Protists Within Corals: The Hidden Diversity

Area of Science:

• Marine Biology
• Microbial Ecology
• Protistology

Background:

• Coral reefs host diverse microbial communities crucial for health and resilience.
• Previous research primarily focused on prokaryotes and Symbiodinium, neglecting other protists due to methodological challenges.
• Host DNA often masks eukaryotic diversity in coral metagenomic analyses.

Purpose of the Study:

• To develop and apply novel blocking primers for Scleractinia sequences to overcome methodological constraints.
• To investigate the diversity of protists in Pocillopora damicornis sensu lato from contrasting thermal regions.
• To identify previously overlooked protist taxa associated with coral holobionts.

Main Methods:

• Designed blocking primers targeting Scleractinia 18S rRNA gene variable regions (18SV1V2 and 18SV4).
• Applied these primers to environmental samples from Pocillopora damicornis colonies in Djibouti and New Caledonia.
• Utilized high-throughput sequencing to analyze eukaryotic microbial communities.

Main Results:

• Identified Symbiodinium clades A/C/D, Licnophora, and unidentified coccidia genera.
• Discovered that coccidian sequences form a monophyletic clade with protists from various other coral genera.
• Observed distinct geographic distributions for Licnophora, coccidians, and Symbiodinium clades C and A/D.

Conclusions:

• Developed effective blocking primers to reveal hidden protist diversity in corals.
• Highlighted the presence and potential ecological significance of Licnophora and coccidians in coral ecosystems.
• Demonstrated geographic structuring of protist communities within coral holobionts, mirroring Symbiodinium patterns.