Domoic acid toxicity of large new cells of Pseudo-nitzschia multiseries resulting from sexual reproduction

During normal vegetative growth in culture, the pennate diatom Pseudo-nitzschia multiseries decreases in cell length and also in cellular content of the neurotoxin domoic acid (DA), causative agent of Amnesic Shellfish Poisoning. Diatoms commonly undergo sexual reproduction in order to regenerate their large cell size. Sexual reproduction in species Pseudo-nitzschia was recently documented. After mixing exponentially growing cells of the opposite mating type and of the appropriate minimal size, pairing was observed of parent cells, gamete production, fusion of gametes to form zygotes, and enlargement of auxospores within which formed the long initial cells. The latter are called ‘large new cells’ after they exit auxospores and undergo the first vegetative division. This paper documents the DA production by large new cells, relative to parent cells. Also reported is the range of cell sizes that favour auxosporulation. Such information may provide insights into the timing and toxicity of Pseudo-nitzschia spp. blooms in the field.