236
J. A. ALLEN A N D M. R. GARRETT
the importance of each varying in different species. Taurine was not
determined in these earlier analyses, but Jeuniaux et al. (1961b) found
taurine in considerable quantities in Leander ; however, in this species it
shows little change with changing salinity but, when Eriocheir is
transferred from fresh water to sea water there is a rise in the taurine
level.
The first demonstration of taurine playing an important role in
intracellular osmotic regulation in an animal was in Asterias rubens
Linnd (Jeuniaux et al., 1962a and b). They found that when Asferias,
that had previousIy been living in full salinity, were introduced into
water of 60% salinity they first became very bloated, but that after
48 h they became less bloated and resumed normal activity and survived in the brackish water for at least ten days. During their adaptation t o dilute sea water the osmotic pressure of the perivisceral fluid is
the same as that of the external medium; however, the tissues of the
gastric caeca showed only a slight increase in hydration (72% of fresh
weight in experimental animals as compared with 68% of those in full
sea water). At the same time, the concentration of free amino acids and
taurine had decreased from 22-1 m moles/100 g fresh tissue to 12-2 m
moles/100 g fresh tissue-which is equivalent t o a depression of freezing
point of 0*28OC, while the dilution of the intracellular contents only
accounts for the equivalent of 0-04"C. The change in the intracellular
concentration of the amino acids is almost exclusively due t o the loss
of glycine and taurine (1300-710 mg/100 g fresh tissue and 490280 mg/100 g fresh tissue respectively).
Similar studies on intracellular isosmotic regulation in Mytilus,
Gryphaea and Ostrea show the importance of taurine and also glycine,
glycine-betaine and alanine (Brideax-Gr6goire, 1964a and b). Thus
when Mytilus edulis is adapted t o water of half salinity, the isosmotic
intracellular regulation is accomplished by a slight change in hydration
and above all by a decrease in concentration of sodium and chloride ions
and amino acids of which taurine accounts for approximately 10%.
Taurine appears to have a special relevance in the isosmotic regulation
of euryhaline bivalves. Thus, Lange (1963) measured total ninhydrin
positive substances (i.e., amino acids and taurine), and taurine
separately in Mgtilus and found that both were linearly correlated with
salinity, but, in addition, taurine formed an increasing percentage of the
total with decreasing salinity (Fig. 2). Lange (1963) points out that
taurine in iMytilus exerts a " sparing effect " on the use of amino acids
in the osmotic equilibration of the cells. Florkin (1963) had already
suggested that all major organic solutes of the cells are non-essential
t o the animals.
J. A. ALLEN A N D M. R. GARRETT
the importance of each varying in different species. Taurine was not
determined in these earlier analyses, but Jeuniaux et al. (1961b) found
taurine in considerable quantities in Leander ; however, in this species it
shows little change with changing salinity but, when Eriocheir is
transferred from fresh water to sea water there is a rise in the taurine
level.
The first demonstration of taurine playing an important role in
intracellular osmotic regulation in an animal was in Asterias rubens
Linnd (Jeuniaux et al., 1962a and b). They found that when Asferias,
that had previousIy been living in full salinity, were introduced into
water of 60% salinity they first became very bloated, but that after
48 h they became less bloated and resumed normal activity and survived in the brackish water for at least ten days. During their adaptation t o dilute sea water the osmotic pressure of the perivisceral fluid is
the same as that of the external medium; however, the tissues of the
gastric caeca showed only a slight increase in hydration (72% of fresh
weight in experimental animals as compared with 68% of those in full
sea water). At the same time, the concentration of free amino acids and
taurine had decreased from 22-1 m moles/100 g fresh tissue to 12-2 m
moles/100 g fresh tissue-which is equivalent t o a depression of freezing
point of 0*28OC, while the dilution of the intracellular contents only
accounts for the equivalent of 0-04"C. The change in the intracellular
concentration of the amino acids is almost exclusively due t o the loss
of glycine and taurine (1300-710 mg/100 g fresh tissue and 490280 mg/100 g fresh tissue respectively).
Similar studies on intracellular isosmotic regulation in Mytilus,
Gryphaea and Ostrea show the importance of taurine and also glycine,
glycine-betaine and alanine (Brideax-Gr6goire, 1964a and b). Thus
when Mytilus edulis is adapted t o water of half salinity, the isosmotic
intracellular regulation is accomplished by a slight change in hydration
and above all by a decrease in concentration of sodium and chloride ions
and amino acids of which taurine accounts for approximately 10%.
Taurine appears to have a special relevance in the isosmotic regulation
of euryhaline bivalves. Thus, Lange (1963) measured total ninhydrin
positive substances (i.e., amino acids and taurine), and taurine
separately in Mgtilus and found that both were linearly correlated with
salinity, but, in addition, taurine formed an increasing percentage of the
total with decreasing salinity (Fig. 2). Lange (1963) points out that
taurine in iMytilus exerts a " sparing effect " on the use of amino acids
in the osmotic equilibration of the cells. Florkin (1963) had already
suggested that all major organic solutes of the cells are non-essential
t o the animals.