Chondrostoma olisiponensis
Encyclopedia
The Lisbon’s arched-mouth nase (Chondrostoma olisiponensis) is a freshwater fish recently discovered in the lower Rio Tejo basin, Portugal
.
. Adults range from 5 to 11 cm, though there are records of specimens reaching ca. 18 cm. It can be distinguished from the other Iberian Chondrostoma
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 Chondrostoma lusitanicum
, 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 species in the genus, 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.
that the species had split 7•9-12•5 million years ago (middle–upper Miocene
) from its most recent ancestor. This period coincides with a phase of endorheism in the Iberian Peninsula
.
The species was found to be closely related to lemmingii and arcasii groups of Chondrostoma
genus.
The species still waits for a conservation status assignment.
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
.
Identification
The Lisbon’s arched-mouth nase is a small cyprinidCyprinid
The family Cyprinidae, from the Ancient Greek kyprînos , consists of the carps, the true minnows, and their relatives . Commonly called the carp family or the minnow family, its members are also known as cyprinids...
. Adults range from 5 to 11 cm, though there are records of specimens reaching ca. 18 cm. It can be distinguished from the other Iberian Chondrostoma
Chondrostoma
Chondrostoma is a genus of ray-finned fish in the family Cyprinidae. They are commonly known as nases, though this term is also used locally to denote particular species, most frequently the Common Nase Chondrostoma (from the Ancient Greek roots (khondros, “lump”) + (stoma, “mouth”) =...
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 Chondrostoma lusitanicum
Boga-Portuguesa
The Boga-portuguesa is a species of ray-finned fish in the Cyprinidae family.It is found only in Portugal.-References:* World Conservation Monitoring Centre 1996. . Downloaded on 19 July 2007....
, 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 species in the genus, 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 and phylogenetic relationships
It was estimated from a molecular clockMolecular clock
The molecular clock is a technique in molecular evolution that uses fossil constraints and rates of molecular change to deduce the time in geologic history when two species or other taxa diverged. It is used to estimate the time of occurrence of events called speciation or radiation...
that the species had split 7•9-12•5 million years ago (middle–upper Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
) from its most recent ancestor. This period coincides with a phase of endorheism in the Iberian Peninsula
Iberian Peninsula
The Iberian Peninsula , sometimes called Iberia, is located in the extreme southwest of Europe and includes the modern-day sovereign states of Spain, Portugal and Andorra, as well as the British Overseas Territory of Gibraltar...
.
The species was found to be closely related to lemmingii and arcasii groups of Chondrostoma
Chondrostoma
Chondrostoma is a genus of ray-finned fish in the family Cyprinidae. They are commonly known as nases, though this term is also used locally to denote particular species, most frequently the Common Nase Chondrostoma (from the Ancient Greek roots (khondros, “lump”) + (stoma, “mouth”) =...
genus.
Distribution
This species is endemic 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 still waits for a conservation status assignment.