. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 10 Comparative Animal Physiology OSMOTIC ADJUSTMENT TO THE MEDIUM; POIKILOSMOTIC ANIMALS The statement is sometimes made in textbooks that all marine invertebrates are isotonic with the ocean; this was found true for a great variety of species.^*^' ^''' '^^' Some crustaceans and a few annelids show deviation in osmo- concentrations, but most marine invertebrates are isotonic and adapt their VOL 100 4 000 3500 2000 -. OBSERVED 60 â To T^ CONCENTRATION OF SEA WATER IN PER CENT Fig. 3. Volume changes in cubic micra
. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 10 Comparative Animal Physiology OSMOTIC ADJUSTMENT TO THE MEDIUM; POIKILOSMOTIC ANIMALS The statement is sometimes made in textbooks that all marine invertebrates are isotonic with the ocean; this was found true for a great variety of species.^*^' ^''' '^^' Some crustaceans and a few annelids show deviation in osmo- concentrations, but most marine invertebrates are isotonic and adapt their VOL 100 4 000 3500 2000 -. OBSERVED 60 â To T^ CONCENTRATION OF SEA WATER IN PER CENT Fig. 3. Volume changes in cubic micra (XlO") in fertilized Arhacia eggs as a function of dilution of sea water as per cent normal sea water. â¢, Lower curve, observed volumes; Oi upper curve, volumes calculated on basis of gas laws. From Lucke and McCutcheon.''^ internal concentration to external changes. The limitation on the distribution of all osmolabile animals is probably the dilution at which their enzyme systems can still carry out sufficient metabolism for active life. The simplest and most economical osmotic adjustment is found in marine and parasitic organisms, which are highly permeable to water and gain or lose water accord- ing to the concentration of the medium. No osmotic work is done, and body volume is not regulated. Osmotic Change without Volume Regulation: Unicellular Animals. Much evidence indicates that marine Protozoa are isotonic with sea water. The flagellate, Noctiluca, is in osmotic equilibrium with sea water but may have a lower specific gravity owing to the presence of considerable amounts of a salt of lower specific gravity than sodium chloride (Goethard and Hensius, quoted by Krogh ^â *'0- This salt is probably ammonium chloride, which is ionic at the remarkably low pH of in the cytoplasm. "- When Noctihica is put into diluted sea water it swells and finally bursts at concentrations correspond- ing to a specific gravity between and ^*^ Thus the only adap
Size: 1685px × 1483px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookpublisher, booksubjectphysiologycomparative
