Author: (Bleeker, 1858)
FBname: River threadfin
Comments: Known only from three rivers on two Indonesian islands:  Kapuas River, Kalimantan and Musi and Batanghari rivers, Sumatra.  These rivers were part of one large river, the ancient Central or North Sunda River, on the Sundaland during the Pleistocene, the last cold period about 12,000 years ago.  Geographic evidence indicates that the species was well adapted to the freshwater basins in this extensive Pleistocene river, whereas other <i>Polydactylus</i> species are generally marine.  With Sundaland submerged to about 100 m, this species is now restricted to the 3 presently known localities.  The longer pectoral filaments and a more slender body have been considered as an adaptation to its freshwater existence.  The long pectoral filaments are useful as a sense organ to search for food in muddy waters (Ref. 40968).  A food fish along the Kapuas River, Borneo (Ref. 9685).