the third maxilliped; it has a fissure which is a narrow slit, but which gapes open in other species. The third maxilliped is also larger, covering the epistome and the antennules in J. lagostoma but not in other species.
Within the species, two distinct colour morphs can be seen. The "yellow" morph has a bright yellow or orange exoskeleton
, with white patches on the underside of the walking legs and claws. The "purple" morph has a dark purple exoskeleton, but with the same white patches as on the yellow morph. A few intermediate individuals occur, which are predominantly yellow, but with purple patches on the carapace. On Ascension Island, the yellow morph is the more frequent one, while on , the distribution is more equal. Darker individuals are thought to be better concealed from predators, but more prone to heat stress during long migrations; is much smaller than Ascension Island, and the migration routes are therefore shorter, which may explain the difference in frequency of the two morphs.
have been introduced
to Ascension Island, and now compete with J. lagostoma; they include mice
, rat
s and rabbit
s.
J. lagostoma is active at night and after rain, when it emerges from its burrow
s, which can be up to 1 metres (3.3 ft) deep. In 1915, H. A. Baylis reported that it feeds on "decaying vegetation and perhaps a certain amount of excreta from sea-birds"; most of its diet is thought to be made up of plant matter, but can also include animals. In the Wideawake Fairs, J. lagostoma feeds on chicks and eggs of the sooty tern, and they have been proposed as a limiting factor
in the breeding of petrel
s on Ascension Island. In May, green sea turtle
s (Chelonia mydas) hatch, and J. lagostoma is one of several predators to target the emerging hatchling
s, alongside the Ascension frigatebird
(Fregata aquila) and feral cat
s. The crabs find water on and under rocks, especially after condensation
has begun to form on their cool surfaces at night.
In the late nineteenth century, a bounty
was levied on J. lagostoma in order to reduce its numbers. Hunters were paid 6 pence (alternatively paid in rum
) for every hundred claws collected. In 1879, the total bag for the island comprised 66 cats, 4,013 mice, 7,683 rats and 80,414 land crabs; in the eight years to 1887, bounties were collected on more than 330,000 crabs. The current population is much smaller, and the low level of recruitment
and lack of juveniles
suggests that the species may become endangered.
are marine and plankton
ic. In order to release their offspring, the adults therefore have to migrate to the sea, as seen in other land crabs, such as the Christmas Island red crab
, Gecarcoidea natalis. In most members of the family Gecarcinidae, migration coincides with the rainy season, which reduces the risk of desiccation; migration in J. lagostoma occurs from January until March, while the period of highest rainfall is from March to May.
The crabs travel approximately 450 m (1,476.4 ft) per day, and mating can take place anywhere along the route. The proportion of males on the migration therefore decreases as the migration continues. The eggs
are larger than in other gecarcinid species and consequently fewer in number; females with a carapace width of 94 mm (3.7 in) had a mean fecundity
of 72,000. Spawning occurs in the last quarter of the lunar cycle, during neap tides, on rocky shores.
in 1837, under the name Gecarcinus lagostoma. The specific epithet means "hare-lip", from the Greek
(, "hare") and (, "mouth"); Milne-Edwards also named the species in French
("hare-lipped land crab"). Milne-Edwards erroneously gave the type locality as "" (Australasia
); he had been given the material he used for the description by Jean René Constant Quoy
and Joseph Paul Gaimard
, who were working on the molluscs collected on the Astrolabe excursion, which had visited Australasia and stopped at Ascension Island in 1829. G. lagostoma was placed in the subgenus Johngarthia by Michael Türkay in 1970, who raised the subgenus to the rank
of genus
in 1987.
Many subsequent voyages halted at Ascension Island, and many visitors commented on the land crabs they found there, including William Dampier
, Charles Darwin
and Charles Wyville Thomson
. Bernard Stonehouse
reported on an expedition by the British Ornithologists' Union
to Ascension Island, stating:
The closely related crabs from the islands of the Gulf of Guinea
were formerly included in Gecarcinus lagostoma, but are now treated as a separate species, Johngarthia weileri
.
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
that lives on Ascension Island
Ascension Island
Ascension Island is an isolated volcanic island in the equatorial waters of the South Atlantic Ocean, around from the coast of Africa and from the coast of South America, which is roughly midway between the horn of South America and Africa...
and three other islands in the South Atlantic. It grows to a carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
width of 110 mm (4.3 in) on Ascension Island, where it is the largest native land animal. It exists in two distinct colour morphs, one yellow and one purple, with few intermediates. The yellow morph dominates on Ascension Island, while the purple morph is more frequent on Atol das Rocas. The species differs from other Johngarthia
Johngarthia
Johngarthia is a genus of crabs in the land crab family Gecarcinidae, formerly included in the genus Gecarcinus, and containing the following five species:...
species by the form of the third maxilliped.
Johngarthia lagostoma lives in burrows among vegetation, at altitudes of up to 400 m (1,312.3 ft), emerging at night to feed on plant matter and occasionally on animals. From January to March there is an annual migration to the sea to release the plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
ic larvae
Crustacean larvae
Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow...
. The species was first described (as Gecarcinus lagostoma) by Henri Milne-Edwards
Henri Milne-Edwards
Henri Milne-Edwards was an eminent French zoologist.Henri Milne-Edwards was the 27th child of William Edwards, an English planter and militia colonel in Jamaica and Elisabeth Vaux, a French. He was born in Bruges, Belgium, where his parents had retired. At that time, Bruges was a part of the...
in 1837 from material sent to him by the naturalists Jean René Constant Quoy
Jean René Constant Quoy
Jean René Constant Quoy was a French zoologist.Along with Joseph Paul Gaimard he served as naturalist aboard La Coquille under Louis Isidore Duperrey during its circumnavigation of the globe , and the Astrolabe under the command of Jules Dumont d'Urville...
and Joseph Paul Gaimard
Joseph Paul Gaimard
Joseph Paul Gaimard was a French naval surgeon and naturalist.Along with Jean René Constant Quoy he served as naturalist on the ships L'Uranie under Louis de Freycinet 1817-1820, and L'Astrolabe under Jules Dumont d'Urville 1826-1829...
, collected by the French ship Astrolabe.
Distribution and biogeography
Johngarthia lagostoma is found on Ascension IslandAscension Island
Ascension Island is an isolated volcanic island in the equatorial waters of the South Atlantic Ocean, around from the coast of Africa and from the coast of South America, which is roughly midway between the horn of South America and Africa...
, , and . On Ascension Island, J. lagostoma is restricted outside the breeding season
Breeding season
The breeding season is the most suitable season, usually with favourable conditions and abundant food and water, for breeding among some wild animals and birds . Species with a breeding season have naturally evolved to have sexual intercourse during a certain time of year in order to achieve the...
to the slopes of Green Mountain
Green Mountain
Green Mountain is a common name for "The Peak", the highest point, on Ascension Island which has gained some fame for claims that it is one of very few large-scale artificial forests.-History and Vegetation:...
, where there is sufficient moisture and vegetation, the rest of the island being too arid for the crab to survive. All the land above 400 metres (1,312.3 ft) is suitable habitat for the crabs, as is much of the land above 200 m (656.2 ft). They are occasionally found at lower altitudes, including the well-watered gardens of Georgetown
Georgetown, Ascension Island
Georgetown is the capital and chief settlement of Ascension Island, situated on the west coast of the island.The town is centred around St Mary's Church, part of the Anglican Diocese of St Helena and the former Exiles Club, which is on the site of the original Royal Marines barracks from the times...
, and the sooty tern
Sooty Tern
The Sooty Tern, Onychoprion fuscatus , is a seabird of the tern family . It is a bird of the tropical oceans, breeding on islands throughout the equatorial zone. Colloquially, it is known as the Wideawake Tern or just wideawake...
breeding colony in the south-west of the island (known as the Wideawake Fairs). On , J. lagostoma is abundant wherever plants grow, included the highest parts of the island.
The geographic distribution of J. lagostoma across a small number of islands in the southern Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
is very unusual, and difficult to explain by planktonic dispersal. Its nearest relatives are the other species of Johngarthia
Johngarthia
Johngarthia is a genus of crabs in the land crab family Gecarcinidae, formerly included in the genus Gecarcinus, and containing the following five species:...
, two of which (J. malpilensis and J. planata) inhabit islands in the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
off Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
, and one (J. weileri
Johngarthia weileri
Johngarthia weileri is a species of land crab in the genus Johngarthia from the eastern Atlantic Ocean.-Distribution:Johngarthia weiler is found on the coast of Cameroon and on the islands in the Gulf of Guinea.-Taxonomy:...
) is found on islands in the Gulf of Guinea
Gulf of Guinea
The Gulf of Guinea is the northeasternmost part of the tropical Atlantic Ocean between Cape Lopez in Gabon, north and west to Cape Palmas in Liberia. The intersection of the Equator and Prime Meridian is in the gulf....
. Some authors have suggested the existence of former islands, now submerged, which could have acted as "stepping stone
Step-stone bridge
A Step-stone bridge is a simple bridging allowing a pedestrian to cross a natural watercourse or pond, or a garden's water feature where water is allowed to course between stone steps. Unlike other bridges it has no spans. Step-stone bridges, along with log bridges are likely to be the oldest...
s" for the colonisation of Ascension Island; the isolation of Ascension Island from any other land mass makes transportation of either larvae or adults difficult.
Description
Mature specimens of J. lagostoma are typically 70–110 mm (2.8–4.3 ) wide across the carapaceCarapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
on Ascension Island; individuals from are somewhat smaller. In the family Gecarcinidae, species are normally separated by the form of the first pleopod (gonopod), which is used by males during mating, but there is no difference in the gonopod between J. lagostoma and J. planata. Instead, J. lagostoma differs from other species in the genus by the form of the third maxilliped; it has a fissure which is a narrow slit, but which gapes open in other species. The third maxilliped is also larger, covering the epistome and the antennules in J. lagostoma but not in other species.
Within the species, two distinct colour morphs can be seen. The "yellow" morph has a bright yellow or orange exoskeleton
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
, with white patches on the underside of the walking legs and claws. The "purple" morph has a dark purple exoskeleton, but with the same white patches as on the yellow morph. A few intermediate individuals occur, which are predominantly yellow, but with purple patches on the carapace. On Ascension Island, the yellow morph is the more frequent one, while on , the distribution is more equal. Darker individuals are thought to be better concealed from predators, but more prone to heat stress during long migrations; is much smaller than Ascension Island, and the migration routes are therefore shorter, which may explain the difference in frequency of the two morphs.
Ecology and conservation
Before Ascension Island was colonised by Europeans in the 19th century, Johngarthia lagostoma was the only large land animal on the island. Since then, many species of mammalMammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
have been introduced
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
to Ascension Island, and now compete with J. lagostoma; they include mice
Mouse
A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...
, rat
Rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...
s and rabbit
Rabbit
Rabbits are small mammals in the family Leporidae of the order Lagomorpha, found in several parts of the world...
s.
J. lagostoma is active at night and after rain, when it emerges from its burrow
Burrow
A burrow is a hole or tunnel dug into the ground by an animal to create a space suitable for habitation, temporary refuge, or as a byproduct of locomotion. Burrows provide a form of shelter against predation and exposure to the elements, so the burrowing way of life is quite popular among the...
s, which can be up to 1 metres (3.3 ft) deep. In 1915, H. A. Baylis reported that it feeds on "decaying vegetation and perhaps a certain amount of excreta from sea-birds"; most of its diet is thought to be made up of plant matter, but can also include animals. In the Wideawake Fairs, J. lagostoma feeds on chicks and eggs of the sooty tern, and they have been proposed as a limiting factor
Limiting factor
A limiting factor or limiting resource is a factor that controls a process, such as organism growth or species population, size, or distribution. The availability of food, predation pressure, or availability of shelter are examples of factors that could be limiting for an organism...
in the breeding of petrel
Petrel
Petrels are tube-nosed seabirds in the bird order Procellariiformes. The common name does not indicate relationship beyond that point, as "petrels" occur in three of the four families within that group...
s on Ascension Island. In May, green sea turtle
Green Sea Turtle
The Green sea turtle or green turtle is a large sea turtle of the family Cheloniidae. It is the only species in the genus Chelonia. Its range extends throughout tropical and subtropical seas around the world, with two distinct populations in the Atlantic and Pacific Oceans...
s (Chelonia mydas) hatch, and J. lagostoma is one of several predators to target the emerging hatchling
Hatchling
In oviparous biology, a hatchling is the newborn of animals that develop and emerge from within hard-shell eggs. The offspring of birds are often hatched naked and with their eyes closed. The hatchling relies totally on its parents for feeding and warmth. Hatchlings precede nestlings in the chick's...
s, alongside the Ascension frigatebird
Ascension Frigatebird
The Ascension Frigatebird breeds only on the tiny Boatswain Bird Island just off Ascension Island in the tropical Atlantic Ocean. It formerly bred on the larger island, but was exterminated by introduced cats, Brown Rats, and human persecution.It breeds on the rocky slopes of Boatswainbird...
(Fregata aquila) and feral cat
Feral cat
A feral cat is a descendant of a domesticated cat that has returned to the wild. It is distinguished from a stray cat, which is a pet cat that has been lost or abandoned, while feral cats are born in the wild; the offspring of a stray cat can be considered feral if born in the wild.In many parts of...
s. The crabs find water on and under rocks, especially after condensation
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
has begun to form on their cool surfaces at night.
In the late nineteenth century, a bounty
Bounty (reward)
A bounty is a payment or reward often offered by a group as an incentive for the accomplishment of a task by someone usually not associated with the group. Bounties are most commonly issued for the capture or retrieval of a person or object. They are typically in the form of money...
was levied on J. lagostoma in order to reduce its numbers. Hunters were paid 6 pence (alternatively paid in rum
Rum
Rum is a distilled alcoholic beverage made from sugarcane by-products such as molasses, or directly from sugarcane juice, by a process of fermentation and distillation. The distillate, a clear liquid, is then usually aged in oak barrels...
) for every hundred claws collected. In 1879, the total bag for the island comprised 66 cats, 4,013 mice, 7,683 rats and 80,414 land crabs; in the eight years to 1887, bounties were collected on more than 330,000 crabs. The current population is much smaller, and the low level of recruitment
Recruitment (biology)
In biology, recruitment occurs when juvenile organisms survive to be added to a population. The term is generally used to refer to a stage whereby the organisms are settled and able to be detected by an observer....
and lack of juveniles
Juvenile (organism)
A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size. Juveniles sometimes look very different from the adult form, particularly in terms of their colour...
suggests that the species may become endangered.
Life cycle
Although juvenile and adult J. lagostoma are almost exclusively terrestrial, the larvaeCrustacean larvae
Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow...
are marine and plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
ic. In order to release their offspring, the adults therefore have to migrate to the sea, as seen in other land crabs, such as the Christmas Island red crab
Christmas Island red crab
The Christmas Island red crab, Gecarcoidea natalis, is a species of land crab that is endemic to Christmas Island and the Cocos Islands in the Indian Ocean...
, Gecarcoidea natalis. In most members of the family Gecarcinidae, migration coincides with the rainy season, which reduces the risk of desiccation; migration in J. lagostoma occurs from January until March, while the period of highest rainfall is from March to May.
The crabs travel approximately 450 m (1,476.4 ft) per day, and mating can take place anywhere along the route. The proportion of males on the migration therefore decreases as the migration continues. The eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
are larger than in other gecarcinid species and consequently fewer in number; females with a carapace width of 94 mm (3.7 in) had a mean fecundity
Fecundity
Fecundity, derived from the word fecund, generally refers to the ability to reproduce. In demography, fecundity is the potential reproductive capacity of an individual or population. In biology, the definition is more equivalent to fertility, or the actual reproductive rate of an organism or...
of 72,000. Spawning occurs in the last quarter of the lunar cycle, during neap tides, on rocky shores.
Taxonomy and history
Johngarthia lagostoma was first described by Henri Milne-EdwardsHenri Milne-Edwards
Henri Milne-Edwards was an eminent French zoologist.Henri Milne-Edwards was the 27th child of William Edwards, an English planter and militia colonel in Jamaica and Elisabeth Vaux, a French. He was born in Bruges, Belgium, where his parents had retired. At that time, Bruges was a part of the...
in 1837, under the name Gecarcinus lagostoma. The specific epithet means "hare-lip", from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
(, "hare") and (, "mouth"); Milne-Edwards also named the species in French
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...
("hare-lipped land crab"). Milne-Edwards erroneously gave the type locality as "" (Australasia
Australasia
Australasia is a region of Oceania comprising Australia, New Zealand, the island of New Guinea, and neighbouring islands in the Pacific Ocean. The term was coined by Charles de Brosses in Histoire des navigations aux terres australes...
); he had been given the material he used for the description by Jean René Constant Quoy
Jean René Constant Quoy
Jean René Constant Quoy was a French zoologist.Along with Joseph Paul Gaimard he served as naturalist aboard La Coquille under Louis Isidore Duperrey during its circumnavigation of the globe , and the Astrolabe under the command of Jules Dumont d'Urville...
and Joseph Paul Gaimard
Joseph Paul Gaimard
Joseph Paul Gaimard was a French naval surgeon and naturalist.Along with Jean René Constant Quoy he served as naturalist on the ships L'Uranie under Louis de Freycinet 1817-1820, and L'Astrolabe under Jules Dumont d'Urville 1826-1829...
, who were working on the molluscs collected on the Astrolabe excursion, which had visited Australasia and stopped at Ascension Island in 1829. G. lagostoma was placed in the subgenus Johngarthia by Michael Türkay in 1970, who raised the subgenus to the rank
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...
of genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
in 1987.
Many subsequent voyages halted at Ascension Island, and many visitors commented on the land crabs they found there, including William Dampier
William Dampier
William Dampier was an English buccaneer, sea captain, author and scientific observer...
, Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
and Charles Wyville Thomson
Charles Wyville Thomson
Sir Charles Wyville Thomson was a Scottish zoologist and chief scientist on the Challenger expedition.-Career:...
. Bernard Stonehouse
Bernard Stonehouse
Bernard Stonehouse is a British scientist who specialised in polar research and popular science. He was born in Hull on 1 May 1926. He joined the Royal Navy in 1944, and served from 1946–1950 for the Falkland Islands Dependencies Survey...
reported on an expedition by the British Ornithologists' Union
British Ornithologists' Union
The British Ornithologists' Union aims to encourage the study of birds in Britain, Europe and elsewhere, in order to understand their biology and to aid their conservation....
to Ascension Island, stating:
We met land crabs, too, and were sadly disappointed. They were small, no larger than an ordinary edible crab, with bloated shells and moderately long pincers. Some were of beetroot purple, others yellow or orange, apparently two colour-phases of the same species. They were shy, freezing with pincers erect when alarmed, usually to be found within a short distance of their burrows and ready to scuttle down at the drop of a hat. In rainy weather they promenaded more freely, sometimes appearing at the side of road with arms waving like diminutive but aggressive hitch-hikers. Fringed mandibles [third maxillipeds] suggest a permanently turned-down mouth, giving them a disgruntled, unhappy expression; they were disagreeable rather than sinister and fell far short of their reputation. The first land crab I met was sitting in a prickly pear bush, sadly munching one of the brilliant red fruits and dribbling juice. I could never take them seriously after that.
The closely related crabs from the islands of the Gulf of Guinea
Gulf of Guinea
The Gulf of Guinea is the northeasternmost part of the tropical Atlantic Ocean between Cape Lopez in Gabon, north and west to Cape Palmas in Liberia. The intersection of the Equator and Prime Meridian is in the gulf....
were formerly included in Gecarcinus lagostoma, but are now treated as a separate species, Johngarthia weileri
Johngarthia weileri
Johngarthia weileri is a species of land crab in the genus Johngarthia from the eastern Atlantic Ocean.-Distribution:Johngarthia weiler is found on the coast of Cameroon and on the islands in the Gulf of Guinea.-Taxonomy:...
.