Induced Hatching to Avoid Infectious Egg Disease in Whitefish

Abstract

Reacting to a threat before physical contact, e.g., induced by air- or water-borne substances [1], appears to be an elegant way of defense. The reaction may be behavioral [2–5], developmental, morphological, or physiological [5–7], and it can involve a shift in niche or life history [8, 9]. Hatching from eggs is a shift in niche and in life history. From niche shift and life history models [10–14], one would predict that the timing of hatching is, to some degree, phenotypically plastic, i.e., early or delayed hatching is likely to be inducible [15–19]. Temporary increased larval mortality (e.g., increased predation on larvae) would favor delayed hatching, while relatively high egg mortality would favor early hatching. Here, I show experimentally that eggs of the whitefish (Coregonus sp.) hatch earlier in the presence of a virulent egg parasite and that this early hatching is induced by water-borne cues emitted from infected eggs.