Astacoides
Encyclopedia
Astacoides is a genus of freshwater
crayfish
endemic to Madagascar
. The first specimens were brought to Europe in 1839, and seven species are now recognised, most of which are on the IUCN Red List
. They are large and slow-growing, and are threatened by habitat loss
and overexploitation
by local people. They are only found in a relatively small part of the island, mostly in undisturbed upland areas. They belong to the Gondwana
-distributed family Parastacidae
, but their nearest relatives live in Australasia
, there being no native crayfish in mainland Africa
or India
.
length of up to 80 millimetres (3.1 in) in the case of A. betsileoensis. Males and females are similar, except for the organs directly involved in reproduction. Thomas Henry Huxley, in his book The Crayfish, noted that Astacoides has fewer pairs of gill
s than any other crayfish, with only 12 pairs compared to 21 pairs in Astacopsis.
length of 30 mm (1.2 in). They appear to breed once a year, with females bearing eggs
for around four months, peaking from July to October. The eggs hatch in October or November, and the juveniles
are independent by January.
The fish Channa maculata
is an invasive species
in parts of Madagascar, and it is known to feed on young crayfish. Astacoides is also harvested by local people, often before the crayfish are able to reach reproductive age. The greater threat to Astacoides crayfish, however, is from habitat loss
. The importance of habitat loss may have been underestimated in the past because most studies have focussed on the Ranomafana National Park
, where the forests are largely intact but crayfish are still harvested by local people.
Crayfish are only found in a relatively small area of Madagascar, covering parts of Toamasina
, Antananarivo
, Fianarantsoa
and Toliara
provinces
; the total area they inhabit is around 60000 square kilometres (23,166.1 sq mi) and ranges from the Isaha valley south to the Hauts Plateaux (near Anjozorobe
). In common with other tropical crayfish, Astacoides only lives at higher altitudes, from 500 metres (1,640.4 ft) above sea level to 2000 m (6,561.7 ft).
is difficult to explain. The other members of the family Parastacidae
are found in South America
and Australasia
, suggesting a Gondwana
n origin for the family. However, there are no native crayfish in either Africa
or India
, the two landmasses with the most recent connections to Madagascar in the geological past. The genus which shares the greatest similarities with Astacoides is the Tasmania
n genus Astacopsis. Given the large distance between Tasmania and Madagascar, it has been suggested that although the freshwater crayfish are a monophyletic group, their common ancestor may have lived in the seas, with separate crayfish lineages colonising the rivers separately.
returned from an expedition to Madagascar bearing specimens of a crayfish he had collected there. He gave some of the material to the Muséum national d'histoire naturelle
in Paris
and some to Félix Édouard Guérin-Méneville
. Both Guérin-Méneville and, at the museum, Henri Milne-Edwards
and Jean Victoire Audouin
wrote papers describing the new species, with the name Astacoides Goudotii Guérin, 1839 published on 29 April, and Astacus madagascarensis Milne-Edwards & Audouin, 1839 published on May 9. Some years later, and apparently unaware of the two French descriptions, Charles Spence Bate
published what he thought was the first account of Madagascan crayfish. He had been brought specimens by J. Caldwell, and described them in 1865 under the name Astacus Caldwelli Bate, 1865. By the end of the 19th century, scientists had settled on the name Astacus madagascarensis, treating the others as synonyms
, and to preserve nomeclatural stability, the name A. goudotii was suppressed by the International Commission on Zoological Nomenclature
in 1958.
The next new taxon to be described was the variety betsileoensis described by Georges Petit in 1923. In 1927, he divided the Madagascan crayfish into the "macrophthalmes", with large eyes, a convex carapace and flattened chela
e, and the "microphthalmes", with small eyes, cylindrical carapace and more robust chelae. In their 1929 monograph, Théodore Monod
and Petit recognised four "varieties", betsileoensis and madagascariensis (the "macrophthalmes") and brevirostris and granulimanus (the "microphthalmes"). In 1964, Lipke Holthuis
realised that due to the suppression of the name goudotii, the epithet caldwelli would have to be used, although Holthuis continued to treat the different taxa as subspecies. In 1974, Horton H. Hobbs, Jr.
published a monograph which finally raised the various taxa observed to that point to the rank of species
, and introduced two new species. Since then, the only change has been the addition of a new species, described in 2005, and commemmorating Hobbs, Astacoides hobbsi.
(EN), four are "Data Deficient
" (DD), and one is of "Least Concern
" (LC).
Fresh Water
Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...
crayfish
Crayfish
Crayfish, crawfish, or crawdads – members of the superfamilies Astacoidea and Parastacoidea – are freshwater crustaceans resembling small lobsters, to which they are related...
endemic to Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
. The first specimens were brought to Europe in 1839, and seven species are now recognised, most of which are on the IUCN Red List
IUCN Red List
The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...
. They are large and slow-growing, and are threatened by habitat loss
Habitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...
and overexploitation
Overexploitation
Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Sustained overexploitation can lead to the destruction of the resource...
by local people. They are only found in a relatively small part of the island, mostly in undisturbed upland areas. They belong to the Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
-distributed family Parastacidae
Parastacidae
Parastacidae is the family of freshwater crayfish found in the southern hemisphere. The family is a classic Gondwana-distributed taxon, with extant members in South America, Madagascar, Australia, New Zealand and New Guinea, and extinct taxa also in Antarctica.Three genera are to be found in Chile,...
, but their nearest relatives live in 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...
, there being no native crayfish in mainland Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
or India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
.
Description
Astacoides species are large for freshwater crayfish, reaching a 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...
length of up to 80 millimetres (3.1 in) in the case of A. betsileoensis. Males and females are similar, except for the organs directly involved in reproduction. Thomas Henry Huxley, in his book The Crayfish, noted that Astacoides has fewer pairs of gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
s than any other crayfish, with only 12 pairs compared to 21 pairs in Astacopsis.
Biology
Very little field work has been carried out on Madagascan crayfish, leaving their biology poorly known. They are slow-growing animals, among the slowest of any crayfish; A. crosnieri may take 10 years to reach a 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...
length of 30 mm (1.2 in). They appear to breed once a year, with females bearing 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...
for around four months, peaking from July to October. The eggs hatch in October or November, and the 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...
are independent by January.
The fish Channa maculata
Channa maculata
Channa maculata, the blotched snakehead, is a species of snakehead. It is native to southern China and northern Vietnam, but has been widely introduced to other countries, where it is an invasive species. Adults typically grow to a length of , but a maximum of has been recorded....
is an invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
in parts of Madagascar, and it is known to feed on young crayfish. Astacoides is also harvested by local people, often before the crayfish are able to reach reproductive age. The greater threat to Astacoides crayfish, however, is from habitat loss
Habitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...
. The importance of habitat loss may have been underestimated in the past because most studies have focussed on the Ranomafana National Park
Ranomafana National Park
Ranomafana National Park is located in the southeastern part of Madagascar in Haute Matsiatra and Vatovavy-Fitovinany. With more than 41,600 hectares of moist forest climate, the park is home to several rare species of flora and fauna such as the lemur...
, where the forests are largely intact but crayfish are still harvested by local people.
Distribution
Toamasina Province
Toamasina is a former province of Madagascar with an area of 71,911 km². It had a population of 2,855,600 . Its capital was Toamasina, the most important seaport of the country....
, Antananarivo
Antananarivo Province
Antananarivo is a former province of Madagascar with an area of 58,283 km². It had a population of 5,370,900 . Its capital was Antananarivo.Except for Antsiranana, Antananarivo Province bordered all of the country's other provinces:*Mahajanga - north...
, Fianarantsoa
Fianarantsoa Province
Fianarantsoa is a former province of Madagascar.*Area: 103,272 km2.*Population of 3,366,291 .*Capital: Fianarantsoa.*President: Fidy Mpanjato Rakotonarivo .One of its towns was Andohapatsakana...
and Toliara
Toliara Province
Toliara is a former province of Madagascar with an area of 161,405 km². It had a population of 2,229,550 . Its capital was Toliara...
provinces
Provinces of Madagascar
||Madagascar is divided into six "autonomous provinces" :#Antananarivo Province#Antsiranana Province#Fianarantsoa Province#Mahajanga Province#Toamasina Province#Toliara Province...
; the total area they inhabit is around 60000 square kilometres (23,166.1 sq mi) and ranges from the Isaha valley south to the Hauts Plateaux (near Anjozorobe
Anjozorobe
Anjozorobe is a large town in Analamanga Region, Madagascar, approximately 90 kilometres north-east of the capital Antananarivo.Anjozorobe is famous with its corridor and with a pilgrim city of Anosivolakely where the Virgin Maria is reported to have appeared in 1990.Anjozorobe Forest Corridor is...
). In common with other tropical crayfish, Astacoides only lives at higher altitudes, from 500 metres (1,640.4 ft) above sea level to 2000 m (6,561.7 ft).
Biogeography
The presence of Astacoides on the island of MadagascarMadagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
is difficult to explain. The other members of the family Parastacidae
Parastacidae
Parastacidae is the family of freshwater crayfish found in the southern hemisphere. The family is a classic Gondwana-distributed taxon, with extant members in South America, Madagascar, Australia, New Zealand and New Guinea, and extinct taxa also in Antarctica.Three genera are to be found in Chile,...
are found in South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
and 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...
, suggesting a Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
n origin for the family. However, there are no native crayfish in either Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
or India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, the two landmasses with the most recent connections to Madagascar in the geological past. The genus which shares the greatest similarities with Astacoides is the Tasmania
Tasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...
n genus Astacopsis. Given the large distance between Tasmania and Madagascar, it has been suggested that although the freshwater crayfish are a monophyletic group, their common ancestor may have lived in the seas, with separate crayfish lineages colonising the rivers separately.
Taxonomic history
In 1839, the French explorer-naturalist Justin GoudotJustin Goudot
Justin Goudot was a French explorer, and naturalist collector.Goudot, born in the Jura , lived in Bogata. He was attached to Muséum national d'histoire naturelle in Paris as a collector naturalist...
returned from an expedition to Madagascar bearing specimens of a crayfish he had collected there. He gave some of the material to the Muséum national d'histoire naturelle
Muséum national d'histoire naturelle
The Muséum national d'Histoire naturelle is the National Museum of Natural History in Paris, France.- History :The museum was formally founded on 10 June 1793, during the French Revolution...
in Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
and some to Félix Édouard Guérin-Méneville
Félix Édouard Guérin-Méneville
Félix Édouard Guérin-Méneville was a French entomologist.Guérin-Méneville changed his surname from Guérin in 1836. He was the author of the illustrated work Iconographie du Règne Animal de G. Cuvier 1829–1844, a complement to the work of Georges Cuvier and Pierre André Latreille, which lacked...
. Both Guérin-Méneville and, at the museum, 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...
and Jean Victoire Audouin
Jean Victoire Audouin
thumb|Victor AudouinJean Victoire Audouin , sometimes Victor Audouin, was a French naturalist, an entomologist, ornithologist and malacologist.Audouin was born in Paris and studied medicine...
wrote papers describing the new species, with the name Astacoides Goudotii Guérin, 1839 published on 29 April, and Astacus madagascarensis Milne-Edwards & Audouin, 1839 published on May 9. Some years later, and apparently unaware of the two French descriptions, Charles Spence Bate
Charles Spence Bate
Charles Spence Bate, or Spence Bate, FRS was a British zoologist and dentist, who who practiced first at Swansea, and then Plymouth, taking over his father's practice. He was an authority on the Crustacea, and a frequent correspondent of Charles Darwin, mostly concerning their shared interest in...
published what he thought was the first account of Madagascan crayfish. He had been brought specimens by J. Caldwell, and described them in 1865 under the name Astacus Caldwelli Bate, 1865. By the end of the 19th century, scientists had settled on the name Astacus madagascarensis, treating the others as synonyms
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
, and to preserve nomeclatural stability, the name A. goudotii was suppressed by the International Commission on Zoological Nomenclature
International Commission on Zoological Nomenclature
The International Commission on Zoological Nomenclature is an organization dedicated to "achieving stability and sense in the scientific naming of animals". Founded in 1895, it currently comprises 28 members from 20 countries, mainly practicing zoological taxonomists...
in 1958.
The next new taxon to be described was the variety betsileoensis described by Georges Petit in 1923. In 1927, he divided the Madagascan crayfish into the "macrophthalmes", with large eyes, a convex carapace and flattened chela
Chela
Chela has two main meanings. One derivation comes from Hindi from Sanskrit , meaning "slave" or "servant". In English, the word means a religious student or disciple...
e, and the "microphthalmes", with small eyes, cylindrical carapace and more robust chelae. In their 1929 monograph, Théodore Monod
Théodore Monod
Théodore André Monod was a French naturalist, explorer, and humanist scholar.-Exploration:...
and Petit recognised four "varieties", betsileoensis and madagascariensis (the "macrophthalmes") and brevirostris and granulimanus (the "microphthalmes"). In 1964, Lipke Holthuis
Lipke Holthuis
Lipke Bijdeley Holthuis was a Dutch carcinologist, considered one of the "undisputed greats" of carcinology, and "the greatest carcinologist of our time"....
realised that due to the suppression of the name goudotii, the epithet caldwelli would have to be used, although Holthuis continued to treat the different taxa as subspecies. In 1974, Horton H. Hobbs, Jr.
Horton H. Hobbs, Jr.
Horton Holcombe Hobbs, Jr. was an American taxonomist and carcinologist, specialising in freshwater decapods. He was also a capable artist, musician, cook and botanist....
published a monograph which finally raised the various taxa observed to that point to the rank of species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, and introduced two new species. Since then, the only change has been the addition of a new species, described in 2005, and commemmorating Hobbs, Astacoides hobbsi.
Taxonomy
Of the seven described species, two are considered endangered speciesEndangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
(EN), four are "Data Deficient
Data Deficient
Data Deficient is a category applied by the IUCN, other agencies, and individuals to a species when the available information is not sufficient for a proper assessment of conservation status to be made...
" (DD), and one is of "Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
" (LC).
- Astacoides betsileoensis Petit, 1923 –
- Astacoides caldwelli (Bate, 1865) –
- Astacoides crosnieri Hobbs, 1987 –
- Astacoides granulimanus Monod & Petit, 1929 –
- Astacoides hobbsi Boyko, 2005 –
- Astacoides madagascarensis (H. Milne-Edwards & Audouin, 1839) –
- Astacoides petiti Hobbs, 1987 –