A scuticociliate causes mass mortality of Diadema antillarum in the Caribbean Sea
A newly identified scuticociliate pathogen caused extensive mortality of the sea urchin Diadema antillarum across the Caribbean, disrupting herbivory and accelerating reef decline. Using molecular, histological, and experimental evidence, researchers confirmed the Philaster‑like ciliate as the causative agent, raising urgent questions for regional conservation.
Subject Tags
- Reefs
Abstract
Echinoderm mass mortality events shape marine ecosystems by altering the dynamics among major benthic groups. The sea urchin Diadema antillarum, virtually extirpated in the Caribbean in the early 1980s by an unknown cause, recently experienced another mass mortality beginning in January 2022. We investigated the cause of this mass mortality event through combined molecular biological and veterinary pathologic approaches comparing grossly normal and abnormal animals collected from 23 sites, representing locations that were either affected or unaffected at the time of sampling. Here, we report that a scuticociliate most similar to Philaster apodigitiformis was consistently associated with abnormal urchins at affected sites but was absent from unaffected sites. Experimentally challenging naïve urchins with a Philaster culture isolated from an abnormal, field-collected specimen resulted in gross signs consistent with those of the mortality event. The same ciliate was recovered from treated specimens postmortem, thus fulfilling Koch’s postulates for this microorganism. We term this condition D. antillarum scuticociliatosis.
Citation
Hewson, I., Ritchie, I. T., Evans, J. S., Altera, A., Behringer, D., Bowman, E., ... & Breitbart, M. (2023). A scuticociliate causes mass mortality of Diadema antillarum in the Caribbean Sea. Science Advances, 9(16), eadg3200.
TNC Authors
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Aldo Croquer
The Nature Conservancy
Email: aldo.croquer@TNC.ORG