What are true and fast knifefish?
- Thread starter Pyluper
- Start date
'Knife-fish' is a general term for any and all freshwater teleost fishes with a continuous undulating anal fin, with a reduced/vestigial caudal, no ventrals, etc. Gymnarchus niloticus is unique in that it has no caudal/anal/pelvic, just pectoral and dorsal. But is still called a knife-fish because of the main undulating dorsal-fin they employ for somewhat similar means of movement.
The true knife-fishes are the electric Latin American spp. of the order Gymnotiformes, that can be easily differentiated from other 'knife-fishes' besides Xenomystus by the complete absence of a dorsal-fin. They are capable of controlled electric sinusoidal wave-output for communication and navigation, and in the case of Electrophorus spp. hunting as well.
A false knife-fish- Gymnarchus niloticus- aba-aba- is able to employ weak electronavigation due to them being fairly closely related to the African elephant-nose fishes, Mormyridae. But they are quite morphologically unique and easy to identify anyhow.
The false knife-fishes are the Afro-Asian spp. of the Notopteridae (and Gymnarchus, but again that is moreso an odd exception). This includes the African Papyrocranus and Xenomystus; as well as Asian Notopterus and Chitala. They are, for the most part, incapable of electricity output on a level anywhere remotely close to the true knife-fishes, have a fully-functional dorsal fin (besides Xenomystus, which is easy to identify apart from all others by head/eye-shape alone), employ slightly different means of swimming, have completely different overall morphologies, etc.
Clown knifefish- Chitala ornata- and Aba-aba- G. niloticus- are both what would be called 'false knife-fish'.
