Gerarchia e comportamento riproduttivo in Nothobranchius furzeri (Jubb).

In this preliminary study we have analysed dominance hierarchy and mating behaviour in Nothobranchius furzeri, a fish with an extremely short lifespan (< 12 weeks). We observed these parameters in a group of 4 males and 7 females for a period of 5 weeks. Rank is correlated with the animal’s body size (the largest male was the dominant), but also prior experience of wins/losses affects aggressive behaviour in this species. Males with a similar rank and size were most often engaged in fights. Mating behaviour seems not to be ruled out by a female mate choice (there is no parental care: parents die before eggs hatch). Sexual competition occurs between males only. Dominant male spends much time in mating attempts and in the defence of the spawning site. It has the highest mating success but spends much energy. Subordinates rarely manage to reach females when no food is available and when the dominant individual is vigilant, but they increase their mating attempts, behaving as “sneakers”, when the dominant is distracted by food.