Dietary l-tryptophan modulates agonistic behavior and brain serotonin in male dyadic contests of a cichlid fish
- 8 Downloads
Although some studies have investigated the effects of dietary l-tryptophan on agonistic behavior, research on adult fish specimens is still lacking. Moreover, submissive behaviors have been generally overlooked. We focused on agonistic behavior between males of the cichlid fish Cichlasoma dimerus, in dyadic encounters held in a novel context after being fed or not with an l-tryptophan enriched diet (TRP) for 2 weeks. We arranged three different dyads: control/control (control conditions: not TRP enriched), control/TRP, and TRP/TRP. We also registered the response of the brain serotonergic system in four brain regions. TRP/TRP dyads showed higher latencies to first attack, lower overall aggression, and lower proportions of bites and passive copings (submissive display) compared to control/control. TRP dominant males performed fewer bites with respect to controls, and subordinate males opposed to TRP males showed fewer passive copings. Higher serotonergic activities were found in subordinates’ optic tectum and in the telencephalon and preoptic area/hypothalamus of TRP males. Altogether, results point out that dietary l-tryptophan reduced males’ motivation to attack and dominant aggression, which consequently influenced subordinate agonistic repertory. In addition, males within TRP/TRP dyads showed a switch in their behavioral agonistic repertory. These behavioral outcomes were probably due to modifications at brain serotonergic functioning.
KeywordsAgonistic behavior Brain Cichlids l-Tryptophan Serotonin
Control dietary protocol
CTL vs. TRP male
CTL vs. CTL male
Total body length
l-Tryptophan supplemented dietary protocol
TRP vs. TRP male
Our research has been funded by the following grants: Agencia de Promoción Científica y Tecnológica (Grant PICT 1482) and Universidad de Buenos Aires (Grant UBACyT 20020130200038BA). We would particularly like to thank Mariel Tripoli for her statistical recommendations and two anonymous reviewers for numerous meaningful suggestions.
Complaince with ethical standards
All experiments were conducted in conformity with international standards on animal welfare, as well as being in accordance to institutional (Comisión Institucional para el Cuidado y Uso de Animales de Laboratorio, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires) and national (Comité Nacional de Ética en la Ciencia y la Tecnología, MINCyT, Argentina) regulations. All procedures were in compliance with the Guide for Care and Use of Laboratory Animals (National Research Council 2011).
- Almirón AE, Casciotta JR, Ciotek L, Giorgis P (2015) Guía de los Peces del Parque Nacional Pre-Delta. Administración de Parques Nacionales, Ciudad Autónoma de Buenos AiresGoogle Scholar
- Basic D, Krogdahl Å, Schjolden J, Winberg S, Vindas MA, Hillestad M, Mayer I, Skjerve E, Höglund E (2013) Short-and long-term effects of dietary l-tryptophan supplementation on the neuroendocrine stress response in seawater-reared Atlantic salmon (Salmo salar). Aquacul 388:8–13CrossRefGoogle Scholar
- Fulton TW (1904) The rate of growth of fishes. Twenty-second Annual Report, Part III. Fisheries Board of Scotland, Edinburgh, pp 141–241Google Scholar
- Haller J (2014) The glucocorticoid/aggression relationship in animals and humans: an analysis sensitive to behavioral characteristics, glucocorticoid secretion patterns, and neural mechanisms. In: Miczek KA, Meyer-Lindenberg A (eds) Neuroscience of aggression. Springer, Heidelberg, pp 73–109Google Scholar
- Haller J, Harold G, Sandi C, Neumann ID (2014) Effects of adverse early life events on aggression and anti-social behaviours in animals and humans. J Endocrinol 26:724–738Google Scholar
- McDonald MD (2017) An AOP analysis of selective serotonin reuptake inhibitors (SSRIs) for fish. Comp Biochem Physiol C: Toxicol Pharmacol 197:19–31Google Scholar
- Mir JI, Shabir R, Mir FA (2012) Length-weight relationship and condition factor of Schizopyge curvifrons (Heckel, 1838) from River Jhelum, Kashmir, India. World J Fish Mar Sci 4:325–329Google Scholar
- National Research Council (2011) Guide for the care and use of laboratory animals. The National Academies Press, Washington, DCGoogle Scholar
- Ramallo MR, Birba A, Honji RM, Morandini L, Moreira RG, Somoza GM, Pandolfi M (2015) A multidisciplinary study on social status and the relationship between inter-individual variation in hormone levels and agonistic behavior in a Neotropical cichlid fish. Horm Behav 69:139–151PubMedCrossRefGoogle Scholar
- Summers CH, Korzan WJ, Lukkes JL, Watt MJ, Forster GL, Øverli Ø, Höglund E, Larson ET, Ronan PJ, Matter JM, Summers TR, Renner KJ, Greenberg N (2005) Does serotonin influence aggression? Comparing regional activity before and during social interaction. Physiol Biochem Zool 78:679–694PubMedCrossRefPubMedCentralGoogle Scholar
- Winberg S, Nilsson GE (1993) Roles of brain monoamine neurotransmitters in agonistic behaviour and stress reactions, with particular reference to fish. Comp Biochem Physiol A: Mol Integr Physiol 106:597–614Google Scholar