Wednesday, March 23, 2011
March 23, 2011 : Knifefish
The family Notopteridae contains eight species of osteoglossiform (bony-tongued) fishes, commonly known as featherbacks and knifefishes. They are small fishes living in freshwater or brackish environments in Africa and Southeast Asia.
With the denotation of "knifefish", the Notopterids should not be confused with Gymnotiforms, the electric knifefishes. Although their manner of swimming is similar, the two groups are not closely related.
A few of the larger species, especially Chitala chitala, are food fish and occasionally aquarium pets. The name is from Greek noton meaning "back" and pteron meaning "fin".
Featherbacks have slender, elongated, bodies, giving them a knife-like appearance. The caudal fin is small and fused with the anal fin, which runs most of the length of the body. Where present, the dorsal fin is small and narrow, giving rise to the common name of "featherback". The fish swims by holding its body rigid and rippling the anal fin to propel itself forward or backwards.
Notopterids have specialized swim bladders. The organ extends throughout the body and even into the fins in some cases. Although the swim bladder is not highly vascularised, it can absorb oxygen from air and also functions to produce sound by squeezing air through a narrow passage into the pharynx.
At least some species prepare nests and guard the eggs until they hatch.