Achondrostoma (Achondrostoma arcasii)

Achondrostoma arcasii, lateral view
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Achondrostoma fact file

Achondrostoma description

GenusAchondrostoma (1)

A freshwater fish of Portugal and Spain, Achondrostoma arcasii is a little known species threatened by the loss of its habitat. It can be distinguished from related species by having four or five rows of scales between the lateral line and the pelvic fins, as well as a rounded snout, with an enlarged, horny lower lip, and particularly large eyes (2) (3).

Chondrostoma arcasii, Rutilus arcasii.
Length: c. 15 cm (2)
Maximum length: 25 cm (2)

Achondrostoma biology

Achondrostoma arcasii is a poorly-studied species, and there is very little known about its biology and behaviour. However, it is thought to be a short-lived species with a fairly opportunistic diet, eating a variety of aquatic invertebrates (2).

Like other members of the Cyprinidae family, Achondrostoma arcasii lacks teeth, instead possessing a pair of enlarged bones in the throat, which have structures known as ‘pharyngeal teeth’ that are used to process food (4).


Achondrostoma range

Achondrostoma arcasii is found in Portugal and Spain, where it occurs in most rivers north of Jucar and Tagus, including rivers around the Atlantic drainage. It has been introduced to the Guadiana drainage (1) (2).


Achondrostoma habitat

Achondrostoma arcasii inhabits the middle reaches of freshwater rivers, as well as lakes, mountain streams and reservoirs in hilly areas (1).


Achondrostoma status

Achondrostoma arcasii is classified as Vulnerable (VU) on the IUCN Red List (1).

IUCN Red List species status – Vulnerable


Achondrostoma threats

Achondrostoma arcasii is threatened by the loss and degradation of its habitat, and its population is thought to be in decline. Canal construction, water pollution, dam construction and introduced species have all be identified as threats to this species (1) (2).


Achondrostoma conservation

Although Achondrostoma arcasii has not been the target of any specific conservation measures, it is listed on Annex II of the European Union Habitats Directive and on Appendix III of the Bern Convention, which aims to conserve wild flora and fauna and their natural habitats (1) (5) (6).


Find out more

Find out more about Achondrostoma arcasii:



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Animals with no backbone, such as insects, worms, spiders and corals.
Lateral line
A row of receptors that can detect movement via vibrations in water. The receptors are typically embedded in the skin, and in fish they form a line along the sides of the body.
Pelvic fins
In fish, the pair of fins found on the underside of the body.


  1. IUCN Red List (June, 2011)
  2. FishBase - Achondrostoma arcasii (June, 2011)
  3. Robalo, J.I., Almada, V.C. and Levy, A. and Doadrio, I. (2007) Re-examination and phylogeny of the genus Chondrostoma based on mitochondrial and nuclear data and the definition of 5 new genera. Molecular Phylogenetics and Evolution, 42: 362-372.
  4. Campbell, A. and Dawes, J. (2004) Encyclopedia of Underwater Life. Oxford University Press, Oxford.
  5. Council of Europe: Bern Convention (June, 2011)
  6. EU Habitats Directive (June, 2011)

Image credit

Achondrostoma arcasii, lateral view  
Achondrostoma arcasii, lateral view

© Juan Antonio Delgado Sáez

Juan Antonio Delgado Sáez
Departamento de Ecología, Universidad Complutense de Madrid
Tel: +34 (91) 394 5085
Fax: +34 (91) 394 5081


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