Specialized cells of several kinds, namely, (a) mucous-gland cells, (b) large bi- or tria nucleate glandular cells, and (c) mast cells occur in the gills of some species of freshwater teleosts.
The typical ‘goblet’ type of mucous glands are present in large number in freshwater species, such as Catla catla, Labeo rohita, Ophiocephalus punctatus, and Mastacembalus armatus. In Catla catla, these glands respond to the ‘chloride testy’. This indicates that, besides discharging mucus, they also play some part in the elimination of chloride. In Ophiocephalus punctatus, Clarias batrachus, and Heteropneustes fossilis only some of the mucous cells give a positive reaction with the AgNO3/HNO3 test for chloride. This may mean that a few of them are in a state of active secretion of chlorides, while others are in a non-secretory phase.
Large eosinophil glands with 2 or 3 nuclei also occur, chiefly in the siluroids. The function of these hypertrophied multicellular glands is not clear.
Judged by the AgNO3/HNO3 test, Catla catla possesses the highest number of chloride cells. In Hilsa ilisha, Rita rita, Ophiocephalus striatus and Mastacembalus armatus, only a ‘network of silver’ exists on the surface of the primary and secondary lamellae.
The ‘chloride cells’ are said to be a characteristic of marine fishes in which an extrarenal mechanism for the elimination of excess of salts from the body fluid is necessary for correct osmo-regulation. These cells are also said to make their appearance in fresh-water fishes that have been experimentally subjected to a saline medium. The presence and occurrence of ‘chloride cells’ in fresh-water fishes living in their natural habitat is, therefore, interesting. The discovery of the presence of actively secreting chloride cells in certain species of fresh-water teleosts and their mucoid nature are new results reported here.
- Copyright © 1964 by the Company of Biologists Ltd.