Abstract
Increasingly over the past century, seasonal fish kills associated with toxic blooms of Prymnesium parvum have devastated aquaculture and native fish, shellfish, and mollusk populations worldwide. Protracted blooms of P. parvum can result in major disturbances to the local ecology and extensive monetary losses. Toxicity of this alga is attributed to a collection of compounds known as prymnesins, which exhibit potent cytotoxic, hemolytic, neurotoxic and ichthyotoxic effects. These secondary metabolites are especially damaging to gill-breathing organisms and they are believed to interact directly with plasma membranes, compromising integrity by permitting ion leakage. Several factors appear to function in the activation and potency of prymnesins including salinity, pH, ion availability, and growth phase. Prymnesins may function as defense compounds to prevent herbivory and some investigations suggest that they have allelopathic roles. Since the last extensive review was published, two prymnesins have been chemically characterized and ongoing investigations are aimed at the purification and analysis of numerous other toxic metabolites from this alga. More information is needed to unravel the mechanisms of prymnesin synthesis and the significance of these metabolites. Such work should greatly improve our limited understanding of the physiology and biochemistry of P. parvum and how to mitigate its blooms.
Highlights
Several species of Prymnesium Massart are known to synthesize noxious chemicals as measured by their effects on erythrocytes and gill-breathing organisms (Table 1) [1,2,3,4,5,6,7,8,9]
The toxic principles of P. parvum f. patelliferum are similar in their effects and it is possible that they may be identical, or at least closely-related, compounds to those we review here [5,13]
The present review focuses on the toxic principles isolated from P. parvum, with exceptions noted
Summary
Several species of Prymnesium Massart are known to synthesize noxious chemicals as measured by their effects on erythrocytes and gill-breathing organisms (Table 1) [1,2,3,4,5,6,7,8,9] This organism is especially notorious for seasonal harmful algal blooms (HAB) wherein cell densities increase rapidly with the accompanying presence of potent ichthyotoxins [3,10]. P. parvum is unicellular, ranging in size from 8–15 μm in length by 4–10 μm wide and having two flagella of roughly equal length positioned at the anterior end (Figure 1) [14,15,16] These oblong cells possess two prominent ochre-colored chloroplasts positioned on either side of a centrally-located nucleus. Proposed vectors of transfer include contaminated bilge water, bird guano and encystment [11,15]
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