126
GRAEME CAMPBELL
rise in the oxygen content of the swim bladder gases. Fange suggested
that this might occur because of a loss of sympathetic vasoconstrictor
tone in the gas gland. However, Fahlen et al. (1965) havc shown that
adrenergic nerve terminals, deriving from cell bodies in the coeliac sympathetic ganglion, form pericellular networks about the adrenergic neurons of the gas gland ganglion in cod. This raises the possibility that by
sectioning the splanchnic nerve one removes an inhibitory influence on
synaptic transmission in the gas gland ganglion, thus enhancing a secretory activity being mediated by that neural pathway.
A few passing observations have been made on the sympathetic innervation of the urinogenital system. Stimulation of the sympathetic
ganglia in selachians causes contractions of the oviducts, as does the
application of acetylcholine ( Bottazzi, 1902; Young, 1933~). Similar
responses of the ovaries occur in the teleosts Lophius and Uranoscopus
(Young, 1936). In addition, stimulation of the sympathetic innervation
of the urinary bladder in these teleosts causes a contraction and the
expulsion of urine, a response also mimicked by acetylcholine. Young
found that the excitatory responses of the bladder to nerve stimulation
were reduced by atropine, suggesting that the nerves are cholinergic.
The number of investigations of nervous control of dermal chromatophores in fish is so great that no detailed discussion will be given here
(see Parker, 1948; Fingerman, 1963; chapter by Fujii, Volume 111).
The main conclusion reached has been that the melanophores in many
if not all teleosts are under the control of sympathetic adrenergic nerve
fibers, stimulation of which causes concentration of the melanophore
pigment. A comparable sympathetic adrenergic innervation of dermal
photophores has been postulated for the teleost Porichthys ( Nicol, 1957).
Although it has been suggested that there are cholinergic sympathetic
fibers which mediate pigment dispersal in melanophores, it seems to
this reviewer that there is no definitive evidence for their existence. In
selachians, color changes are generally slow or absent, but evidence has
been produced for melanophore-concentrating nerves in Mustelus ( e.g.,
Parker, 1935). In a few teleosts, catecholamines cause dispersal rather
than the normal concentration of melanophore pigments (e.g., Enami,
1955), and it is not clear how this will affect the chromatophore innervation. There is very little information concerning the innervation of other
chromatophore typcs ( xanthophores and erythrophores ) , although it is
well known that they may, for example, disperse under conditions which
induce melanophore conccntration ( e.g., Hewer, 1927). Virtually nothing
is known of the control of internal melanophores. Perhaps the most
striking feature of chromatophore control in fish is that the animals can
not only match the shade of the background but can also match its
GRAEME CAMPBELL
rise in the oxygen content of the swim bladder gases. Fange suggested
that this might occur because of a loss of sympathetic vasoconstrictor
tone in the gas gland. However, Fahlen et al. (1965) havc shown that
adrenergic nerve terminals, deriving from cell bodies in the coeliac sympathetic ganglion, form pericellular networks about the adrenergic neurons of the gas gland ganglion in cod. This raises the possibility that by
sectioning the splanchnic nerve one removes an inhibitory influence on
synaptic transmission in the gas gland ganglion, thus enhancing a secretory activity being mediated by that neural pathway.
A few passing observations have been made on the sympathetic innervation of the urinogenital system. Stimulation of the sympathetic
ganglia in selachians causes contractions of the oviducts, as does the
application of acetylcholine ( Bottazzi, 1902; Young, 1933~). Similar
responses of the ovaries occur in the teleosts Lophius and Uranoscopus
(Young, 1936). In addition, stimulation of the sympathetic innervation
of the urinary bladder in these teleosts causes a contraction and the
expulsion of urine, a response also mimicked by acetylcholine. Young
found that the excitatory responses of the bladder to nerve stimulation
were reduced by atropine, suggesting that the nerves are cholinergic.
The number of investigations of nervous control of dermal chromatophores in fish is so great that no detailed discussion will be given here
(see Parker, 1948; Fingerman, 1963; chapter by Fujii, Volume 111).
The main conclusion reached has been that the melanophores in many
if not all teleosts are under the control of sympathetic adrenergic nerve
fibers, stimulation of which causes concentration of the melanophore
pigment. A comparable sympathetic adrenergic innervation of dermal
photophores has been postulated for the teleost Porichthys ( Nicol, 1957).
Although it has been suggested that there are cholinergic sympathetic
fibers which mediate pigment dispersal in melanophores, it seems to
this reviewer that there is no definitive evidence for their existence. In
selachians, color changes are generally slow or absent, but evidence has
been produced for melanophore-concentrating nerves in Mustelus ( e.g.,
Parker, 1935). In a few teleosts, catecholamines cause dispersal rather
than the normal concentration of melanophore pigments (e.g., Enami,
1955), and it is not clear how this will affect the chromatophore innervation. There is very little information concerning the innervation of other
chromatophore typcs ( xanthophores and erythrophores ) , although it is
well known that they may, for example, disperse under conditions which
induce melanophore conccntration ( e.g., Hewer, 1927). Virtually nothing
is known of the control of internal melanophores. Perhaps the most
striking feature of chromatophore control in fish is that the animals can
not only match the shade of the background but can also match its