The Chemical Composition of the Blood of Some Aquatic Chordates, Including Members of the Tunicata, Cyclostomata and Osteichthyes

Abstract

1. Fairly complete analyses have been given of the blood of certain tunicates, cyclostomes, and bony fishes. 2. The plasma of the tunicates Phallusia mammillata and Salpa maxima closely resembles sea water in ionic composition, except for a very reduced sulphate content. Protein is less than 1 g./l. 3. The serum of Myxine glutinosa is isosmotic with sea water within about 1%. Every ion is regulated; sodium and phosphate exceed their respective values in sea water, and the remaining ions are lower, especially sulphate and magnesium. Two values for urea are 122 and 255 mg./kg. water, the higher figure being about 0.3% of the total concentration of ions and non-electrolytes. 4. The composition of the plasma of Lampetra fluviatilis from fresh water resembles that of Coregonus clupeoides, a fresh-water teleost. Muraena helena, a marine teleost, maintains a total concentration of ions about one-third that of sea water. It differs from fresh-water teleosts chiefly in maintaining much higher sodium and chloride concentrations. 5. The implications of the dichotomy in osmotic and ionic regulation of myxinoids and petromyzonts are considered, and also the glomerular nature of the cyclostome and fish kidney.