DAO 74:57-65 (2007)  -  doi:10.3354/dao074057

Phylogeny of Neoparamoeba strains isolated from marine fish and invertebrates as inferred from SSU rDNA sequences

Iva Dyková1,2,*, Barbara Nowak3, Hana Pecková1, Ivan Fiala1,2, Philip Crosbie3, Helena Dvoráková1

1Biology Centre of the Academy of Sciences of the Czech Republic, Institute of Parasitology, and 2Faculty of Biological Sciences, University of South Bohemia, Branisovská 31, 370 05 Ceské Budejovice, Czech Republic
3School of Aquaculture, Aquafin CRC, Tasmanian Aquaculture and Fisheries Institute, University of Tasmania, Launceston, Tasmania 7250, Australia

ABSTRACT: We characterised 9 strains selected from primary isolates referable to Paramoeba/Neoparamoeba spp. Based on ultrastructural study, 5 strains isolated from fish (amoebic gill disease [AGD]-affected Atlantic salmon and dead southern bluefin tuna), 1 strain from netting of a floating sea cage and 3 strains isolated from invertebrates (sea urchins and crab) were assigned to the genus Neoparamoeba Page, 1987. Phylogenetic analyses based on SSU rDNA sequences revealed affiliations of newly introduced and previously analysed Neoparamoeba strains. Three strains from the invertebrates and 2 out of 3 strains from gills of southern bluefin tunas were members of the N. branchiphila clade, while the remaining, fish-isolated strains, as well as the fish cage strain, clustered within the clade of N. pemaquidensis. These findings and previous reports point to the possibility that N. pemaquidensis and N. branchiphila can affect both fish and invertebrates. A new potential fish host, southern bluefin tuna, was included in the list of farmed fish endangered by N. branchiphila. The sequence of P. eilhardi (Culture Collection of Algae and Protozoa [CCAP] strain 1560/2) appeared in all analyses among sequences of strain representatives of Neoparamoeba species, in a position well supported by bootstrap value, Bremer index and Bayesian posterior probability. Our research shows that isolation of additional strains from invertebrates and further analyses of relations between molecular data and morphological characters of the genera Paramoeba and Neoparamoeba are required. This complexity needs to be considered when attempting to define molecular markers for identification of Paramoeba/Neoparamoeba species in tissues of fish and invertebrates.

KEY WORDS: Neoparamoeba strains · Paramoeba eilhardi · Phylogeny · Invertebrate infections

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