Reproductive hierarchy dynamics in males of the cichlid fish Cichlasoma dimerus (Heckel, 1840) under laboratory conditions

FELIPE ALONSO; MATIAS PANDOLFI

Huerta Grande

Congreso; Primer Reunión Conjunta de Neurociencias; 2009

Argentine Society for Neurosciences (SAN) and the Argentine Workshop in Neurosciences

Social status or dominance may be a determining factor on mating success. Cichlids are a group of fish with complex social behaviors that are being intensively studied in the area of social control of reproduction. The SouthAmerican species Cichlasoma dimerus has been widely studied in our laboratory. During the reproductive season, this species presents a dominance hierarchy in which only some males have access to territories that they defend and where they reproduce in monogamy. In the present work the access to reproductive territories and females in relation to the social status of each male were studied in two conditions: when there were no territories established and when they where established and a reproductive opportunity was generated by the removal of the dominant male. Four males and a female were placed in a neutral tank (53 litres) in order to establish the social hierarchies. Once the reproductive couple is formed, the dominant male was removed before spawning to study the social dynamic (N=4). Dominance indexes were calculated and males were sacrficed afterwards. For each individual, its reproductive strategy was registered and correlated with organo-somatic indexes, body coloration patterns, weight and body length. Plasma cortisol levels where about three-fold higher in the most subordinated individuals and gonadotropins pituitary content showed a reduction in those males with a lower hierarchy. Body color patterns were related with dominance status. Overall, our findings highlight a complex association between social behaviour and hierarchies, pituitary hormones (¦Â-FSH and ¦Â-LH) and adrenal steroids related to stress (cortisol).