Development of the gut in the South African cyprinid fish Barbus aeneus (Burchell)

In Barbus aeneus, an omnivorous cyprinid, the pattern of coiling of the gut is well established at a fork length of 60 mm, when five sections can be distinguished, the third and fourth forming the ascending and returning arms of a loop recurved upon itself. The ratio of the gut length to fish length increases in larger fish, with the greatest increase occurring in the looped section. At lengths above 400 mm a second loop begins to develop at the apex of the primary loop. The related piscivorous B. kimberleyensis, cannot readily be distinguished from B. aeneus on external characters below a fork length of 90 mm. The pattern of coiling of the gut is less complex than that in B. aeneus and this appears to offer a method of distinguishing between individuals of the two species at lengths from 35 mm