''Paedocypris'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial no ...

of tiny

cyprinid Cyprinidae is a family of freshwater fish commonly called the carp or minnow family. It includes the carps, the true minnows, and relatives like the barbs and barbels. Cyprinidae is the largest and most diverse fish family and the largest vert ...

fish found in swamps and streams on the

Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainland ...

n islands of

Borneo Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and ea ...

Sumatra Sumatra is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the sixth-largest island in the world at 473,481 km2 (182,812 mi.2), not including adjacent is ...

and

Bintan Bintan Regency (formerly Riau Islands Regency; id, Kabupaten Kepulauan Riau) is an administrative area in the Riau Islands Province of Indonesia. Bintan Regency includes all of Bintan Island (except for the city of Tanjung Pinang which is se ...

. ''Paedocypris progenetica'' has been claimed to be the one of smallest known species of fish in the world. The smallest mature female measured and the largest known individual was .

Species

The three currently recognized species in this genus are: * '' Paedocypris carbunculus''

Britz Britz () is a German locality (''Ortsteil'') within the Berlin borough (''Bezirk'') of Neukölln. History The village of ''Britzig'' was first mentioned in 1273. It was incorporated by the 1920 Greater Berlin Act. It is known for being the site ...

& Kottelat, 2008 * '' Paedocypris micromegethes'' Kottelat,

, H. H. Tan & K. E. Witte, 2006 * '' Paedocypris progenetica'' Kottelat,

, H. H. Tan & K. E. Witte, 2006

Taxonomy

Two species were discovered and identified by ichthyologists Maurice Kottelat from Switzerland and

Tan Heok Hui Heok Hui Tan is a Singaporean ichthyologist at the Lee Kong Chian Natural History Museum of the National University of Singapore. Dr. Tan's main interest lies in the systematics of Southeast Asian freshwater fishes, encompassing taxonomy, ecol ...

from the Raffles Museum of Biodiversity Research and the

National University of Singapore The National University of Singapore (NUS) is a national public research university in Singapore. Founded in 1905 as the Straits Settlements and Federated Malay States Government Medical School, NUS is the oldest autonomous university in th ...

in 1996. Their osteology was studied by Ralf Britz at London's

Natural History Museum A natural history museum or museum of natural history is a scientific institution with natural history scientific collection, collections that include current and historical records of animals, plants, Fungus, fungi, ecosystems, geology, paleon ...

. In 1994, the same ichthyologists had already discovered in Sarawak (Malaysian part of Borneo) another miniature species of the same genus ''Paedocypris''. Like ''P. progenetica'', ''P. micromegethes'' was found in the slow-flowing blackwater streams and

peat swamp Peat swamp forests are tropical moist forests where waterlogged soil prevents dead leaves and wood from fully decomposing. Over time, this creates a thick layer of acidic peat. Large areas of these forests are being logged at high rates. Peat ...

s. The genus, ''Paedocypris'', and two species, ''Paedocypris progenetica'' and ''Paedocypris micromegethes'', were first described in 2006. ''Paideios'' is

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

for children and ''cypris'' is Greek for

Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never fa ...

and is a common suffix for

genera; the

gender Gender is the range of characteristics pertaining to femininity and masculinity and differentiating between them. Depending on the context, this may include sex-based social structures (i.e. gender roles) and gender identity. Most cultures ...

is feminine. ''Progenetica'' (from the word ''progenetic'') is used as an

adjective In linguistics, an adjective ( abbreviated ) is a word that generally modifies a noun or noun phrase or describes its referent. Its semantic role is to change information given by the noun. Traditionally, adjectives were considered one of the m ...

. ''Micromegethes'' is Greek for small in size, and is used as a noun in

apposition Apposition is a grammatical construction in which two elements, normally noun phrases, are placed side by side so one element identifies the other in a different way. The two elements are said to be ''in apposition'', and one of the elements is ...

. ''Paedocypris'' is considered a

danionin The danionins are a group of small, minnow-type fish belonging to the family Cyprinidae. Members of this group are mostly in the genera ''Danio'', ''Devario'', and ''Rasbora''._They_are_primarily_native_to_the_outheast_Asia,_as_well_as_southeast_ ...

genus by Tyson Roberts. '' Sundadanio'' and ''Paedocypris'' were found to share a

sister group 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 ...

relationship, supporting its close relationship to danionin genera; however, this study included danionins among the subfamily Rasborinae.

Appearance

Their miniature transparent bodies lack the typical features characteristic of adult fish, for instance a bony skull structure around its brain, and it retains the postanal larval fin-fold along the ventral edge of the caudal peduncle, characteristic of fish larvae. They have a unique

sexual dimorphism 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 an ...

: The males have highly modified

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

s, with the first ray terminating with a hook-like projection of keratinized skin, supported by hypertrophied pelvic musculature. Males also have a pad of keratinized skin in front of the pelvic fins. These modified fins are thought to be used to grasp the female during mating, or to keep position over a spawning surface.

Smallest vertebrate

''Paedocypris progenetica'' has been claimed to be the smallest known species of fish and

vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, wi ...

in the world, particularly before the description of the frog ''

Paedophryne amauensis ''Paedophryne amauensis'' is a species of microhylid frog endemic to eastern Papua New Guinea. At in snout-to-vent length, it is considered the world's smallest known vertebrate. (See also Ecological guild.) The species was listed in the '' ...

'' in 2012. The smallest mature ''P. progenetica'' female is only in

standard length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish m ...

, smaller than the female of any other vertebrate species, including those of ''P. amauensis''. The largest known individual is . Male individuals of the

anglerfish The anglerfish are fish of the teleost order Lophiiformes (). They are bony fish named for their characteristic mode of predation, in which a modified luminescent fin ray (the esca or illicium) acts as a lure for other fish. The luminescen ...

species ''

Photocorynus spiniceps ''Photocorynus spiniceps'' is a species of anglerfish in the family Linophrynidae. It is in the monotypic genus ''Photocorynus''. The known mature male individuals are 6.2–7.3 millimeters (0.25-0.3 inches), smaller than any other ma ...

'' have been documented to be at maturity, and thus claimed to be a smaller species. However, these survive only by sexual

parasitism Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

, and the female individuals reach the significantly larger size of .Raffles Museum news, 2006.
RMBR: So which is the smallest species of fish in the world? (Part II)

Habitat and conservation

''Paedocypris progenetica'' lives in the blackwater

s of the

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

n islands of

and

. ''P. micromegethes'' lives in the peat swamps of

Sarawak Sarawak (; ) is a state of Malaysia. The largest among the 13 states, with an area almost equal to that of Peninsular Malaysia, Sarawak is located in northwest Borneo Island, and is bordered by the Malaysian state of Sabah to the northeast, ...

in northern

, Malaysia. ''P. carbunculus'' is found in peat swamps in

Central Kalimantan Central Kalimantan ( id, Kalimantan Tengah) is a province of Indonesia. It is one of five provinces in Kalimantan, the Indonesian part of Borneo. Its provincial capital is Palangka Raya and in 2010 its population was over 2.2 million, while the ...

, Borneo, Indonesia. Members of this genus are habitat specialists that only live in acidic water. Within peat swamp forests, they are usually found to inhabit deeper, cooler water layers close to the bottom half of the water columns. They also tend to inhabit shaded areas in which light is usually absent from their environment. Their small size helps them to survive droughts, as they can live in small remaining puddles. However, their small ranges and specialised habitat make them extremely vulnerable to

habitat loss Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

, such as drainage of peat swamps and fires, and some populations have already disappeared. It has been speculated that some other miniature fish from the habitat and region may already have become

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

, even before being scientifically described or discovered. In Malaysia alone, it has been estimated that—in addition to ''Paedocypris''—up to 15% of the freshwater fish species are associated with peat swamps, and based on current destruction rates all Bornean and Sumatran peatlands may be gone by 2040.

References

Kottelat, M., Britz, R., Hui, T., & Witte, K. (2006). Paedocypris, a New Genus of Southeast Asian Cyprinid Fish with a Remarkable Sexual Dimorphism, Comprises the World's Smallest Vertebrate. Proceedings: Biological Sciences, 273(1589), 895-899.

External links

BBC: Is it really the smallest fish after all?Pharyngula: PaedocyprisSome records in the fish world
{{Taxonbar, from=Q168599 Cyprinidae genera Freshwater fish of Asia Taxa named by Maurice Kottelat