A study of a catfish has shown that what was previously considered a single species is, in fact, two different fish.
Pterocryptis anomala, a member of the catfish family Siluridae from southern China, was previously considered a synonym of P. cochinchinensis, however, a recent study has split the two species.
The discovery came after a pair of scientists took a closer look at Pterocryptis cochinchinensis following work by Heok Hee Ng and Jorg Freyhof which suggested that the species was confined to Vietnam, and not as widespread as previously believed.
The new study, which was undertaken by Heok Hee Ng of the University of Michigan and Bosco Chan of Kadoorie Farm and Botanic Garden in Hong Kong, has just been announced in the latest issue of the systematics journal Zootaxa.
Two speciesNg and Chan's study showed that Pterocryptis cochinchinensis wasn't restricted to Vietnam, but also occured on Hainan Island, off the southeastern coast of China.
The fish that came from southern China and Hong Kong Special Administrative Region were a separate fish, that had previously gone under the name of P. anomala, but had been previously lumped back with Pterocryptis cochinchinensis after another scientist considered the two fish to be the same.
Unlike cochinchinensis, in which males have a long genital papilla and females have a large "leaf-shaped" papilla, both sexes of anomala have a small conical genital papilla. The caudal peduncle of anomala is also deeper than that of cochinchinensis.
For full details on how to identify the species see the paper: Ng, HH and B. Chan (2005) - Revalidation and redescription of Pterocryptis anomala (Herre, 1933), a catfish (Teleostei: Siluridae) from southern China. Zootaxa, 1060: 51-64 (2005).
Fact FilePterocryptis anomala
Origin: Hong Kong and Southern China
Size: Around 15cm/6" or larger
Habitat: A nocturnal species which lives among rocks in fast-flowing boulder-strewn rivers.
Related species: There are around more than a dozen species in the genus Pterocryptis, including: anomola; berdmorei; bokorensis; buccata; burmanensis; cochinchinensis; crenula; cucphuongensis; furnessi; gangelica; indicus; inusitata; verecunda and wynaadensis.