A new species of pimelodid catfish has been described from the deep main channels of the Amazon and its tributaries in South America.
The fish, which has been named Propimelodus caesius by Beatrice Parisi, John Lundberg and Carlos Donascimiento in a paper in the Proceedings of the Academy of Natural Sciences of Philadelphia, is believed to be one of the most common catfish species found in the channels of the Amazon.
The new fish species was found in trawl samples collected by John Lundberg of the Department of Ichthyology at the National Academy of Sciences during the Calhamazon Project which aimed to survey the poorly-known fish fauna of the Amazon's river channels.
Although an abundant fish species, the species was previously unknown as it isn't a major food species and lives in the depths of the river where it is effectively out of the reach of commercial fishermen.
Propimelodus caesius grows to around 17cm/7" and has a silvery-blue body, very long maxillary barbels, an elongated caudal fin and a very long adipose, which extends from the posterior portion of the base of the dorsal as far as the caudal peduncle itself.
The species gets its scientitific name - caesius - from the blue colour of the body in life.
P. caesius is believed to be widespread and has been recorded from the Amazon in Brazil and Peru, the Tocatins, Para, Jari, Xingu, Trombetas, Madeira, Negro, Purus, Japura, Jurua and Ica rivers. The authors believe that the species is also likely to occur in low-lying rivers in Colombia, Ecuador and Bolivia, too.
Its closest relative is believed to be P. eigenmanni, from which it differs by its relatively larger eye, violet or blue colour and higher number of vertebrae.
The species is similar in appearance to an unidentified pimelodid caught on the Practical Fishkeeping expedition to Brazil (shown above). This fish, with the same characteristic blue colour and very long adipose fin, was caught while night fishing in the deep water in the main channel of the Rio Negro upriver of Manaus.
For more information on the new species see the paper: Parisi BM, Lundberg JG and C Donascimiento (2006) - Propimelodus caesius, a new species of long-finned pimelodid catfish (Teleostei: Siluriformes) from the Amazon Basin, South America. Proceedings of the Academy of Natural Sciences of Philadelphia. 67-78, April 2006.