MEPS 656:35-50 (2020)  -  DOI: https://doi.org/10.3354/meps13517

ABSTRACT: Climate change events and anthropogenic activities (e.g. translocation of non-indigenous species) have been proposed to account for the rise of jellyfish blooms in coastal environments. Bloom-forming scyphozoan jellyfish of the genus Aurelia have successfully invaded new habitats and have caused damaging blooms. In attempting to understand the underlying reasons for their success, researchers have investigated immediate effects of changing environmental conditions (e.g. temperature) on scyphistomae of single/unknown generations, with a particular focus on asexual reproduction. However, it remains unclear how scyphistomae respond to changing conditions over longer time-scales or across generations, and how those responses influence bloom occurrence. Here, we examined the role of transgenerational acclimation in asexual reproduction of A. aurita scyphistomae in a 72 d orthogonal experiment, combining 3 parental with 3 offspring temperatures of 8, 12 and 16°C. The null hypothesis was that the thermal history of the parental (F₀) generation will not affect asexual reproduction in the offspring (F₁) generation. Our results indicated that, provided with a transgenerational temperature change, parent scyphistomae do modify the reproductive output and timing of offspring. Scyphistomae from ‘cold’ (8°C) parents displayed the greatest reproductive output (2.86 buds per scyphistoma) and earliest budding commencement (23.86 d) at warm temperature (16°C). Scyphistomae from ‘warm’ (16°C) parents displayed the greatest reproductive potential (2.63 buds) at medium temperature (12°C). Cold temperature (8°C) caused considerable inhibition of asexual reproduction in offspring scyphistomae, independent of the parental thermal history. Transgenerational acclimation may benefit potentially invasive jellyfish species facing climate-related and/or human-induced changes in the global marine environment, by facilitating asexual reproduction and subsequent bloom events.

KEY WORDS: Transgenerational acclimation · Phenotypic plasticity · Jellyfish bloom · Invasive species · Temperature · Aurelia aurita