Female sticklebacks transfer information via eggs: effects of maternal experience with predators on offspring

Abstract

There is growing evidence that maternal experience influences offspring via non-genetic mechanisms. When female three-spined sticklebacks (Gasterosteus aculeatus) were exposed to the threat of predation, they produced larger eggs with higher cortisol content, which consumed more oxygen shortly after fertilization compared with a control group. As juveniles, the offspring of predator-exposed mothers exhibited tighter shoaling behaviour, an antipredator defence. We did not detect an effect of maternal exposure to predation risk on the somatic growth of fry. Altogether, we found that exposure to an ecologically relevant stressor during egg formation had several long-lasting consequences for offspring, some of which might be mediated by exposure to maternally derived cortisol. These results support the hypothesis that female sticklebacks might influence the development, growth and behaviour of their offspring via eggs to match their future environment.

Figure 1.

(a) Egg size (mg) from mothers exposed to a predator (experimental, n = 30) was significantly greater than egg size from clutches of mothers not exposed to a predator (control, n = 15). (b) Egg cortisol concentration (ng ml⁻¹) from mothers exposed to a predator (experimental, n = 30) was significantly higher than eggs from mothers not exposed to a predator stressor (control, n = 13). Bars show means ± s.e. Statistical tests were carried out on ln-transformed cortisol values.

Figure 2.

Oxygen consumption (mg O₂ kg⁻¹ h⁻¹) per egg increased over time regardless of treatment. Eggs from mothers exposed to a stressor (experimental: n = 6 clutches, open circles, dashed line) consumed more oxygen than eggs from mothers not exposed to a predator stressor (control: n = 6 clutches, closed circles, solid line) soon after fertilization, but the difference attenuated close to hatching.

Figure 3.

‘Before’ a mild disturbance, the nearest-neighbour distance was significantly shorter between fry from mothers exposed to a predator than from mothers not exposed to a predator. There was no difference in nearest-neighbour distance between control and experimental fry ‘immediately following’ or ‘after’ a mild disturbance. Each bar represents the mean ± s.e. of n = 9 experimental and n = 6 control tanks across all six measurements (filled bar, offspring of control mothers; open bar, offspring of predator-exposed mothers). Statistical tests were carried out on square-root transformed values.