Paralytic phycotoxin uptake by scallops (Pecten maximus)

Abstract

It is difficult to apply sanitary standards for mollusc contamination by paralytic shellfish poisoning to animals not consumed whole. This problem is illustrated by the 1990 embargo on a Japanese shipment of frozen scallop muscle and gonad: the sanitary threshold applied to digestive gland (in Japan) does not guarantee that muscle and especially gonad are toxin-free. Accordingly, we performed experimental contaminations of scallops (Pecten maximus) from Port-en-Bessin (Normandy, France) using a toxic Japanese strain of Alexandrium tamarense. During the contamination/decontamination experiment on different tissues (digestive gland, muscle, gonad), extracts were obtained using cold acetic acid 0.1 N to maintain the perfect integrity of the toxin profile. These initial trials indicated that with a daily concentration of 2 × 10⁶ cells. 1^-1 a maximum toxicity equivalent to 850 μg.100 g^-1 of digestive gland meat was attained in 2 weeks. Concerning toxin profiles, it would appear that gonad can selectively accumulate gonyautoxins, particularly GTX2/GTX3, even though the relative amount of uptake always follows the order hepatopancreas > gonad > muscle. Morcover, studies of Japanese scallops imported in 1990 showed that 80% of the gonad and muscle samples included all or part of the kidneys and excretory organs, whose relationship with gonad toxicity need further clarification. Finally, the toxin profile of the different organs during decontamination revealed an inversion of the relative proportions of GTX2/GTX3 epimers, as noted by other authors. Confirmation of selective biological conversion between organs will require further study.