Research ProjectEcology of Marine Parasites and Diseases

Diversity, Distribution, and Host Specificity of Marine Parasites and Disease

  • Kristy and Katrina collect oysters at Punta Chame, Panama.

    Dr. Katrina Lohan and Kristina Hill-Spanik collecting oysters off rocks at Punta Chame, Panama. Photo credit: Carmen Schlöder

  • Kristy, Greg, and Mark looking for oysters in Panama

    Kristina Hill-Spanik and Drs. Greg Ruiz and Mark Torchin collecting oysters from mangroves at Punta Caracol, Panama. Photo credit: Katrina Lohan

  • Ruth DiMaria sampling diseased portions of seagrass leaves from the Indian River Lagoon, Florida.

    Ruth DiMaria sampling diseased leaves from seagrasses collected from the Indian River Lagoon, Florida. Photo credit: Katrina Lohan

Project Goal

We are examining patterns of marine parasite diversity, the host and habitat specificity of different parasites, the ecology of multi-host systems, including potential environmental reservoirs, and the genomic and genetic population diversity of different species and strains of marine parasites.


We are examining patterns of parasite diversity across multiple geographic scales. The primary hosts we study, bivalves and seagrasses, are model organisms for this work. Both host groups include parasites with varying levels of host specificity, allowing us to examine the evolutionary, ecological, and genomic mechanisms that allow a parasite to infect many different host species.

Parasites are generally much smaller than their hosts, making them notoriously difficult to identify. Some of the larger metazoan parasites* can be viewed using a microscope. However, even most of these larger parasites require additional research tools for species-level identification. Thus, we primarily use DNA markers to identify parasites and examine their population genetic diversity* and structure. Some of the DNA tools we use include Sanger and high throughput sequencing* (454 and Illumina platforms), metabarcoding*, microsatellites*, and phylogenetics*.

Our work has examined the diversity of parasites in bivalves living along both coasts of Panama, leading to the discovery of an invasive oyster and many parasite species not previously known in these waters. This research is ongoing, as we continue to process bivalve samples that were collected over a latitudinal gradient to see how parasite diversity changes with latitude. We also examined the diversity of parasites throughout the environment in Panama, focusing on water and sediment samples collected around the Panama Canal, to see how much overlap exists across this corridor. Finally, we are examining the species and population genetic diversity of parasites associated with seagrasses in coastal waters, assessing the host specificity of these parasites in Florida and the genetic diversity of these parasites associated with the dominant seagrass in temperate waters, Zostera marina, across both US coasts.

As part of this research, we are also examining the ecology and epidemiology* of the infectious diseases caused by these parasites, which can range dramatically in severity across geographic locations and hosts.

Feature Stories

Molecular Data Leads to Surprising Discoveries about Oysters in Panamanian Waters. By Katrina Lohan and Monaca Noble. May 2015


KM Pagenkopp Lohan, RC Fleischer, ME Torchin, and GM Ruiz (2017) Protistan Biogeography: A Snapshot Across a Major Shipping Corridor Spanning Two Oceans. Protist, 168: 183-196.

KM Pagenkopp Lohan, KM Hill-Spanik, ME Torchin, M Aguirre-Macedo, RC Fleischer, & GM Ruiz (2016) Richness and Distribution of Tropical Oyster Parasites in Two Oceans. Parasitology, 143: 1119-1132.

KM Pagenkopp Lohan, RC Fleischer, KJ Carney, KK Holzer, & GM Ruiz (2016) Amplicon-based pyrosequencing reveals high diversity of protistan parasites iships’ ballast water: implications for biogeography and infectious diseases. Microbial Ecology, 71 (3): 530-542.

KM Pagenkopp Lohan, KM Hill-Spanik, ME Torchin, EE Strong, RC Fleischer, & GM Ruiz (2015) Molecular phylogenetics reveals first record and invasion of Saccostrea species in the Caribbean. Marine Biology, 162: 957–968.


Katrina Lohan

Term Definition
Metazoan parasites  Multicellular eukaryotic parasites   
Population genetic diversity  The total number of genetic characteristics in the genetic makeup of a species population.
High throughput sequencing  Faster and less expensive methods of sequencing and analyzing large genomes.
Metabarcoding A method of DNA barcoding that uses universal PCR primers to identify DNA from a mixture of organisms 
Microsatellites A microsatellite is a tract of repetitive DNA in which certain DNA motifs (ranging in length from 2–5 base pairs) are repeated, typically 5-50 times.
Phylogenetics Phylogenetics is the branch of life science concerned with the analysis of molecular sequencing data to study evolutionary relationships among groups of organisms.