''Rheocles'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Madagascar rainbowfish Bedotiinae are a subfamily of the rainbowfish family Melanotaeniidae, commonly known as the Madagascar rainbowfish, Madagascan rainbowfish, or Malagasy rainbowfish due to their endemism to Madagascar. It includes two genera, ''Bedotia'' and ''Rhe ...

. ''Rheocles'' has a restricted distribution, being found only in certain forested freshwater habitats in the central and eastern highlands of

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

including the Nosivolo River. The genus appears to feed almost exclusively on allochthonous material, primarily insects falling onto the water surface.

Taxonomy

In a 1990 study, this genus is

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

. However, in a 2004 analysis, it was found that ''Rheocles'' was

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

, forming two distinct

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

s. ''R. alaotrensis'', ''R. lateralis'', and ''R. wrightae'' (all species that are not discernibly

sexually dimorphic Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

was recovered as the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

of the rest of the bedotiids, including ''Bedotia'' sister to ''R. vatosa'' + ''R. derhami''. ''R. pellegrini'' and ''R. sikorae'' were excluded from this study due to lack of available material, however, ''R. sikorae'' is considered to be the sister taxon to ''R. wrightae''.

Species

There are currently seven recognized species in this genus: * ''

Rheocles alaotrensis The katrana (''Rheocles alaotrensis'') is a species of fish in the Bedotiidae family. It is endemic to the basin of Lake Alaotra in Madagascar. Its natural habitats are rivers and freshwater lakes. It is threatened by habitat loss Habita ...

'' ( Pellegrin, 1914) (Katrana) * ''

Rheocles derhami ''Rheocles derhami'' is a species of rainbowfish in the subfamily Bedotiinae, the Madagascar rainbowfishes. It is endemic to the Ambalona River and Mangarahar River in Madagascar. Its natural habitat is rivers. It was described by Melanie Stia ...

'' Stiassny & D. M. Rodríguez, 2001 * ''

Rheocles lateralis ''Rheocles lateralis'', is a species of rainbowfish in the subfamily Bedotiinae, the Madagascar rainbowfishes. It is endemic to Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madaga ...

'' Stiassny & Reinthal, 1992 * ''

Rheocles pellegrini ''Rheocles pellegrini'' is a species of rainbowfish from the subfamily Bedotiinae. It is endemic to Madagascar. Its natural habitat is rivers. This species was described by John Treadwell Nichols and Francesca Raimonde La Monte in 1931 from a ...

'' (

Nichols Nichols may refer to: People *Nichols (surname) *Nichol, a surname Places Canada * Nichols Islands, Nunavut United States * Nichols, California, an unincorporated community * Nichols Canyon, Los Angeles, California * Nichols, Connecticut * Nich ...

& La Monte, 1931) * ''

Rheocles sikorae ''Rheocles sikorae'' is a species of rainbowfish in the subfamily Bedotiinae, the Madagascar rainbowfishes. It is endemic to Madagascar where found in tropical rivers and streams. It can reach the maximum recorded length of . Distribution and st ...

'' ( Sauvage, 1891) * ''

Rheocles vatosoa ''Rheocles vatosoa'' is a species of rainbowfish in the subfamily Bedotiinae, the Madagascar rainbowfishes. It is endemic to Madagascar. Its natural habitat is the Lokoho River basin. It is threatened by habitat loss Habitat destruction (a ...

'' Stiassny, D. M. Rodríguez & Loiselle, 2002 * ''

Rheocles wrightae ''Rheocles wrightae'', is a species of rainbowfish in the subfamily Bedotiinae, the Madagascar rainbowfishes. It is endemic to Madagascar where its occurs in the Manambola River, near Anosibe. It is threatened by habitat loss. It was described ...

'' Stiassny, 1990

Description

''Rheocles'' species are robust bedotiids with little lateral body compression. ''R. vatosa'' and ''R. derhami'' are

, with males exhibiting larger adult size, enhanced coloration and pigmentation, as well as pronounced development of the unpaired fins.

Conservation

Its close association with forested biotopes suggests that, like so many other rainforest-adapted series, ''Rheocles'' is extremely vulnerable to

deforestation Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated d ...

pressure.

References

{{Taxonbar, from=Q150130 Bedotiinae Taxa named by David Starr Jordan Taxa named by Carl Leavitt Hubbs Endemic fauna of Madagascar Ray-finned fish genera