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Molecular evidence for cosmopolitan distribution of platyhelminth parasites of tunas (Thunnus spp.)


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Aiken, H, Bott, NJ, Mladineo, I, Montero, FE, Nowak, BF and Hayward, CJ 2007 , 'Molecular evidence for cosmopolitan distribution of platyhelminth parasites of tunas (Thunnus spp.)' , Fish and Fisheries, vol. 8, no. 3 , pp. 167-180 , doi: 10.1111/j.1467-2679.2007.00248.x.

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Global distribution of platyhelminth parasites and their host specificities are not well
known. Our hypothesis was that platyhelminth parasites of large pelagic fishes are
common around the world. We analysed molecular variation in three different taxa
of platyhelminth parasites infecting four species of tunas: yellowfin tuna (Thunnus
albacares, Scombridae) from Western Australia, southern bluefin tuna (Thunnus
maccoyii, Scombridae) from South Australia, Pacific bluefin tuna (Thunnus orientalis,
Scombridae) from Pacific Mexico and northern bluefin tuna (T. thynnus, Scombridae)
from two localities in the Mediterranean (Spain and Croatia). Comparisons of ITS2
and partial 28S rDNA demonstrated two congeneric species of blood flukes (Digenea:
Sanguinicolidae) from multiple hosts and localities: Cardicola forsteri from southern
bluefin and northern bluefin tunas, and Cardicola sp. from Pacific bluefin and
northern bluefin tunas; and a gill fluke, Hexostoma thynni (Polyopisthocotylea:
Hexostomatidae), from yellowfin, southern bluefin and northern bluefin tunas.
Partial 28S rDNA indicates that a second type of fluke on the gills, Capsala sp.
(Monopisthocotylea: Capsalidae), occurs on both southern bluefin and Pacific bluefin
tunas. This appears to be the first report of conspecific platyhelminth parasites of
teleosts with a wide-ranging geographical distribution that has been confirmed
through molecular approaches. Given the brevity of the free-living larval stage of
both taxa of flukes on the gills (H. thynni and Capsala sp.), we conclude that the only
feasible hypothesis for the cosmopolitan distribution of these flatworms is migrations
of host tunas. Host migration also seems likely to be responsible for the widespread
occurrence of the two species of blood flukes (Cardicola spp.), although it is also
possible that these were translocated recently by the spread of infected intermediate

Item Type: Article
Authors/Creators:Aiken, H and Bott, NJ and Mladineo, I and Montero, FE and Nowak, BF and Hayward, CJ
Keywords: 28S rDNA, biogeography, ITS2 rDNA, Platyhelminthes, Thunnus
Journal or Publication Title: Fish and Fisheries
Publisher: Blackwell Publishing Ltd
ISSN: 1467-2960
DOI / ID Number: 10.1111/j.1467-2679.2007.00248.x
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