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
Sessility (motility) organisms, in which individuals of a particular species group closely to one another for beneficial purposes, and can be seen in coral reefs and cochineal populations. This allows for faster reproduction and better protection from predators. The circa littoral zone of coastal environments and biomes are dominated by sessile organisms such as oysters. Carbonate platforms grow due to the buildup of skeletal remains of sessile organisms, usually microorganisms, which induce carbonate precipitation through their metabolism. In anatomy and botany, "sessility" refers to an organism or biological structure that has no "peduncle" or stalk. See Peduncle (anatomy), Peduncle (botany) and Sessility