Direct and Indirect Induction of a Compensatory Phenotype that Alleviates the Costs of an Inducible Defense
In this schema, “Predation risk” is the starting point and “Enlargement of the external gills” is the end point. Dotted arrows originate at possible signals, solid arrows show adaptive causal connections, and the hollow arrow points to an unavoidable cost. Thus, hypoxia is an unavoidable cost of the adaptive behavioural response “Decreased surfacing”. Enlargement of the external gills can be reached by two pathways, a multi-step pathway via the antipredator behaviour (decreased surfacing) and the consequent hypoxia, and a direct pathway via predator-produced cues.