The feeding mechanism of Balannoglossus is based on the studies of Barrington (1940). It feeds on sand particles along with organic food particles through the mouth. It digests the organic panicles and discharge the sand out from the anus in the form of characteristic castings. Some forms neither eat sand nor emit castings. These forms also feed on diatoms and other micro-organisms.
The feeding is of muco-ciliary type. The epidermal cells of proboscis secrete large amounts of the mucous which flows in the form of strands. The food particles are entangled in the mucous and passed back along the proboscis to the collarette. The feeding is also assisted by powerful currents of water caused by the cilia of gill-slits. Dorsal cilia at the base of the proboscis beat latero-ventrally to direct the mucous strands towards the centrally situated mouth.
An “U” shaped epidermal groove, the preoral ciliary organ, is situated at the base of proboscis and bordered by strong cilia, tastes the quality of the food and water entering the mouth. Large unsuitable particles are efficiently rejected from entering the mouth by the ventral part of the collarette which docs so by covering the mouth. Consequently the particle slips posteriorly on to the collar, back of the mouth.
The entire alimentary canal is lined with minute cilia which direct the food laden mucous cord backward.
The physiology of digestion is poorly known. Barrington (1904) reported that the slime of proboscis contains potent amylase which probably helps in digestion of glycogen According to him the cells of hepatic caeca secrete amylase, maltase, a weak protease and lipase, thus proteins, fats and carbohydrates, all, are digested. Knight Johnes has claimed that peristalsis occur in the proximal part of oesophagus.
The undigested waste is removed in the form of castings which are in the form of coils round the anal aperture of the burrow.