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27 February 2007 |
Mussel of the Month
The June 2004 Mussel of the Month is Hyridella menziesi. Hyridella menziesi is one of the few species of freshwater mussels found in New Zealand.
[Since June 2004 when we selected this species as Mussel of the Month, the subgenus Echyridella was raised to a full genus. As the type of that genus, this species is now known as Echyridella menziesi. — DLG]
South Island, New Zealand.
One of the interesting biogeographic puzzles related to the freshwater mussels of the southern continents is, How did freshwater mussels get to New Zealand? Most authorities have regarded the three species found there to be related to (i.e., in the same genera) Australian species. But Australia is over 1000 km from New Zealand, across the Tasman Sea. How could such a barrier been breched by freshwater mussels? Before the acceptance of continent drift, the favored argument was that mussels were carried from Australia to New Zealand by birds or via their host fish... across a vast sea... and start a new population of mussels. That sounds kind of far-fetched, but without our current understanding of plate tectonics, it sounded more plausible than mussels being carried aboard floating continents.
But today we have a better explanation for the distribution of mussels (and many other animals and plants) that occur on both Australia and New Zealand. In the distant past, Australia and New Zealand were joined as part of an enormous super-continent called Gondwana. The mussels were spread widely on Gondwana, and when it rifted apart, the parts carried their mussels with them. Thus, the freshwater mussels didn't need to cross an ocean barrier — the barrier popped up in their midst!
Classification:
Phylum Mollusca
Class Bivalvia
Subclass Palaeoheterodonta
Order Unionoida
Superfamily Etherioidea Deshayes, 1830
Family Hyriidae Swainson, 1840
Subfamily Hyridellinae McMichael, 1956 (1934)
Genus Hyridella Swainson, 1840
Species Hyridella menziesi (Gray, 1843)
For more information on Hyridella menziesi and the distribution of freshwater mussels on New Zealand, check out the following:
- McMichael, D.F. 1958. The nature and origin of the New Zealand freshwater mussel fauna. Transactions of the Royal Society of New Zealand 85: 427-432.
- McMichael, D.F. & I.D. Hiscock. 1958. A monograph of freshwater mussels (Mollusca: Pelecypoda) of the Australian region. Australian Journal of Marine and Freshwater Research 9: 372-508.
- Graf, D.L. & D. Ó Foighil. 2000. Molecular phylogenetic analysis of 28S rDNA supports a Gondwanan origin for Australasian Hyriidae (Mollusca: Bivalvia/ Unionoida). Vie Milieu 50: 245-254.
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