Jasnos, O. | Search bioRxiv

bioRxiv2025

Algae-specific Immune Modulation Influences Responses to Heat and Pathogen Challenge in a Symbiotic Coral

The role of symbiotic algae in coral life history and host health is well documented, but the immune and physiological trade-offs of hosting these symbionts remain less explored. While association with the algal symbionts of the genus Durusdinium is known to confer thermotolerance, it has also been linked to coral tissue loss under stress. We investigated whether algal type influences host immunity and stress responses in the tropical coral Pocillopora acuta. Durusdinium-hosting (D-hosting) P. acuta have distinct transcriptomic profiles, higher immune-related gene expression, and elevated baseline levels of immunity transcription factor NF-{kappa}B as compared to corals hosting Cladocopium (C-hosting). Under heat challenge, D-hosting P. acuta exhibited tissue loss, oxidative stress, immune and microbial dysregulation, whereas C-hosting P. acuta were more susceptible to bleaching, metabolic dysregulation, and decline in nitrogen-fixing and antioxidant-producing bacteria. Finally, infection with the the bacterium Vibrio coralliilyticus caused high tissue loss in D-hosting corals, but not in C-hosting corals. Our results suggest a mechanism for how Durusdinium association enhances thermotolerance yet predisposes corals to tissue damage under stress, suggesting immune trade-offs that can compromise host survival under multiple stressors.

genomics↗

bioRxiv2024

Antibiotic treatment and microbiome depletion slow cnidarian regeneration

Cnidarian microbiomes play an essential role in physiology and development, but how these communities influence tissue regeneration is poorly understood. Here, we examined the effects of antibiotic exposure on regeneration and microbial communities in two cnidarian models, the sea anemones Nematostella vectensis (non-symbiotic, hereafter, Nematostella) and Exaiptasia pallida (symbiotic, hereafter, Aiptasia). Bisected animals were incubated in either sterile or antibiotic-containing artificial seawater for seven days and regeneration was monitored daily. After seven days, tentacle number and length were measured, and microbial communities were profiled using metabarcoding of the V4 region of the 16S rRNA. Microbiome disruption was observed under antibiotic treatment in both species, resulting in decreased microbial load and shifts in relative abundances of some microbial taxa. However, Nematostella exhibited a greater reduction in microbial diversity and community shifts under antibiotic exposure, whereas Aiptasia showed only moderate changes in diversity. In both species, microbiome disruption was associated with slower regeneration rates and reduced tentacle number and length, suggesting a functional role for the microbiome in cnidarian regeneration. Our findings suggest that host-microbiome interactions in both symbiotic and aposymbiotic anemones are important for the maintenance of regenerative processes. These findings provide insight into how cnidarians and their microbiomes respond to environmental stressors, with implications for predicting cnidarian resilience in the context of emerging threats to the marine environment.

developmental biology↗