English: Supplementary Video: shows spawning behaviour of the cichlid fish Lamprologus callipterus, filmed inside a 1000 liter tank at Ethologische Station Hasli (Department of Behavioural Ecology, IEE, University of Bern, Switzerland). The experimental setting of our publication was in smaller 100 liter tanks, with one male, five females and five plexi-glass prepared empty shells (shells of the snail Neothauma tanganicense), of which two shells were accessible to the females and could be videotaped.

The first part shows a male at the shell entrance, where a female is currently egglaying deep inside the shell (not visible). The male shows the typical spawning behaviours: (1) male puts his mouth inside the shell (“head-in”); (2) male puts his mouth inside the shell and opens/closes his mouth in rapid sequence, which produces the water current into the shell (“mouthing”); (3) male positions his genital papilla over the shell entrance and releases sperm (“spawning”).

The last part shows a shell prepared with plexi-glass. In the experimental setting of our publication two of these shells where placed close together, always without the blue covering. In this example video, the blue covering was removed when the female had probably almost finished spawning and thereby both the male and the female were disturbed. Nevertheless, the female shows twice “shifting” behaviour, which in our undisturbed experimental setting usually occurred after male mouthing. Clearly visible are the yellow eggs attached to the plexi-glass. Eggs are usually laid singly with a 2 minute interval. The egg can be seen protruding from the female papilla when she moves deep into the shell, after which she carefully attaches the egg to the surface of the plexi-glass or the shell (unfortunately not filmed).