Species in the genusMyxidiumbütschli, 1882 (Myxosporea: Bivalvulida) parasitizing the gall bladders of gadid fish in the northeast Atlantic

Abstract

We redescribe 4 species of myxosporeans of the genus Myxidium parasitizing the gall bladders of commercially important gadid fish in the northeast Atlantic: Myxidium sphaericum, M. bergense, M. oviforme and M. gadi. We also test the hypothesis that M. bergense is a junior synonym of M. sphaericum. The fish species examined were cod Gadus morhua, haddock Melanogrammus aeglefinus, saithe Pollachius virens, and whiting Merlangius merlangus. We found M. sphaericum only in whiting, M. bergense in cod (northern Norway only) and haddock, M. oviforme only in cod, and M. gadi only in saithe. We found M. sphaericum only in samples from south of 58°N, and M. bergense only in those from north of 58°N. We consider that the species originally described as M. sphaericum from the pelagic fish Belone belone may be different from the species later reported as M. sphaericum from whiting and other demersal fish. We confirm that M. bergense is a valid species distinct from both the original M. sphaericum and that found in demersal fish.