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Physiological mechanisms of buoyancy in eggs from brackish water cod
Author(s) -
Thorsen A.,
Kjesbu O. S.,
Fyhndr H. J.,
Solemdal P.
Publication year - 1996
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.1996.tb01440.x
Subject(s) - biology , brackish water , buoyancy , fishery , ecology , zoology , oceanography , salinity , mechanics , physics , geology
Newly fertilized eggs of brackish water (Gotland, Baltic Sea) and marine (Lofoten, Norway) cod were investigated with regard to specific gravity, wet and dry weight, water content, chorion weight, and content of protein, free amino acids (FAA), and ions. The eggs had neutral buoyancies equivalent to a salinity of 14 . 3% (range 11 . 5–16 . 2%) in brackish water, and 33 . 0% (range 31 . 8–34 . 5%) in the marine environment. A buoyancy model was developed and showed that this difference was mainly caused by differences in egg water content which was 96.6 ± 0 . 47% and 92.7 ± 0.45% in the brackish and marine eggs, respectively. The higher water content of the brackish eggs resulted from increased water uptake during final oocyte maturation due to higher intracellular contents of FAA, Cl – and NH 4 + . SDS polyacrylamide gel electrophoresis of eggs and oocytes, and measurements of egg protein content suggested that the FAA pool of both egg types originated from hydrolysis of specific yolk proteins. The main contributor seemed to be a protein with a molecular weight of 100 kDa.