New akysid catfish is a mimic

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A new akysid catfish has been described from southern Thailand in a recent issue of the journal Zootaxa.

Akysis pulvinatus, named by Heok Hee Ng, is described from the upper Tapi River drainage and hillstreams flowing into the Andaman Sea on the western half of the Isthmus of Kra in southern Thailand.

The new species differs from all other members of the genus in having a long adipose-fin base (23.0"25.2% SL), deep caudal peduncle (9.4"10.3% SL), long head (27.6"29.8% SL), , smooth posterior edge of pectoral spine, gently forked caudal fin with lower lobe longer than upper, yellow snout, and the presence of rounded pale colored patches on the body.

Akysis pulvinatus is named for the long adipose fin (Latin pulvinus = elevation, in reference to the adipose fin).

According to the author, the type locality is ...a stream with both slow-flowing (8 m wide) and riffle (5 m wide) areas...The substrate consisted of gravel and larger rocks, with the catfish being found between the rocks, particularly in the riffle areas. The water was clear, with a temperature of 29.3C and a pH of 8....

MimicryAkysis pulvinatus is thought to be a Mllerian mimic of Pseudobagarius leucorhynchus, another akysid catfish sometimes found in the same habitat.

Both akysids share a similar boldly striped yellow and brown colour pattern and both species also possess venomous pectoral-fin spines; it is hypothesized that the striped pattern may serve as aposematic (warning) colouration.

For more information, see the paper: Ng, H.H. (2007) Akysis pulvinatus, a new species of catfish (Siluriformes: Akysidae) from southern Thailand. Zootaxa 1608, pp. 51"58.