Acquired stimulus control of drug-induced changes in aggressive display in Betta splendens

Male Siamese fighting fish exhibit stereotyped aggression reactions to their mirror reflections. When distinctive neutral stimuli (flickering colored lights) were repeatedly associated with drug-potentiated aggression (morphine sulfate) and drug-depressed aggression (phenergan), the stimuli came to exert specific stimulus control over aggressive display even after the drugs were discontinued.     

Effects of mercury chloride (HgCl2) on Betta splendens aggressive display

Mercury chloride (HgCl2) is a toxic mercury salt and a major pollutant, that can be found in soil, water and air, with influences on behavior, physiology and adaptation to the environment. In this study two experiments were designed to examine interactions and effects of HgCl2 on some behavioral patterns of Siamese fighting fish (Betta splendens). In the first experiment we tested the effect of a progressive dose (five 0.04 mg) on aggressive display with exposure to a mirror, whereas in the second experiment we tested the effect of an acute dose (0.2 mg) on the aggressive display with exposure to a mirror. The experiments were performed on 5 consecutive sessions at intervals of 18 hours between sessions. Differences of performance were shown by subjects in the acute and progressive treatments when compared with a control treatment in the majority of behaviors evaluated, namely Floating, Slow Swimming, Wavy Swimming, Emerging, Bend, Square Move and Motor Display Components. Acute treatment was different from control only on Show Body, while the progressive group differed on Resting, Horizontal Display and Appropriate Display Components. Differences between Correlate Display Components and Total were also shown. Both the acute and progressive contamination with HgCl2 decrease the motor activity in the aggressive display, mirror-image test of Betta splendens, mainly on the progressive dose. This implies an impairment on feeding behavior, predator avoidance, reproductive behavior, mate choice and territoriality. These results suggest that in this fish species, the progressive dose has a greater effect on behavior in general and that both the acute and progressive contamination with mercury chloride affect many other aspects of behavior.     

Consequences of aggressive threats by Betta splendens

Male Siamese fighting fish continued to approach visual stimuli associated with conspecifics in the absence of opportunities to perform threat displays or to attack. Dominant fish performed more operant responses than subordinates when such responses led to the appearance of their own mirror images, and all fish learned to delay their threat displays if these resulted in disappearance of the mirror image. In a second experiment, subjects overwhelmingly preferred to view conspecifics (to whom they frequently displayed) compared to no stimulus or members of other species (to whom they did not display). The functions of threat displays in aggressive encounters is discussed.     

Chemical modulation of agonistic display in Betta splendens.

Mirror-induced aggressive display of male Siamese fighting fish was reduced by water-borne traces of (a) a pair of male combatants, (b) a nondisplaying fish of either sex, and (c) bits of torn cadual fin. These findings may indicate a mechanism whereby males tolerate the presence of conspecifics to permit nonagressive social interactions.     

On the choice between eating and aggressive display in the Siamese fighting fish (Betta splendens)

In Expt 1, male Betta splendens were given a choice between food and a mirror image in a T-maze. All fish consistently preferred food. In Expt 2, the choice of fish that lived in the T-maze for the duration of the experiment was compared with the choice of fish that were transferred to the T-maze for each experimental session. Fish that lived in the T-maze consistently preferred food, but fish that were transferred showed a shift in preference toward mirror image. Differential inhibition of hunger and aggression by fear is suggested as the cause of the preference shift.     

Decreased aggressive and locomotor behaviors in Betta splendens after exposure to fluoxetine

The failure of sewage treatment plants to remove pharmaceuticals such as fluoxetine from waste water has become a concern given that these products are being detected in the surface waters of many countries of the world. The effects of fluoxetine in sub-lethal doses on the neural systems and behaviors of aquatic life are worthy of investigation. This study investigated the effects of sub-lethal amounts fluoxetine dissolved in water on the aggressive and locomotor behaviors of 44 male Betta splendens. Fish treated with 705 microg/l of fluoxetine and 350 microg/l of fluoxetine generally demonstrated significant decreases in locomotion and number of aggressive attacks compared to 0 microg/l of fluoxetine (controls) on Days 11 and 19 of drug exposure and persisted for at least 13 days after removal of fluoxetine. Consistent with decreases in the number of aggressive attacks, there was a significant increase in aggression-response time to a perceived intruder for treated males on Days 11 and 19 and persisted for 6 days following removal of fluoxetine. However, the differences in aggressive and locomotor behaviors seen in the fluoxetine-treated groups were indistinguishable from controls three weeks following drug removal.     

Effects of pH on the rate of aggressive display for mirror image reinforcement in siamese fighting fish (Betta splendens)

A hypothesis suggesting that fluctuations in hydrogen ion (pH) intensity may suppress the rate of aggressive display in Betta splendens was offered. The effect of pH upon the rate of ring swimming for aggression-releasing mirror image presentation was therefore investigated under pH intensities of 5.0, 7.0, and 9.0 in a steady-state design. The results indicated no significant variation in the rate of response over pH levels. Two possible mechanisms of pH resistance are discussed.     

Metabolic costs of aggressive behaviour in the Siamese fighting fish,Betta splendens

Aggressive conflicts between males are often resolved by means of multiple ritualized agonistic displays without damaging escalation. Apparently, in such cases by using those displays opponents exchange important motivational and physical information on which they base a decision to stay or leave the interaction. In the Siamese fighting fish, the time spent spreading the dorsal fin and erecting the gill coverts predicts who will be the winner or loser of the interaction. Two experiments were carried out to study whether display performance might be costly. First, oxygen consumption was measured during mirror‐image stimulation. This experiment showed that oxygen consumption was positively correlated with gill cover erection and dorsal fin spread. In the second experiment, a fight between two opponents was simulated and the oxygen consumption of the expected winner and loser was compared. Metabolic rates were not different between winners and losers before and during the fight, but winners showed higher oxygen consumption in the night after the fight. These results are in accordance with costs of display performance and with long‐lasting physiological consequences of winning or losing a fight. Aggr. Behav. 32:1–7, 2006. © 2006 Wiley‐Liss, Inc.     

Prior-residence effect in Betta splendens

Male Siamese fighting fish were presented with the visual image of an aggressive male conspecific for a 150-min test, with attack behaviors monitored continually. A 10-day period of residency in either the test tank or its exact replica resulted in more persistent attack than 10 min of residency. Testing in water other than that in which subjects had resided for 10 days did not produce a reduction in attack. Finally, the extent of attack behavior occurring early in testing was highly and positively correlated with subsequent attack duration; that is, at the start of an encounter, and before severe physical damage has been caused, Bettas may communicate to opponents their "intention" to engage in persistent, injurious aggression.     

Socially mediated learning in male Betta splendens

Seven experiments showed that in the absence of social stimulation male Siamese fighting fish would approach any of several visual and spatial cues that had previously been paired with the animals' mirror images. These findings demonstrate that learned modifications of swimming mediated by social stimuli are possible in Bettas. The present results also suggest that territorial defense in some teleosts may, in part, be mediated by the association of social cues with visual and spatial stimuli.     

Sensitization of escape in female Betta splendens

Following 1 day of cohabitation with a male, female Siamese fighting fish showed heightened escape from male conspecifics (enclosed behind glass). Escape from males was general in that no particular male stimulus was required to provoke female escape. However, female conspecifics remained relatively attractive following exposure to a male. Tactile stimulation of females by males (biting, perhaps) plays some role and may be required in sensitizing females' escape from males. © 1996 Wiley-Liss, Inc.     

Predictors of dominance in male Betta splendens

The formation of dominance/subordinancy relations in pairs of male Siamese fighting fish was examined in six experiments. Dominant animals typically were those fish that built the largest nests and that attacked an image of a live, displaying male most intensely prior to combat. However, pretest performance on an operant task and reaction to an animal's own mirror image were not useful predictors of subsequent dominance. These findings are consistent with the suggestion that domesticated Bettas have a territorial social strategy that includes both nest-building and fighting behaviors.     

Social overstimulation reduces subsequent aggression in Betta splendens

This paper examines the waning of intense aggressive behaviors in Siamese fighting fish subjected to continuous visual social stimulation. Damaging biting during subsequent fighting was dramatically reduced in fish which had been surrounded for several weeks by conspecifics, even though the overstimulated fish performed only opercular and fin displays to the fish surrounding them, not biting. The latency to opercular display was diminished, but the rate once opercular display began was not significantly different. In the 18 encounters observed, a socially overstimulated fish never dominated a control fish. This result suggests a visually mediated mechanism, which reduces biting tendency when there is prolonged, inescapable visual exposure to mildly aggression-releasing stimuli similar to those which trigger biting in live encounters. © 1994 Wiley-Liss, Inc.     

Visual reinforcement in the female Siamese fighting fish, Betta splendens

Operant conditioning with Betta splendens (Bettas) has been investigated extensively using males of the species. Ethological studies of female Bettas have revealed aggressive interactions that qualitatively parallel those between male Bettas. Given these similarities, four experiments were conducted with female Bettas to examine the generality of a widely reported finding with males: mirror-image reinforcement. Swimming through a ring was reinforced by a 10-s mirror presentation. As with males, ring swimming was acquired and maintained when mirror presentations were immediate (Experiments 1, 2, and 3) and delayed (Experiment 4). The failure of conventional extinction (Experiments 1 and 2) and response-independent mirror presentations (Experiment 3) to maintain responding confirmed the reinforcing properties of mirror presentation. These results extend previous findings of mirror images as reinforcers in males of the same species and illustrate a complementarity between behavioral ecology and the experimental analysis of behavior.     

Effect of telencephalon ablation on the reinforcing and eliciting properties of species-specific events in Betta splendens

In male Betta splendens, aggressive behavior is drastically attenuated following telencephalon ablation. Because instrumental training and Pavlovian conditioning experiments with intact fish have suggested that associative factors may play an important role in the performance of agonistic behaviors, the effect of ablation on instrumental learning and Pavlovian conditioning was studied. In Experiment 1, ablation had no effect on the learning of the instrumental tunnel-swimming response reinforced by mirror presentation (i.e., viewing a conspecific), although the mirror presentations in yoked-control groups elicited fewer responses in ablates than in normal and sham-operated control fish. Yoked controls further established that instrumental responding was maintained by the reinforcement contingency and was not merely the result of increased motor activity. Experiment 2 studied Pavlovian conditioning of the components of the agonistic display. Unconditioned fin erection, gill erection, and tail beating (i.e., unconditioned responses, URs) to the mirror US all were less frequent in ablates than in normals or shams. Of these, only gill cover erection showed evidence of true conditioning (i.e., conditioned responses; CRs) in which responses to the conditioned stimulus (CS) are due to the pairings of CS and US (unconditioned stimulus). However, ablates suffered no impairment of conditioned gill erections. Ablates performed fewer fin erections to the CS; however, fin erection responses were not due to CS-US pairings but were attributable to pseudoconditioning. These results are related to hypotheses postulating the involvement of learning mechanisms in ablation-produced deficits and normal aggressive behavior.