The social behavior of pirá-brasília, Simpsonichthys boitonei Carvalho, 1959, can be divided in two groups: the reproductive and the agonistic. In reproductive behavior was observed that the male courts the female when she approaches, through the vibration of body and change in the color pattern, from red to dark blue. The male drives the female until substratum, where they penetrate and accomplish the spawn after lateral compression of the male's body on the female. The ritual of spawn repeats several times until the female leaves. The agonistic behavior is more frequent among males, but can happen occasionally between males and females and within females. The behavior patterns of menace are: extension of fins, caudal-fin open and close, increase in pectoral-fin movements, operculum expansion and red coloration increasing. After the exhibition of these patterns can happen attack or escape. In many times escape happens without apparent opponent threatens or attack, but for the opponent's simple presence. The males are territorial, defending the permanence place - with preference of inferior area of water column - that is still used for food search and for reproduction. Dominance happens among males and also among females. Elaborated behaviors of court and territory can be important for those animals that live in temporary pools, whose physical and chemical characteristics can be not very stable.
Aggressive behavior; annual fishes; reproduction; territory
