264
AUBREY GORBMAN
tegumentary pigmentation but also melanophore granule dispersion.
Thyroxine had the opposite effect. However, in young Misgurnus fossilis
(Zaks and Zamkova, 1947) and salmon (Dales and Hoar, 1954), goitrogens did not affect melanin pigmentation. La Roche et al. (1966b) (and
in earlier publications by La Roche, especially La Roche and Leblond,
1952) have found in both rainbow trout and salmon, that radiothyroidectomy affects the morphology of skin (thinning of both epidermal and
dermal elements ) which is corrected by thyroxine administration.
There is now an extensive literature that indicates a role for thyroid
hormone in central nervous function and behavior of teleosts. Much of
this has been gathered by Hoar ( 1959) and Baggerman ( 1960, 1962).
The eventual significance of this work is that it may form a basis for explanation of important events like population migration. One thing is
certain, and it is that if thyroid hormones affect migratory behavior
( M. Fontaine et al., 1952), they are not the only hormones involved; this
may account for the imperfect correlation between migratory behavior of
salmon and thyroid state, summarized by Hoar ( 1959).
Among the provocative publications in this field are two of Hoar et al.
(1952, 1955) who found that thyroid and sex hormones affect the pattern
of motor behavior and orientation of goldfish and young salmon, and that
thyroxine stimulates the degree of motor activity. Sage (1968) similarly
found that thyroxinized guppies have an altered swimming and increased
jumping behavioral pattern, without increasing oxygen consumption.
Thiourea has an opposite effect on motor behavior in guppies. Baggerman
(1963, and earlier), working with sticklebacks and juvenile salmon, has
provided evidence that thyroxine and goitrogen treatment alter “salinity
preference.” When thyroxinized young salmon, for example, are presented
a choice between freshwater and saltwater, they “prefer” saltwater to a
greater degree than do controls. Thiourea treatment favors freshwater
preference. These data, although they demonstrate an interesting hormone-altered behavior, do not actually explain migratory tendency since
the salmon do not begin their downstream migration in a salinity gradient.
In an imperfect and difficult experiment, Norris (1966) recently planted
radiothyroidectomized and intact steelhead trout, Salmo gairdneri, in a
small lake. He observed the tendency of these young fish to migrate out
of the lake downstream and found no clear difference. Unfortunately,
mortality and the difficulty of recovering specimens in such a “natural”
situation reduced the numbers of specimens to a relatively small value,
making a firm conclusion difficult.
Effects of thyroxine upon behavior (reviewed by Gorbman, 1959)
point out the need for more precise study of the effects of changes in
thyroid state upon particular phases of central nervous function. A be-
AUBREY GORBMAN
tegumentary pigmentation but also melanophore granule dispersion.
Thyroxine had the opposite effect. However, in young Misgurnus fossilis
(Zaks and Zamkova, 1947) and salmon (Dales and Hoar, 1954), goitrogens did not affect melanin pigmentation. La Roche et al. (1966b) (and
in earlier publications by La Roche, especially La Roche and Leblond,
1952) have found in both rainbow trout and salmon, that radiothyroidectomy affects the morphology of skin (thinning of both epidermal and
dermal elements ) which is corrected by thyroxine administration.
There is now an extensive literature that indicates a role for thyroid
hormone in central nervous function and behavior of teleosts. Much of
this has been gathered by Hoar ( 1959) and Baggerman ( 1960, 1962).
The eventual significance of this work is that it may form a basis for explanation of important events like population migration. One thing is
certain, and it is that if thyroid hormones affect migratory behavior
( M. Fontaine et al., 1952), they are not the only hormones involved; this
may account for the imperfect correlation between migratory behavior of
salmon and thyroid state, summarized by Hoar ( 1959).
Among the provocative publications in this field are two of Hoar et al.
(1952, 1955) who found that thyroid and sex hormones affect the pattern
of motor behavior and orientation of goldfish and young salmon, and that
thyroxine stimulates the degree of motor activity. Sage (1968) similarly
found that thyroxinized guppies have an altered swimming and increased
jumping behavioral pattern, without increasing oxygen consumption.
Thiourea has an opposite effect on motor behavior in guppies. Baggerman
(1963, and earlier), working with sticklebacks and juvenile salmon, has
provided evidence that thyroxine and goitrogen treatment alter “salinity
preference.” When thyroxinized young salmon, for example, are presented
a choice between freshwater and saltwater, they “prefer” saltwater to a
greater degree than do controls. Thiourea treatment favors freshwater
preference. These data, although they demonstrate an interesting hormone-altered behavior, do not actually explain migratory tendency since
the salmon do not begin their downstream migration in a salinity gradient.
In an imperfect and difficult experiment, Norris (1966) recently planted
radiothyroidectomized and intact steelhead trout, Salmo gairdneri, in a
small lake. He observed the tendency of these young fish to migrate out
of the lake downstream and found no clear difference. Unfortunately,
mortality and the difficulty of recovering specimens in such a “natural”
situation reduced the numbers of specimens to a relatively small value,
making a firm conclusion difficult.
Effects of thyroxine upon behavior (reviewed by Gorbman, 1959)
point out the need for more precise study of the effects of changes in
thyroid state upon particular phases of central nervous function. A be-