SOME EVOLUTIONARY PATTERNS IN FISHES' BLOOD

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Abstract
A study was made, by elec-trophoretic techniques, of the plasma proteins of 26 species of elasmo-branch and teleost fishes from the Gulf of Mexico. An increase was found in the amount of plasma proteins from lower to more specialized fishes. Elasmobranchs lacked albumin in the plasma. This analbumin-emia also held true for all the gars and half of the Clupeidae; it generally disappeared in the specialized fishes, but not entirely, and was found in 2 species of Perciformes. There was a gradual increase in the number of globulin fractions of the plasma, from lower to higher fishes, among the Orders of fishes, which did not always hold true at species levels. Closely related species could be distinguished by the presence or absence and varying amounts of plasma proteins, but there were exceptions and certain species in the same family could only be differentiated doubtfully on that basis. Plasma proteins of the fishes examined showed a trend of increasing complexity from the generalized to the more specialized fishes. The content of the electrolytes, Na, K and Cl, in the plasma of marine sharks was much higher than in teleosts, in confirmation of earlier workers. Cholesterol in the plasma of sharks and gars was found in the same range as in mammals, but in the remaining teleost fishes it was a great deal higher. Relations between cholesterol and plasma proteins in the blood of fishes resemble pathological conditions in man.