a blind pouch of the intestine that in many fishes and some insects serves to enlarge the digestive surface and to neutralize food when it passes from the acid medium of the stomach to the alkaline medium of the intestine. In fishes the pyloric ceca usually depart from the small intestine near the stomach outlet or directly from the pylorus. In cartilaginous fishes, pyloric ceca are found in small number in only a few isolated species. For example, the Greenland shark has two. Sturgeons have numerous pyloric ceca, which are joined by connective tissue into a single branched appendage that is united with the intestine by a common opening. Bony fishes having pyloric ceca may have from one (angler) to several dozen (Salmonidae, Clupeidae, and Gadidae) such pouches. Some mackerel have 200 pyloric ceca. In most bony fishes the pyloric ceca open into the intestine singly or in small groups. In some fishes they are joined into bundles, and in tuna they are united in a single formation.
Among insects, pyloric ceca are found in Orthoptera, Coleoptera, and dipteran larvae. They are distributed either along the entire length of the midgut or at its anterior section.