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20-497: Geosesarma is genus of small freshwater or terrestrial crabs , typically less than 10 mm (0.4 in) across the carapace . They live and reproduce on land with the larval stages inside the egg . They are found from India , through Southeast Asia , to the Solomon Islands and Hawaii . In the pet trade, they are sometimes called vampire crabs . This has nothing to do with their feeding habits, but rather with

40-544: A "pseudolung" in their gill chamber that allows them to breathe in air. These developments have preadapted freshwater crabs for terrestrial living, although freshwater crabs need to return to water periodically to excrete ammonia . Freshwater crabs are found throughout the tropical and subtropical regions of the world. They live in a wide range of water bodies, from fast-flowing rivers to swamps , as well as in tree boles or caves . They are primarily nocturnal , emerging to feed at night; most are omnivores , although

60-417: A limited distribution, although various crabs from other families are also able to tolerate freshwater conditions ( euryhaline ) or are secondarily adapted to fresh water. The phylogenetic relationships between these families is still a matter of debate, so how many times the freshwater lifestyle has evolved among the true crabs is unknown. The eight families are: The fossil record of freshwater organisms

80-549: A small geographical area. This is at least partly attributable to their poor dispersal abilities and low fecundity , and to habitat fragmentation caused by the world's human population. In West Africa , species that live in savannas have wider ranges than species from the rainforest ; in East Africa , species from the mountains have restricted distributions, while lowland species are more widespread. Every species of freshwater crab described so far has been assessed by

100-469: A small number are specialist predators, such as Platythelphusa armata from Lake Tanganyika , which feeds almost entirely on snails . Some species provide important food sources for various vertebrates . A number of freshwater crabs (for example species from the genus Nanhaipotamon ) are secondary hosts of flukes in the genus Paragonimus , which causes paragonimiasis in humans. The majority of species are narrow endemics , occurring in only

120-481: Is a stub . You can help Misplaced Pages by expanding it . Freshwater crab More than 1,300 described species of freshwater crabs are known, out of a total of 6,700 species of crabs across all environments. The total number of species of freshwater crabs, including undescribed species , is thought to be up to 65% higher, potentially up to 2,155 species, although most of the additional species are currently unknown to science. They belong to eight families, each with

140-748: Is advised to have a depth of at least double their body height to account for any evaporation. Without access to water Geosesarma crabs will dry out and perish. It is also important never to mix any other species of Geosesarma together. While they are a semi social species of crab, they are extremely aggressive towards other species and will almost always kill other species present in their territory. Environmental Parameters for keeping Geosesarma crabs in captivity Water temperature: 22–25°C (71–78°F) Air Temperature: 22–28°C (71–82°F) PH: Between 7.5–8.0 KH (carbonate hardness): Between 0–10 GH (general hardness) Between 4–16 Ammonia: 0 Nitrite: 0 Nitrate: Lower than 20 ppm This Brachyura article

160-541: Is home to 24). Other countries with species are Argentina , Bolivia , Chile , Paraguay and Uruguay . More than a third of the species are considered threatened , and in Brazil alone 26 species are officially recognized as threatened, including 8 critically endangered . This list contains all the described species as of 2013 : Haumuriaegla glaessneri is a species known only from fossils of Haumurian age ( Late Cretaceous ) found near Cheviot, New Zealand . At

180-480: Is one that consists of 80% land and 20% water. With natural soil and dense planting making up the majority of the terrestrial area. As these species live in the ground, primarily in burrows, soil is vital for their well being, stress reduction and breeding. While they also require water to survive, it is primarily used for molting and hydration. Both of which can easily be met with a small water volume, enough to cover their entire body completely will suffice. However it

200-492: Is related to the behaviour of carrying fertilised eggs on the pleopods . The carapace length of the largest species may approach 6 cm (2.4 in), but most are considerably smaller. Aeglids are omnivorous , preferring plant matter, but also eating adult insects , molluscs , fish and fly larvae . The internal anatomy has been described for Aegla cholchol and generally resembles that of other anomurans, particularly galatheoid squat lobsters. The morphology of

220-465: Is typically poor, so few fossils of freshwater crabs have been found. The oldest is Tanzanonautes tuerkayi , from the Oligocene of East Africa , and the evolution of freshwater crabs is likely to postdate the break-up of the supercontinent Gondwana . Members of the family Aeglidae and Clibanarius fonticola are also restricted to fresh water, but these "crab-like" crustaceans are members of

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240-489: The International Union for Conservation of Nature ; of the species for which data are available, 32% are threatened with extinction . For instance, all but one of Sri Lanka 's 50 freshwater crab species are endemic to that country, and more than half are critically endangered . Aeglidae The Aeglidae are a family of freshwater crustaceans currently restricted to South America . They are

260-420: The antennal gland bladder differs from that in other anomurans in having a twisted tubular structure which was interpreted as an adaption to the freshwater lifestyle. Mating is preceded by a period of courtship , and does not coincide with moulting , as it does in many other decapods . The eggs of aeglids hatch as juveniles which closely resemble the adults. They are cared for by their parents and live at

280-412: The aquarium trade. Geosesarma (Vampire Crabs) have become extremely popular in the exotic animal hobby over recent years. However there is a lot of misconception about how to best keep them. They are often mistaken for aquatic crabs and kept in unsuitable conditions with excessive amounts of water, which will ultimately leads to shortened life spans. The ideal captive environment for Geosesarma species

300-455: The bottom of the body of water. Aegla , the only extant genus in the family, contains around 74 described extant species. Of the 63 species and subspecies described by 2008, two are found in lakes, four in caves , and the remaining 57 are found mainly in rivers. 42 species are found in Brazil , all restricted to the country's southern and southeastern regions ( Rio Grande do Sul alone

320-510: The bright, contrastingly yellow eyes of some Geosesarma species. Geosesarma contains these species: As of March 2015, professor Peter Ng of National University of Singapore has named 20 Geosesarma species, and he "has another half a dozen or so newly collected Geosesarma species from Southeast Asia in his lab, and these species still need to be named and described." Geosesarma dennerle and Geosesarma hagen , both originally from Java , are threatened by illegal overcollection for

340-436: The egg. The broods comprise only a few hundred eggs (compared to hundreds of thousands for marine crabs), each of which is quite large, at a diameter around 1 mm (0.04 in). The colonisation of fresh water has required crabs to alter their water balance; freshwater crabs can reabsorb salt from their urine , and have various adaptations to reduce the loss of water. In addition to their gills , freshwater crabs have

360-399: The infraorder Anomura (true crabs are Brachyura ). The external morphology of freshwater crabs varies very little, so the form of the gonopod (first abdominal appendage, modified for insemination) is of critical importance for classification . Development of freshwater crabs is characteristically direct, where the eggs hatch as juveniles , with the larval stages passing within

380-399: The only anomurans to be found in fresh water except for a single hermit crab species, Clibanarius fonticola , on Espiritu Santo , Vanuatu . They live between 20° S and 50° S , at altitudes between 320 and 3,500 m (1,050–11,480 ft). Aeglids resemble squat lobsters in that the abdomen is partly tucked under the thorax . The notable sexual dimorphism in the abdomen

400-533: The time of its discovery, Haumuriaegla was the only known fossil from the family and the only marine member. Protaegla miniscula was discovered in rocks of Albian age from the Tlayúa Formation , near Tepexi de Rodríguez , Mexico . The family as a whole is thought to have originated around 75 million years ago in a marine environment, and then entered South America from the Pacific side during

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