The red dwarf rasbora (''Microrasbora rubescens'') is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of freshwater

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

belonging to

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Danionidae The danionins are a group of small, minnow-type fish belonging to the family Danionidae. Species of this group are in the genera clades ''Danio'' and '' Devario'' (which also includes ''Chela'', ''Laubuka'', ''Microdevario'', and ''Microrasbora ...

. It is the only species in the genus ''Microrasbora''. The generic name means "small Rasbora", however these are more closely related to the

danio ''Danio'' is a genus of small freshwater fish in the family (biology), family Cyprinidae found in South Asia, South and Southeast Asia, commonly kept in aquarium, aquaria. They are generally characterised by a pattern of horizontal stripes, rows ...

s than

rasbora ''Rasbora'' is a genus of fish in the family Danionidae. They are native to freshwater habitats in South and Southeast Asia, as well as southeast China. A single species, ''R. gerlachi'', is only known from an old specimen that reputedly origina ...

s. They inhabit freshwater in

Myanmar Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...

and

Yunnan Yunnan; is an inland Provinces of China, province in Southwestern China. The province spans approximately and has a population of 47.2 million (as of 2020). The capital of the province is Kunming. The province borders the Chinese provinces ...

, China.

Taxonomy

''Microrasbora'', until recently, included a number of described species. '' Microrasbora erythromicron'' was first shown to be a member of the genus ''

Danio ''Danio'' is a genus of small freshwater fish in the family (biology), family Cyprinidae found in South Asia, South and Southeast Asia, commonly kept in aquarium, aquaria. They are generally characterised by a pattern of horizontal stripes, rows ...

'' in 1999. (1999): Two new species of ''Microrasbora'' from Thailand and Myanmar, with two new generic names for small Southeast Asian cyprinid fishes (Teleostei: Cyprinidae). ''Journal of South Asian Natural History'' 4(1): 49-56. This move has been confirmed by numerous studies. (2007): Phylogenetic relationships of ''Danio'' within the order Cypriniformes: a framework for comparative and evolutionary studies of a model species. ''Journal of Experimental Zoology B: Molecular and Developmental Evolution'' 308B(5): 1-13. (HTML abstract) 2009. Molecular phylogenetic interrelationships of the south Asian cyprinid genera ''Danio'', ''Devario'', and ''Microrasbora'' (Teleostei, Cyprinidae, Danioninae). Zoologica Scripta 38:237-256. Three other species, '' M. gatesi'', '' M. kubotai'', and '' M. nana'' were moved to a new genus, '' Microdevario'', leaving ''Microrasbora rubescens'' as the only confirmed species in the genus. However, Fang et al. did not comment on the placement of ''Microrasbora microphthalma'', although ''

Eschmeyer's Catalog of Fishes Catalog of Fishes is a comprehensive on-line database and reference work on the scientific names of fish species and genera. It is global in its scope and is hosted by the California Academy of Sciences. It has been compiled and is continuously up ...

'' has placed this species in '' Microdevario''.

Description

The dwarf red rasbora reaches up to in length. Its

meristics Meristics is an area of zoology and botany which relates to counting quantitative features of animals and plants, such as the number of fins or scales in fish. A meristic (countable trait) can be used to describe a particular species, or used to i ...

are that there are 2 spines and 6-7 soft rays in the

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

and 3 spines and 10-12 soft rays in the

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

. The females are less instensly coloured than the males and are larger and have a much deeper body.

Habitat

The dwarf red rasbora is endemic to Lake Inle which is situated in a valley where the rocks form a

karst Karst () is a topography formed from the dissolution of soluble carbonate rocks such as limestone and Dolomite (rock), dolomite. It is characterized by features like poljes above and drainage systems with sinkholes and caves underground. Ther ...

and which lies 900m above sea level in the

Shan Plateau The Shan Hills (; ''Shan Yoma''), also known as Shan Highland, is a vast mountainous zone that extends through Yunnan to Myanmar and Thailand. The whole region is made up of numerous peaks separated mostly by narrow valleys, as well as a few b ...

region of Shan State. Within the lake this species can be found in the midwater and in the marginal waters of Lake Inle where it is associated with submerged vegetation and forms large schools.

Conservation

The red dwarf rasbora is exploited for the aquarium trade and it is thought this may have some impact on the population. It is also threatened by the introduction of exotic fish species to the lake, particularly ''

Parambassis ''Parambassis'' is a genus of freshwater fish in the Asiatic glassfish family Ambassidae of order Perciformes. The type species is the Iridescent glassy perchlet (''Ambassis apogonoides''). These fishes originate mostly from Southeast Asia, b ...

'' and ''

Tilapia Tilapia ( ) is the common name for nearly a hundred species of cichlid fish from the coelotilapine, coptodonine, heterotilapine, oreochromine, pelmatolapiine, and tilapiine tribes (formerly all were "Tilapiini"), with the economically mos ...

'' species, which act as both predators on and competitors with the red dwarf rasbora. In addition the lake has been polluted from a number of sources, especially from the growing human population in settlements around the lake, while sedimentation and agricultural runoff enters the lake from its drainage basin. The invasive

water hyacinth ''Pontederia crassipes'' (formerly ''Eichhornia crassipes''), commonly known as common water hyacinth, is an aquatic plant native to South America, naturalized throughout the world, and often invasive species, invasive outside its native rang ...

has covered large areas of the lake and this has reduced the area of open water in the lake, this effect being exacerbated by water abstraction and sedimentation.

References

Danioninae Freshwater fish genera Taxa named by Nelson Annandale {{Danioninae-stub