Tetra a tall dorsal fin characterized by a short connection to the fish’s body. Additionally, tetras possess a long anal fin stretching from a position just posterior of the dorsal fin and ending on the ventral caudal peduncle, and a small, fleshy adipose fin located dorsally between the dorsal and caudal fins. This adipose fin represents the fourth unpaired fin on the fish (the four unpaired fins are the caudal fin, dorsal fin, anal fin, and adipose fin), lending to the name tetra, which is Greek for four. While this adipose fin is generally considered the distinguishing feature, some tetras (such
Copella (genus) observation. The pectoral fins are positioned immediately behind the operculum or gill cover, while the pelvic fins are further back along the body, about midway between the head and the caudal peduncle. The dorsal fin is positioned above and slightly behind the pelvic fins, and midway between the pelvic fins and the tail fin is the anal fin. The tail fin is forked in shape. Males usually possess more elongated and ornate unpaired fins than females. In the case of "C. arnoldi", the tail fin of the male is somewhat asymmetrical, the upper lobe being larger than the lower lobe,