Blue Whale Catfish

Cetopsis coecutiens, the candiru-açú, piracatinga, bagre ciego (lit. blind catfish), or the blue whale catfish, is a species of catfish found throughout the Amazon basin in Bolivia, Brazil, Colombia, Peru and Venezuela. The fish was first described by Hinrich Lichtenstein in 1819, who named it for its resemblance to certain cetaceans. C. coecutiens is one of the largest species of "candiru" catfish. While these catfish are reported to grow to a size of 265 millimetres (10.4 in), some specimens greater than 300 millimetres (12 in) have been caught in the wild.

Cetopsis coecutiens closely resembles its sister species, C. candiru, but it may be distinguished from its other relatives through the presence of the eyes, conical teeth, a relatively deep body, filaments on the dorsal and pectoral fins arising from the first fin rays, and dark pigmentation on the previously mentioned fins.