A new species of nase has been described from near Lisbon, Portugal.
The new species is named the Lisbon arched-mouth nase, Chondrostoma olisiponensis, by Hugo Gante, Carlos Santos and Maria Alves in a paper published in a recent issue of the journal Zootaxa.
Chondrostoma olisiponensis is distinguished from other members of the genus in lacking a horny blade on the lower jaw and an intense reddish coloration at the base of the fins, possessing a pronouncedly arched mouth, elongated pelvic fins that reach the anus and often pass the anal-fin insertion in males, dorsal, pelvic and anal fins usually with 8 branched rays, 36"43 lateral line scales, 7.0"8.5 scale rows above the lateral line, 13"16 circumpeduncular scales, denticulated grinding teeth surfaces, 6"5/5 pharyngeal teeth and 15"19 gill rakers on the first arch.
The new species is named after the old Latin name of Lisbon (Olisipo), the area where this species occurs, and is only known from the lower Tejo River drainage in the vicinity of Lisbon.
The presence of extended pelvic fins in males is unusual within the genus, and the authors hypothesize that this feature may play a role in courtship and spawning.
Because this species is locally rare and apparently has a very restricted distribution, the authors consider it to be critically endangered following IUCN guidelines.
For more information, see the paper: Gante, HF, CD Santos and MJ Alves (2007) A new species of Chondrostoma Agassiz, 1832 (Cypriniformes: Cyprinidae) with sexual dimorphism from the lower Rio Tejo Basin, Portugal. Zootaxa 1614, pp. 23"35.