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
Apistogramma eremnopyge Apistogramma eremnopyge Apistogramma eremnopyge is a species of cichlid. It is only known from the Rio Pintuyacu, a tributary of the Rio Itaya near Iquitos, Peru. Most of the tributaries of this river system carry acid blackwater (pH ~ 5). This is a small cichlid, standard length which can be easily distinguished from its congeners by the presence of a prominent dark blotch on the lower part of the caudal peduncle in both sexes. The male is strikingly coloured with vivid blue and red patterning on the cheek and operculum and maroon, orange and blue colouring on the dorsal fin.