Vergleichende Untersuchungen über die angeborene Grössenunterscheidung beiTilapia nilotica undHemihaplochromis multicolor (Pisces; Cichlidae)

Female mouth-brooding Cichlid fishes pick up the young fry again when disturbed. The young, for their part, collect about the head of the mother fish and, contacting it, try to enter the mouth cavity. This ‘contact behaviour’ is based upon an inborn readiness to react on the visual stimulus offered by the mother. Mother fishes inTilapia nilotica are much larger than those ofHemihaplochromis multicolor. By comparative experimental studies with models of various size (black balls of different diameters) it is shown that the young of the 2 species strictly prefer different sizes of the model, corresponding with the different sizes of the parent fishes.