Serotonin (5-HT), a neurotransmitter and neurohormone, has been detected in marine sponges (Phylum Porifera) using chromatography, histochemistry, and immunohistochemistry. However, it is not found in sponge transcriptomes. The current debate concerns which cells in the holobiont produce serotonin: the sponge itself or its associated microorganisms.
We are therefore interested in assessing the extent of serotonin presence in the Phylum Porifera and whether its presence and concentration relate to microbial abundance in sponges. We used cell dissociation protocols and enzyme-linked immunosorbent assay on fresh samples, cryopreserved cells, and fractions enriched with microorganisms and sponge cells. Additionally, we performed alignments and phylogenetic analyses on the predicted Amphimedon queenslandica 5-HT7R gene and examined confocal z-stack projections of labeled 5-HT larvae. Serotonin levels differ among species within the phylum Porifera, and phylogenetic results support the absence of other Porifera and bilaterian orthologs to the A. queenslandica 5-HT7R gene. However, the assembly of this sponge genome has been called into question, adding to the controversy.
Recently, 33 new sponge genomes have been sequenced, and we are now investigating whether TPH, one of the enzymes involved in serotonin synthesis, is present in these sponge proteomes or instead occurs in their associated microbiomes.
