Home | Archived February 20, 2019 | (i) |
![]() |
![]() |
||||||||||||||
|
|||||||||||||||
|
Where Disease May Mean Good HealthThe Role of Parasites in Natural Ecosystems
Paradoxically, healthier, less degraded ecosystems tend to have more parasites with complex life cycles (that is, they pass through multiple hosts to complete their life cycle) than do altered ecosystems, because these parasites depend on functioning ecosystems. The types of change most likely to affect parasite communities are alterations in host communities resulting from climate change and environmental degradation. Environmental degradation can include introduced species, habitat fragmentation, pollution, and overharvesting. In turn, because parasites, particularly those transmitted through predation (when an organism eats an infected host), have the potential to organize their host communities, changes to parasite communities can profoundly alter natural systems. Recently, the University of California, Santa Barbara (UCSB), was awarded $2.2 million over the next 5 years by the National Science Foundation to study the role of parasites in natural ecosystems. The money will largely fund student research under the direction of three coprincipal investigators, all specialists in parasite ecology: Armand Kuris, a professor of zoology at UCSB; Andrew P. Dobson, a professor of zoology at Princeton; and myself, a marine biologist with the USGS' Western Ecological Research Center and an adjunct professor of biology at UCSB. Because salt marshes have proved to be a model system for understanding the ecology of parasites with complex life cycles, we will study parasites of the abundant horn snail, Cerithidea californica, found in salt marshes. The snail acts as a hub in the life cycle of 17 parasitic trematode (worm) species. A trematode castrates the snail it infects and each day produces scores of free-swimming stages of offspring that leave infected snails to search out a second, intermediate host, such as a fish, clam, crab, or snail. In the second host, the trematode can greatly alter host behavior to increase the chance of transmission to a final host. Wading birds, shorebirds, and seabirds prey selectively on second, intermediate hosts and become parasitized by adult worms. In the final host, the small worms live in the gastrointestinal tract, mate, and produce eggs that pass into the marsh with the host's feces, where they encounter snails and complete their life cycle. Each of the 17 trematode species that use C. californica has a different life cycle.
The new research ties in with current research by the USGS and UCSB funded by the U.S. Environmental Protection Agency to develop monitoring tools using parasites to evaluate the health of salt marshes. Mathematical models, molecular tools, laboratory experiments, field experiments, and large-scale comparative field studies will all be used in the investigation. In addition to work at two UCSB natural reserves, Carpinteria Salt Marsh and Coal Oil Point, our research will take us to estuaries in California's Morro Bay and Mugu Lagoon, along the Pacific Coast of Baja California, Mexico, and to Japan.
|
![]() |
![]()
in this issue:
Marine Environmental Careers Symposium Congressional Briefing on Wetlands TalksDOE and College of William and Mary
![]() |
Home | Archived February 20, 2019 |