THE BEHAVIOUR AND PHYSIOLOQY OF HERRINQ AND OTHER CLUPEIDS 311
original took place within 24 hr. Total body weight changed in a
similar way.
Unpublished data by Holliday on the ionic composition of the blood
and muscle of the transferred fish (summarized in Table VIII) showed
corresponding changes.
Outside the tolerance range the changes were more extreme and not
reversible, the fish dying within 24 hr. It can be seen from Table VIII
that muscle concentrations closely paralleled blood changes ; it would
appear that muscle concentration changes are largely the result of
changes in intracellular water.
3. Sites of regulation
The problem facing the herring in low salinities is the excretion of
excess water through the kidney. Holliday and Blaxter (1961) found
that the kidney of the herring had a very high glomerular count, being
obviously well adapted to dealing with this water (see Fig. 8). Nash
(1931) also found that Sadinella macrophthalmus and Sardinellu
anchovia had high glomerular counts. The clupeids strongly resemble
freshwater fishes in this respect. Unlike that in a freshwater fish the
nephron of the herring contpins no distal tubule. This segment is
normally responsible for resorption of salts from the urine in freshwater fishes. It seems likely that the absence of this precludes salt
conservation, and hence most herring cannot live in water below
5-6%, although some do, e.g., in the eastern Baltic.
The regulation of ionic composition of the tissues is almost certainly
carried out through the general gill epithelium. It now seems unlikely
that the acidophil cells, described by Keys and Willmer (1932) as being
chloride secreting, are concerned with this function (see Parry et al.,
1959). This would not affeot the general conclusion of Graham (1956),
on Pornolobus, that those fish having the greater relative head size
(and hence gill area) would be more efficient at ionic regulation and
hence survive better in certain environments.
4 . Effects of endocrines
Hoar (1952) suggested that the high degree of osmotic regulation
taking place in Pornolobus in fresh water made such a heavy demand on
the hormones of the thyroid gland that growth was retarded; this
situation did not exist in the marine forms of this fish, which had a
higher growth rate (discussed in Section V, E).
original took place within 24 hr. Total body weight changed in a
similar way.
Unpublished data by Holliday on the ionic composition of the blood
and muscle of the transferred fish (summarized in Table VIII) showed
corresponding changes.
Outside the tolerance range the changes were more extreme and not
reversible, the fish dying within 24 hr. It can be seen from Table VIII
that muscle concentrations closely paralleled blood changes ; it would
appear that muscle concentration changes are largely the result of
changes in intracellular water.
3. Sites of regulation
The problem facing the herring in low salinities is the excretion of
excess water through the kidney. Holliday and Blaxter (1961) found
that the kidney of the herring had a very high glomerular count, being
obviously well adapted to dealing with this water (see Fig. 8). Nash
(1931) also found that Sadinella macrophthalmus and Sardinellu
anchovia had high glomerular counts. The clupeids strongly resemble
freshwater fishes in this respect. Unlike that in a freshwater fish the
nephron of the herring contpins no distal tubule. This segment is
normally responsible for resorption of salts from the urine in freshwater fishes. It seems likely that the absence of this precludes salt
conservation, and hence most herring cannot live in water below
5-6%, although some do, e.g., in the eastern Baltic.
The regulation of ionic composition of the tissues is almost certainly
carried out through the general gill epithelium. It now seems unlikely
that the acidophil cells, described by Keys and Willmer (1932) as being
chloride secreting, are concerned with this function (see Parry et al.,
1959). This would not affeot the general conclusion of Graham (1956),
on Pornolobus, that those fish having the greater relative head size
(and hence gill area) would be more efficient at ionic regulation and
hence survive better in certain environments.
4 . Effects of endocrines
Hoar (1952) suggested that the high degree of osmotic regulation
taking place in Pornolobus in fresh water made such a heavy demand on
the hormones of the thyroid gland that growth was retarded; this
situation did not exist in the marine forms of this fish, which had a
higher growth rate (discussed in Section V, E).