Latest Research in Parasitology
The parasitology group at the GCRL has been directed by Dr. Robin Overstreet since 1969. Dr. Overstreet is the most prominent organismal animal parasitologist in North America and is one of the most respected parasitologists in the world today. His career is featured in GCRL's “Pioneers in Marine and Fisheries Research” series.
Dr. Overstreet leads an active group of scientists and four Ph.D. students. Most of their work involves parasitic flatworms or flukes, known to scientists as the Trematodes, a class of parasitic worms in the phylum Platyhelminthes. The group studies evolutionary relationships among the worms, describes new species, investigates life-histories of parasites, and assesses the effects of parasites on their hosts. The research involves parasites from all over North America and the world.
Because of the close relationship between parasites and their hosts, the study of parasites typically involves study of host animals as well, as shown in these descriptions of parasitology research at GCRL.
Dr. Robin Overstreet searching for parasites on a great blue heron.
Mullet Parasites Near and Far
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 Pulis with a netted alligator to be checked for parasites
Eric field sampling in La Plata, Argentina
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.
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 left shows the newly discovered worm.
Haploporids, Roundworms and Other Trematodes
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.
|Michael examining parasite specimens||Parasitic nematodes and a small fish in the stomach of a cormorant.|
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.
On a Freshwater Quest for 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. 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 in Blow Holes
Juan Carillo 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.
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
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.
GCRL Parasitology Group
The current research highlighted here is largely supported by the U.S. Department of the Interior's Fish and Wildlife Service.