Fig. 3

Temperature effects on enrichment and (sub)cellular localization of isotopically labeled carbon and nitrogen in heat-stressed medusae. A ¹³C enrichment from ¹³C-bicarbonate (H¹³CO₃⁻) assimilated into algal symbiont cells and B translocated to their host amoebocyte cells. C Ratio of ¹³C enrichment between host amoebocytes and their algal symbionts. D ¹⁵N-enrichment induced by the assimilation of ¹⁵N-ammonium (NH₄⁺) into algal symbiont cells and E into host amoebocytes. Sampling points correspond to days 5 (SP1) and 11 (SP2) of the experiment. Individual groups were compared using Tukey’s HSD (indicated above the boxplots). Asterisks indicate significant differences between treatments (*p < 0.050, **p < 0.010, ***p < 0.001). Asterisks in brackets show significant differences when only SP2 is considered. F–K Correlative SEM (F, I) and NanoSIMS (G, H, J, K) isotope ratio images of medusa sections under control conditions (F–H) and heat stress (I–K) at SP2. The corresponding ¹²C₂⁻ and ¹⁴N¹²C⁻ images are available in Figure S5. The SEM images are artificially colored, with oral epidermis (oral epi) in beige, mesoglea (m) in blue, amoebocyte (am) in yellow, amoebocytes nuclei in purple, symbionts (s) in green, and lipid droplets (ld). The color scales of the NanoSIMS images are logarithmic