Quality surveillance of the waters in the production areas of bivalve mollusc in Galicia (NW Spain) is performed by our unit, the CCCMM (Marine Environmental Quality Monitoring Center). This surveillance includes monitoring of oceanographic conditions, biotoxins and phytoplankton. In the course of routine DSP monitoring, using the mouse bioassay of Yasumoto 1978, we have observed strange symptoms in some mice injected with DSP extract, notably photosensitivity and marked fluid discharge between the skull and the skin. Deaths occurs between 18 and 48 hours after injection. Histopathological analysis reveals marked congestion in all organs, and severe damage to the liver and spleen, all consistent with the action of a toxic compound. The presence of PSP, OA and derivatives, PTX, YTX, ASP and KT-3 was ruled out. Simultaneous routine phytoplankton counts did not reveal the presence of any harmful species known associated with these observations. The putative toxic responsible for the observed symptoms was soluble in acetone, in ether and in 80% MeOH, but not in hexane.

Further studies revealed that the symptoms can be prevented if, after injection, the mice are kept in the dark. This observation is consistent with the presence in the samples of a phototoxic, leading us to suspect a pyropheophorbide like compound. Chromatographic determination confirmed the presence of pyropheophorbide a at a concentration in excess of 0.5 mg/g hepatopancreas. Intraperitoneal injection of pyropheophorbide a into healthy mice provoked the same strange symptoms as observed in the DSP bioassay, strongly suggesting that these symptoms are at least partially due to this compound.