Identification of Monitoring Organ in Bivalves for Early Warning of Paralytic Shellfish Toxins Accumulation

Bivalve farming plays a dominant role in mariculture in China. Paralytic shellfish toxins (PSTs) can be accumulated in bivalves and cause poisoning the consumers. A sensitive detection of PSTs can provide early warning to decrease poisoning events in bivalve consuming. PSTs are traditionally examined using the whole soft-tissues. However, PSTs accumulation varies dramatically in different tissues of bivalves. Some tough tissues/organs (such as mantle), which account for a large proportion of the total soft body, exhibit a lower accumulation of PSTs and make the toxin extraction time- and reagent-consuming, potentially decreasing the accuracy and sensitivity of PSTs monitoring in bivalves. To develop a sensitive and cost-effective approach for PSTs examination in massively farmed bivalves, we fed three commercially important bivalves, Yesso scallop Patinopecten yessoensis, Pacific oyster Crassostrea gigas, and blue mussel Mytilus edulis with PSTs-producing dinoflagellate Alexandrium catenella, and detected PSTs concentration in different tissues. For all three bivalve species, the digestive gland accumulated much more PSTs than other tissues, and the digestive gland’s toxicity was significantly correlated with the PSTs toxicity of the whole soft-tissues, with r2 = 0.94, 0.92, and 0.94 for Yesso scallop, Pacific oyster, and blue mussel, respectively. When the toxicity of the whole soft-tissues reached 80 µg STXeq(100g)−1, the regulatory limit for commercial shellfish, the digestive gland’s toxicity reached 571.48, 498.90, and 859.20 µg STXeq(100g)−1 in Yesso scallop, Pacific oyster, and blue mussel, respectively. Our results indicate that digestive gland can be used for the sensitive and cost-effective monitoring of PSTs in bivalves.