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1973
The Effect of Thyroxine and Thiourea on Territorial
Behavior in Cichlid Fish.
Peter Harry Spiliotis
Louisiana State University and Agricultural & Mechanical College
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Spiliotis, Peter Harry, "The Effect of Thyroxine and Thiourea on Territorial Behavior in Cichlid Fish." (1973). LSU Historical
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SPILIOTIS, Peter ferry, 1946THE EFFECT OF THYROXINE AND THIOUREA ON
TERRITORIAL BEHAVIOR IN CICHLID FISH.
The Louisiana State University and Agricultural
and Mechanical College, Ph.D., 1973
Psychology, general
University Microfilms, A XEROX Company, Ann Arbor, Michigan
THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED.
THE EFFECT OF THYROXINE AND THIOUREA ON
TERRITORIAL BEHAVIOR IN CICHLID FISH
A Dissertation
Submitted to the Graduate Faculty of the
Louisiana State University and
Agricultural and Mechanical College
in partial fulfillment of the
requirements for the degree of
Doctor of Philosophy
in
The Department of Psychology
by
Peter Harry Spiliotis
B .A ., The University of North Carolina, 1969
M .A ., Louisiana State University, 1971
December, 1973
ACKNOWLEDGMENT
The author would like to thank his major professor Dr, Donald
R. Hoffeld for his guidance and assistance during this project.
The
author would also like to express gratitude to members of his committee,
Dr. Albert H. Meir, Dr, Billy M, Seay, Dr, Arthur J. Riopelle, and
Dr. Nathan W. Gottfried.
Special thanks is extended to Dr. Laurence
Siegel, Chairman of the Department of Psychology and Dr. Irwin A. Berg,
Dean of the School of Arts and Sciences who made available funds in
support of this dissertation.
I am Indeed grateful to the typist, Mrs.
Mary Mevers.
ii
TABLE OF CONTENTS
Page
TITLE P A G E .......................................................
i
ACKNOWLEDGMENT..................................................
ii
LIST OF T A B L E S ..................................................
iv
A B S T R A C T .........................................................
v
INTRODUCTION .....................................................
I
Functional Considerations of Thyroid Hormones ...............
Territorial Behavior and Its Components . . . ...............
P u r p o s e .......................................................
3
8
13
M E T H O D ...........................................................
15
Subjects.......................................................
A p p a r a t u s .....................................................
P r o c e d u r e .....................................
Statistical Analysis and Informal Dat a .......................
15
15
16
19
RESULTS...........................................................
21
R e l i a b i l i t y ...........................
Quantitative Behavior Measures................................
Qualitative Observational Data................................
S u m m a r y ................................................
21
21
26
30
D I S C U S S I O N .......................................................
33
Hormones and Territoriality ..................................
Activity and Locomotor Levels ................................
Pigmentation and Coloration Displays.........................
Drug D o s a g e ...................................................
Rhythmicity . . . . . . . . .
........ . . . . . . . . . . .
33
37
37
39
40
R E F E R E N C E S .......................................................
41
A P P E N D I X .........................................................
51
V I T A .............................................................
55
iii
LIST OF TABLES
Table
1.
2.
3.
Page
Mean Frequency of Behavior Categories for each
Defended Territory inGroup I .........................
22
Mean Frequency of Behavior Categories for each
Defended Territory in Group I I .........................
23
Mean Frequency of Behavior Categories for each
Defended Territory in Group III ......................
24
iv
ABSTRACT
Two species of mature cichlids, Cichlasoma meeki and Cichlasoma
biocellatum, exhibited behavioral changes in critical stimuli involved
in defense of a territory after prolonged thyroxine treatment.
Fish
exhibited increased locomotor activity, changes in integument pigmenta­
tion which corresponded to adopted functional behaviors, and spent con­
siderably more time on the surface of aquaria.
flutter behavior.
Only C. meeki showed
Dominant territorial fish tended to increase the
area of their territory and their dominance over nonterritorial members.
In C. meeki prolonged thyroxine resulted in significant increases in
two behavior categories from baseline--territorial mouth fighting
(Tm, p ^.005) and nipping of the subtrate outside the territorial pit
(N, p<.025).
Similar increases in the frequency of nipping (p <^.025)
occurred in C. biocellatum.
These changes suggest that thyroxine may
have a role in agonistic behavior during defense of a territory and
also effects critical stimuli involved in territorial behavior.
The
standard aquarium setting and social category system place limitations
on the extent that intensification of territorial behavior can be
evaluated.
Thiourea treated C. meeki abandoned previously defended
territories, developed darker integument pigmentation, grouped together
and schooled stationary at the bottom of each aquaria.
The diminution in
activity consisted of uncoordinated jerky movements, persistent beating
of pectoral fins, and periodic bouts of agonistic behavior.
Within 2
weeks of the thiourea treatment, all behavior categories significantly
decreased (p -^.025).
Thiourea treatment decreased the number of
critical sign stimuli necessary for the execution of territorial
behavior.
Thiourea dosage level was critical and JJ. meeki are suscep­
tible to prolonged thiourea treatment.
vi
INTRODUCTION
In vertebrate evolution, the forebrain haa attained an increas­
ing dominate control over certain behavior responses, with the result
that they tend to escape hormonal control.
In lower vertebrates, the
influence of the forebrain may be less marked, and behavior sequences
may be increasingly controlled by hormones (Beach, 1947, 1948).
According to Beach, hormones act as chemical sensitizers which alter
the responsiveness of the CNS to stimuli from the environment.
How­
ever, there is little evidence for the exact functional role of the fish
thyroid (Matty, I960) and the physiological effects and peripheral
target of the fish thyroid hormones have been difficult to elucidate
definitively (Berg, Gorbman, & Kobayaski, 1959; Gorbman, 1969).
Fish are low in the vertebrate series and therefore may provide
insight into the ways in which hormones have gained control over
behavior in the course of vertebrate evolution.
Moreover, fish possess
a repertoire of behaviors which are relatively simple and much more
rigid and stereotyped than those of higher vertebrates.
In conjunction,
territorial behavior exemplifies some adaptive features of fish.
Territorial behavior in fish serves to:
(1) regulate the population;*
(2) provide food reserve for adults and young; (3) increase geograph­
ical range of the species; (4) provide undisturbed areas for pairing
and spawning; and (5) provide conditions for obtaining the best suitable
mate for reproduction (Lorenz, 1937).
Therefore, the thyroid hormone
2
control or influence in territorial behavior in fish may express basic
functional relationships in the execution of adaptive behavior.
Ethologists approach the analysis of behavior within the frame­
work of the "black box."
The black box is the machinery inside the
animal through which behavior, that is muscular and glandular activity
(the output) is produced, under the influence of sensory stimuli.
By
observing the output, under different input conditions the experimenter
can predict the presence of mechanisms in the black box and define them
on the basis of the functions he found them to fulfill.
The behavioral
unit for the occurrence of which the ethologist investigates the causes
of behavior is the Fixed Action Pattern (FAP) (Lorenz, 1937).
The FAF
or consummatory behavior (Craig, 1918), consists of stereotyped activi­
ties which are aa typical for a species as morphological structures and
therefore can be used as taxonomic features (Whitman, 1899).
Holzapfel
(1940) extended the idea of FAP to the attainment of suitable living
conditions (right temperature, salinity, _gH, territorial behavior, and
familiar environment).
The variable behavior sequence or appetitive
behavior which precedes the attainment of a FAP encompasses the animal
searching for the situation in the environment which releases the FAP.
Moreover, as previously stated by Beach (1947), hormones act as chemi­
cal sensitizers which alter the responsiveness of the central nervous
system to stimuli from the environment.
In this manner, the extent of
the appetitive behavior, the timing of events, and their intensity of
expression may depend on hormones (Beach, 1947).
Tinbergen's (1950)
hierarchial system of behavior has shown how the change in gonadal
3
hormonal level in the blood activates nervous centers and initiates
generalized appetitive behavior.
This in turn is followed by pro­
gressively more specialized acts as the appropriate releasers are en­
countered, and the innate releasing mechanisms activated until the
final consummatory act is performed.
The external environment guides
and directs the different activities involved.
Therefore, in order to
investigate fish behavior in a thorough manner, one must incorporate
sophisticated ethological measurements of behavior in connection with
physiological techniques.
Functional Considerations of Thyroid Hormones
Thyroid tissue is present in all vertebrate groups (Gorbman,
1959).
In lower vertebrates, thyroid follicles are present but are not
encapsulated and organized into a compact gland.
Thus thyroid tissue
in teleost may be scattered in connective tissue throughout from the
pharyngeal region to distant areas such as the ventral aorta, eye,
brain, spleen, and kidney (Baker et al., 1955; Baker, 1958; Chavln,
1956; Frisen & Frisen, 1967; Baker-Cohen, 1959).
In the teleost, four general areas of investigation have been
researched:
(1) metabolic actions (2) structural effects (3) reproduc­
tion (4) effects on the central nervous system and behavior.
The best
known property of thyroid hormones in homoiothermic animals is the
control over energy (heat) and oxygen production.
The basal metabolic
rate (BMR) falls rapidly after thyroidectomy and may be elevated above
the normal level by administering thyroid hormones.
In adult
poikilotherms or cold blooded animals such action by thyroxine has
4
been inconclusive, indicating that control over respiratory and
calorigenic metabolism may not be a function of thyroxine (Matty, 1957;
Hoar, 1958; Fromm & Reineke, 1957; Pickford & Atz, 1957).
However,
thyroid function in poikilotherms has been found associated with phases
of metabolism other than respiratory rate.
Hochacka (1962) reported
that thyroxine operates as an activator in carbohydrate metabolism in
the trout, whereas Fontaine and Hatey (1950) reported increased level
of glucose with prolonged thyroxine treatment in the salmon.
Thyroxine
has also been shown to effect metabolic processes producing increased
ammonia excretion in the goldfish (Hoar, 1958) and nitrogen metabolism
in the brown trout (Thornbum & Matty, 1963).
Moreover, observations
on fishes seem to imply that the piscine thyroid is also Involved in
the metabolism of salts and water (Fontaine, 1956; Smith, 1956; Gorbman
& Berg, 1955); however more recent evidence (Dharmamba, et aJL., 1967)
questions whether thyroxine has an important influence in osmoregulation
as was initially expected since other hormones (corticosteriods and
neurohypophyseal peptides) play a larger role.
A second group of phenomona is related to structural changes
derived from thyroid treatment.
Thyroid action has been reported to
effect the integument and its derivatives in fish.
Numerous authors
have observed a common pigmentary response in the skin of fishes
(trout, salmon, and guppy) called "silvering” (Robertson, 1949; Sage,
1967, 1968; Matty & Sheltawy, 1967).
This "silvering" effect from pro­
longed thyroxine treatment seems to have resulted from changes in
integumentary guanin metabolism (Matty & Sheltawy, 1967).
Increases in
5
pigmentation in the skin of carp (Sembrat, 1956) and Channa punctalis
(Belsare, 1966) have been reported with antithyroid drug, thiouracil or
thiourea and opposite effects were reported for thyroxine treatment.
In contrast, thyroxine treatment also increased black pigmentation in
goldfish (Muller, 1953) and in Anquille anquilla (Vilter, 1946).
In
addition, thiourea treated fish also exhibit melanophore' granule dis­
persion (Belsare et aj.., 1966).
Moreover, LaRoche & Leblund (1952) and
LaRoche e£ a_l. (1966) found that radiothyroidectomized trout showed
increased melanin pigmentation and thinning of both epidermal and dermal
elements.
Morphological changes were corrected with an Increase in the
number of pigment cells per surface area after throxine administration
(LaRoche et al.. 1966).
The relation of body growth to thyroid function in teleosts
remains uncertain and a conclusive demonstration that thyroid treatment
will stimulate overall growth has yet to be reported.
Radio-
thyroidectomy in the platyfish (Baker-Cohen, 1961) and trout (LaRoche,
1966) markedly retarded the rate of growth and development in each
species.
Thyroid products have been reported to have growth stimulating
properties when administered to guppies (Smith, et al., 1953; Sage,
1965, 1968), trout (Barrington et al.. 1961), sunfish (Gross et al.,
1963), salmon (Piggins, 1962) and goldfish (Bjorklund, 1965).
However,
thyroid treatment of salmon by some investigators resulted in retarded
growth rate (Dales & Hoar, 1954; Honma & Murakawa, 1955; LaRoche &
Leblond, 1952).
Two experiments by Sage with guppies (1965, 1968)
using the antithyroid agent thiourea resulted in inhibited growth.
A
6
treatment group receiving both thiourea and thyroxine showed an inter­
mediate growth rate.
The action of thyroid hormones in growth seems to
be secondary in fish as in mammals (Simpson, et a_K
, 1950;
Solomon & Greep, 1959), and a more complex analysis of its role is
needed in order to explain contradictory results.
The third area of investigations is the relation of the teleost
thyroid to reproduction.
Circumstantial evidence indicates an influ­
ence of the thyroid gland upon reproductive behavior.
A direct gameto-
genic effect of thyroid hormones has not so far been observed, and one
is forced to conclude that the thyroid normally plays a synergistic,
auxiliary or complementary role (Matty, 1960).
Many seasonal changes
which appear in the teleost thyroid are however related to reproduction
(Fickford & Atz, 1957; Matty, 1960).
Treatment with antithyroid drugs
has resulted in inhibited maturation of the gonads of Fundulus
heteroclitus (Chambers, 1953), and in regressed gonadal states in the
minnow Phoxinus phoxinus (Barrington & Matty, 1952) and Lebistes
reticulatus (Smith, Sladek & Kellner, 1953).
A fourth series of actions is the role of the thyroid hormones
in the central nervous system and behavior in teleost.
Experimental
investigations have indicated that thyroid hormones affect the pattern
of motor behavior, level of activity, and aggregate behavior.
Hoar
et al. (1952) and Hoar (1955) reported that goldfish and salmon treated
with thyroxine displayed greater locomotor activity, swim closer to
the surface of the water, and have less intense groupings.
Thiourea
treated subjects were less active, increased intensity of groupings, and
7
schooled near the bottom of the tank.
More recently, Sage (1968) re­
ported similar results with 4 week exposure treatments with thyroxine
and thiourea to guppies.
Thyroxine treated fish showed increased
swimming, higher incidence of jumping behavior (flutter behavior, per­
sistent swimming against the walls of the aquarium), and more time in
the periphery of the tank.
Thiourea treated fish exhibited less
swimming and an absence of jumping behavior and spent less time in the
periphery than controls.
In addition, Froselius (1957)reported an
increase of appetitive behavior and general locomotor activity in the
anabantid fish after injections of thyroxine.
Hoar et al. (1952) sug­
gests that the thyroid hormone in the blood activates nervous centers
and initiates generalized appetitive behavior.
This in turn will be
followed by progressively more specialized acts as the appropriate
releasers are encountered and the innate releasing mechanisms activated
until the final consummatory act is performed.
In general, thyroid hormones affect behavior by bringing about
an increase in activity.
This increment may be a result of hormonal
influence on metabolism or direct action on neural mechanisms in the
CNS underlying the behavioral responses (increased locomotor and
general activity) (Lfley, 1969).
Electrophysiologlcal studies have indi­
cated that thyroid hormones may directly affect the CNS and sense organ
states by influencing the responsiveness of the CNS to external stimuli
(Hoar, 1965).
Thyroid treated goldfish were more responsive to elec­
trical stimulation than untreated fish (Hoar et al., 1955) and showed
changes in the properties of their electrical potentials for optically
8
generated CNS activity (Hara et al.. 1965; Hara et al., 1966) and
olfactory activity (Oshima and Gorbman, 1966a, 1966b, 1965).
In addition, there appears to be a distinct interrelationship
between the thyroid gland and the sympathetic nervous system
(Waldstein, 1966; Harrison, 1964).
The effects of sympathetic cate­
cholamines, particularly epinephrine, mimic some of the physiological
actions (tachycardia, increased oxygen consumption, and accelerated
lipolysis) of thyroid hormones (Gelhorn & Feldman, 1941; Comsa, 1950).
Secondly, the hormones interact synergistically, so that the action of
sympathetic catecohlamines is Increased by administration of thyroid
hormones (Brewster, Issac, Osgood, & King, 1956; Raab, 1944) or
hyperthyroidism (Horstmann, 1954; Swanson, 1956, 1957; Rosenblum, Hahn,
& Levine, 1933), thereby augmenting the effects of epinephrine and
norepinephrine.
In a like manner, the effects of sympathetic cate­
cholamines are diminished by spontaneous or experimental hypothyroidism
(Rosenblum et al.. 1933; Brewster et. al., 1956; Raab, 1944).
A third
line of interrelationship involves the ability of adrenergic blocking
agents to reduce the hemodynamic and metabolic effects of thyroid
hormones (Brewster et al,, 1956).
The locus of the synergistic inter­
action of these hormones remains to be elucidated.
Territorial Behavior and Its Components
Tinbergen (1936) defined "territory" as an area which is
defended by a fish shortly before and during the formation of a sexual
alliance.
Noble (1939) presented a more general definition indicating
that territorial behavior is exhibited when a territory is defended.
9
Among many piscine species, as gonads mature, nuptial coloration and
other secondary sex characteristics become present, shortly thereafter,
the elements of sexual and territorial behavior appear.
Territories are
established more commonly at the onset of breeding season as a place
where sexual bonds are formed (Noble, 1939) and where spawning will
occur (Breder, 1936).
Territorial behavior facilitates the formation
of behavior interrelationships or bonds between partners (Noble, 1939;
Neil, 1964).
The territory probably represents an area most suited to
the physiological requirements of the individual, who rapidly develops
a special attachment to the site (Aronson, 1957).
As invaders of the
same species as well as members of other species invade the territory,
the territorial holding fish will execute aggressive actions (agonistic
behavior) in order to defend the territory.
With the initiation of
sexual pairing, agonistic behavior by the pair gradually changes the
social structure of the fish school into a territorial society in which
the distances between the members is increased and maintained by some
real fighting and a great deal of threatening (Baerends & Baerends Van
Roon, 1950).
The method of defense varies with the "weapons of the
species" (Aronson, 1959), piscine defenses include threats, biting,
chasing, fighting, and tail beating, etc.
In cichlids, one sexually active male becomes dominant over the
rest in a restricted area.
This male becomes brightly colored and
inhibits the development of similar colors in subordinate males.
ever, threat and not color is of greater
How­
importance in securing a
dominant position in the social hierarchy and establishing a territory
(Nobel & Curtis, 1 9 39 ).
There is a hierarchy of displays, their
potency and importance being reflected by form, frequency, and dura­
tion (Ruwet & Voss, 1966; Voss & Ruwet, 1 9 6 6 ), seeming to express
degrees of intimidation, the milder degree being a harmless warning
and the more severe a direct threat.
Serious fighting occurs in which
rival fish grip each others jaws and wrestle by pushing and pulling
each other to and fro, but most belligerent conflicts are resolved
without real damage, with defeated fish showing attitudes of submis­
sion.
Real
fighting has been replaced by symbolic combat (Nobel &
Curtis, 1939; Baerends & Baerends Van Roon, 1 9 5 0 ).
Agonistic behavior is considered "reproductive" insofar as it
is an essential preliminary to reproduction, but it may also occur
during territorial behavior at times and places unrelated to breeding,
such as maintenance of individual distance and breeding habits (Breder,
1936; Baerends 6c Baerends Van Roon, 1952; Noble et al.. 1 9 3 8 ).
Such
activities are unlikely to be under the same hormonal control as
seasonly changing reproductive behavior (gonadotropic and gonadal
hormones) (Blum 6c Fiedler, 1965; Smith et a l .. 1 9 67 ).
Hoar (1965) and
Baggerman (1966) suggest that during the period before the onset of
breeding the level of agonistic or aggressive behavior is controlled
by the level of gonadotropic hormone activity (physiologically like
FSH, LH, and prolactin).
Gradually the mechanisms controlling this
behavior becomes more sensitive to gonadal hormones (androgens,
estrogens, and progesterone) with the waning of gonadotropic influence
(Gottfried 6c Van Mullen, 1967).
11
Territorially induced aggressive behaviors have been called
fixed action patterns (Lorenz, 1937; Holzapfel, 1940).
In a given
situation, a specific stimulus in the environment releases an inborn
reaction or motor pattern.
However, in territorial behavior simple
stimulus response components fall short of fully explaining the con­
trolling causal mechanisms.
In fact, the optimal external stimulus
may consist of a summation of several stimuli simultaneously which
normally are separated from each other in time (principle of
heterogeneous summation) (Seitz, 1940).
Seitz (1940) evaluated a set
of stimuli releasing fighting responses in cichlids and concluded that
the intensity of a response depended not only on what sign stimuli are
present but how many are present.
Three sign stimuli presented
simultaneously elicited a more intense response than two stimuli.
Furthermore, different responses may be given to the same external
stimulus, varying with the endocrine state, experience, fatigue, and
fear (Collias, 1944).
In defense of a territory, demands are placed
on the territorial holding fish to have the abilities to discriminate
species, sexes, gravid individuals, partners, movement patterns and
territorial boundaries.
Stimulus Factors.
Physical stimuli are important factors con­
trolling the execution of the various aspects of reproductive behavior
(territorial and courtship) but the integration and coordination of the
components depend on a continuous interplay of external and internal
factors since not only do hormones affect behavior, but also behavior
affects the endocrine state (Lehman, 1965; Hinde, 1965).
12
In fish, external visual factors that involve the use of
color, color changes, and movement patterns of either the whole body
or part of it, are important for processing information for territorial
defense (Fruer & lies, 1972).
Visual factors involved in movement
patterns, integument pigmentation, and other structural specializations
have been reported to be very specific for eliciting particular behavior
patterns in territorial defense (Tinbergen, 1951; Baerends & Baerends
Van Roon, 1950; Neil, 1964; Tavolga, 1956; Noble & Curtis, 1939),
enabling fish to (1) advertise the fact that a particular male has
established a territory;
(2) designate the position of an individual
in the social hierarchy; and (3) coordinate their movements for appro­
priate displays (Fryer & lies, 1972).
The role of visual stimuli in
courtship behavior has also been emphasized (Breder & Coates, 1935;
Clark & Aronson, 1951; Baerends et al., 1955; Liley, 1966).
Olfactory stimuli also play a role in intraspecies communica­
tion.
Cichlids employ chemical pheremones in recognizing their young
(Kuhme, 1963), initiating courtship behavior (Tavolga, 1955), species
recognition (Noble & Curtis, 1939), and during a fright reaction to
impending danger (Pfeiffer, 1962; Noble, 1939).
Other nonvisual
stimuli are also important means of communication.
Sound production
in cichlids has been reported to be an integral part of courtship and
territorial behavior involving courtship movements, mate location, and
fighting between rival males (Kramer, 1965; Bauer, 1963).
Character­
istic sound productions were recorded for particular threat displays
and aggressive acts during defense of a territory (Rodman, 1966).
13
Mechanical and tactile stimulation is widespread during territorial
and courtship behavior.
The rate of water movement and texture of
bottom (Fabricus, 1950; Winn, 1953) act as stimuli for breeding.
During territorial defense and courtship behavior, biting, butting,
mouthing and other bodily parts have been observed in many species
(Aronson, 1949; Noble & Curtis, 1939; Gottier, 1969; Baerends &
Baerends Van Roon, 1952).
More recently, electrical signals initiated by the central
nervous system and discharged from electric organs have been detected
as sensory signals in agonistic communication (Black-Cleworth, 1970).
Electrical discharge frequency wa3 used in the identification of dis­
plays in fighting behavior between rival males and in the expression of
varying degrees of dominance and submission.
The agonistic patterns of
the electric fish Gymnotus is clearly related in both form and function
to aggressive displays in other teleost and indicated that sensory
mechanisms are involved in agonistic behavior (Black-Cleworth, 1970).
Purpose
The purpose of this study was to Investigate the qualitative
and quantitative effects of thyroxine and the antithyroid drug
thiourea on the factors or stimuli involved in regulating the extent,
timing of events, and intensity of expression of appetitive behaviors
during territorial behavior in cichlid fish.
Thyroxine has been
reported to increase the responsiveness of the CNS to external stimuli
(Hoar, 1965, 1967; Oshima & Gorbman, 1966, 1968; Hara et al.. 1967),
14
augment the effects of sympathetic catecholamines (Waldstein, 1966;
Brewster _et al., 1956), affect the pattern of motor behavior, level of
activity, aggregate behavior (Hoar, 1952, 1955, 1958; Sage, 1967, 1968)
and integument pigmentation (Malty & Sheltawy, 1967; Belsare, 1966;
Robertson, 1949; Sage, 1968).
These behaviors and stimuli (pigmenta­
tion, pattern of motor movement, level of activity, aggregate behavior)
have been found to be critical sign stimuli during appetitive behavior
in the releasing of consummatory acts during territorial behavior
(Lorenz, 193/, Tinbergen, 1942; Noble, 1939; Breder, 1936; Baerends &
Baerends Van Roon, 1950; Neil, 1964).
The present investigation was
specifically designed to provide an evaluation of the extent of terri­
torial behavior by cichlids residing in aquaria and to what extent
changes detected by the social category system for cichlids (Costelloe,
1970) can be used to reflect levels of agonistic behavior and terri­
toriality after thyroxine and thiourea treatment.
In this manner, a
qualitative and quantitative evaluation of several external stimuli
that have been reported to be influenced by thyroid hormones can
be evaluated simultaneously in the context of territorial defense.
METHOD
Subjects
Forty-eight mature Cichlasoma meeki (firemouths) and twentyfour mature Cichlasoma biocellatum (Jack Dempsey) were observed.
fish were obtained from an aquarium dealer.
These
Additional fish were on
hand for replacement in case of mortalities.
Apparatus
Experimental subjects were contained in 20 gallon standard
(12"x;2”x30") aerated aquariums.
aquaria.
Eight firemouths were in each of six
Three of the populated tanks connected by syphons were grouped
to a fourth unpopulated tank occupied by a pump (Group I).
In this
manner, complete circulation and water changes were provided for the
group.
The three remaining tanks populated with firemouths were
arranged in a similar manner (Group II).
The twenty-four Jack Dempseys
were populated in a like manner composing Group III.
maintained at 76-80° F by individual heaters.
Temperature was
Lighting was provided
by incandescent lamps (30 watts in the overhead tank lids).
A
16L:8D photoperiod was regulated electrically by a Tork Control Timer.
This photoperiod has been reported to engender an increase in
agonistic and reproductive behavior in contrast to a much shorter
period, 8L:16D (Hoar, 1962).
The additional fish for possible replace­
ment were contained in a separate tank under the same standard living
15
16
conditions as experimental fish.
Twice daily, fish were fed a dry
commercial fish food, Tetra-Min.
Procedure
Observational sessions were divided into three phases for Group
I but into two phases for both Groups II and III.
During each phase,
observations of male/female fish pair or a single dominant fish
defending a territory were taken.
Phase 1 consisted of establishing
a baseline of territorial behavior for each of the three groups.
Phase 2 tested the effect of hormone treatment with either thyroxine
(Groups I and III) or thiourea (Group II) on social behavior of
territorial fish.
Phase 3 consisted of removing the remaining
thyroxine from Group I and reversing the treatment to thiourea.
The
data collection procedure was similar to that recently developed by
Costelloe (1970) for the social behavior of cichlid fish.
tanks were checked for the number of territories.
Experimental
Each territorial
fish or fish pair was observed for 3' 45" or one session, divided Into
15-fifteen second intervals during which each behavioral category that
occurred in the interval was recorded only at its first instance,
making a maximum total of 15 response categories/session.
More com­
plete details of this procedure can be found elsewhere (Costelloe,
1970; Hoffeld, 1972).
noon and 6:00 P.M.
Observations were taken twice daily, at 12:00
Five experimental observers participated equally
in each phase.
Phase _1.
During phase 1, the 3 populated aquaria for Groups I,
II, and III were observed.
Social behavior exhibited by each
17
territorial dyad or dominant fish was recorded in order to establish
a baseline level for each group.
Informal records were taken of size
of territorial fish, activity and locomotor levels, pigmentation,
aquarium location, and intersubject distance were recorded.
During
phase 1, two observers recorded at each session in order to provide a
measure of interobserver reliability during the baseline phase of the
experiment.
The social category system for cichlids has been reported
to be generally reliable (Costelloe, 1970), correlations ranging from
.76 to .99.
Phase 1 lasted one week (5 days - 10 sessions).
Phase 2 .
In phase 2, subjects received hormonal treatment.
In Groups I and III, subjects received synthetic thyroxine sodium
(1: 2,000,000 in concentration) added to the water in each of the 4
tanks.
All four tanks in Group II received the antithyroid drug
thiourea (1: 1,000 in concentration).
Additional hormone doBes for
replacement were added 3 times weekly; however Group II did not receive
additional drug treatment after week 3.
A single blind technique was
used, concealing the treatment group from observers.
observers observed drug treated groups equally.
Each of the 5
Phase 2 lasted three
weeks (15 days - 30 sessions).
Phase 3.
Immediately following the last session of Phase 2, .
a Barnstead filter was connected to the pump system in Group I in
order to remove residual hormone.
for 3 days.
This filter remained installed
During treatment reversal or Phase 2, Group I received
thiourea treatment for 2 weeks but in a lower concentration (1: 2,000)
than administered to Group II in Phase 2,
Observational procedures
18
were the same as Phase 2,
Phase 3
lasted 3 weeks (15 days - 30
sessions).
Behavior Categories.
The behavior categories and codings given
below are listed on the basis of frequency of appearance by either
member of a territorial pair or a dominant territorial fish in the
experimental tank (Costelloe, 1970).
Other behavior categories
occurred but in insufficient number to be considered for analysis.
Territorial Behaviors.
Interaction between a member of the
territorial pair or a dominant territorial fish with another
fish.
Territorial Frontal (Tf) - When adversaries approach
frontally gill covers become erect broadening the head.
Territorial Chasing (Tc) - Resident fish lays median
fins against body and tries to overtake the intruder
with quick darting movements.
Territorial Bite-Butt (Tb) - The fish swims rapidly
toward adversary and contacts with another fish other than
the mate.
Territorial Braking (Too) - Both approach and retreat are
seen alternately as distance between fish narrows.
Territorial Mouth-fighting (Tm) - Upon reaching opponent,
the mouth is open and both try to grip the other's jaw
firmly. They push and pull, beating heavily with tails
and pectorals.
Miscellaneous Behaviors.
Activity by any territorial fish.
Pit Digging (P) - From the horizontal position the fish
turns vertically with head downward in the pit. When it
reaches the substrate it opens its mouth, penetrates
gravel and closes mouth. Fish swims backward and resumes
position. Advances and ejects gravel.
Nipping (N) - The fish bites at the substrate gravel out­
side of its pit, occasionally taken into the mouth but
not carried.
19
Statistical Analysis and Informal Data
The experimental design is shown in the diagram below:
Phase 1
Phase 2
Phase 3
Group I
10 sessions/
territory
three 10 session
Intervals (30)
(thyroxine)
three 10 session
intervals (30)
(thiourea)
Group II
10 sessions/
territory
three 10 session
intervals (30)
(thiourea)
Group III
10 sessions/
territory
three 10 session
intervals (30)
(thyroxine)
The Wilcoxon Matched-Pairs Signed-Ranks Test (1945) was used
to assess differences between the baseline level (Phase 1) and
subsequent drug treated weeks for behavior categories occurring within
each territory in each of the 3 groups.
This nonparametric technique
is particularly applicable in cases where subjects can be used as
their own control.
The test utilizes information about the relative magnitude and
direction of differences within pairs.
In this manner, for territories
defended during each session of Phase I, the frequencies of each
behavior category were matched and compared with the behavior frequen­
cies occurring within the same territories during each of the drug
treated weeks.
This evaluation would provide a judgment of which
member of the pair is "greater than."
Additional data was recorded by observers during each session
on an informal basis.
Changes in activity (hypoactive-norma1-
hyperactive), locomotor level (slow-normal-fast), pigmentation
20
(bright-normal-dark), aquarium pit location, relative size of terri­
torial holding fish, intersubject distance (intergrouping-dispersion),
and location of non-territorial fish were surveilled and recorded on a
separate charted data sheet.
RESULTS
Reliability
The use of the social category system as a quantitative me a ­
sure of territorial behavior was generally reliable for the seven
behavior categories that were consistently observed.
The inter­
observer reliability taken during Phase 1 showed that observers did
not differ more than 2 counts (Tf, Tb, Tc) for any behavior category
per session.
The scores of the additional observers deviated from
those of the designated observers within the following percentage
ranges, T f (77-100%), Tb(83-100%), Tc(82-100%).
Two categories
differed only by one count (N, 86-100%; P, 84-100%), while the re­
maining two categories, Tea and Too, were recorded consistently (100%)
by both observers.
Quantitative Behavior Measures
The number of territories defended and the mean frequencies
for each behavioral category in the three groups is shown in Tables 1,
2, and 3.
During each session of the baseline phase (week 1), 2
territories in each of the aquaria were defended by either a male/
female pair or by a dominant fish, resulting in 60 territorial observa­
tions.
These established territories were the basis of comparison for
the effect of subsequent drug treatment.
During the 3 weeks of Phase 2, the number of territories for
the thyroxine treated fish in Group I (Table 1) remained the same for
21
TABLE 1
MEAN FREQUENCY OF BEHAVIOR CATEGORIES FOR EACH
DEFENDED TERRITORY IN GROUP I
Phase I
phase 2
(Thyroxine)
Phase 3
(Thiourea)
N
1
- 60
2
60
3
Tf
1.92
Tm
Too
Tc
Tb
N
P
.53
.05
4.38
4.67
6.77
.68
.48*
.42
.130
3.57*
4.50
4.73
2.83
60
.82
.77
,02
4.35
4.13
7.20
.85
4
56
1.38
1.36***
.23^
4.00
4.84
9.27*
5
25
4.15
1.56
.520
2.52***
5.24***
6.04*** 1.60
6
1
1.83**
1.50*
o
o
TS
Week
.00***
1.67***
.00***
.00***
7
0
.00*
.000
.00***
.00***
.00***
.00***
.00***
1.05
* Significant difference at .025
** Significant difference at .01
*** Significant difference at .005
0 Not amenable to statistical analysis
N>
to
TABLE 2
MEAN FREQUENCY OF BEHAVIOR CATEGORIES FOR EACH
DEFENDED TERRITORY IN GROUP II
Week
N
Phase 1
1
60
Phase 2
(Thiourea)
2
27
3
4
Tf
Tm
Too
Tc
Tb
N
P
.47
.17
7.42
3.95
3.68
2.43
.70**
.30**
.11
4.70***
3.04**
4.70***
3.30
0
.00***
.00***
.00
,00***
,00***
.00***
.00***
0
.00***
.00***
.00
.00***
.00***
.00***
.00***
2.05
* Significant difference at .025
** Significant difference at .01
*** Significant difference at .005
^ Not amenable to statistical analysis
TABLE 3
MEAN FREQUENCY OF BEHAVIOR CATEGORIES FOR EACH
DEFENDED TERRITORY IN GROUP III
Week
Bn
Too
Tc
Tb
N
P
•
5.38
.82
6.23
3.55
.00^
4.92
.63
6.77
2.67
.09
.oo0
6.37
1.13
7.14
2.57
.00
o.
o
o
Phase 2
(Thyroxine)
Tf
o
o
Phase 1
N
5.98
1.02
7.62*
2.13
1
60
.12
.07
2
60
.07
.02
3
56
.27
4
58
.22
* Significant difference at .025
0 Not amenable to statistical analysis,
25
weeks 2 and 3 but dropped to 56 during the 4th week.
In Group III
(Table 3), the fish treated with thyroxine, also consistently defended
their established territories during week 2 but deviated to 56 in week
3 and to 58 in the fourth week.
The thiourea treated fish in Group
II (Table 2) however showed a sharp decline in the number of terri­
tories defended to 27 during week 2.
no territories were defended.
During the third and fourth week,
In Phase
2, the previously thyroxine
treated fish of Group I received a lower thiourea doBage during and
also showed a sharp decrease in the number of territories from 56 to
25 during the fifth week.
During week 6, only 1 territory was observed,
while no territories were defended in the seventh week.
The differences between the baseline and subsequent
weeks for each behavior category within each territory was evaluated
by the Wilcoxon Matched-Pairs Signed-Ranks Test.
The probability
levels associated with these comparisons for a one-tailed test are given
in Table 1 for Group I and Table 2 for Group II.
Only one of the com­
parisons in Group III (Jack Dempseys) attained statistical signifi­
cance at the
.025 level shown in Table 3.
Group I.
During phase 2, fish treated with thyroxine showed a
significant decrease (p
.025) in frequency of 2 categories, Tf and
Tc, after the initial drug administration during week 2 (see Table 1
for mean frequency).
However, throughout weeks 3 and 4 both of these
behaviors increased in frequency.
No significant statistical differ­
ences between the baseline levels and behaviors observed in week 3 were
attained for any categories.
In the final week of thyroxine treatment
26
(week 4), a level of statistical significance was attained in two
behavior categories, mouth fighting (Tm) (p -^.005) and nipping
(p < .025).
In Phase 3, after one week of thiourea treatment, 3
behavior categories decreased significantly from their baseline level-chasing (p < .005), biting-butting (p <, .005), and nipping (p <
.005),
Attention should be given however to the high frequencies of the
behavior categories occurring during this period (week 5) in the remain­
ing defended territories (see Table 1).
By the end of week 6, all
behavior categories decreased statistically (p < .025) from previous
established territorial behavior.
Group II.
The firemouths treated with the higher dosage of
thiourea in Phase 2 decreased significantly at least at the .01
level from their baseline for all behavior categories except pit
digging (p ^
.025),
By the end of week 3, this category also
attained significance (p ^ .005).
Group III.
The only category which changed significantly for
the thyroxine-treated Jack Dempseys was nipping.
This increase
(p < .025) occurred during the last week of hormone treatment.
Qualitative Observational Data
In each aquarium, the.establishment and maintenance of a terri­
tory by both Cichlasoma meeki and Cichlasoma biocellatum followed a
general pattern.
The size of the 20 gallon aquarium limited the number
of fish that became dominant and defended territories.
Although many
of the members were able to assume'territories, the activity of the
27
dominant territorial fish made the establishment of more than two terri­
tories impossible.
In each case, the largest fish in the aquarium
secured the largest territory and controlled a large portion of the
bottom area.
The fish defending the other territory were situated at
the other end of the aquarium in smaller areas.
Each territorial fish
dug one or more pits in its territory soon after the establishment of
the territory.
The remaining school or nonterritorial fish were located
in the surface area or small interspace between territories.
These
fish often tried to come down to the bottom or encroach on defended
territory but were driven away (intraterritorial fighting).
territorial fighting occurred when
by another.
Intra­
fish entered the territory claimed
Boundary fighting also occurred between the owners of the
two contiguous territories.
In this case, the more dominant fish
succeeded in pushing the opponent back, temporarily extending his terri­
tory while contracting the territory of the less dominant fish.
Threats and fighting were used to attain a dominant position in
the social hierarchy and to establish control over a territory.
Threat
(Tf) and chasing others away from a territory (Tc) were used to avoid
indulging in serious combat.
More serious threatening occurred in the
face to face confrontation (Too) in which rival males, with mouths open
and gill covers erect, both approached and retreated from each other.
This behavior was more frequent in the firemouths than in the Jack
Dempseys.
Recourse to more belligerent combat occurred when threat or
chasing failed to drive off a rival fish.
The more serious fighting
consisted of biting (Tb) and mouth fighting (Tm), in which rivals
28
locked jaws and wrestled by pulling each other to and fro.
Terri­
torial biting occurred more frequently in the territorial fish posses­
sing the smaller territory.
These fish resorted to physical contact in
the restricted quarters in order to maintain a territory.
Actual
damage was avoided since defeated fish eventually recognized their
plight and gave signs of submission (posture it adopted and coloration)
or evacuated the territory.
Group
During the thyroxine treatment phase, fish were rated
by observers to be generally more active and faster in their movements
than before.
The dominant territorial fish increased its territorial
boundaries resulting in the reduction of the adjoining territory, and,
in one aquarium, the abandonment of the territory by the subdominant
fish (see Table 1, reduction in number of territories during week 4).
The nonterritorial fish were clustered mainly in the top and center of
the periphery of the tank, swimming against the aquarium glass (flutter
behavior).
These fish appeared skittish and were easily frightened
(extremely sensitive to tap on the glass wall).
The principal color
of the fish (firemouths) remained light silvery gray but the throat and
reproductive marking were judged to be brighter than the pre-hormonal
level.
Vertical bands located between the eye and caudal fin were
more apparent in the nonterritorial fish, exhibiting submission,
whereas dominant territorial fish displayed longitudinal black blocks.
The subsequent thiourea treatment to the firemouths during
Phase 2 resulted in dramatic changes in behavior within the 5th week.
There was a decrease in the number of fish defending territories and
29
fish tended to group together (school) at the bottom center of the tank.
There were sporadic bouts of agonistic behavior between fish in the
group but no discernible dominant fish after the first session of week
6.
During the seventh week, the fiBh were more dispersed but were
situated on the bottom.
The fish remained hypoactive but often moved
sporadically with fast jerky locomotor movements.
behavior was the beating of the pectoral fins.
The most prevalent
All fish became pre­
dominantly brownish gray with no visible pigmented vertical bands.
Reproductive markings were judged darker, often being completely
masked.
There was little feeding during the sixth and seventh week.
Group II.
The firemouths receiving the higher dosage of
thiourea showed immediate effects to the drug.
Only 27 of the previous
60 territories were defended during week 2, none after the third day
of treatment.
tank.
Fish grouped together and schooled at the bottom of each
There was no apparent dominant fish at this time, but periodical­
ly members exhibited diminished agonistic behaviors toward each other
while in the group.
There was a diminution in locomotor movement and
activity, consisting mainly of uncoordinated jerky movements over
short distances and persistent beating of the pectorals.
There was a
rapid change in pigmentation in contrast to the untreated condition.
All fish were principally brownish gray, with a deep reddish brown
throat and darkened reproductive markings, at times, completely masked.
During this period, there was limited feeding and members appeared
sick.
Eight of the fish died before the end of week four.
Group I I I .
In Phase 2, the Jack Dempseys treated with
30
thyroxine became more active in general during week four.
One tank
housed a dominant territorial fish that became extremely hyperactive,
using fast coordinated locomotor movements to drive the other fish into
a top corner of the aquarium.
The subdominant fish in this aquarium
abandoned its territory and entered the nonterritorial group,
which
often showed postures of submission to this extremely dominant terri­
torial fish.
The nonterritorial fish in the two other tanks alternated
their position from the center to the top of the aquarium away from the
ensuing territorial fish.
In two tanks, fish pairs separated leaving
the male defending the territory and unreceptive to entrance into his
territory by his former partner.
In each aquarium, by the end of the
thyroxine treatment period, all remaining territorial fish had in­
creased their area of control or dominance in the aquarium.
No
flutter behavior was observed by the Jack Dempseys in any of the aquaria.
In a large ma j orlty of the Jack Dempseys, the vertica1 band formed by
the pigmentation in the integument, which represent reactions to
aggression or disturbance, became more pronounced while the ventral
part of the body became a darker black.
The reproductive colors or
spots were judged brighter.
Summary
All fish treated with thyroxine for 3 weeks exhibited Increased
locomotor activity, changes in integument pigmentation which corres­
ponded to adopted functional behaviors, and spent considerably more
time in the top of the aquaria.
behavior.
Only Cichlasoma meeki showed flutter
During this period, the dominant territorial fish tended to
31
increase the area of the territory and their control or dominance over
the nonterritorial members.
Quantitative differences in territorial
behaviors between the baseline and thyroxine treated periods were not
decisive.
In Cichlasoma meeki. the two behavior categories (Tc,
chasing; Tf, frontal display) decreased and differed significantly
(p •< .025) after the initial administration of thyroxine during week 2.
During the final week of thyroxine treatment, territorial mouth fight­
ing (Bn) and nipping (N) increased and approached statistical signifi­
cance (Tm, p <
,005; N, p ^
.025).
Only one behavior category, nipping
(N, p <; .025), reflected quantitative changes during week 4 from
previous territorial behaviors in Cichlasoma biocellatum.
Fish treated with thiourea exhibited dramatic changes in be­
havior.
Group II, the higher dosage group exhibited the effects imme­
diately and more dramatically; however the effect of the drug became
lethal to 8 of the fish during the last week of observation.
Thiourea
treated fish abandoned previously defended territories, grouped
together and schooled at the bottom of each aquarium.
There was a
diminution of overt activity, consisting mainly of uncoordinated
jerky movements over short distances and persistant beating of the
pectoral fins.
Integument pigmentation became darker in all fish.
Quantitative statistical differences (at least p < . 0 1 ) were found
in the high dosage group for all categories except pit digging (P)
after only one week of thiourea treatment.
significance (p <
.005) after week 3.
This behavior approached
In Group I, only 3 categories
(Tc, chasing; Tb, biting-butting; N, nipping) achieved
32
a level of significance (p
.005) after one week of thiourea treat­
ment, but by the end of week 6, all territorial categories differed
statistically from their baseline (p
.025).
DISCUSSION
Hormones and Territoriality
It is well established that intraspecies aggression by threat
or fighting is used to attain the dominant position in a hierarchy and
to establish control over a territory in cichlids (Baerends & Baerends
Van Roon, 1950; Seitz, 1940; Hoffeld, 1972).
Moreover, the importance
of an interaction between internal and external factors necessary for
activation of a system of territorial behavior patterns has been
stressed (Seitz, 1940; Heiligenberg, 1965).
In this study, after the
initial administration of thyroxine during Phase 2 to Firemouth
cichlids, or C. meeki, there was a sudden unexpected statistically
significant decrease in agonistic behaviors with two categories--Tc and
Tf.
This decrement was accompanied by dominant fish remaining in their
pits and digging at the substrate.
After this brief diminution how­
ever, agonistic behavior Increased in all categories with further
thyroxine treatment as expected.
Prolonged thyroxine treatment sig­
nificantly increased the frequency of two behavior categories, mouth
fighting and nipping during the defense of a territory by Cichlasoma
meeki.
Under comparable conditions, Cichlasoma biocellatum showed an
increase in nipping only.
and potent "test
Mouth fighting is considered a more fierce
of strength" (Fryer & lies, 1972; Ruwet & Voss,
1966) in cichlids and occurs less frequently than other territorially
induced agonistic behaviors (Costelloe, 1970).
Jack Dempseys form
34
more stable societies and are less excitable than Cichlasoma meeki
(Baerends & Baerends Van Roon, 1950).
This attribute may account for
the lack of significant increases in mouth fighting among C. biocellatum
after thyroxine treatment.
Increased nipping or biting off the
substrate outside of the pit occurred in both species and accompanied
an increase in control over area outside the pit in the aquaria by the
dominant fish.
Not only are these results suggestive of increased
dominance or territorial behavior (Lorenz, 1937) but they can be
interpreted as increased displaced aggression.
According to a number
of modern ethologists (Baerends, 1966; Heiligenberg, 1965; Bastock, et
al., 1953) biting of gravel from the substrate is derived from attack
behavior through redirection and it is considered a displacement activ­
ity,
Heiligenberg (1965) has shown that as aggressive tendencies
increase, but the performance of overt attacks to an adequate object
inhibited, Pelmatochromis tended to start
biting off the substrate.
Moreover, when opponents became present, the tendency to attack de­
creased after biting of the substrate.
Biting of the substrate or
nipping can be considered an alternative for attack behavior in reducing
aggression if the environment does not provide external situations to
evoke overt aggressive behavior.
The experimental approach to investigate behavior in respect
to group structure and organization faces the problem of artificiality.
Most naturalistic observations do not permit a finer analysis of causal
relations but the aquarium setting is an artificial setting, restricting
the amount and extent of territorial behavior.
Casual factors are
35
difficult to isolate in defense of a territory because any one event is
accompanied by many others.
Moreover, when subjected to experiment,
captive fish also meet many situations which they would never encounter
in nature and which, if they did, they would try to avoid.
However,
aquarium observations can provide valuable information related to
natural conditions.
In the present experiment, there appeared to be
an increase in dominance or control over a larger area of the aquarium
by the dominant territorial fish after prolonged thyroxine treatment.
Nonterritorial fish were clustered in the top and center of tanks,
restricting their ability to execute retaliatory behaviors and thus
making it untenable to rely solely on an increase in fighting and
threat displays (behavior category system) as an intensification of
territorial behavior.
The study did however provide reliable
evidence for increased mouth fighting, a rather fierce agonistic
pattern for cichlids between dominant fish and nonterritorial holding
fish.
The extent that other territorial behaviors (chasing, biting,
frontal display, and braking) could have been more feasibly evaluated
was restricted by the crowding of the nonterritorial fish.
The in­
crease in mouth fighting and dominance suggests that thyroxine has a
role in agonistic behavior during territorial behavior.
More direct
control of influence of aggressive behavior in cichlids seems to be
through the gonadotropins of the pituitary and reproductive hormones
(Blum & Fiedler, 1965; Baggerman, 1966. Metuzals, et: ajl., 1968) or
through synergistic effects between reproductive and thyroid hormones
(Matty, 1960).
36
That thiourea treatment has a detrimental effect on clchlid
fish defending territories was clearly demonstrated; however, because
of its toxic effect, a strict evaluation or interpretation cannot be
made.
Fish progressively abandoned territories and schooled stationary
at the bottom of the tank with no discemable dominant fish.
Moreover,
sporadic bouts of agonistic behavior occurred periodically between
fish during the early stages of thiourea treatment.
Baerends and
Baerends Van Roon (1950) claim that adult cichlids enter schools only
when conditions are unfavorable for reproduction, the worse the condi­
tions the denser the school becomes.
A plausible assumption for the
underlying mechanisms controlling schooling behavior is that thiourea
inhibits gonadal hormones which prevent schooling (Barrington & Matty,
1952; Smith, et al., 1953).
It is noteworthy that after thiourea
treatment, periodic bouts of agonistic behavior occurred, reproductive
colors faded, and activity dissipated as the amount of territorial be­
havior decreased.
The course and effect of these stimuli, critical for
territorial behavior, appear to adhere to the principle of heterogeneous
summation (Seitz, 1940): inasmuch as some stimuli which normally evoke
a response are absent, the response may be reduced quantitatively but
not qualitatively.
The intensity of the response depends on how many
of the sign stimuli are present but not on which.
This principle may
account for the high level of some agonistic behavior shown in Group I
by previously thyroxine treated firemouths during the early stages of
thiourea treatment before they too abandoned their territory, and pro­
gressively decreased their number of agonistic displays.
treatment decreased the number of effective sign stimuli.
Thiourea
37
Activity and Locomotor Levels
This study confirms earlier findings (Hoar, 1955; Sage, 1968;
Fontaine, 1963) that thyroxine treated fish have greater general
activity, exhibit flutter behavior, tend to reside in the tank periph­
ery, and have greater locomotor activity.
In contrast, the anti­
thyroid drug, thiourea, rendered fish motionless for variable periods
of time with occasional movement in short erratic bursts, and resulted
in fish schooling near the bottom of aquaria.
The behavioral effects
precipitated by the toxic level of thiourea could be an adaptation to
severe stress; however, these results are comparable to previous
findings.
The changes in territorial behavior may be a result of
direct hormonal influence on general metabolism, direct action on
neural mechanisms (Hoar, 1952; Liley, 1969) in the CNS underlying the
behavior responses, or brought into use by normal evironmental stimuli
acting via the endocrine system (Sage, 1968).
Pigmentation and Coloration Displays
The results of this experiment indicate similar effects of
thyroid hormones on integument pigmentation.
The "silvering effect"
or lighting of color (Robertson 1949; Sage, 1967; Matty & Sheltawy,
1967) caused by increased guanine metabolism, was most apparent in the
firemouths.
On the other hand, an increase in black pigmentation
(melanophores) (Muller, 1953; ViIter, 1946) after thyroxine treatment
was observed in the Jack Dempseys, reaffirming an apparent dual role
of thyroid hormones in pigmentation (Pickford & Atz, 1957).
In the context of territorial behavior, the concomitant pigment
38
changes associated with defense of a territory became more pronounced
following prolonged thyroxine treatment.
In Cichlasoma meeki.
vertical bands, indicating an emotional state of BubmiBsion and dis­
turbance (Neil, 1964), were clearly more pronounced in nonterritorial
fish.
Consistent observations of these crossbands (melanophores) in
Cichlasoma biocellatum were less frequent; but this contrast may corre­
spond to the fact that meeki behave more "nervously" than Cichlasoma
biocellatum which show their cross bands for only a few seconds
(Baerends & Baerends Van Roon, 1950).
The accentuation of these
behavior patterns, expressing emotional states, could possibly be
guided by the synergistic interaction of thyroxine and sympathetic
nervous system effects (Waldstein, 1966; Harrison, 1964).
Increased
sympathetic secretions have been reported to produce "excitement pallor"
(Parker, 1948; Von Firsch, 1911), activation of melanophore granules
(Rasquin, 1958; Odiorne, 1957), and the ease to which emotional dis­
plays can be released (Marrone, et al., 1966).
This evidence supports
the view that thyroid hormones may affect integument pigmentation
directly or indirectly through the sympathetic nervous system.
The effect of thiourea treatment In Cichlasoma meeki corrobo­
rates previous reports that thiourea stimulated pigmentation and
darkening of colors (Belsare, 1946; Sembrat, 1966).
Special emphasis
should be given to the fact that the darkening effect of thiourea
treatment faded reproductive colors.
These changes in sexual colora­
tion may have been produced by a retarding effect on gonadal hormones
(Barrington & Matty, 1952; Smith, et _al., 1953).
Reproductive
39
markings or colors were judged brighter by observers after thyroxine
treatment and suggests a complementary role of thyroid hormones with
sex hormones (Pickford & Atz, 1957; Matty, 1960).
Drug Dosage
The importance of hormonal dosage levels in Investigating
aggressive behavior in cichlids has been reported (Blum & Fiedler,
1965).
Moreover, interspecies variation in susceptibility to drugs
makes it impossible with certainty that the drug will behave in the
same way as it did with other species.
The thyroxine dosage level
(1: 2,000,000) was adequate in producing observable behavioral effects
in both species of cichlid comparable to effects reported in other
species of fish.
For the two thiourea treated groups, a relationship
did exist between the dosage level and the magnitude of its effects;
however one must take into account that Group I had received previous
thyroxine treatment.
The higher dosage level (1; 1000) resulted in
more immediate and dramatic effects than the lower dosage (1: 2,000)
level.
Toxic signs appeared during the last week of treatment and 8
fish died (below LD-50).
Surveillance of the fish of both groups
after the termination of the experiment revealed that the effect of
thiourea was Irreparable for Cichlasoma meeki; even if replaced in
clean water.
Other species of fish such as salmon (Hoar, 1952),
goldfish (Hoar, 1955), guppies (Sage, 1968) and Phoxlnus phoxinus
(Barrington & Matty, 1955) have been reported to have sustained
thiourea treatment under similar conditions without lethal effects.
40
It appears that Cichlasoma meeki are more susceptible to prolonged
thiourea treatment and allow a toxic level to accumulate.
Rhythmicity
Recent interest has been directed in how physiological rhythms
manifest themselves in overt behavioral rhythms.
Investigators have
focused on the cyclic pattern of daily activity in bass (Davis, 1963)
locomotor levels in salmon (Hoar, 1942, 1958) and swimming activity
in the minnow (Muller, 1968).
Moreover, differences in photoperiods
have affected the daily levels of agonistic and reproductive behavior
in salmon (Hoar, 1962).
This investigation was not designed specifi­
cally to detect periodic changes in social behavior in cichlids.
The
social category system of data collection is not amenable to a thorough
evaluation of this problem, however differences were present between
the morning and afternoon sessions from composite comparisons across
all behavior categories and experimental conditions.
A simple sign
test distinguished that daily sessions were different (simply + or -)
for both Group I (p < ,001) and II (p ^ . 0 2 ) .
Comparisons of the weekly
frequencies of all behavior categories between morning and afternoon
sessions for each group are provided in Tables A, B and C of the
Appendix.
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A P P E N D I X
52
table a
COMPARISON OF FREQUENCIES OF BEHAVIOR CATEGORIES BETWEEN
MORNING (AM) AND AFTERNOON (PM) SESSIONS FOR GROUP I
Week
Tf
AM PM
Tm
AM PM
Too
PM
am
Tc
AM PM
Tb
AM PM
N
AM PM
P
AM PM
Phase 1
1
81 34
18 14
3 0
134 129 156 124 206 200
28 13
Phase 2
(thyroxine)
2
3
4
19 10
26 23
57 20
16 9
37 9
39 37
3 5
1 0
12 0
117 97 173 97 163 135
125 136 132 117 213 219
135 89 176 95 271 238
74 53
27 24
39 20
Phase 3
(thiourea)
5
6
7
76 27
11 0
0 0
28 11
9 0
0 0
11 2
0 0
0 0
270 114 147 80
30 7
Total
55
0
0
8 105
0 10
0
0
25 106
0
0
0
0
47
0
0
40
0
0
0
0
0
566 539 752 458 959 839 208 110
53
TABLE B
COMPARISON OF FREQUENCIES OF BEHAVIOR CATEGORIES BETWEEN
MORNING (AM) AND AFTERNOON (PM) SESSIONS FOR GROUP II
Week
Tf
A M PM
Tta
AM PM
14 14
Phase 1
1
72 51
Phase 2
(thiourea)
2
3
4
12
0
0
Total
7
0
0
84 58
Too
AM PM
Tc
AM PM
Tb
AM PM
N
AM PM
P
AM PM
6
4 194 241 120 117 256 265
87 59
3
0
0
2
0
0
1
0
0
50 39
0 0
0 0
19 17
8
5 258 294 173 146 348 300 137 98
5
0
0
64
0
0
53
0
0
53
0
0
29
0
0
92
0
0
35
0
0
54
TABLE C
COMPARISON OF FREQUENCIES OF BEHAVIOR CATEGORIES BETWEEN
MORNING (AM) AND AFTERNOON (PM) SESSIONS FOR GROUP III
Week
Tf
AM PM
Ttn
AM PM
Too
AM PM
Tc
AM PM
Tb
A M PM
N
AM PM
P
A M PM
Phase I
1
6
1
4
0
0
0 181 142
22
27
169 195 112 101
Phase 2
(thyroxine)
2
3
4
4
11
13
0
4
0
1
3
0
0
1
0
0
0
0
0 177 118
0 195 172
0 197 144
18
25
22
20
38
37
223 247 102
197 2 03 87
211 231 58
34. 5
8
1
0
0 750 576
87 122
Total
97
63
66
800 876 359 327
VITA
Peter Harry SpiliotlG was born November 11, 1946 In Wilmington,
North Carolina.
He received his Bachelor of Arts degree from the
University of North Carolina in 1969 and his Master of Arts from
Louisiana State University in 1971.
He is presently a candidate for
the degree of Doctor of Philosophy at Louisiana State University.
55
EXAMINATION AND THESIS REPORT
Candidate:
Peter Harry Spiliotis
M a jo r Field:
Title of Thesis:
Psychology
The Effect of Thyroxine and Thiourea on Territorial
Behavior in Cichlid Pish
Approved:
M ajor professor
ff
Dean of the Graduate) School
EXAMINING COMMITTEE:
D ate o f E xam in atio n :
November 14, 1973