Ichthyobodo necator (Kinetoplastida) — a complex of sibling species

[摘要] ABSTRACT: Ichthyobodo necator is a parasitic flagellate that attacks fishes, causing disease problems in freshwater worldwide. Findings of similar flagellates in strictly marine fishes have indicated that ichthyobodiosis may be caused by more than1 flagellate species. We obtained partial small subunit rDNA (ssu rDNA) sequences of 14 Ichthyobodo isolates originating from fishes in Norway, Japan, Singapore, South Africa and Brazil, and identified 8 strains or species, including 2 speciesinfecting cultured salmon in Norway. An Ichthyobodo species isolated from the skin of Atlantic salmon parr in freshwater is suggested to represent I. necator sensu stricto, while another species, showing particular affinity for the gills,infects salmon in both fresh- and seawater. Atlantic cod is infected with a marine Ichthyobodo species unrelated to those infecting salmonids; 2 cyprinids originating from different parts of the world had related Ichthyobodo strains/species,and 2 isolates from unrelated North and South American fishes were also closely related. The phylogenetic relationships of the Ichthyobodo isolates is described, and the implications of the molecular findings on past and future morphologicalstudies of Ichthyobodo spp. are discussed.

[学科分类] 生物科学（综合）

[关键词] Ichthyobodo necator;ssu rDNA 18s;Kinetoplastida;Species complex;Parasitic flagellates