title: Evolutionary divergence of the swim bladder nematode Anguillicola crassus after colonization of a novel host, Anguilla anguilla.
abstract: BACKGROUND
  Anguillicola crassus, a swim bladder nematode naturally parasitizing the Japanese eel, was introduced about 30 years ago from East Asia into Europe where it colonized almost all populations of the European eel. We conducted a common garden experiment under a reciprocal transfer design infecting both European and Japanese eels with populations of A. crassus from Germany, Poland and Taiwan. We tested, whether differences in infectivity, developmental dynamics and reproductive output between the European and Asian parasite populations occur while harboured in the specimens of native and colonized eel host, and if these differences are genetically based or are plastic responses to the new environment.
  
  
  RESULTS
  Under common garden conditions an evolutionary change in the both European parasite populations of A. crassus compared with their Taiwanese conspecifics was observed for infectivity and developmental dynamics, but not for reproductive output. When infecting the European eel, current European populations of the parasite were less infective and developed faster than their Taiwanese conspecifics. In the reciprocally infected Japanese eel the genetically induced differences between the parasite strains were less apparent than in the European eel but higher infectivity, faster development and higher larval mortality of the European parasite populations could be inferred.
  
  
  CONCLUSIONS
  The differences in infectivity and developmental dynamics between European and Taiwanese populations of A. crassus found in our study suggest rapid genetic divergence of this parasite after a successful host switch in Europe.
authors.affiliation: Department of Ecology and Parasitology, Zoological Institute, Karlsruhe Institute of Technology, Kornblumenstrasse 13, Karlsruhe, Germany. weclawski.urszula@googlemail.com
authors.forename: Urszula
authors.initials: U
authors.lastname: Weclawski
authors.forename: Emanuel G
authors.initials: EG
authors.lastname: Heitlinger
authors.forename: Tobias
authors.initials: T
authors.lastname: Baust
authors.forename: Bernhard
authors.initials: B
authors.lastname: Klar
authors.forename: Trevor
authors.initials: T
authors.lastname: Petney
authors.forename: Yu San
authors.initials: YS
authors.lastname: Han
authors.forename: Horst
authors.initials: H
authors.lastname: Taraschewski
mesh_terms: D000400:Air Sacs / Q000469:parasitology*; D000811:Anguilla; D000818:Animals; D005075:Biological Evolution; D017176:Dracunculoidea / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology; D005393:Fish Diseases / Q000469:parasitology*; D056084:Genetic Fitness; D058507:Host Specificity; D012098:Reproduction