Inter-Research > DAO > v150 > p61-67  
Diseases of Aquatic Organisms

via Mailchimp

DAO 150:61-67 (2022)  -  DOI:

A phylogeny based on cytochrome-c oxidase gene sequences identifies sympatric Ichthyophonus genotypes in the NE Pacific Ocean

Jacob L. Gregg1,*, Paul K. Hershberger1, Abigail S. Neat1,4, Hiruni T. Jayasekera1, Jayde A. Ferguson2, Rachel L. Powers3, Maureen K. Purcell3

1U.S. Geological Survey - Western Fisheries Research Center, Marrowstone Marine Field Station, 616 Marrowstone Point Road, Nordland, WA 98358, USA
2ADF&G Fish Pathology Section, Division of Commercial Fisheries, 333 Raspberry Road, Anchorage, AK 99518, USA
3U.S. Geological Survey - Western Fisheries Research Center, 6505 N.E. 65th Street, Seattle, WA 98115, USA
4Present address: Department of Botany and Plant Pathology, Oregon State University, 4575 SW Research Way, Corvallis, OR 97333, USA
*Corresponding author:

ABSTRACT: In recent decades, evidence has accumulated to suggest that the widespread and highly variable parasite Ichthyophonus hoferi is actually a species complex. Highly plastic morphology and a general lack of defining structures has contributed to the likely underestimate of biodiversity within this group. Molecular methods are a logical next step in the description of these parasites, but markers used to date have been too conserved to resolve species boundaries. Here we use mitochondrial encoded cytochrome-c oxidase (MTCO1) gene sequences and phylogenic analysis to compare Ichthyophonus spp. isolates from several marine and anadromous fish hosts. The resulting phylogeny displays lineage separation among isolates and possible host/niche segregation not previously described. The parasite type that infects Pacific herring Clupea pallasii, Atlantic herring C. harengus, Atlantic salmon Salmo salar, and Pacific staghorn sculpin Oligocottus maculosus (Clade A) is different from that which infects Chinook salmon Oncorhynchus tshawytscha, walleye pollock Gadus chalcogrammus, Greenland halibut Reinhardtius hippoglossoides, and Pacific halibut Hippoglossus stenolepsis (Clade B). MTCO1 sequences confirmed the presence of a more divergent Ichthyophonus sp. isolated from American shad Alosa sapidissima in rivers of eastern North America (Clade C), while American shad introduced to the Pacific Ocean are infected with the same parasite that infects Pacific herring (Clade A). Currently there are no consensus criteria for delimiting species within Ichthyophonidae, but MTCO1 sequences hold promise as a potential species identifying marker and useful epizootiological tool.

KEY WORDS: Ichthyophonus · Cytochrome-c oxidase · COX1 · Pacific herring · Chinook salmon · Pacific halibut · American shad

Full text in pdf format
Cite this article as: Gregg JL, Hershberger PK, Neat AS, Jayasekera HT, Ferguson JA, Powers RL, Purcell MK (2022) A phylogeny based on cytochrome-c oxidase gene sequences identifies sympatric Ichthyophonus genotypes in the NE Pacific Ocean. Dis Aquat Org 150:61-67.

Export citation
Share:    Facebook - - linkedIn

 Previous article Next article