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Genetic heterogeneity of betanodaviruses in juvenile production trials of Pacific bluefin tuna, Thunnus orientalis (Temminck & Schlegel)
Author(s) -
Sugaya T,
Mori K,
Nishioka T,
Masuma S,
Oka M,
Mushiake K,
Okinaka Y,
Nakai T
Publication year - 2009
Publication title -
journal of fish diseases
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 85
eISSN - 1365-2761
pISSN - 0140-7775
DOI - 10.1111/j.1365-2761.2009.01057.x
Subject(s) - biology , hatchery , thunnus , juvenile , tuna , fishery , haplotype , zoology , genetics , gene , genotype , fish <actinopterygii>
Pacific bluefin tuna, Thunnus orientalis (Temminck & Schlegel), is one of the most important commercially exploited fish species in the world, and juvenile production techniques have been developed for its culture and stock enhancement in Japan. However, recent juvenile production has often failed because of the occurrence of viral nervous necrosis caused by betanodaviruses. In this study, we examined the genetic variability of betanodaviruses detected in the diseased juveniles to understand the transmission of the disease in a tuna hatchery. A total of 94 nucleotide sequences of betanodavirus (partial sequence of the coat protein gene, RNA2) were obtained from fish samples by reverse‐transcriptase polymerase chain reaction amplification and 13 haplotypes were recognized among the sequences. The haplotype distributions in the viral populations from the diseased juveniles were related to the broodstocks from which the juveniles originated, suggesting that vertical transmission had occurred in the hatchery. The statistical parsimony network of viral haplotypes suggests that the nucleotide substitutions among the samples were accumulated in a recent population growth.