title: Assessing the effects of trematode infection on invasive green crabs in eastern north america.
abstract: A common signature of marine invasions worldwide is a significant loss of parasites (= parasite escape) in non-native host populations, which may confer a release from some of the harmful effects of parasitism (e.g., castration, energy extraction, immune activation, behavioral manipulation) and possibly enhance the success of non-indigenous species. In eastern North America, the notorious invader Carcinus maenas (European green crab) has escaped more than two-thirds its native parasite load. However, one of its parasites, a trematode (Microphallus similis), can be highly prevalent in the non-native region; yet little is known about its potential impacts. We employed a series of laboratory experiments to determine whether and how M. similis infection intensity influences C. maenas, focusing on physiological assays of body mass index, energy storage, and immune activation, as well as behavioral analyses of foraging, shelter utilization, and conspicuousness. We found little evidence for enduring physiological or behavioral impacts four weeks after experimental infection, with the exception of mussel handling time which positively correlated with cyst intensity. However, we did find evidence for a short-term effect of M. similis infection during early stages of infection (soon after cercarial penetration) via a significant drop in circulating immune cells, and a significant increase in the crabs' righting response time. Considering M. similis is the only common parasite infecting C. maenas in eastern North America, our results for minimal lasting effects of the trematode on the crab's physiology and behavior may help explain the crab's continued prominence as a strong predator and competitor in the region.
authors.affiliation: Long Island University, 720 Northern Blvd., Brookville, NY, 11548, United States of America; Smithsonian Environmental Research Center, 647 Contees Wharf Rd., Edgewater, MD, 21037, United States of America.
authors.forename: April M H
authors.initials: AM
authors.lastname: Blakeslee
authors.affiliation: University of Georgia, 140 E. Green St., Athens, GA, 30602, United States of America.
authors.forename: Carolyn L
authors.initials: CL
authors.lastname: Keogh
authors.affiliation: Smithsonian Environmental Research Center, 647 Contees Wharf Rd., Edgewater, MD, 21037, United States of America; Marine Resources Research Institute, South Carolina Department of Natural Resources, 217 Fort Johnson Road, Charleston, SC, 29422, United States of America.
authors.forename: Amy E
authors.initials: AE
authors.lastname: Fowler
authors.affiliation: University of South Carolina, Department of Biological Sciences and Marine Science Program, 715 Sumter Street, Columbia, SC, 29208, United States of America.
authors.forename: Blaine D
authors.initials: BD
authors.lastname: Griffen
mesh_terms: D000818:Animals; D049872:Bivalvia / Q000502:physiology; D003386:Brachyura / Q000502:physiology*; D005260:Female; D008297:Male; D009656:North America; D011235:Predatory Behavior / Q000502:physiology*; D013559:Symbiosis / Q000502:physiology; D014200:Trematoda / Q000502:physiology*; D014201:Trematode Infections / Q000503:physiopathology*