A new freshwater species of the genus Dolops (Crustacea : Branchiura) parasitic on a galaxiid fish of Tasmania - with comments on disjunct distribution patterns in the southern hemisphere

Abstract

A new species of Dolops is described from Lake Surprise, Tasmania, where it has been found on a galaxiid fish. Hitherto the genus has been known only from freshwater in S. America and Africa. Taxonomic errors involving an alleged Asiatic member of the genus are rectified and recent gross mistreatment of the classification of the Branchiura is discussed. The genus Dolops is re-defined. Evidence bearing on the history and dispersal of Dolops and other organisms is reviewed, particular attention being directed to the freshwater bivalve molluscs formerly assigned to the Mutelidae. While the African and S. American muteloids belong to closely related families of the Muteloidea, the Australasian forms formerly thought of as representatives of this group have no place in this superfamily. They, and certain S. American bivalves, however, show unambiguous trans-Antarctic affinities as they belong to a common family, the Hyriidae. Taking into account recent work, both geological and biological, and in spite of powerful voices raised in objection, the disjunct distribution of several groups of animals in the Southern Hemisphere seems to be most plausibly explained as a result of continental drift, though no dogmatic claims are made.