Parasitology Research at GCRL

Mullet Parasites Near and Far

Eric Pulis with a netted alligator to be checked for parasites
Eric Pulis with a netted alligator to be checked for parasites.

Eric Pulis, Dr. Overstreet’s most senior Ph. D. student, came to GCRL from the University of North Dakota. He is investigating the evolutionary relationship of a family of trematodes, the Haploporidae, that parasitizes primarily mullets around the world. The project involves comparing sequences of DNA from various species of worms and estimating their relationships using phylogenetic trees.

Eric has searched for mullet parasites in the U.S., China, Australia, and Central and South America and has discovered dozens of new species. He is re-organizing the taxonomic classification of the Haploporids.

Eric Pulis field sampling in La Plata, ArgentinaEric Pulis field sampling in La Plata, Argentina.

In a project close to home, Eric recently found and named a new genus and species of trematode. The worm parasitizes the scrawled cowfish which inhabits the Gulf of Mexico. The scanning electron micrograph on the right below shows the newly discovered worm.
Dr. Maxwell Barson, on board R/V Tommy Munro
Scanning electron micrograph of a new genus and species of trematode which parasitizes the scrawled cowfish of the Gulf of Mexico. The worm was discovered and named by Eric Pulis.

Haploporids, Roundworms, and Other Trematodes

Michael Andres examining parasite specimens
Michael Andres examining parasite specimens.
Michael Andres has conducted Ph.D. research in the lab for the past several years. Mike came to GCRL from Texas A&M University. Mike is studying the relationships of different groups of worms using DNA sequencing. His main project is an investigation of the interrelationships of the European haploporids.
Parasitic nematodes and a small fish in the stomach of a cormorant.
Parasitic nematodes and a small fish in the stomach of a cormorant.

Michael is also elucidating the life cycles of common marine roundworms from the Gulf of Mexico These nematodes live as adults in the stomachs of marine mammals, marine fish, or marine birds, depending on their genus. Their larval stages develop in marine creatures like shrimp, squids, and small fish, but the larvae are too underdeveloped to identify without the use of DNA sequences. Michael matches larval stages and adult stages to get a better picture of the complex marine food webs of the Gulf of Mexico.

Michael's favorite project involves describing new marine species in the trematode family Opecoelidae. Members of this prominent group have a complex life cycle with early stages parasitizing snails on the sea floor. Maturing stages parasitize arthropods like the common penaeid shrimps. Adults live in the intestines of many of the marine reef fishes common to the Gulf and Caribbean Sea, including the snappers, grunts, groupers, and all our inshore drums.

A Quest for Freshwater Parasitic Worms

Thomas (T.J.) Fayton is conducting his Ph.D. research under the joint tutelage of Dr. Overstreet and Dr. Richard Heard, the invertebrate zoologist at GCRL. T.J. is a graduate of Vassar College in New York. He once visited GCRL on a road trip and liked it so much he stayed to study parasites.

T.J. Fayton on a collecting trip
T.J. Fayton on a collecting trip on a Florida river.

T.J. is most interested in trematode life cycles and the behavior of their free-living larval stages that act as transmission stages from the first mollusc host to the second host. T.J. is fond of field work and his search for snails and worms takes him all over the continent. He is often away for weeks, rambling around North America collecting worms.

T.J. concentrates on the life cycles of freshwater opecoelids and has uncovered 13 undescribed species and many of their cryptic life cycle stages from salmonid fishes in the Pacific Northwest and California, and from various minnows and sunfishes from Kentucky, North Carolina, New York, New England, Pennsylvania, Virginia, and from the clear springs on the panhandle of Florida. These Florida springs are especially interesting from a parasitological standpoint because the water chemistry is dominated by ancient coral deposits, providing a unique habitat for a different mollusc fauna. The different molluscs have led to coevolutionary relationships with parasites resulting in a highly endemic assemblage of trematodes in aquatic habitats of the Florida panhandle east of the Mobile River Drainage.

T.J. recently published his first scientific paper in the Journal of Comparative Parasitology.

Fayton, T. J., and D. C. Kritsky (2013) Acolpenteron willfordensis n. sp. (Monogenoidea: Dactylogyridae) parasitic in the kidney and ureters of the spotted sucker Minytrema melanops (Rafinesque) (Cypriniformes: Catostomidae) from Econfina Creek, Florida. Comparative Parasitology 80(1):1-8

Parasites of Dolphins

Juan Carillo in the parasitology lab
Juan Carrillo in the parasitology lab.

Juan Carrillo is the newest Ph.D. student. He graduated from the Universidad de Murcia in Spain. Juan studies parasites from bottlenose dolphins, specifically ciliates that live in the blow hole, and platyhelminths and nematodes that live in the digestive tract. He collects and identifies eggs from feces. Unlike most parasitologists who work on dolphins, Juan specializes on the study of live parasites. Juan recently collected parasites from live dolphins at the Dolphin Research Center in Marathon, Florida, where he obtained ciliates by swabbing the blow holes and collecting feces.

Juan is investigating the normal parasite diversity and abundance on healthy dolphins to determine whether stranded dolphins exhibit elevated or normal levels of parasitism. It has never been possible to identify worms to the species level with great confidence solely by microscopic examination of their eggs. Juan plans to incorporate molecular tools by extracting and amplifying DNA sequenced from eggs to match with adult forms that are easily identifiable.

Steve Curran working with student in the lab
Steve Curran working with student Jessica Parker Brown in the lab.

Postdoctoral Fellows

Dr. Steve Curran, shown here mentoring Jessica Parker Brown, is a post-doctoral fellow responsible for several research activities. These include monographing chalcinotrematine haploporid trematodes using morphological taxonomic techniques, examining evolutionary relationships of haploporids using comparison of ribosomal DNA sequence fragments, and collecting and examining trematode parasites. Dr. Curran also trains graduate students, undergraduates and interns in collection of invertebrates, vertebrates, parasites, and taxonomy. Dr. Curran received his B.S. and M.S. from the University of Connecticut.  He graduated from The University of Southern Mississippi in 2006 with a Ph.D. in Coastal Sciences.



Citizen Scientist Contributions

Parasitology volunteer Dr. Janet Wright prepares to examine a nutria speciman for parasites.
Parasitology volunteer Dr. Janet Wright prepares to examine a nutria speciman for parasites.

Two energetic citizen scientists assist Dr. Overstreet and the Parasitology Group. Dr. Janet Wright, a resident of Ocean Springs and retired professor of Biology at Dickinson College in Carlisle, Pennsylvania, has worked in Dr. Overstreet’s lab for four years. Janet is an avid naturalist especially interested in mammal ecology. She spends her free time searching for scat in hopes of learning about the habits of local wildlife.

Janet's current work involves developing a multiplex PCR analysis to cost-effectively distinguish among five species of nematodes belonging in the genus Anasakis from the Gulf of Mexico. Species of Anasakis use fish as intermediate hosts and parasitize marine mammals as adults. These worms are potentially harmful to humans if the larval stages are inadvertently consumed while eating raw or undercooked fish.

Dennis (Denny) Hugg's keen interest in parasites began when he was a graduate student at Tulane University in the 1960s. Denny served as the teaching assistant for Franklin Sogandares, a prominent parasitologist who studied marine parasites. One of Denny’s undergraduate students was Dr. Armand Kuris, now professor of Parasitology at the University of California, Santa Barbara, and current president of the American Society for Parasitologists.

After Tulane, Denny served in the military for 32, followed by twelve years as a contract engineer to the Federal Aviation Administration. In 2009, he began volunteer service to the GCRL Parasitology section as a field assistant. He and other researchers are establishing the genetic DNA links between immature strigeid trematodes carried by water snakes, with adults experimentally grown during a 1963 experiment with a laboratory (clean) opossum.

Denny is collecting additional new material in his travels around the country, including parasites from snakes and turtles, to supplement older material dating back to 1961. The combined collections will be studied to better understand the relationships between parasite specimens previously judged to be conspecific based on morphology and optical microscopy techniques less accurate than the DNA analyses now employed at GCRL.

Bottlenose Dolphin Surveillance Team

The Parasitology Group is working jointly with the GCRL Microbiology Group on a CIAP-funded project to study influences on dolphin health, including parasites and viruses. Eric Pulis, Mike Andres, and Juan Carrillo are working with Robin Overstreet, one of the two co-PIs, to better understand the parasites and possible stresses caused by those parasites in dolphins. Their research will involve diagnostic aspects of parasites from necropsies, assessments of non-invasive indicators of dolphin health, parasite indicators of marine mammal origin (inshore/offshore pods) and migration, and public health aspects of known and potential zoonotic agents.

A more detailed description of the project is available online.

Reference: U.S. Department of Interior, US Fish and Wildlife Service/Mississippi Department of Marine Resources/Coastal Impact Assistance Program, Mississippi Department of Marine Resources. MS. R. 798. A bottlenose dolphin surveillance team for Mississippi Sound. Principal Investigator Darrell Jay Grimes; Co-Principal Investigator Robin M. Overstreet. 1 September 2010 - 31 December 2014.

Research Sponsors

Research conducted by the GCRL Parasitology Group has been sponsored by these and other groups.

National Science FoundationNational Oceanic and Atmospheric AdministrationU.S. Fish and Wildlife ServiceU.S. Department of Commerce Mississippi Department of Marine Resources