Dietary l-tryptophan alters aggression in juvenile matrinxã Brycon amazonicus

Abstract

This study evaluated the effect of dietary supplementation with L: -tryptophan (L-TRP), a serotonin precursor, on the aggressiveness of juvenile matrinxã Brycon amazonicus. Fish were kept in individual aquaria for 7 days receiving the diets: D1 (control: 0.47% of TRP), D2 (0.94% of TRP), D3 (1.88% of TRP), and D4 (3.76% of TRP). After this, they were grouped with an intruder fish to establish a resident-intruder relationship during periods of 20 min. Blood cortisol, glucose, chloride, sodium and calcium; hemoglobin, hematocrit, red blood cell count and volume; liver glycogen and lipids were measured. Territoriality had significant effect on the aggressiveness of matrinxã (the residents were more aggressive than intruders, P < 0.001) and tryptophan significantly affected their behavior. Fish fed with the D2 diet presented a longer latency until the first attack (P = 0.0069) and bit the intruder fewer times (P = 0.0136) during the period of observation, compared to the control group. The frequency of bites and chases after the first attack was not affected by the dietary supplementation of TRP. Physiological variables were not significantly affected by the diet, except for a moderate increase in cortisol level in fish fed with D2 diet after the fight, indicating slight activation of the hypothalamus-pituitary-interrenal axis. The results show that juvenile matrinxã have aggressive and territorial behavior and that a diet containing 9.4 g TRP kg(-1) alter their aggressiveness, without affecting the stress-related physiological parameters.

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

“…While the aforementioned study used fish without previous residency, our study used fish that were isolated for 10 days before the social challenge. Previous studies have shown that, after 10 days of isolation, matrinxã are extremely aggressive against an intruder, defending its territory without stopping aggression even when the intruder submits by not attacking the resident (Wolkers et al 2012(Wolkers et al , 2014. In mammals, studies show that the hypothalamic attack area is strongly activated by territorial fights in various species (Delville et al 2000;Halasz et al 2002) and that lesions in this area reduced aggression evoked by an intruder in territorial settings (Olivier 1977;Olivier et al 1983).…”

“…The fish used in the social challenge (intruder) were also maintained in isolation for an equal period in plastic boxes. The social interaction was recorded, and the number of bites and chases (Wolkers et al 2012) performed by the resident fish was evaluated. Immediately after the trial, challenged resident fish were anesthetized; blood was withdrawn from the caudal vein; and the brain was removed and immediately frozen on dry ice to evaluate hormonal, metabolic and neurochemical parameters.…”

“…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.…”

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“…Aggression is one of the important behavior in carnivorous fishes like Pabda and feed supplemented with tryptophan can suppress this behavior and similar studies have been found viz. Oncorhynchus mykiss (Winberg, et al, 2001), Amazonian characid, Brycon amazonicus (Wolkers, Serra, Hoshiba, & Urbinati, 2012), Rainbow trout (Overli, Harris, &Winberg, 1999 andLepage, et al, (2002), Atlantic cod (Hoglund, Bakke, Øverli, Winberg, & Nilsson, 2005). Hseu et al, 2003 found that dietary supplementation of L-tryptophan in juveniles rainbow trout diet leads to inhibit aggression behavior.…”

Growth, cannibalism, and survival relations in larvae of European catfish, Silurus glanis (Actinopterygii: Siluriformes: Siluridae)—attempts to mitigate sibling cannibalism

“…The adjustment of feeding schedules, in terms of food amount, energy content and uniform distribution of food can greatly reduce losses due to cannibalism in intensive culture (Kubitza and Lovshin 1999). Dietary supplementation of tryptophan (TRP) has been shown to reduce aggressive behaviour in several fish species, including the orangespotted grouper, Epinephelus coioides (Hamilton, 1822) (see Hseu et al 2003); the Atlantic cod (Höglund et al 2005); the rainbow trout, Oncorhynchus mykiss (Walbaum, 1792) (see Winberg et al 2001); and an Amazonian characid, Brycon amazonicus (Spix et Agassiz, 1829) (see Wolkers et al 2012). The aforementioned studies suggested that effects of TRP on the reduction of aggressive behaviour in fish originated from a higher brain serotonin (5-HT) activity.…”