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ABSTRACTThis work extends a previous report on the outbreak of an unknown neurotoxic sea slug along the southwestern Atlantic coast by providing identification to species level. In this study a c. 550 base pair (bp) region of the cytochrome c oxidase subunit 1 mitochondrial gene used for genetic barcoding was sequenced from three individual slugs sourced from three locations in Argentina. These data, in concert with previous description on the morphology and the presence of a neurotoxin of similar effect of that produced by pleurobranchs from New Zealand, confirm the identity of these sea slugs as Pleurobranchaea maculata. This is the first record of the species in the Atlantic Ocean, thus suggesting an exotic origin. Given the fast spread of reports in the southwestern Atlantic (c. 2000 km of coastline in 6 years) we recommend urgent studies to determine the origin, toxicity, population genetics and impacts on local ecosystems.

Microcystisis a widely distributed genus of cyanobacteria that often forms surface blooms. The ability of Microcystiscolonies to regulate buoyancy in response to variations in nutrients and light, and in the presence of low rates of turbulent mixing, is well described. Here, we report on the movement of individual cells within Microcystis wesenbergiicolonies. Cells actively rearranged themselves within colonies, but randomly relative to other cells. Of the known types of cyanobacterial movement, gliding or twitching mediated by type IV pili was deemed the most likely causative mechanism. Transmission electron microscopy showed, however, no pilus-like structures on M. wesenbergiicell surfaces. We speculate that intra-colony movement may optimize colony fitness by helping individual cells to meet specific physiological requirements that may differ between the core and outer parts of the colony. This may increase fitness of cells and explain the recent dominance of M. wesenbergiiin some New Zealand lakes.

Planktonic cyanotoxin poisoning events are well documented. More recently, benthic cyanobacteria have also been associated with bird, cattle and dog fatalities. Extensive mats of benthic cyanobacteria can contain high concentrations of toxins. This study investigated cyanotoxin production in cyanobacterial strains isolated from benthic freshwater mats dominated by cyanobacteria in Canterbury, New Zealand. Twenty-seven strains were isolated from ten water bodies and characterized using morphological and molecular phylogenetic characteristics. All strains were screened for genes involved in the biosynthesis of common cyanotoxins. Positive results were confirmed and cyanotoxin concentrations quantified using liquid chromatography–mass spectrometry. One chroococcalean, twenty oscillatorialean and six nostocalean strains were isolated into culture. All strains were cryopreserved and banked in the Cawthron Institute Culture Collection of Micro-algae. Genes associated with anatoxin-a biosynthesis were identified in nine Phormidiumstrains. Anatoxin-a was detected in all these strains, one of these strains also produced homoanatoxin-a.