Caledochytrium aldermanii gen. Et sp. nov.; a new Labyrinthulomycete displaying a novel reproductive strategy.

The morphology, reproduction, molecular phylogeny and chemical physiology of a new genus and species of thraustochytrid, Caledochytrium aldermanii gen. et sp. nov is described here. Caledochytrium aldermanii has, amongst its means of reproduction, a novel method not previously reported, in which a mature cell vacuolates and produces secondary cell(s) within the vacuole. Daughter cells are released by rupture of the mother cell. The daughter cell may already contain a tertiary cell within it. Caledochytrium aldermanii displays a range of dispersal mechanisms from sporangia, including unflagellated aplanospores moving on ectoplasmic nets, and ovoid spores with paired flagellae typical of thraustochytrids. In media cultures, pyriform spores with flagellae are also produced, as well as round, flagellated cells resembling gametes. In pollen cultures, some sporangia release an amoeba, which produces two aplanospores, which then divide further. The development of residual elements as thraustochytrid cells die is also described. The plasticity of growth and reproductive strategies in these thraustochytrids is discussed, together with their pathogenicity, which suggests the organism is an environmental saprotroph and an opportunist pathogen in the presence of stressed animal hosts. Initial investigations of compounds of commercial importance produced by C. aldermanii are also described.