Behaviorally Induced Maternal Stress in a Fish Influences Progeny Quality by a Hormonal Mechanism

The survival and quality of progeny can be strongly influenced by nongenetic effects derived from the physiological condition of the mother during gametogenesis. The influence of maternal condition on the size and quality of larvae at dispersal was examined for the tropical damselfish, Pomacentrus amboinensis, through a series of field studies during 1994. In this species, males guard a demersal nest of eggs contributed to by nearby females. The largest and most dominant female stays near the nest and contributes most to the egg clutches, limiting egg contributions from subordinate females. Maternal effects dramatically influenced the size of larval progeny at hatching, four days after laying. Much of the variability in progeny size was explained by levels of the stress-associated steroid hormone, cortisol, in the female. A field experiment manipulating maternal levels of cortisol found that cortisol levels strongly influenced the morphology and yolk size of larval progeny at hatching. Variation in the density of egg predators and competitors together explained 38% of the observed variance in maternal cortisol levels. These competitors and predatory fish appear to elevate maternal cortisol levels and consequently influence larval morphology through a stress-related response. This study suggests that the behavioral interaction regime of a fish population can determine larval quality and potentially govern a female’s contribution to the next generation.