The time course of aggressive behaviour in juvenile matrinxã Brycon amazonicus fed with dietary L‐tryptophan supplementation

Abstract

This study evaluated the influence of dietary L-tryptophan (TRP) supplementation on the time course of aggressive behaviour and on neuroendocrine and hormonal indicators in juvenile matrinxã Brycon amazonicus. Supplementation with TRP promoted a change in the fight pattern at the beginning of an interaction with an intruder, resulting in decreased aggressive behaviours during the first 20 min. The decrease in aggression did not persist throughout the interaction but increased at 3 and 6 h after the beginning of the fight. Monoamine levels in the hypothalamus were not influenced by TRP before or after the fight; however, the hypothalamic serotonin (5-HT) concentration and the 5-hydroxyindole-3-acetic acid (5HIAA):5-HT ratio were significantly correlated with the reduction in aggressive behaviour at the beginning of the fight. Cortisol was not altered by TRP before the fight. After the fight cortisol increased to higher levels in B. amazonicus fed with supplementary TRP. These results indicate that TRP supplementation alters the aggressive behaviour of B. amazonicus and that this effect is limited to the beginning of the fight, suggesting a transient effect of TRP on aggressive behaviour. This is the first study reporting the effects of TRP supplementation on the time course of aggressive interaction in fishes.

Effect of dietary l-tryptophan on cannibalism, survival and growth in pikeperch Sander lucioperca (L.) post-larvae

“…The aforementioned studies suggested that effects of TRP on the reduction in aggressive behavior in fish originated from a higher brain 5-HT activity. However, no significant effect of TRP on hypothalamic 5-HT levels was detected, though suppressed aggressive behavior in the Amazonian characid Brycon amazonicus (Wolkers et al 2014) were also found. The results of the present study showed that dietary supplementation with TRP suppressed aggressive behavior in post-larvae of pikeperch.…”

“…No significant effect of TRP supplementation on the survival in the orange-spotted grouper (Hseu et al 2003) and European catfish Silurus glanis (Król et al 2014) was found. Compared with survival obtained in the other, previous studies will be pointless because usually TRP effect on aggressive behavior was tested in juvenile fish (not in the larvae or post-larvae as here) or in non-obligate carnivores taxa, e.g., rainbow trout, and sometimes the aspect of survival was beyond the scope of these studies (Winberg et al 2001;Höglund et al 2005;Wolkers et al 2014). …”

“…TRP-supplemented diets were effective in increasing the levels of serotonin (5-HT) in the tissue of pikeperch, which supported the statement that effects of TRP on the reduction in cannibalism in fish originated from a higher brain 5-HT activity. However, in view of the rapid increases in TRP hydroxylase enzyme activity and in 5-HT concentration, mechanisms other than increased 5-HT biosynthesis may be involved in the control of aggression by TRP (Jacobs and Fornal 1991;Aldegunde et al 2000;Wolkers et al 2014).…”

Social challenge increases cortisol and hypothalamic monoamine levels in matrinxã (Brycon amazonicus)

“…The social challenge consisted of introducing a fish of mass as similar as possible (\10 % difference) in the aquarium of the resident for 20 min to promote a fight. Previous studies from our laboratory demonstrated that 10 days of isolation elicit highly aggressive behavior in resident matrinxã (Wolkers et al 2014). This approach permits evaluation of the neuroendocrine alterations in fish that perform an intense aggressive behavior associated with territory defense.…”

“…Thus, the aim of the present study was to evaluate the profile of hypothalamic monoamines, serum cortisol and glucose levels of Brycon amazonicus elicited by a social challenge (introduction of an intruder in its territory) in a fish with pre-established residence. Previous studies from our laboratory demonstrated that juvenile Brycon amazonicus, the species used in this study, are highly aggressive against an intraspecific intruder in its territory (Wolkers et al 2012(Wolkers et al , 2014, making this a suitable model to study aggressive behavior in fish.…”