234
J. A. A U E N AND M. R. GARRETT
taurine concentration increased relatively more than other amino acids
with increasing salinity and thereby it exerts a sparing effect on the use
of essential amino acids in osmoregulation. However, the role of
taurine in this respect is not true of all marine animals.
Jeuniaux et al. (196lb) in a study of the euryhaline carideans
Palaemon elegans Rathke (Leader squiElu) and P . ( L . ) serrutus
(Pennant) and their adaptation to brackish water (30% sea water)
showed that a variation in the osmotic pressure of the external medium
equal to a depression of freezing point of 1 . 7 O C brings about changes
of 0.3"C and 0~6°C respectively in the osmotic pressure of the blood.
The intracellular osmotic pressure is adjusted to the osmotic pressure of
the blood in part by changes in water content of the muscles and
(4) by the variation in concentration of a number of intracellular
amino acids, namely glutamine, glycine, proline and alanine, but, not
taurine. Taurine is present in considerable quantity but, in the case of
Palaemon, whereas there is an 85% decrease in amino acids on transference t o 30% sea water, the taurine level only falls by 70/-10%.
Similarly in Carcinus, in which the osmotic pressure of the blood is
maintained above that of the surrounding medium when the latter is
diluted, the osmotic pressure of the muscle fibres changes proportionately with the blood (Shaw, 1958b). The reduction in the osmotic
pressure of the muscle fibre is brought about, in part at least, by the
loss of the non-ion fraction composed of free amino acids, taurine,
betaine and trimethylamine oxide. These account for about two thirds
of the total osmotic activity. The regulation of these substances is
therefore quite different from that of the inorganic muscle ions, the
concentration of which, in earlier work (Shaw, 1955, 1958a) had been
shown to be governed solely by the dilution of the muscle contents by
the osmotic intake of water following the dilution of the blood. The
experiments on Carcinus showed that the regulation of intracellular
organic nitrogenous substances was completely reversible, the normal
muscle concentrations being regained when thc animal was replaced in
full salinity seawater. He suggested two possibilities which might
explain this regulation. Either the substances are removed from the
muscle fibrc during blood dilution, or they are combined with other
muscle constituents, thus losing their activity. The concentration of
these substances in the blood is always low, which might suggest that
if they are not temporarily removed from the fibre, they combine with
large molccules within the cell, and are thus rendered osmotically
inactive, but this has yet to be confirmed (see p. 238). Analysis of
other crustaceans, which are purely marine and do not adapt to
brackish water (e.g. Homarus and Nephrops) has shown that in these
J. A. A U E N AND M. R. GARRETT
taurine concentration increased relatively more than other amino acids
with increasing salinity and thereby it exerts a sparing effect on the use
of essential amino acids in osmoregulation. However, the role of
taurine in this respect is not true of all marine animals.
Jeuniaux et al. (196lb) in a study of the euryhaline carideans
Palaemon elegans Rathke (Leader squiElu) and P . ( L . ) serrutus
(Pennant) and their adaptation to brackish water (30% sea water)
showed that a variation in the osmotic pressure of the external medium
equal to a depression of freezing point of 1 . 7 O C brings about changes
of 0.3"C and 0~6°C respectively in the osmotic pressure of the blood.
The intracellular osmotic pressure is adjusted to the osmotic pressure of
the blood in part by changes in water content of the muscles and
(4) by the variation in concentration of a number of intracellular
amino acids, namely glutamine, glycine, proline and alanine, but, not
taurine. Taurine is present in considerable quantity but, in the case of
Palaemon, whereas there is an 85% decrease in amino acids on transference t o 30% sea water, the taurine level only falls by 70/-10%.
Similarly in Carcinus, in which the osmotic pressure of the blood is
maintained above that of the surrounding medium when the latter is
diluted, the osmotic pressure of the muscle fibres changes proportionately with the blood (Shaw, 1958b). The reduction in the osmotic
pressure of the muscle fibre is brought about, in part at least, by the
loss of the non-ion fraction composed of free amino acids, taurine,
betaine and trimethylamine oxide. These account for about two thirds
of the total osmotic activity. The regulation of these substances is
therefore quite different from that of the inorganic muscle ions, the
concentration of which, in earlier work (Shaw, 1955, 1958a) had been
shown to be governed solely by the dilution of the muscle contents by
the osmotic intake of water following the dilution of the blood. The
experiments on Carcinus showed that the regulation of intracellular
organic nitrogenous substances was completely reversible, the normal
muscle concentrations being regained when thc animal was replaced in
full salinity seawater. He suggested two possibilities which might
explain this regulation. Either the substances are removed from the
muscle fibrc during blood dilution, or they are combined with other
muscle constituents, thus losing their activity. The concentration of
these substances in the blood is always low, which might suggest that
if they are not temporarily removed from the fibre, they combine with
large molccules within the cell, and are thus rendered osmotically
inactive, but this has yet to be confirmed (see p. 238). Analysis of
other crustaceans, which are purely marine and do not adapt to
brackish water (e.g. Homarus and Nephrops) has shown that in these