Fig 1.
Life cycle of Cassiopea xamachana.
C. xamachana can reproduce sexually and asexually, with strobilation induced by Symbiodinium Colonization. Polyps can regenerate after strobilation. The red box highlights the life stage examined in this study. Figure was modified from Ohdera 2018.
Fig 2.
Experimental design to assess the impact of thermal stress on C. xamachana development.
Three groups were used: 1) Control – polyps and symbionts both cultured and maintained at 26°C. 2) Heat – polyps infected with symbionts cultured at 34°C and maintained at 34°C; 3) Recovery – polyps infected with symbionts cultured at 34°C but maintained at 26°C; and Two separate temperature and light-controlled incubators (Percival Scientific, Perry, USA) were used. With equal light intensity and duration, one incubator was set to 26°C and the other to 34°C, used for the corresponding groups throughout the experiment.
Fig 3.
Percentage of polyps undergoing strobilation over time in each treatment group.
Control group completed strobilation by day 19, while strobilation in the recovery group was delayed until day 36. No strobilation was observed in the heat group. N = 50.
Fig 4.
Effects of heat stress on S. microadriaticum.
(a) Symbiont cell density did not differ significantly across treatments. (b) Chlorophyll content was significantly reduced under thermal stress. (c) Symbionts exposed to heat (right) appeared visibly lighter in color compared to the darker brown control cultures (left).
Fig 5.
Effects of heat stress on C. xamachana developmental morphology and symbiont density.
a) Most ephyrae in the recovery group displayed an inverted bell shape as shown in the photo. b) Inverted bell shape ephyrae had significantly higher symbiont densities than normal-shaped ephyrae within the recovery group and than in the control group. c) Visual comparison shows reduced symbiont density in ephyrae from the recovery group with a normal morphology compared to the control.
Fig 6.
Asexual reproduction via budding over time in each treatment group.
Polyps infected with heat-stressed symbionts (heat and recovery groups) produced more planuloid buds compared to the control.