''Iberochondrostoma olisiponensis'', the Lisbon arched-mouth nase, is a freshwater fish discovered in 2007 in the lower Rio Tejo basin,

Portugal Portugal, officially the Portuguese Republic ( pt, República Portuguesa, links=yes ), is a country whose mainland is located on the Iberian Peninsula of Southwestern Europe, and whose territory also includes the Atlantic archipelagos of ...

Identification

The Lisbon arched-mouth nase is a small

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 verte ...

. Adults range from 5 to 11 cm, though there are records of specimens reaching ''

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'' 18 cm. It can be distinguished from the other Iberian

nase ''Chondrostoma'' (from the Ancient Greek roots (''khondros'') 'lump' + (''stoma'') 'mouth' = 'lump-mouth') is a genus of ray-finned fish in the family Cyprinidae. They are commonly known as nases, although this term is also used locally to de ...

species by the lack of horny blade on the lower jaw, the absence of intense reddish coloration at the base of the fins and by its pronouncedly arched mouth. It has elongated pelvic fins that reach the anus and often pass the anal-fin insertion in males, and dorsal, pelvic and anal fins usually have 8 branched rays. This species has 36 to 43 scales in the lateral line, 7.0 to 8.5 scales above the lateral line, 13 to 16 circumpeduncular scales, denticulated (vs. smooth) grinding teeth surfaces, 6-5/5 pharyngeal teeth and 15 to 19 gill rakers. It is further distinguished from ''

Iberochondrostoma lusitanicum ''Iberochondrostoma lusitanicum'', or the boga-portuguesa (its common names in English and Portuguese are the same), is a species of freshwater fish in the family Cyprinidae. It is found only in a very restricted area in Portugal, and is threaten ...

'', a phylogenetically close species that lives in the same area, by having a higher body, a relatively longer head, and a larger eye. The origins of anal and pelvic fins are displaced anteriorly, while the origin of pectoral fins is displaced posteriorly. Pelvic and pectoral fins and last anal-fin ray are longer in the new species. Unlike the other phylogenetically related species, the Lisbon's arched-mouth nase shows external sexual dimorphism, with males having longer pelvic fins whose extremities pass the anus and often overlap with the anal fin.

Origin

It was estimated from a

molecular clock The molecular clock is a figurative term for a technique that uses the mutation rate of biomolecules to deduce the time in prehistory when two or more life forms diverged. The biomolecular data used for such calculations are usually nucleoti ...

that the species had split 7•9-12•5 million years ago (middle–upper

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

) from its most recent ancestor. This period coincides with a phase of endorheism in the

Iberian Peninsula The Iberian Peninsula (), ** * Aragonese and Occitan: ''Peninsula Iberica'' ** ** * french: Péninsule Ibérique * mwl, Península Eibérica * eu, Iberiar penintsula also known as Iberia, is a peninsula in southwestern Europe, defi ...

Distribution

This species is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to the lower Rio Tejo basin. It was only found in three tributaries of the Tejo River, namely, Trancão, Maior, and Muge.

Conservation

The Lisbon's arched-mouth nase was found to be locally rare. Additionally, its distribution is limited to an area of high human impact on water resources, through water extraction for agriculture, introduction of exotic species, water pollution and land reclamation, which pose serious risks to its survival. The species has been placed in the category Critically Endangered B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v) according to IUCN criteria.

References

Gante, H. F., Santos, C. D., Alves, M. J. (2010) Phylogenetic relationships of the newly described species ''Chondrostoma olisiponensis'' (Teleostei: Cyprinidae). Journal of Fish Biology. 76, 4, 965–974. Gante, H. F., Santos, C. D., Alves, M. J. (2007) A new species of ''Chondrostoma'' Agassiz, 1832 (Cypriniformes : Cyprinidae) with sexual dimorphism from the lower Rio Tejo Basin, Portugal. Zootaxa. 1616, 23–35. Gante, H., Santos, C. D., Alves, M. J., Rodrigues, J. (2012) Iberochondrostoma olisiponensis. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. . Downloaded on 2 June 2013.

External links

* {{Taxonbar, from=Q1107187 Iberochondrostoma Endemic fauna of Portugal Endemic fish of the Iberian Peninsula Fish described in 2007