Fig. 6: Conceptual diagram summarizing differences in DOM uptake strategies and symbiont contribution to heterotrophic diet in the HMA and LMA sponge. | The ISME Journal

Fig. 6: Conceptual diagram summarizing differences in DOM uptake strategies and symbiont contribution to heterotrophic diet in the HMA and LMA sponge.

From: Heterotrophy in the earliest gut: a single-cell view of heterotrophic carbon and nitrogen assimilation in sponge-microbe symbioses

Fig. 6

DOM is the primary carbon source for both the LMA and HMA sponge, accounting for ~90% of the in situ heterotrophic diet in both species. Both host sponge cells and bacterial symbionts are active in DOM assimilation, with the relative contributions differing based on the abundance of microbial symbionts. Higher symbiont biomass in the HMA sponge compared with that of the LMA sponge (25% vs. <0.5% of the total cellular biomass) leads to symbionts accounting for a larger contribution of the assimilated DOM in the HMA sponge than in LMA sponge (~65% vs. <5%). POM uptake accounts for about 10% of the diet in both sponges and is assimilated exclusively by the host sponge cells. Accordingly, the quantitative contribution of symbionts to the overall heterotrophic diet (DOC + POC) is ~60 and <1% for the HMA and the LMA sponge species, respectively.

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