Genetic relationships among members of the Ichthyobodo necator complex: implications for the management of aquaculture stocks

Ichthyobodo necator (costia) is a common and important flagellate parasite that infests the skin and gills of many freshwater and marine fish. Costia infestations are often fatal and cause significant aquaculture losses worldwide. Recently it has been demonstrated that Ichthyobodo is a multispecies...

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Bibliographic Details
Published in:Journal of fish diseases 2005-02, Vol.28 (2), p.111-118
Main Authors: Callahan, H A, Litaker, R W, Noga, E J
Format: Article
Language:English
Subjects:
Animals
aquaculture
Aquaculture - methods
Base Sequence
Bayes Theorem
Brackish
Cloning, Molecular
costia
ectoparasite
fish
Fishes - parasitology
Freshwater
Geography
internal transcribed spacers
Kinetoplastida - genetics
Likelihood Functions
Marine
Models, Genetic
Molecular Sequence Data
Phylogeny
RNA, Ribosomal - genetics
Sequence Alignment
Sequence Analysis, DNA
small subunit ribosomal RNA
Species Specificity
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Summary:Ichthyobodo necator (costia) is a common and important flagellate parasite that infests the skin and gills of many freshwater and marine fish. Costia infestations are often fatal and cause significant aquaculture losses worldwide. Recently it has been demonstrated that Ichthyobodo is a multispecies complex with differing host preferences. Knowing if those species have broad or narrow host specificity has important implications for the management of costia. To address the question of host specificity, genomic DNA was isolated from Ichthyobodo trophonts collected from rainbow trout, Oncorhynchus mykiss, koi, Cyprinus carpio, mirror carp, C. carpio, goldfish, Carassius auratus, channel catfish, Ictalurus punctatus, swordtail, Xiphophorus helleri, and Japanese flounder, Paralichthys olivaceus. The small subunit ribosomal RNA (SSU rRNA) gene from each isolate was analysed with previously published Ichthyobodo sequences using Bayesian phylogenetic methods. The internal transcribed spacers (ITS) from six isolates were also PCR‐amplified, cloned and sequenced. Both the SSU rRNA phylogenetic analysis and the ITS rRNA sequence data support grouping the 22 Ichthyobodo isolates examined into a complex of nine different species. Many of these species were frequently isolated from multiple hosts, indicating that exchange of infested fish from one region to another has a high potential for spreading the disease. In one instance, the same species was obtained from marine and freshwater fish, further suggesting that certain Ichthyobodo species may not be limited by salinity.
ISSN:0140-7775
1365-2761
DOI:10.1111/j.1365-2761.2004.00603.x