A review of knowledge of a group of closely related, economically important toxic Gymnodinium/Gyrodinium (Dinophyceae) species in New Zealand

The focus of the toxic shellfish events in 1994 in New Zealand has turned to a new lipid-soluble, so-called ''Southland toxin'', which has been detected in shellfish from Southland since mid-January. Intraperitoneal injection of these toxin extracts kills mice within minutes. Consequently shellfish harvest in many areas in the South Island were banned. Gymnodinium cf. mikimotoi NZ, which was concurrently found with the contaminated shellfish, was subsequently confirmed as the species responsible for the 1994 toxic shellfish event. In South Island waters in the past, fish kills have also been associated with another species, identified as Gyrodinium cf. aureolum NZ. Recent overseas studies have shown that Gymnodinium mikimotoi s. l. and Gyrodinium aureolum s.l. are very closely related, and some workers suggest they may be congeneric or even conspecific. This paper summarises the relationships of the New Zealand species, Gymnodinium cf. mikimotoi NZ and Gyrodinium cf. aureolum NZ with each other, and with closely related species from other parts of the globe. Conclusions concerning G. cf. mikimotoi NZ, and other closely related species, whether they are regarded as a threat to human health risk, are also summarised. It is recommended that any form or species that falls between the definition of Gymnodinium and Gyrodinium be assigned the older name Gymnodinium, pending the results of further work on the Gymnodiniaceae in future.