Body Fluid Partitioning in Reptilia

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The total body water and its apportionment among the major fluid compartments was studied in fifteen species or subspecies of reptiles, representing four orders and seven families. Five were freshwater forms, five marine, four terrestrial, and one brackish water. No parameter appeared to be related to size of animals employed. Hematocrit as well as specific gravity of both plasma and whole blood were lower in freshwater forms than in marine or terrestrial ones. Body water content of marine and terrestrial species was lower than that of freshwater forms. Extracellular fluid volume was higher in both marine and terrestrial than in freshwater forms, and this pattern was reflected in both sub-compartments, plasma and interstitial fluid, as well as in whole blood volume. Elevation of extracellular fluid volume was entirely at the expense of the intracellular compartment. The departure of marine and terrestrial forms from the pattern of freshwater species was in every case more pronounced in marine than in terrestrial reptiles. The body fluid apportionment of the brackish water diamondback terrapin resembled that of the marine species. However, intracellular water was the lowest of any species studied, and extracellular volume was the highest. The latter was accounted for entirely by an elevated interstitial fluid volume. The total body water and its apportionment among the major fluid compartments was studied in fifteen species or subspecies of reptiles, representing four orders and seven families. Five were freshwater forms, five marine, four terrestrial, and one brackish water. No parameter appeared to be related to size of animals employed. Hematocrit as well as specific gravity of both plasma and whole blood were lower in freshwater forms than in marine or terrestrial ones. Body water content of marine and terrestrial species was lower than that of freshwater forms. Extracellular fluid volume was higher in both marine and terrestrial than in freshwater forms, and this pattern was reflected in both sub-compartments, plasma and interstitial fluid, as well as in whole blood volume. Elevation of extracellular fluid volume was entirely at the expense of the intracellular compartment. The departure of marine and terrestrial forms from the pattern of freshwater species was in every case more pronounced in marine than in terrestrial reptiles. The body fluid apportionment of the brackish water diamondback terrapin resembled that of the marine species. However, intracellular water was the lowest of any species studied, and extracellular volume was the highest. The latter was accounted for entirely by an elevated interstitial fluid volume.