What are Parasitologists Doing in the United States Geological Survey? Author(s): Rebecca A. Cole Source: Comparative Parasitology, 69(2):132-134. 2002. Published By: The Helminthological Society of Washington DOI: http://dx.doi.org/10.1654/1525-2647(2002)069[0132:WAPDIT]2.0.CO;2 URL: http://www.bioone.org/doi/full/10.1654/1525-2647%282002%29069%5B0132%3AWAPDIT%5D2.0.CO %3B2
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bComp. Parasitol. 69(2), 2002, pp. 132–134
President’s Symposium
What are Parasitologists Doing in the United States Geological Survey? REBECCA A. COLE United States Department of the Interior, United States Geological Survey, National Wildlife Health Center, 6006 Schroeder Road, Madison, Wisconsin 53711, U.S.A. (e-mail: Rebecca㛮
[email protected])
tion. Today I will share a few of the current projects that demonstrate the role parasitology and parasitologists are playing in the USGS and its science program. Parasitology research emanating from the National Wildlife Health Center (NWHC) in Madison, Wisconsin, begins in the diagnostic section. The diagnostic parasitology laboratory serves as a window on the parasite fauna in wildlife submitted from wildlife mortality events across the nation. The diagnostic area monitors normal and abnormal situations, identifying trends in animal populations that have succumbed or may succumb to parasitic disease. The trematode Leyogonimus polyoon has killed over 24,000 birds to date in northeastern Wisconsin and was first diagnosed in American coots submitted to the diagnostic parasitology laboratory at the NWHC in 1996 from a mortality event in Shawano, Wisconsin. Until 1996, L. polyoon had never been reported in the New World. Coots and moorhens in Europe and Russia have been listed as hosts of L. polyoon, but large-scale mortality has never been attributed to this parasite in the Old World. In fact, the life cycle of L. polyoon was unknown. Mortality in the American coot and the potential spread of L. polyoon to other New World waterfowl along the migratory routes of the coot spurred research to document the parasite’s life cycle. The life cycle has been described, and survey work during die-offs in years following the initial mortality event suggest that the American coot is the only viable New World definitive host. For the last 25 yr the NWHC has focused primarily on avian disease. However, in the last 8 yr the NWHC, and particularly the parasitology laboratory, has expanded its research to include cold-blooded species such as fish and frogs, especially in systems altered by significant human impact such as the Colorado River. The Colorado River and its biota in the Grand
The United States Geological Survey (USGS) was formed in 1879 as the nation’s primary natural science and information agency. The mission of the agency is to provide scientific information to ‘‘describe and understand the Earth; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect our quality of life.’’ Prior to 1996, the USGS comprised 3 divisions or disciplines: geology, mapping, and water. Historically, the agency was most noted for cartographic products that were used widely by both government and private sector. With the inclusion of the National Biological Service into the USGS in 1996 as the Biological Resource Discipline (BRD), a living resources dimension was added to the earth sciences character of the USGS. With the addition of BRD, the bureau is able now to contribute both the physical and biological sciences to address the nation’s resource management problems. The USGS has a strategic direction to combine and enhance its diverse programs, capabilities, and talents and increase customer involvement to strengthen its scientific leadership and contribution to the resolution of complex issues. The ability to strengthen the scientific leadership is accomplished through partnerships that gather, synthesize, and utilize scientific information. Partners include, but are not limited to, other Federal and State agencies, Universities, and in some cases not-for-profit agencies. Within this atmosphere of partnerships, parasitology as a discipline has a diverse presence: 3 centers in the USGS, the National Wildlife Health Center in Madison, Wisconsin; the Western Ecological Research Center in Santa Barbara, California; and the Pacific Island Ecosystems Research Center in Hilo, Hawaii, employ parasitologists studying parasites as disease agents, ecosystem indicators, or integral parts of ecosystem func132
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Canyon changed dramatically following the closure of Glen Canyon Dam in 1963 (National Academy of Sciences, 1991). Today the river shelters approximately 24 fish species, of which 20 are nonnative. Only 4 of the 8 documented native species remain: Catostomus discobolus, Catostomus latipinnis, Gila cypha, and Rhinichthys osculus; and 1 of these (G. cypha) is federally listed as an endangered species. The predam Colorado River was an ephemeral, warm water river where flow fluctuated greatly by season. After the closure of Glen Canyon Dam, the river turned into a perennially cold, clear water river. Native fish in the Grand Canyon stretches of the Colorado River now reproduce only in tributaries (Valdez and Ryel, 1995; Arizona Game and Fish Department, 1996). The Little Colorado River (LCR) is the largest tributary in the Grand Canyon and is the primary spawning area for all native fish species (Arizona Game and Fish Department, 1996). During routine health checks on fish from the LCR in 1996, we recovered the Asian tapeworm, Bothriocephalus aceilognathi. Concerns grew over the presence of this parasite in the Grand Canyon fish because of impending plans to alter water flow from Glen Canyon Dam. Altered water flow will warm the Colorado River, creating a river habitat comparable to pre-dam river and stabilizing native fish populations. These conditions might also allow B. aceilognathi to spread throughout the Grand Canyon river system. In the NWHC parasitology lab, Dr. Anindo Choudhury and graduate student Scott Hansen are documenting the presence of B. aceilognathi in the fish of the LCR across seasons and experimentally examining the impact of tapeworm infection on growth of G. cypha. Dr. Tim Hoffnagle, a fisheries biologist of the Oregon Department of Fish and Wildlife, is a coinvestigating partner. To date, we have examined 1,435 fish and documented the tapeworm year-round in several native fish species. We know which copepods are present in the LCR and tributaries and have started the experimental phase of infections in the laboratory. Remotely deployed temperature probes in tributaries have supplied data for seasonal temperature variation that will be correlated with zooplankton abundance. Data from this research will help managers anticipate both the effects of Glen Canyon Dam management on the spread of this parasite into the Col-
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orado River and the parasite’s impact on growth of native fishes in the Grand Canyon. These data will also be consulted to develop delisting criteria to remove G. cypha from the endangered species list. The NWHC is also engaged in substantial work on amphibians and their parasites. Mounting evidence of worldwide amphibian population decline has spurred increased amphibian disease monitoring by NWHC. For example, developmental malformations in anurans, particularly Rana pipiens, have led to research focused on the etiological role of parasites in metamorphic limb malformations in frogs. Anna Schotthoefer from the University of Illinois, Urbana, and Anson Koehler are working in my laboratory to determine which developmental stages of R. pipiens are susceptible to limb development disruption by Ribeiroia sp. and how various doses of cercariae impact malformation. We are combining this laboratory study with landscape data collected in an EPAfunded study that examined amphibian health at selected sites in Minnesota as indicators of ecosystem integrity. Part of the health assessment of amphibians for this 3-yr project included an examination of the parasite community. The EPA-funded study was conducted with researchers at the Natural Resources Research Institute at the University of Minnesota in Duluth and the University of Illinois, Urbana. Examination of the databases will allow us to identify what landscape features are most predictive for the presence of Ribeiroia sp. and possible malformations. Another study focusing on parasites as indicators is being conducted by Dr. Kevin Lafferty of the Western Ecological Research Center. He is working in West Coast salt marshes to develop indicators of ecosystem health based on parasites. The first strategy focuses on gill ciliates in fishes. Ciliate populations are kept in check by the fish immune system, but in polluted or otherwise stressful environments, ciliate intensity increases. The second approach is more counterintuitive and involves a suite of digenean trematode species that parasitize horn snails. After cercariae leave the snail, they search out a clam, crab, or fish, encyst, and, if eaten by a bird, complete the life cycle. Changes in the environment may affect larval digeneans at many points in their complex life cycles. Bird abundance and diversity is likely to be the most im-
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portant factor structuring the trematode community, but the presence of second intermediate hosts such as fishes, clams, and crabs must also play a role. Thus, a diverse and abundant trematode community should be reflective of a diverse and rich community of free-living species in the marsh. Preliminary work indicates that degraded conditions have fewer trematodes and that trematode prevalence increases following the restoration of degraded areas. Such predictions can be made broadly for many wetland systems around the world. There are several practical advantages to using trematodes as indicators. First, snails are easy to collect, and it is relatively easy to dissect them and identify trematodes species. Therefore, this assessment can be much less expensive than biotic surveys of birds, fishes, and invertebrates. Secondly, unlike the ‘‘snapshot’’ view generally available from biotic surveys, the community of trematodes in a snail reflects the accumulated history of exposure to parasites. Thus, a sample represents a view of the salt marsh community integrated over a relatively long period, often stretching over many years. Although this approach shows substantial promise as a wetland indicator, it has not been fully applied, and it has been appropriately tested in fully documented sites. To better understand what the trematode community indicates about a site, it is important to study trematode communities among and within salt marshes that are already understood. This is being achieved by working alongside a large group of wetland scientists in a new EPAfunded West Coast wetlands center. These scientists are jointly assessing wetland function using a variety of established and novel techniques. A third researcher in the USGS, Dr. Carter Atkinson at the Pacific Island Ecosystems Research Center (PIERC), is examining the bio-
complexity of introduced avian diseases in Hawaiian forest birds. Humans have been instrumental in the introduction of mosquitoes, avian malaria, and avian pox, which have had profound effects on the Hawaiian avian fauna. Dr. Atkin’s research has documented the devastating impacts of these diseases on bird survival. The impact has been so severe that in many locations native Hawaiian forest birds have been eliminated or forced to high elevation forests with lower mosquito numbers. With National Science Foundation Biocomplexity funding, the PIERC and statisticians at the NWHC have initiated collaborative research involving scientists from the USGS, the Smithsonian, and several universities. A 5-yr project integrating across biological scales from the gene to the landscape will be conducted to understand system dynamics; persistence of disease in forest bird populations; how land use and habitat changes affect the stability of the systems; and how conservation strategies might alter the decline and extinction of the endemic avian fauna of Hawaii. These projects demonstrate the role of parasitological research at all levels of USGS-BRD, highlighting the integral role of parasites within our ecosystems as a tool for understanding and managing our natural resources. LITERATURE CITED Arizona Game and Fish Department. 1996. The ecology of Grand Canyon backwaters. Final Report. Submitted to Glen Canyon Environmental Studies, U.S. Bureau of Reclamation, Flagstaff, Arizona. Arizona Game and Fish Department, Phoenix, Arizona. National Academy of Sciences. 1991. Colorado River ecology and dam management. National Academy of Sciences Press, Washington, D.C. Valdez, R. A., and R. J. Ryel. 1995. Life history and ecology the humpback chub (Gila cypha) in the Colorado River, Grand Canyon, Arizona. Final report to U.S. Bureau of Reclamation, Salt Lake City, Utah. Contract No. 0-CS-40-09110. Bio/ West, Inc., Logan, Utah.
