Johngarthia lagostoma: Difference between revisions
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Mature specimens of ''J. lagostoma'' are typically {{convert|70|-|110|mm}} wide across the [[carapace]] on Ascension Island; individuals from {{lang|pt|Atol das Rocas}} are somewhat smaller.<ref name="Hartnoll2006"/> 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 ''[[Johngarthia planata|J. planata]]''.<ref name="Türkay">{{cite journal |author=Michael Türkay |year=1970 |title=Die Gecarcinidae Amerikas. Mit einem Anhang über ''Ucides'' Rathbun (Crustacea: Decapoda) |journal=[[Senckenbergiana Biologica]] |volume=51 |issue=5/6 |pages=333–354 |url=http://decapoda.nhm.org/pdfs/27369/27369.pdf |format=[[Portable Document Format|PDF]]}}</ref> 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 [[antennule]]s in ''J. lagostoma'' but not in other species.<ref name="Türkay"/> |
Mature specimens of ''J. lagostoma'' are typically {{convert|70|-|110|mm}} wide across the [[carapace]] on Ascension Island; individuals from {{lang|pt|Atol das Rocas}} are somewhat smaller.<ref name="Hartnoll2006"/> 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 ''[[Johngarthia planata|J. planata]]''.<ref name="Türkay">{{cite journal |author=Michael Türkay |year=1970 |title=Die Gecarcinidae Amerikas. Mit einem Anhang über ''Ucides'' Rathbun (Crustacea: Decapoda) |journal=[[Senckenbergiana Biologica]] |volume=51 |issue=5/6 |pages=333–354 |url=http://decapoda.nhm.org/pdfs/27369/27369.pdf |format=[[Portable Document Format|PDF]]}}</ref> 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 [[antennule]]s in ''J. lagostoma'' but not in other species.<ref name="Türkay"/> |
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Within the species, two distinct [[colour morph]]s can be seen.<ref name="Hartnoll2006"/> 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.<ref name="Hartnoll2006"/> On Ascension Island, the yellow morph is the more frequent one, while on {{lang|pt|Atol das Rocas}}, the distribution is more equal.<ref name="Hartnoll2006"/> Darker individuals are thought to be better concealed from [[predator]]s, but more prone to [[heat stress]] during long migrations;<ref name="Hartnoll2009">{{cite journal |author1=Richard G. Hartnoll |author2=Annette C. Broderick |author3=Brendan J. Godley |author4=Kate E. Saunders |year=2009 |title=Population structure of the land crab ''Johngarthia lagostoma'' on Ascension Island |journal=[[Journal of Crustacean Biology]] |volume=29 |issue=1 |pages=57–61 |doi=10.1651/08-2992.1 |url=http://www.seaturtle.org/PDF/Hartnoll_2009_JCrustacBiol.pdf |format=[[Portable Document Format|PDF]]}}</ref> {{lang|pt|Atol das Rocas}} is much smaller than Ascension Island, and the migration routes are therefore shorter, which may explain the difference in frequency of the two morphs.<ref name="Hartnoll2006"/> |
Within the species, two distinct [[colour morph]]s can be seen.<ref name="Hartnoll2006"/> 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.<ref name="Hartnoll2006"/> On Ascension Island, the yellow morph is the more frequent one, while on {{lang|pt|Atol das Rocas}}, the distribution is more equal.<ref name="Hartnoll2006"/> Darker individuals are thought to be better concealed from [[predator]]s, but more prone to [[heat stress]] during long migrations;<ref name="Hartnoll2009">{{cite journal |author1=Richard G. Hartnoll |author2=Annette C. Broderick |author3=Brendan J. Godley |author4=Kate E. Saunders |year=2009 |title=Population structure of the land crab ''Johngarthia lagostoma'' on Ascension Island |journal=[[Journal of Crustacean Biology]] |volume=29 |issue=1 |pages=57–61 |doi=10.1651/08-2992.1 |url=http://www.seaturtle.org/PDF/Hartnoll_2009_JCrustacBiol.pdf |format=[[Portable Document Format|PDF]] }}{{dead link|date=November 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> {{lang|pt|Atol das Rocas}} is much smaller than Ascension Island, and the migration routes are therefore shorter, which may explain the difference in frequency of the two morphs.<ref name="Hartnoll2006"/> |
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==Ecology and conservation== |
==Ecology and conservation== |
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==Taxonomy and history== |
==Taxonomy and history== |
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''Johngarthia lagostoma'' was first described by [[Henri Milne-Edwards]] in 1837, under the name ''Gecarcinus lagostoma''.<ref name="Hartnoll2006">{{cite journal |author1=Richard G. Hartnoll |author2=Terri Mackintosh |author3=Tara J. Pelembe |year=2006 |title=''Johngarthia lagostoma'' (H. Milne Edwards, 1837) on Ascension Island: a very isolated land crab population |journal=[[Crustaceana]] |volume=79 |issue=2 |pages=197–215 |doi=10.1163/156854006776952900 |url=http://www.ascensionconservation.org.ac/pdf/11-G-Hartnoll-Macintosh-Pelembe.pdf |format=[[Portable Document Format|PDF]]}}</ref> The [[specific name (zoology)|specific epithet]] ''{{lang|el|lagostoma}}'' means "[[cleft lip and palate|hare-lip]]", from the [[Greek language|Greek]] {{lang|el|[[:wikt:λαγός|λαγός]]}} (''{{lang|el|lagos}}'', "hare") and {{lang|el|[[:wikt:στόμα|στόμα]]}} (''{{lang|el|[[:wikt:stoma|stoma]]}}'', "mouth");<ref>{{cite book |author=[[Eric Partridge]] |year=2009 |title=Origins: an Etymological Dictionary of Modern English |publisher=[[Routledge]] |isbn=978-0-203-42114-7 |chapter=A list of learned compound-forming elements |pages=3964–4213 |url=https://books.google.com/books?id=xA9dxrhfa5kC&pg=PA4066}}</ref> Milne-Edwards also named the species in [[French language|French]] ''{{lang|fr|gécarcin bec-de-lièvre}}'' ("hare-lipped land crab").<ref>{{cite book |author=[[Henri Milne-Edwards]] |year=1837 |title=Histoire naturella des Crustacés. II |chapter=Tribu des gécarciniens |pages=16–27 |url=https://archive.org/details/histoirenaturell02miln}}</ref> Milne-Edwards erroneously gave the [[type locality (biology)|type locality]] as "{{lang|fr|l'Australasie}}" ([[Australasia]]);<ref name="Hartnoll2006"/> 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 ''[[French ship Astrolabe (1811)|Astrolabe]]'' excursion, which had visited Australasia and stopped at Ascension Island in 1829.<ref name="Manning">{{cite journal |author=[[Raymond B. Manning]] & [[Fenner A. Chace, Jr.]] |year=1990 |title=Decapod and stomatopod Crustacea from Ascension Island, South Atlantic Ocean |journal=[[Smithsonian Contributions to Zoology]] |volume=503 |pages=1–91 |url=http://si-pddr.si.edu/jspui/bitstream/10088/5649/2/SCtZ-0503-Lo_res.pdf |format=[[Portable Document Format|PDF]] |doi=10.5479/si.00810282.503}}</ref> ''G. lagostoma'' was placed in the subgenus ''Johngarthia'' by Michael Türkay in 1970, who raised the subgenus to the [[taxonomic rank|rank]] of [[genus]] in 1987.<ref name="Hartnoll2006"/> |
''Johngarthia lagostoma'' was first described by [[Henri Milne-Edwards]] in 1837, under the name ''Gecarcinus lagostoma''.<ref name="Hartnoll2006">{{cite journal |author1=Richard G. Hartnoll |author2=Terri Mackintosh |author3=Tara J. Pelembe |year=2006 |title=''Johngarthia lagostoma'' (H. Milne Edwards, 1837) on Ascension Island: a very isolated land crab population |journal=[[Crustaceana]] |volume=79 |issue=2 |pages=197–215 |doi=10.1163/156854006776952900 |url=http://www.ascensionconservation.org.ac/pdf/11-G-Hartnoll-Macintosh-Pelembe.pdf |format=[[Portable Document Format|PDF]] |deadurl=yes |archiveurl=https://web.archive.org/web/20071110155436/http://www.ascensionconservation.org.ac/pdf/11-G-Hartnoll-Macintosh-Pelembe.pdf |archivedate=2007-11-10 |df= }}</ref> The [[specific name (zoology)|specific epithet]] ''{{lang|el|lagostoma}}'' means "[[cleft lip and palate|hare-lip]]", from the [[Greek language|Greek]] {{lang|el|[[:wikt:λαγός|λαγός]]}} (''{{lang|el|lagos}}'', "hare") and {{lang|el|[[:wikt:στόμα|στόμα]]}} (''{{lang|el|[[:wikt:stoma|stoma]]}}'', "mouth");<ref>{{cite book |author=[[Eric Partridge]] |year=2009 |title=Origins: an Etymological Dictionary of Modern English |publisher=[[Routledge]] |isbn=978-0-203-42114-7 |chapter=A list of learned compound-forming elements |pages=3964–4213 |url=https://books.google.com/books?id=xA9dxrhfa5kC&pg=PA4066}}</ref> Milne-Edwards also named the species in [[French language|French]] ''{{lang|fr|gécarcin bec-de-lièvre}}'' ("hare-lipped land crab").<ref>{{cite book |author=[[Henri Milne-Edwards]] |year=1837 |title=Histoire naturella des Crustacés. II |chapter=Tribu des gécarciniens |pages=16–27 |url=https://archive.org/details/histoirenaturell02miln}}</ref> Milne-Edwards erroneously gave the [[type locality (biology)|type locality]] as "{{lang|fr|l'Australasie}}" ([[Australasia]]);<ref name="Hartnoll2006"/> 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 ''[[French ship Astrolabe (1811)|Astrolabe]]'' excursion, which had visited Australasia and stopped at Ascension Island in 1829.<ref name="Manning">{{cite journal |author=[[Raymond B. Manning]] & [[Fenner A. Chace, Jr.]] |year=1990 |title=Decapod and stomatopod Crustacea from Ascension Island, South Atlantic Ocean |journal=[[Smithsonian Contributions to Zoology]] |volume=503 |pages=1–91 |url=http://si-pddr.si.edu/jspui/bitstream/10088/5649/2/SCtZ-0503-Lo_res.pdf |format=[[Portable Document Format|PDF]] |doi=10.5479/si.00810282.503}}</ref> ''G. lagostoma'' was placed in the subgenus ''Johngarthia'' by Michael Türkay in 1970, who raised the subgenus to the [[taxonomic rank|rank]] of [[genus]] in 1987.<ref name="Hartnoll2006"/> |
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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]].<ref name="Manning"/> [[Bernard Stonehouse]] reported on an expedition by the [[British Ornithologists' Union]] to Ascension Island, stating:<ref>{{cite book |author=Bernard Stonehouse |year=1960 |title=Wideawake Island: The Story of the B.O.U. Centenary Expedition to Ascension |location=London |publisher=[[Hutchinson (publisher)|Hutchinson]]}} Cited in Manning & Chace (1990).</ref> |
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]].<ref name="Manning"/> [[Bernard Stonehouse]] reported on an expedition by the [[British Ornithologists' Union]] to Ascension Island, stating:<ref>{{cite book |author=Bernard Stonehouse |year=1960 |title=Wideawake Island: The Story of the B.O.U. Centenary Expedition to Ascension |location=London |publisher=[[Hutchinson (publisher)|Hutchinson]]}} Cited in Manning & Chace (1990).</ref> |
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Revision as of 07:28, 29 November 2017
| Johngarthia lagostoma | |
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| Yellow morph of J. lagostoma | |
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| Species: | J. lagostoma
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| Binomial name | |
| Johngarthia lagostoma (H. Milne-Edwards, 1837)
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| Synonyms [1] | |
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Gecarcinus lagostoma H. Milne-Edwards, 1837 | |
Johngarthia lagostoma is a species of
maxilliped
.
Johngarthia lagostoma lives in burrows among vegetation, at altitudes of up to 400 m (1,300 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
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
.
Distribution and biogeography
Johngarthia lagostoma is found on
sooty tern breeding colony in the south-west of the island (known as the Wideawake Fairs).[2] On Ilha Trindade, J. lagostoma is abundant wherever plants grow, included the highest parts of the island.[3]
The
stepping stones" for the colonisation of Ascension Island; the isolation of Ascension Island from any other land mass makes transportation of either larvae or adults difficult.[2]
Description
Mature specimens of J. lagostoma are typically 70–110 millimetres (2.8–4.3 in) wide across the
antennules in J. lagostoma but not in other species.[4]
Within the species, two distinct
heat stress during long migrations;[5] Atol das Rocas is much smaller than Ascension Island, and the migration routes are therefore shorter, which may explain the difference in frequency of the two morphs.[2]
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.[5] Since then, many species of mammal have been introduced to Ascension Island, and now compete with J. lagostoma; they include mice, rats and rabbits.[5]
J. lagostoma is active at night and after rain,Ascension frigatebird (Fregata aquila) and feral cats.[7] The crabs find water on and under rocks, especially after condensation has begun to form on their cool surfaces at night.[3]
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.[8] 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.[9] The current population is much smaller, and the low level of recruitment and lack of juveniles suggests that the species may become endangered.[5]
Life cycle
Although juvenile and adult J. lagostoma are almost exclusively terrestrial, 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.[10]
The crabs travel approximately 450 m (1,480 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.neap tides, on rocky shores.[10]
Taxonomy and history
Johngarthia lagostoma was first described by
type locality as "l'Australasie" (Australasia);[2] 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.[8] G. lagostoma was placed in the subgenus Johngarthia by Michael Türkay in 1970, who raised the subgenus to the rank of genus in 1987.[2]
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.[8] Bernard Stonehouse reported on an expedition by the British Ornithologists' Union to Ascension Island, stating:[13]
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 were formerly included in Gecarcinus lagostoma, but are now treated as a separate species, Johngarthia weileri.[8]
References
- PDF) on 2011-06-06.)
{{cite journal}}: Unknown parameter|deadurl=ignored (|url-status=suggested) (help - ^ PDF) on 2007-11-10.)
{{cite journal}}: Unknown parameter|deadurl=ignored (|url-status=suggested) (help - ^ .
- ^ Senckenbergiana Biologica. 51 (5/6): 333–354.
- ^ ]
- ^ H. A. Baylis (1915). "Oligochaeta". Natural History Report, British Antarctic ("Terra Nova") Expedition, 1910, Zoology. 2 (2): 13–18. Cited in Manning & Chace (1990).
- .
- ^ .
- ISBN 978-0-385-00314-8. Cited in Manning & Chace (1990).
- ^ .
- ISBN 978-0-203-42114-7.
- ^ Henri Milne-Edwards (1837). "Tribu des gécarciniens". Histoire naturella des Crustacés. II. pp. 16–27.
- Hutchinson. Cited in Manning & Chace (1990).