Antipredator defences of young are independently determined by genetic inheritance, maternal effects and own early experience in mouthbrooding cichlids

Abstract

Summary Predation is a prime force of natural selection. Vulnerability to predation is typically highest early in life, hence effective antipredator defences should work already shortly after birth. Such early defences may be innate, transmitted through non‐genetic parental effects or acquired by own early experience. To understand potential joint effects of these sources of antipredator defences on phenotypic expression, they should be manipulated within the same experiment. We investigated innate, parental and individual experience effects within a single experiment. Females of the African cichlid Simochromis pleurospilus were exposed to the offspring predator Ctenochromis horei or a benign species until spawning. Eggs and larvae were hand‐reared, and larvae were then exposed to odour cues signalling the presence or absence of predators in a split‐brood design. Shortly after independence of maternal care, S. pleurospilus undergo a habitat shift from a deeper, adult habitat to a shallow juvenile habitat, a phase where young are thought to be particularly exposed to predation risk. Thus, maternal effects induced by offspring predators present in the adult habitat should take effect mainly shortly after independence, whereas own experience and innate antipredator responses should shape behaviour and life history of S. pleurospilus during the later juvenile period. We found that the manipulated environmental components independently affected different offspring traits. (i) Offspring of predator‐exposed mothers grew faster during the first month of life and were thus larger at termination of maternal care, when the young migrate from the adult to the juvenile habitat. (ii) The offspring's own experience shortly after hatching exerted lasting effects on predator avoidance behaviour. (iii) Finally, our results suggest that S. pleurospilus possess a genetically inherited ability to distinguish dangerous from benign species. In S. pleurospilus, maternal effects were limited to a short but critical time window, when young undergo a niche shift. Instead, own environmental sampling of predation risk combined with an innate predisposition to correctly identify predators appears to prepare the young best for the environment, in which they grow up as juveniles.