The effect of temperature and food supply on the asexual reproduction of moon jelly ( Aurelia sp.1) polyps

Jellyfish outbreaks negatively affect humans who live near the coast,and cause harm to fishery resources and marine ecosystems. Jellyfish appearing around the East China Sea maintain or expand their populations by both sexual and asexual reproduction. In the jellyfish's life cycle,asexual reproduction of polyps is a key stage in determining the number of medusa in the following year; therefore,we focused on this life stage in this study. Previous studies have examined the total number of polyps produced by asexual reproduction under varying environmental conditions,but few studies have examined in detail on the number of new polyps formed via each method of asexual reproduction. Our research aimed to describe the methods of asexual polyp reproduction under different temperatures and food availability levels. In our experiment,following other similar studies we used four temperatures( 9,12,15,and 18[degrees]C) and three food amounts( 5,20,and 40 newly-hatched Artemia nauplius per polyp) in a full-factorial experimental design to observe their effects on the asexual reproduction ability and method of moon jellyfish polyp formation. We systematically recorded the number of new polyps,the method of asexual reproduction,strobilation time,rate of strobilation,and the number of ephyrae released. Stolon formation was the most frequent method of asexual polyp reproduction,followed by direct budding. Longitudinal fission and podocyst methods were rarely observed. Food availability had a significant impact on all of the new moon jellyfish polyps,but the influence of temperature was not significant. Reproduction ability was positively correlated with food availability.Both food and temperature treatments influenced strobilation,and temperature had a greater impact on strobilation than food availability. Temperature significantly increased the incidence of strobilation compared with that of other methods of reproduction,but the effect of food supply was not significant. The rate of strobilation was highest in the moderate temperature group( 12[degrees]C),the 15[degrees]C and 18[degrees]C groups had lower strobilation rates,and the 9[degrees]C group had the lowest strobilation rate. Ephyrae were released at the three higher temperatures( 12[degrees]C,15[degrees]C,and 18[degrees]C). Temperature was the most important factor influencing the progress of the ephyrae released by strobilation,but food supply also had an important influence. The number of ephyrae released per