Rectal gland

The rectal gland is an organ of the cartilaginous fish (Chondrichthyes) that is used to secrete sodium chloride ions (NaCl). Since the body of the cartilaginous fish contains less NaCl than the surrounding seawater, NaCl constantly diffuses into it.

The individual rectal glands are tubular and end blind. They lead into a common passage that ends in the last section of the intestine. A concentrated salt solution is excreted there, the salt concentration of which can be slightly higher than that of seawater.

In freshwater stingrays (Potamotrygonidae), which live permanently in freshwater and can no longer tolerate even small salt concentrations in the water, the rectal glands are reduced and functionless.

literature

• Roger Eckert: Animal Physiology. Thieme, Stuttgart 2002, ISBN 3-136-64004-7 online at GoogleBooks
• Kurt Fiedler: Textbook of Special Zoology, Volume II, Part 2: Fish . Gustav Fischer Verlag, Jena 1991, ISBN 3-334-00339-6 .