Effects of temperature and size class on the gut digesta microbiota of the sea urchin .

Background: Understanding the dynamics of the gut microbiota in sea urchins is crucial for comprehending the ecological balance in marine ecosystems. The gut microbiota plays a vital role in nutrient metabolism, immune system modulation, and pathogen protection. The microbial composition and dynamics of naturally occurring sea urchin have yet to be thoroughly investigated. We hypothesized the gut microbiota of in the Caribbean, varies across life stages and seasons.

Methods: Thirty-six naturally occurring large individuals and six small individuals (42 animals) were collected from shallow waters on the northeastern coast of Puerto Rico in February and August of 2019. The fecal pellet's microbiota was characterized by sequencing V4 region of the 16S rRNA gene.

Results: We found significant differences in the composition of fecal pellet microbiota between seasons and life stages. Phylum Bacteroidota had greater relative abundance in August, while Firmicutes was more dominant in February. and had greater relative abundance in August, while Hepatoplasma, and had greater relative abundance in February. Differences in the gut digest microbiota were not found between small and large urchins, but small urchins displayed a slightly higher diversity and dominance of Bacteroidota and Proteobacteria, while large urchins exhibited a greater relative abundance of Fusobacteria and Desulfobacterota. However, the genera and counts were significantly lower in small individuals.

Discussion: This is the first report for this species in the Caribbean region and adds to our comprehension of the microbiota of the white sea urchin across collection periods and size classes, highlighting the dynamic nature of the gut microbiota.