Project Title

Origin and mechanism of transmission of the ciliate that killed millions of sea urchins.

Mentor’s Name

Haris Lessios, Lessiosh@si.edu

Location of Internship

Galeta, Naos, and Bocas del Toro

Project Summary

The sea urchin Diadema antillarum is a keystone species in coral reefs of the Caribbean because its herbivory limits the growth of algae, which outcompete coral. This sea urchin suffered a mass die-off that eliminated 97% of individuals in 1983-4. In 2022 populations in the West Indies, the Atlantic coast of Mexico and Florida were affected again. The cause of the mortality is the scuticociliate Philaster apodigitiformis. The origin of this pathogenic ciliate is still unknown. The main objective of this project is to determine whether P. apodigitiformis is part of the microbiome of D. antillarum or of other organisms common in the Caribbean that are in contact with the urchin. A second objective is to document the presence of the ciliate exists in organisms of the eastern Pacific.  Molecular methods based on (1) specific probes that detect ciliates of the family Philasteridae through quantitative PCR (qPCR), and (2) DNA sequencing of the 18S gene are being used to test for the presence of P. apodigitiformis in coral reef organisms and in Caribbean sea water. 

Mentorship Goals

Introduce interns in the techniques of sampling of DNA samples from corals, fishes, crustaceans, echinoderms and sea water.  Train them in preparing these samples for qPCR, PCR and sequencing.  Explain how ecological connections of reef biota can be mediated through microorganisms.

Desired Background 

Interns should have interest in ecology and evolution of marine organisms and in learning molecular techniques.  Most of the sampling is done by snorkeling, so interns should be competent swimmers and feel comfortable in working in the water.

Intern’s Role

Interns will be involved in all stages of the project from field to laboratory work.  They will not be expected to analyze the data, but they will be shown how the analyses are done and how conclusions are reached.

Suggested Background Reading

Hewson I. et al. 2023. A scuticociliate causes mass mortality of Diadema antillarum in the Caribbean Sea. Science Advances 9, eadg3200 (2023).  doi: 10.1126/sciadv.adg3200.

H. A. Lessios.  2016. The great Diadema antillarum die-off: 30 years later.  Annual Review of Marine Science 8:267-283 doi:10.1146/annurev-marine-122414-033857

H.A. Lessios. 1988.  Mass mortality of Diadema antillarum in the Caribbean: What have we learned?  Annual Reviews of Ecology and Systematics, 19:371-393. doi.org/10.1146/annurev.es.19.110188.002103