‘Chloride Cells’ in the Gills of Fresh-Water Teleosts

Journal of Cell Science, Mar 1964

J. S. DATTA MUNSHI

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‘Chloride Cells’ in the Gills of Fresh-Water Teleosts

0 (From the Department of Zoology, Banaras Hindu University , Varanasi-5 , India) Specialized cells of several kinds, namely, (a) mucous-gland cells, (b) large bi- or tri" 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 test'. 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. - 'Chloride cells' in the gills of fresh-water teleosts I T has been claimed that the bulk of the sodium, potassium, and chloride absorbed in the gastro-intestinal tract of marine teleosts is excreted by the 'chloride-secreting' cells in the gills (Smith, 1930; Keys, 1931, 1933; Keys and Willmer, 1932); but Bevelander (1935, 1946) believed that the supposed excretory cells are nothing but intra-epithelial mucous glands and that the general respiratory epithelium might be a site of chloride excretion. Liu (1942) attempted to acclimatize the fresh-water air-breathing fish, Macropodus opercularis, to different concentrations of salt solution. He stated that even an exclusively fresh-water fish can tolerate a salt solution nearly as saline as sea-water by virtue of the enormous development of latent 'chloridesecreting cells'. From this experiment he concluded that fresh-water teleosts possess 'chloride-secreting cells' in the gills in a dormant condition. Copeland (1948a, b) noted cytological changes in the chloride cells of Fundulus heteroclitus during adaptation to varying degrees of salinity, and by using the Leschke test demonstrated the presence of a copious amount of chloride in the secretory cells of fishes adapted to the salt-water condition, but only a limited amount of it at the free ends of the cells in fishes adapted to freshwater life. Getman (1950) working on Anguilla rostrata came to a similar conclusion. More recently Vickers (1961) has said, with reference to the gills of Lebistes reticulatus (a fresh-water teleost), that after subjection to hypertonic-salt solutions of varying concentrations, its mucous cells become functionally transformed into chloride cells. The present studies on gill epithelia of fresh-water teleosts were undertaken in order to remove some of the ambiguities and deficiencies in our knowledge. Materials and methods Fishes were collected from the river Ganges and the local ponds. Pieces of their gills were immediately fixed in Zenker, Helly, chrome-Bouin, alcoholic Bouin, Gilson's mercuro-nitric, or Carnoy's fluid after gently removing the adhering mucus with a cotton swab and rinsing them in river water. Sections of the gills were stained with Heidenhain's or Delafield's haematoxylin or Mayer's haemalum, and counterstained with eosin. Mallory's triple stain, borax-carmine followed by picro-indigo-carmine, and other stains were also employed. Parts of the gill lamellae were dissociated in several different fluids such as sodium-chloride solution, Ranvier's alcohol, and borax solution. The dissociated cells were stained with methylene-blue and examined with the microscope. Thionin was used to demonstrate the presence of mucus and mucusproducing cells and mast cells (the latter by their chromotropic reaction). Sections were stained in a 0-2% aqueous solution of thionin, quickly passed through acetone to xylene, and mounted in balsam. The PAS technique was used to demonstrate the mucus-producing cells. Fresh tissues of the gill lamellae were also studied supravitally with neutral red. The Leschke silver technique, as modified by Copeland (1948a, b), was also used to detect the presence of the chloride in the so-called branchial glands. Histological studies were made on the following species of fishes: 1. Hilsa ilisha (Ham.) 2. Gadusia chapra (Ham.) 3. Catla catla (Ham.) 4. Labeo rohita (Ham.) 5. Rohtee cotio (Ham.) Family Clupeidae Cyprinidae 6. Glorias batrachus (Linn.) 7. Heteropneustes fossilis (Bloch) 8. Wallago attu (Bl. & Schn.) 9. Rita rita (Ham.) 10. Mystus aor (Giinther) Group D 11. Ophiocephalus punctatus (Bloch) 12. Ophiocephalus striatus 13. Anabas testudineus (Bloch) 14. Trichogaster fasciatus (Bl. & Schn.) Anabantidae Osphronemidae The chloride test was only applied to nos. 1, 3, 6, 7, 9, 11, 12, and 15 in the above list. Results The principal findings are summarized in tables 1 and 2 (see appendix, p. 88), and illustrated in figs. 1 and 2. The structure of the gills of Labeo rohita, Hilsa ilisha, Rita rita, and Ophiocephalus striatus ha (...truncated)


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J. S. DATTA MUNSHI. ‘Chloride Cells’ in the Gills of Fresh-Water Teleosts, Journal of Cell Science, 1964, pp. 79-89, s3-105/69,