HORMONES AND AGONISTIC BEHAVIOUR: WHAT DOES THE SOUTHAMERICAN CICHLID FISH, CICHLASOMA DIMERUS, TELL US ABOUT THEM.

MARTÍN ROBERTO RAMALLO; AGUSTINA BIRBA; RENATO MASSAAKI HONJI; LEONEL MORANDINI; RENATA GUIMARÃES MOREIRA; GUSTAVO MANUEL SOMOZA; MATÍAS PANDOLFI

Olhão

Simposio; 10th International Symposium on Reproductive Physiology of Fish; 2014

Introduction Cichlasoma dimerus is a southamerican cichlid fish with a hierarchical social system, established and sustained through agonistic interactions. Individuals in the top ranked positions aggressively guard a territory which grants them access to reproduction. There, a territorial pair spawns and later continues with biparental care of the egg and larvae. The aim of this study was to characterize the agonistic behaviour of territorial (T) pairs and non-territorial (NT) male fish, and its relationship with sex and stress hormones. Methods Experimental aquaria were set by placing six size-matched fish (random sex ratio) on 53 l tanks. Once the linear hierarchy was established, top and bottom ranked individuals were identified. When the T pair began with the reproductive displays, agonistic interactions were recorded with a camera (filming time ̴ 22 mins) and quantified for T male and female, and the lowest ranked individual. Aggressive displays included chasings, bites and assaults, while submissive behaviour included escapes and passive coping. Blood samples were obtained, and plasma levels of 11-ketotestosterone (11-KT), testosterone, estradiol (E2) and cortisol were measured by ELISAs. Testes from T and NT males were dissected, weighted to calculate the gonadosomatic index (GSI) and fixed in bouin solution. For each fish, three randomly chosen slices were analyzed to assess testicular cellular composition. Randomly generated points (n=60, CPCe software) were overlaid on each slice photograph, cells identified and the percentage of each type of cell was calculated (type A and B spermatogonia, spermatocytes, spermatids, and spermatozoa). Results and Discussion Territorial males and females spent most of their time biting NT individuals (over 50%), while more than 80% of the behaviours performed by NT males were escapes. Even though T males and females did not differ in the overall frequency of aggressive behaviour, males performed more assaults and chases than females (p