Extracellular ionic and acid-base adjustments of Atlantic salmon presmolts and smolts in fresh water and after transfer to sea water: the effects of ovine growth hormone on the acquisition of euryhalinity

Ergocryptine, an ergot alkaloid that suppresses prolactin (PRL) secretion and also affects growth hormone (GH) levels in mammals, was injected into juvenile rainbow trout, Salmo gairdneri, averaging 8 to 31 g. In fresh water the drug caused few fatalities but lowered plasma Na+, plasma Ca2+, muscle K+, muscle Mg2+, and haematocrit values. The simultaneous injection of low doses of PRL or GH did not significantly modify the results obtained with the drug alone except for an increase in muscle Mg2+ levels. This suggests a possible peripheral action of the drug.Ergocryptine caused the death of S. gairdneri in dilute sea water, while in certain circumstances PRL and GH prevented mortalities. In this medium the drug caused elevated levels of plasma Ca2+ and muscle K+. The simultaneous injection of ergocryptine plus PRL in hyperosmotic media produced an elevated plasma Na+ concentration but a decrease in intracellular Na+ content and concentration.The results suggest that PRL is not critical for the survival of S. gairdneri in fresh water but may still be necessary to maintain body ion concentrations. In hyperosmotic media, however, PRL and GH may be essential for survival and may act on general metabolic processes rather than specific osmoregulatory organs.

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Effect of Dietary Sodium Chloride on Growth of Atlantic Salmon (Salmo salar)

Journal of the Fisheries Research Board of Canada ◽

10.1139/f75-215 ◽

1975 ◽

Vol 32 (10) ◽

pp. 1813-1819 ◽

Cited By ~ 28

Author(s):

H. M. Shaw ◽

R. L. Saunders ◽

H. C. Hall ◽

E. B. Henderson

Keyword(s):

Sodium Chloride ◽

Atlantic Salmon ◽

Fresh Water ◽

Salmo Salar ◽

Sea Water ◽

Dietary Sodium ◽

Plasma Sodium ◽

Food Conversion ◽

Dietary Salt ◽

Dietary Sodium Chloride

Growth and food conversion efficiency in Atlantic salmon smolts (Salmo salar) in either fresh water or sea water were not demonstrably affected by varying the level of dietary sodium chloride. Large dietary salt loads were almost completely absorbed from the gastrointestinal tracts offish within 24 h, and plasma sodium and chloride concentrations were positively affected at this time.Irrespective of whether fish were undergoing random, spontaneous activity or an enforced, uniform low level of activity, growth rates and food conversion efficiencies were similar when fish were fed the same ration but different amounts of sodium chloride.A possible explanation is that normal renal function in fresh water provides for large amounts of hypoosmotic urine in which excess sodium chloride may be discharged without great expenditure of energy. However, in sea water, where urine flow is minimal, the main route of excretion for the excess electrolytes is across the gills, a process requiring energy.

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Osmotic and Ionic Changes in Blood and Muscle of Migrating Salmonids

Journal of Experimental Biology ◽

10.1242/jeb.38.2.411 ◽

1961 ◽

Vol 38 (2) ◽

pp. 411-427

Author(s):

GWYNETH PARRY

Keyword(s):

Atlantic Salmon ◽

Fresh Water ◽

Sea Water ◽

Juvenile Fish ◽

Inorganic Ions ◽

Juvenile Salmon ◽

Adult Fish ◽

Extracellular Compartment ◽

Ionic Changes ◽

Whole Muscle

1. Osmoregulation of the Atlantic salmon in fresh water and sea water, and during transfers from one salinity to another, has been studied by measuring the freezingpoint and the levels of some inorganic ions in the blood plasma, and water content and ions in whole muscle. 2. An increase in blood concentration of about 12% follows the transfer of juvenile fish (smolts) from fresh water to sea water; and a fall of concentration of about 5% follows the transfer of the adult fish from sea water to fresh water. 3. Some changes in analyses of whole muscle indicate changes in the extracellular compartment during transfers from one salinity to another. 4. Osmoregulatory powers of juvenile salmon (smolts) and fresh-run adults are good, but spent fish (kelts) returning from fresh water to sea water, osmoregulate with difficulty or not at all.

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