Myxosporean parasites of marine fishes: their distribution in the world's oceans.

Myxosporeans are among the most common parasites of marine fish. Their economic importance is mainly as pathogens of both wild and farmed fish, but they have also been used as biological tags in population studies of their fish hosts. Here we review the literature and show the distribution of different families of Myxosporea infecting marine fishes in the world's oceans - the North Atlantic, South Atlantic, North Pacific, South Pacific and Indian. We also analyse their distribution in different orders of marine fishes. New families, genera and species of marine Myxosporea are continually being described and many more await description. Some regions, in particular the North Atlantic, have been more thoroughly investigated than others, so the analyses we present may not reflect the true distributions and we acknowledge that these may change considerably as other regions are investigated more fully. The distribution of myxosporean families in different taxonomic groups of marine fishes can indicate phylogenetic relationships between parasite and host and suggest the origins of different myxosporean taxa. We present some examples, while recognizing that new molecular information on phylogenetic relationships within the Myxozoa will lead to major changes in classification.