Friday 10 January 2014

A new species of Characiforme Fish from the Congo Basin.

The Characiformes are a group of freshwater Fish from Africa and South America. They are most numerous in South America, where the group includes Freshwater Barracuda, Characins, South American Darters, Tetras, Trahiras, Freshwater Hatchetfish, Hemiodontids, Pencil Fish and Piranhas. African Characiformes include Lutefish, African Pike, Congo Tetras, African Tigerfish and Distichodontids. The group appear in the fossil record in Brazil in the Early Cretaceous, and apparently diversified during the Cretaceous and spread to Africa before the break-up of Gondwana, though their fossil record is not extensive.

In a paper published in the journal Zootaxa on 31 July 2013, Melanie Stiassny of the Department of Ichthyology at the American Museum of Natural History, John Denton of the Department of Ichthyology and Richard Gilder Graduate School at the American Museum of Natural History and Raoul Monsembula Iyaba of the Département de Biologie at the Université de Kinshasa describe a new species of Distichodontid from the Congo Basin of Central Africa.

The new species is placed in the genus Eugnathichthys, and given the specific name virgatus, meaning banded or streaked, a reference to its colouration. Like the two previously described members of this genus, Eugnathichthys virgatus is a specialist fin-feeder; it survives by biting chunks from the fins of larger Fish and consuming them. 

Eugnathichthys virgatus was discovered during a genetic study of populations of fish of the genus Eugnathichthys. It is essentially a cryptic species, resembling closely Eugnathichthys macroterolepis, but found to be a separate species by genetic analysis. Eugnathichthys virgatus inhabits the Lengoué and Lomako Rivers, while Eugnathichthys macroterolepis inhabits the Nsele and Kasai Rivers.

Eugnathichthys virgatus is an elongate Distichodontid Fish with powerful jaws. It is banded on its dorsal surface, though this banding is relatively inconspicuous except close to its midline. Its fins are orange, with distinct darker bands. Eugnathichthys virgatus reaches 106 mm in length.

Eugnathichthys virgatus. Stiassny et al. (2013).

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