100
JAMES CLARKE FENWICK
strated in “pinealectomized” fish could have resulted from the effect
of high light intensity on the brain itself.
Recent studies by Fenwick (1970b) have shown that intact goldfish
in a light gradient were unevenly distributed and spent most of their
time in the darker half of the tank. Conversely, pinealectomized, bilaterally enucleated, or pinealectomized plus bilaterally enucleated
goldfish were distributed uniformly throughout the gradient. From this
evidence it was concluded that the phototactic response of goldfish
depends upon the presence of the pineal organ as well as the eyes.
Furthermore, in a conditioning situation, pinealectomized animals with
intact vision showed significantly more responses to the conditioned
stimulus than did the controls when the conditioned stimulus was light,
but not when the conditioned stimulus was sound. Blind goldfish, with
or without an intact pineal, could not be effectively conditioned to light
although they did become conditioned to sound. From this data it was
concluded that although the pineal organ of goldfish is a photosensory
organ, in the absence of the eyes, the photic information received by
the pineal cannot be translated into a directional response or be used
as a sensory mechanism for the initiation of active behavior. It appears,
therefore, that the photosensory role of the goldfish pineal organ is to
modulate the response elicited by photic information received by the
eyes.
Although these studies do not provide conclusive evidence of the
mode of action or the exact role of the pineal body in light reception,
they do demonstrate the importance of the pineal body in phototactic
behavior and suggest that the pineal organ and the eyes function as
a unit in phototaxis.
B. The Pineal Body as a Secretory Organ
1. EXTERNAL SECRETION
In addition to its photosensory role, many investigators have shown
that fish pineal produces an apocrine ( Grunewald-Lowenstein, 1956;
Hafeez and Ford, 1967) secretion (Tretjakoff, 1915; N. Holmgren,
1918a,b; Friedrich-Freksa, 1932; U. Holmgren, 1958b; Rasquin, 1958;
Altner, 1965) which contains glycogen ( Grunewald-Lowenstein, 1956;
Rasquin, 1958; U. Holmgren, 1959b). The secretion is generally considered to enter the CSF (Friedrich-Freksa, 1932; Hafeez and Ford,
1967). Although Van de Kamer (1955) suggests that the secretory droplets may be experimental artifacts, the high cellular metabolism demonstrated by the cytological studies of Palayer (1958) and U. Holmgren
JAMES CLARKE FENWICK
strated in “pinealectomized” fish could have resulted from the effect
of high light intensity on the brain itself.
Recent studies by Fenwick (1970b) have shown that intact goldfish
in a light gradient were unevenly distributed and spent most of their
time in the darker half of the tank. Conversely, pinealectomized, bilaterally enucleated, or pinealectomized plus bilaterally enucleated
goldfish were distributed uniformly throughout the gradient. From this
evidence it was concluded that the phototactic response of goldfish
depends upon the presence of the pineal organ as well as the eyes.
Furthermore, in a conditioning situation, pinealectomized animals with
intact vision showed significantly more responses to the conditioned
stimulus than did the controls when the conditioned stimulus was light,
but not when the conditioned stimulus was sound. Blind goldfish, with
or without an intact pineal, could not be effectively conditioned to light
although they did become conditioned to sound. From this data it was
concluded that although the pineal organ of goldfish is a photosensory
organ, in the absence of the eyes, the photic information received by
the pineal cannot be translated into a directional response or be used
as a sensory mechanism for the initiation of active behavior. It appears,
therefore, that the photosensory role of the goldfish pineal organ is to
modulate the response elicited by photic information received by the
eyes.
Although these studies do not provide conclusive evidence of the
mode of action or the exact role of the pineal body in light reception,
they do demonstrate the importance of the pineal body in phototactic
behavior and suggest that the pineal organ and the eyes function as
a unit in phototaxis.
B. The Pineal Body as a Secretory Organ
1. EXTERNAL SECRETION
In addition to its photosensory role, many investigators have shown
that fish pineal produces an apocrine ( Grunewald-Lowenstein, 1956;
Hafeez and Ford, 1967) secretion (Tretjakoff, 1915; N. Holmgren,
1918a,b; Friedrich-Freksa, 1932; U. Holmgren, 1958b; Rasquin, 1958;
Altner, 1965) which contains glycogen ( Grunewald-Lowenstein, 1956;
Rasquin, 1958; U. Holmgren, 1959b). The secretion is generally considered to enter the CSF (Friedrich-Freksa, 1932; Hafeez and Ford,
1967). Although Van de Kamer (1955) suggests that the secretory droplets may be experimental artifacts, the high cellular metabolism demonstrated by the cytological studies of Palayer (1958) and U. Holmgren