title: Host-dependent morphology of Isthmiophora melis (Schrank, 1788) Luhe, 1909 (Digenea, Echinostomatinae)--morphological variation vs. molecular stability.
abstract: BACKGROUND
  Echinostomes are cosmopolitan digenean parasites which infect many different warm-blooded hosts. Their classification is extremely confused; the host spectrum is wide, and morphological similarities often result in misidentification. During our long-term studies on the helminth fauna of rodents and carnivores we have collected 27 collar-spined echinostomes which differ in morphology to an extent that suggests the presence of more than one species. Here, we describe this material, and the extent of host-related variation in this parasite.
  
  
  METHODS
  Specimens of Isthmiophora isolated from four host species (badger, American mink, hedgehog, striped field mouse) were subject to morphological and molecular examination; the data were statistically analysed.
  
  
  RESULTS
  Our results show that genetically all the Isthmiophora specimens obtained from all the examined hosts are conspecific and represent I. melis. On the other hand, the individuals isolated from Apodemus agrarius are morphologically distinct and, based on this criterion alone, should be described as a new species.
  
  
  CONCLUSIONS
  The morphological traits of Isthmiophora melis are much variable and host-dependent; without molecular analysis they would suggest a necessity to describe a new species or even genus. Such a high level of intraspecific variability may be affected by the host's longevity.
authors.affiliation: Department of Parasitology, Institute of Genetics and Microbiology, Wrocław University, Przybyszewskiego 63, 51-148, Wrocław, Poland. joanna.hildebrand@uwr.edu.pl.
authors.forename: Joanna
authors.initials: J
authors.lastname: Hildebrand
authors.affiliation: Department of Parasitology, Institute of Genetics and Microbiology, Wrocław University, Przybyszewskiego 63, 51-148, Wrocław, Poland. maja.adamczyk@uni.wroc.pl.
authors.forename: Maja
authors.initials: M
authors.lastname: Adamczyk
authors.affiliation: Institute of Parasitology, Polish Academy of Science, Twarda 51/55, 00-818, Warszawa, Poland. laskowz@twarda.pan.pl.
authors.forename: Zdzisław
authors.initials: Z
authors.lastname: Laskowski
authors.affiliation: Department of Systematic and Ecology of Invertebrates, Institute of Biology, Wrocław University of Environmental and Life Sciences, Kożuchowska 5b, 51-631, Wrocław, Poland. grzegorz.zalesny@up.wroc.pl.
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Zaleśny
mesh_terms: D000818:Animals; D001699:Biometry; D004450:Echinostomatidae / Q000033:anatomy & histology* / Q000145:classification / Q000235:genetics*; D007312:Eulipotyphla / Q000469:parasitology*; D005838:Genotype; D008853:Microscopy; D051189:Murinae / Q000469:parasitology*; D045969:Mustelidae / Q000469:parasitology*; D010641:Phenotype; D014201:Trematode Infections / Q000469:parasitology / Q000662:veterinary*