[quote=”Stefanie” post=2759] I know that such behaviour (a male killing the offspring of rivals) occurs in many different animal families – is it known from paros?[/quote]
No, as far as I know it is not. But I think the interpretation has to be somewhat slightly different:
The male probably did not kill the offspring of a rival but either has taken the two larvae with him to his cave or simply cleaned an extraneous cave within his own territory; whatever “clean” means in this context. Speaking of a “rival” means an antagonistic behaviour against a second male. But this is a proof only that a male in a territory owns a cave and this cave was not his. It’s more directed against the cave (= the center of a territory) than against another fish (“rival”).
This was not aggression towards a rival but affirmation of the center of the territory. Although – I admit – it’s a slight distinction in the interpretation only, a difference in the perspective of description. I don’t think that the brain of such fish is sufficiently developed to be compared with that of a mammal or even a bird, animals who have developed forms of action against the belongings of their rivals. As far as I know fish only adopt offspring of other pairs but not kill them.
But I don’t know it for sure; it’s a hypothesis. I should be interested how things go on in your tank.