Physiology of Finfish and Shellfish (2+1)

5.2.10. The ultimo-branchial gland

The ultimo-branchial gland originates from the pharyngeal epithelium of the last or ‘ultimate’ gill pouch. It is unpaired. In chondrichthys, an ultimo-branchial gland is present between pericardium and pharynx. In bony fishes, the gland is present between the abdominal cavity and sinus venosus ventral to the oesophagus. In teleosts, the gland is seen as a band of white tissue on the septum ( In anatomy , a septum ( Latin for something that encloses; plural septa) is a wall, dividing a cavity or structure into smaller ones) and may be solid or diffused. The gland may be paired or single and present a variable histological structure that superficially looks like the parathyroid of higher vertebrates. (Parathyroid gland - An endocrine organ usually associated with the thyroid gland and possessed by all vertebrates except the fishes. In response to lowered serum calcium concentration, a hormone is produced which promotes bone destruction and inhibits the phosphorus-conserving activity of the kidneys. The function of parathyroid glands is taken over by other endocrine organs (Corpuscles of Stannius) . 2 cell types have been described in the gold fish. Of these the granulated cells are secretary in nature, while the non granulated ones are tall, columnar and serve as supporting cells.

This organ secretes calcitonin (lowers serum calcium levels) that acts with hypocalcin ( a protein secreted by the corpuscles of stannius also called teleocalcin ) to regulate calcium metabolism. Calcitonin is a hormone which lowers blood Ca2+ levels. While this hormone is secreted from the thyroid gland in mammals. Hypocalcemia (lowering of plasma calcium and phosphorus) is observed when calcitonin is administered to catfish and eel. Removal of the gland causes hypercalcemia. The gland may also be involved in migration and reproductive behaviour of fishes.