The effect of temperature and food supply on the growth and ontogeny of Aurelia sp. 1 ephyrae

Abstract

Blooms of the scyphozoan jellyfish Aurelia spp. are directly affected by the number, survival, and ontogenetic process of the ephyra stage. To determine the combined effect of temperature and food conditions on the production of ephyrae, the rising- and decreasing-temperature experiment was designed to simulate the warming from spring to summer and the cooling from fall to winter, respectively. Results showed that both temperature and prey concentrations significantly affected the ephyra production. Aurelia sp. 1 strobilation occurred from 8 to 17°C, while 13°C was the optimal temperature for ephyra production. At 8, 10, and 17°C, when the parental polyps had abundant food, the released ephyrae had a larger bell diameter and a better nutritional foundation. Abundant food conditions in the field would therefore elevate ephyrae survival rate, accelerate individual development, and thus ensure the population size of medusae. Our results indicate that a longer spring and a relatively higher zooplankton biomass may increase blooms of Aurelia sp. 1. However, the limited food conditions present in autumn and winter most likely mean that the Aurelia sp. 1 ephyrae released during these seasons are not the main source of the following year’s medusa population.