title: Extra-gonadal steroids modulate non-breeding territorial aggression in weakly electric fish.
abstract: The neuroendocrine control of intraspecific aggression is a matter of current debate. Although aggression in a reproductive context has been associated with high levels of circulating androgens in a broad range of species, it has also been shown to occur during the non-breeding season when gonads are regressed and plasma steroid hormone levels are low. In mammals and birds the aromatization of androgens into estrogens plays a key role in the regulation of aggression in both the breeding and non-breeding seasons. This is the first study in a teleost fish to explore the role of steroids in the modulation of non-breeding aggression. Gymnotus omarorum is a highly aggressive teleost fish that exhibits aggression all year-round. We analyzed male-male non-breeding agonistic behavior, compared circulating 11-Ketotestosterone (11-KT) levels between dominants and isolated males, assessed the regulatory role of aromatization of androgens into estrogens, and evaluated the gonads as a source of these sex steroids. We found that high levels of aggression occurred in the non-breeding season despite low plasma 11-KT levels, and that there was no difference in 11-KT levels between dominant and isolated males. We demonstrated that acute aromatase inhibition decreased aggression, distorted contest dynamics, and affected expected outcome. We also found that castrated individuals displayed aggressive behavior indistinguishable from non-castrated males. Our results show, for the first time in teleost fish, that territorial aggression of G. omarorum during the non-breeding season depends on a non-gonadal estrogenic pathway.
authors.affiliation: Unidad Bases Neurales de la Conducta, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo 11600, Uruguay.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Jalabert
authors.affiliation: Unidad Bases Neurales de la Conducta, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo 11600, Uruguay.
authors.forename: Laura
authors.initials: L
authors.lastname: Quintana
authors.affiliation: Laboratorio de Técnicas Nucleares, Facultad de Veterinaria, Universidad de la Republica, Montevideo 11600, Uruguay.
authors.forename: Paula
authors.initials: P
authors.lastname: Pessina
authors.affiliation: Unidad Bases Neurales de la Conducta, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo 11600, Uruguay; Laboratorio de Neurociencias, Facultad de Ciencias, Universidad de la Republica, Montevideo 11400, Uruguay. Electronic address: asilva@iibce.edu.uy.
authors.forename: Ana
authors.initials: A
authors.lastname: Silva
mesh_terms: D000374:Aggression / Q000187:drug effects / Q000502:physiology*; D000728:Androgens / Q000097:blood; D000818:Animals; D002369:Castration / Q000662:veterinary; D004555:Electric Fish / Q000097:blood / Q000502:physiology*; D004967:Estrogens / Q000097:blood; D005260:Female; D012739:Gonadal Steroid Hormones / Q000097:blood*; D008297:Male; D012098:Reproduction / Q000187:drug effects / Q000502:physiology; D012621:Seasons; D013731:Territoriality; D013737:Testis / Q000378:metabolism; D013739:Testosterone / Q000031:analogs & derivatives / Q000097:blood
chemical_list: D000728:Androgens; D004967:Estrogens; D012739:Gonadal Steroid Hormones; D013739:Testosterone; C003600:11-ketotestosterone
keywords: Acute treatment; Aromatase; Castration; Estrogen; Fadrozole; Non-breeding agonistic behavior; Teleost