MEPS 582:79-92 (2017)  -  DOI: https://doi.org/10.3354/meps12314

ABSTRACT: A key step toward better knowledge of the causes and mechanisms of mass occurrences (blooms) in scyphozoan jellyfish is to assess the extent of environmentally induced effects on the phenotype of different phases in their complex life cycle. Laboratory experiments were carried out to quantify the extent of environmentally induced changes in Aurelia sp.9 polyp morphology, and subsequent effects on asexual propagation and ephyra morphology, in response to temperature and food quantity. Size and shape of polyps was highly plastic to environmental variation, and environmentally induced morphology had a significant effect on asexual fecundity and propagation strategy. Polyp size positively correlated with the number of buds, new polyps, and ephyrae produced per polyp, but negatively correlated with investment per bud. Environmentally induced polyp morphology had a significant effect on the morphology of ephyra at release. These findings suggest that asexual fecundity in Aurelia sp.9 polyps is likely ultimately limited by body size, which can be environmentally mediated. This work also shows, for the first time, that polyp and ephyra traits are linked. Environmentally induced variation in polyp morphology can be carried into the next life-cycle phase and affect the morphology of ephyrae at release. We conclude that environmentally induced effects on polyp morphology can potentially control the number of new polyps produced, as well as the number of medusae released into the water column. Hence, in scyphozoan jellyfish, metamorphosis is not necessarily a new beginning, and environmental conditions experienced by the polyp can have a significant effect on traits of subsequent phases.

KEY WORDS: Jellyfish · Blooms · Phenotypic plasticity · Budding · Strobilation · Environmental variation · Life history · Complex life cycle