Scientists have described a new cryptic species of madtom catfish from the rivers of Missouri and Arkansas in the USA.
The new fish, which has just been named Noturus maydeni, is so similar to a sympatric species that the two can only be separated genetically.
Previous studies had suggested that the Ozark madtom, Noturus albater, found in upland streams in the upper White River, Black River and St. Francis River in Missouri and Arkansas, was in fact two distinct species.
Egge and Simmons, who described the new coldwater catfish in a paper in the latest issue of the journal Zoologica Scripta, examined Noturus albater and discovered the presence of the cryptic species.
Although their results were unable to separate the fish within N. albater on morphology, they did find marked differences in their genetics.
Karyotypes, DNA sequences and allozyme variation all showed that there were two distinct groups within N. albater, and Egge and Simmons opted to split the species, naming N. maydeni under the phylogenetic species concept.
The Noturus genus is part of the catfish family Ictaluridae and is endemic to North America and contains more than 26 species.
Noturus albater was first described by Taylor in 1969. You can view the distribution of this species on Fish Mapper.
For more information see the paper: Egge, JJD and AM Simons (2006) - The challenge of truly cryptic diversity: diagnosis and description of a new madtom catfish (Ictaluridae: Noturus). Zoologica Scripta 35: 581-595.