2. THE NEUROHYPOPHYSIS
177
tunately, the glands were not compared with controls from other stages
of the life cycle, and no clear conclusion can be drawn. However, the
results are suggestive, when combined with other data.
The role of neurohypophysial peptides in the females has been suggested by the work of Egami and Ishii (1962); these workers found that
the injection of neurohypophysial extract into gravid specimens of Oryzias
latipes precipitated egg laying. A similar effect was obtained in Gambusia
sp., together with behavior typical of spawning. Extracts from fish or frog
pituitaries were said to be more effective than mammalian preparations.
Although egg laying also occurred in Rhodeus ocellatus ( Shirai, 1962),
species such as Misgurnus anguillicaudatus and certain salmonids did
not respond to neurohypophysial peptides, so the effect may not be
universal ( Egami and Ishii, 1962).
A possible function for neurohypophysial principles in the male has
been suggested by the work of Wilhelmi et al. (1955). It was found that
injection of crude or purified teleost pituitary extracts into Fundulus
heteroclitus produced reflex movements reminiscent of spawning behavior, and this effect could be mimiked by high doses of synthetic
oxytocin or purified arginine vasopressin (20-60 mU/g) . Similar activity
has been found in extracts from Perca fluviatilis (Swift and Pickford,
1965). It is probable that the effect is mediated by the nervous system; it
does not require the presence of the gonads, and it can be elicited in both
sexes (Pickford, 1952; Wilhelmi et al., 1955).
It is too early to be certain of the precise roles of the neurohypophysial
peptides in the physiology of the teleosts. If the scanty shreds of evidence
available are considered (e.g., Lederis, 1963; W. H. Sawyer and Pickford,
1963; Wilson, 1968) , it seems possible that arginine vasotocin is concerned
in osmoregulation and salt-water balance, while 4 Ser, 8 Ile oxytocin has
a role in reproduction, particularly in mating and egg laying. This would
be an interesting parallel with the mammal, where the basic principle
(arginine vasopressin) is concerned in kidney function, and the neutral
principle (oxytocin ) is important in reproduction. However, further work
may well prove that these speculations are unfounded.
IX. LUNGFISH: THE DIPNOI
A. The Structure of ,the Neurohypophysis of the Dipnoi
The Dipnoi, or lungfish, are important because they may be considered to occupy a phyletic position between the ray-finned bony fish and
177
tunately, the glands were not compared with controls from other stages
of the life cycle, and no clear conclusion can be drawn. However, the
results are suggestive, when combined with other data.
The role of neurohypophysial peptides in the females has been suggested by the work of Egami and Ishii (1962); these workers found that
the injection of neurohypophysial extract into gravid specimens of Oryzias
latipes precipitated egg laying. A similar effect was obtained in Gambusia
sp., together with behavior typical of spawning. Extracts from fish or frog
pituitaries were said to be more effective than mammalian preparations.
Although egg laying also occurred in Rhodeus ocellatus ( Shirai, 1962),
species such as Misgurnus anguillicaudatus and certain salmonids did
not respond to neurohypophysial peptides, so the effect may not be
universal ( Egami and Ishii, 1962).
A possible function for neurohypophysial principles in the male has
been suggested by the work of Wilhelmi et al. (1955). It was found that
injection of crude or purified teleost pituitary extracts into Fundulus
heteroclitus produced reflex movements reminiscent of spawning behavior, and this effect could be mimiked by high doses of synthetic
oxytocin or purified arginine vasopressin (20-60 mU/g) . Similar activity
has been found in extracts from Perca fluviatilis (Swift and Pickford,
1965). It is probable that the effect is mediated by the nervous system; it
does not require the presence of the gonads, and it can be elicited in both
sexes (Pickford, 1952; Wilhelmi et al., 1955).
It is too early to be certain of the precise roles of the neurohypophysial
peptides in the physiology of the teleosts. If the scanty shreds of evidence
available are considered (e.g., Lederis, 1963; W. H. Sawyer and Pickford,
1963; Wilson, 1968) , it seems possible that arginine vasotocin is concerned
in osmoregulation and salt-water balance, while 4 Ser, 8 Ile oxytocin has
a role in reproduction, particularly in mating and egg laying. This would
be an interesting parallel with the mammal, where the basic principle
(arginine vasopressin) is concerned in kidney function, and the neutral
principle (oxytocin ) is important in reproduction. However, further work
may well prove that these speculations are unfounded.
IX. LUNGFISH: THE DIPNOI
A. The Structure of ,the Neurohypophysis of the Dipnoi
The Dipnoi, or lungfish, are important because they may be considered to occupy a phyletic position between the ray-finned bony fish and