A Myxosporean of the Order Multivalvulida from the Brains of Lateolabrax japonicus and Some Other Marine Fishes

Abstract

A myxosporean found in the brains of Lateolabrax japonicus, Seriola quinqueradiata, Pagrus major and Takifugu rubripes was characterized by producing two forms of spores; hexaradiate spores with six shell valves and six polar capsules and heptaradiate spores with seven shell valves and seven polar capsules. The description of these forms was given. These two forms of spores coexisted in intracerebral pseudocysts and extracerebral cysts in all the fish studied. The ratio between the two was variable.
The generally accepted principle that the number of shell valves is constant in a given species of the order Multivalvulida and therefore serves as the main family criterion does not apply to this myxosporean. From the observations it may be assumed that one of the two forms is abnormal due to an unusual cell division, or this myxosporean is on an extention of the Trilospora-Kudoa-Pentacapsula-Hexacapsula evolutinary line, but its character is still genetically unfixed. Further research on these questions is needed to discuss the systematic position of this myxosporean.