Morphological Variability Among Broods of First-Stage Blue Crab (Callinectes sapidus) Zoeae.

External morphology has been shown to influence predation and locomotion of decapod larvae and is, therefore, directly related to their ability to survive and disperse. The first goal of this study was to characterize first-stage blue crab zoeal morphology and its variability across larval broods to test whether inter-brood differences in morphology exist. The second was to identify possible correlations between maternal characteristics and zoeal morphology. The offspring of 21 individuals were hatched in the laboratory, photographed, and measured. Zoeae exhibited substantial variability, with all metrics showing significant inter-brood differences. The greatest variability was seen in the zoeal abdomen, rostrum, and dorsal spine length. A principal component analysis showed no distinct clustering of broods, with variation generally driven by larger zoeae. Using observed morphology, models of drag induced by swimming and sinking also showed significant inter-brood differences, with a maximum twofold difference across broods. In contrast to trends in other decapod taxa, maternal characteristics (female carapace width and mass and egg sponge volume and mass) are not significant predictors of zoeal morphology. These results suggest that brood effects are present across a wide range of morphological characteristics and that future experiments involving Callinectes sapidus morphology or its functionality should explicitly account for inter-brood variation. Additionally, inter-brood morphological differences may result in differential predation mortality and locomotory abilities among broods.