MEPS 461:165-174 (2012)  -  DOI: https://doi.org/10.3354/meps09814

ABSTRACT: Egg size is one of the most frequently used surrogate measures of maternal investment and is strongly related to fitness-determining traits, such as offspring size in many marine animals, but the relationship is not universal. Because the amount of yolk allocated to eggs is finite, not all fitness-determining traits can be simultaneously maximised, and trade-offs should be expected. The results of the present study show that egg size (quantified as cross-sectional area) poorly predicts the size of larval morphological traits (length, yolk sac area, oil globule area, myomere depth, and eye area) in the native Australian fish Galaxias maculatus. Egg size was correlated with yolk sac size and larval body depth, but it explained <13% of the total variation in these traits. Moreover, egg size did not predict the time it took for larvae to hatch, nor did it predict the duration from hatching to starvation. However, when egg size and yolk sac size (i.e. yolk remaining at hatching) were both included as predictors, the fits with larval traits improved greatly (r² = 0.02 to 0.46 for larval length, r² = 0.11 to 0.17 for myomere depth, and r² < 0.001 to 0.14 for eye area). These findings indicate that there is a trade-off between the quantity of yolk at hatching and the size of larval morphological traits in G. maculatus. The remaining unexplained variation may be a consequence of trade-offs with other unmeasured traits, such as metabolic rate, and the potential that egg size is not a good proxy for maternal investment.

KEY WORDS: Life history theory · Maternal effects · Offspring size · Phenotypic plasticity