Britannica
Sources used in this answer
What is an adipose fin in ostariophysan fishes?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
ostariophysan
Knifefish, or featherback (Xenomystus nigri)
In ostariophysan fishes, an adipose fin is a small to elongated fleshy or fatty structure that lacks fin ray supports. It is positioned dorsally on the fish's back, located in the space between the rayed dorsal fin and the caudal (tail) fin. While this feature is present in most ostariophysan fishes, it is notably rare in the order Cypriniformes.1