3. FISH PROLACTIN AND GROWTH HORMONE
227
reserves such as fat or glycogen. In practical terms, it follows that increase
in linear dimensions offers the safest criteria for the detection of body
growth, certainly over the short periods involved in experimental studies.
B. Effects of Hypophysectomy on Growth in Fishes
Among teleosts, the basic observation that growth permanently ceases
after removal of the pituitary seems to have been made on only two
genera. Pickford (1953a) was the first to demonstrate conclusively that
a hypophysectomized teleost does not grow, when she reported that hypophysectomized killifish, Fundulus heteroclitus, do not grow in length
and show only irregular changes in weight. Sometimes hypophysectomized fish actually decreased in length, a change which was partially
corrected by TSH therapy ( Pickford, 195413). Pickford ( 1953a,b, 1957)
has emphasized how misleading weight changes can be in respect to
growth, pointing out for example that some hypophysectomized kilmsh
develop oedema because of renal calculi forming in the kidney ducts, and
this may lead to weight increases without any linear growth. Similarly,
the liver in hypophysectomized fish is enlarged and full of fat and glycogen reserves, which sometimes leads to weight increments although the
length of the fish is unaltered.
In agreement with this pioneer work on F . heteroclitus, hypophysectomy arrests growth in length in Poecilia formosa and P. latipinnu, even
under conditions in which intact or sham-operated controls grow vigorously (Ball, 1962, 1965a; Ball et al., 1965). More noticeably than Fund*
lus, hypophysectomized Poecilia usually decrease in length. In an experiment in which 46 P. latipinnu were hypophysectomized and then observed
for 14 days, all the fish decreased in length during this period (mean
1.5 f . O.O%), while intact controls were growing under the same conditions at a mean rate of 0.7 k 0.17% in 14 days.
For elasmobranchs, Vivien (1941), in the only published work on this
topic, showed that hypophysectomized dogfish ceased to grow.
C. Effects of GH on Growth in Hypophysectomized Fishes
Purfied mammalian GH will stimulate linear growth in intact teleost
(Pickford and Thompson, 1948; Swift, 1954), and an extensive series of
investigations has been directed to the analysis of the more significant
fact that purified beef GH will also promote growth in hypophysectomized male F . heteroc2itu.s (Pickford, 1953b, 1954a, 1957, 1959). One
important point that emerges from these experiments is the necessity of
227
reserves such as fat or glycogen. In practical terms, it follows that increase
in linear dimensions offers the safest criteria for the detection of body
growth, certainly over the short periods involved in experimental studies.
B. Effects of Hypophysectomy on Growth in Fishes
Among teleosts, the basic observation that growth permanently ceases
after removal of the pituitary seems to have been made on only two
genera. Pickford (1953a) was the first to demonstrate conclusively that
a hypophysectomized teleost does not grow, when she reported that hypophysectomized killifish, Fundulus heteroclitus, do not grow in length
and show only irregular changes in weight. Sometimes hypophysectomized fish actually decreased in length, a change which was partially
corrected by TSH therapy ( Pickford, 195413). Pickford ( 1953a,b, 1957)
has emphasized how misleading weight changes can be in respect to
growth, pointing out for example that some hypophysectomized kilmsh
develop oedema because of renal calculi forming in the kidney ducts, and
this may lead to weight increases without any linear growth. Similarly,
the liver in hypophysectomized fish is enlarged and full of fat and glycogen reserves, which sometimes leads to weight increments although the
length of the fish is unaltered.
In agreement with this pioneer work on F . heteroclitus, hypophysectomy arrests growth in length in Poecilia formosa and P. latipinnu, even
under conditions in which intact or sham-operated controls grow vigorously (Ball, 1962, 1965a; Ball et al., 1965). More noticeably than Fund*
lus, hypophysectomized Poecilia usually decrease in length. In an experiment in which 46 P. latipinnu were hypophysectomized and then observed
for 14 days, all the fish decreased in length during this period (mean
1.5 f . O.O%), while intact controls were growing under the same conditions at a mean rate of 0.7 k 0.17% in 14 days.
For elasmobranchs, Vivien (1941), in the only published work on this
topic, showed that hypophysectomized dogfish ceased to grow.
C. Effects of GH on Growth in Hypophysectomized Fishes
Purfied mammalian GH will stimulate linear growth in intact teleost
(Pickford and Thompson, 1948; Swift, 1954), and an extensive series of
investigations has been directed to the analysis of the more significant
fact that purified beef GH will also promote growth in hypophysectomized male F . heteroc2itu.s (Pickford, 1953b, 1954a, 1957, 1959). One
important point that emerges from these experiments is the necessity of