Louisiana Universities Marine Consortium, 8124 Highway 56, Cocodrie, LA 70344, USA.
Toxicon. 2010 Feb-Mar;55(2-3):570-9. doi: 10.1016/j.toxicon.2009.10.011. Epub 2009 Oct 14.
Despite high abundances of toxic Pseudo-nitzschia spp. over Louisiana oyster beds (Crassostrea virginica; eastern oyster) there have been no documented cases of amnesic shellfish poisoning (ASP) in the state. Two possible explanations are that oysters do not readily feed on long pointed chains of Pseudo-nitzschia cells or they discriminate against toxic cells while grazing. To test these hypotheses, short-term grazing experiments were conducted with several diatoms, including the domoic acid (DA)-producing Pseudo-nitzschia multiseries (1.31+/-0.057 pg DA cell(-1)) and the non-toxic Pseudo-nitzschia delicatissima, Thalassiosira weissflogii, and Ditylum brightwellii. Grazing rates on the small centric species T. weissflogii were significantly higher than on the larger and pointier D. brightwellii and either Pseudo-nitzschia species. Grazing on toxic P. multiseries and non-toxic P. delicatissima was not significantly different. Pseudofeces production was higher and feces production was occasionally lower in oysters fed Pseudo-nitzschia spp. than in oysters fed the other two diatoms. Our data demonstrate lower filtration rates of C. virginica on Pseudo-nitzschia spp. relative to the other diatoms tested and comparable filtration on toxic and non-toxic Pseudo-nitzschia spp. These findings suggest that eastern oysters do not discriminate amongst food types due to DA content.
尽管路易斯安那牡蛎养殖场（Crassostrea virginica；东方牡蛎）中存在大量的毒性伪菱形藻属（Pseudo-nitzschia spp.），但该州尚未有记录到健忘性贝类中毒（Amnesic Shellfish Poisoning，ASP）的病例。有两种可能的解释，一是牡蛎不易摄食长而尖的伪菱形藻属细胞链，二是在放牧时它们会对有毒细胞进行辨别。为了验证这些假设，进行了几项短期放牧实验，其中包括产生软骨藻酸（Domoic Acid，DA）的伪菱形藻属多系列（1.31+/-0.057 pg DA 细胞（-1））和无毒的伪菱形藻属 delicatissima、Thalassiosira weissflogii 和 Ditylum brightwellii。对较小的中心型物种 Thalassiosira weissflogii 的摄食率明显高于较大且更尖锐的 Ditylum brightwellii 和任何一种伪菱形藻属物种。对有毒的 P. multiseries 和无毒的 P. delicatissima 的摄食没有明显差异。摄食伪菱形藻属 spp. 的牡蛎产生的伪粪便量较高，偶尔也会比摄食其他两种硅藻的牡蛎产生的粪便量低。我们的数据表明，相对于所测试的其他硅藻，C. virginica 对伪菱形藻属的过滤率较低，而对有毒和无毒的伪菱形藻属的过滤率则相当。这些发现表明，东方牡蛎不会因其 DA 含量而对食物类型进行辨别。
