The giant squid, Architeuthis dux, has been reported for centuries, but its distribution and ecology have remained famously mysterious. We investigated the A. dux distribution in the Sea of Japan using the environmental DNA (eDNA) method, which has recently been considered as a useful technique for evaluating the distributions of rare species. To develop the eDNA method to detect A. dux, we first created a species-specific polymerase chain reaction (PCR) primer–probe and tried to detect the eDNA in the western region of the Sea of Japan where A. dux has recently been observed. We successfully collected and amplified the A. dux eDNA in our study area using field water sampling and real-time PCR measurements. A. dux eDNA was detected in winter but not in summer, reflecting the historical record of A. dux observations in the region. The use of eDNA techniques could be a potential method for monitoring "invisible" and rare organisms, even in open ocean habitats.

中文翻译：

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探索传说中的巨型鱿鱼：环境 DNA 方法

巨型鱿鱼 Architeuthis dux 已有数百年的报道，但其分布和生态一直以神秘着称。我们使用环境 DNA (eDNA) 方法调查了日本海的 A. dux 分布，该方法最近被认为是评估稀有物种分布的有用技术。为了开发检测 A. dux 的 eDNA 方法，我们首先创建了一个物种特异性聚合酶链反应 (PCR) 引物探针，并尝试在最近观察到 A. dux 的日本海西部地区检测 eDNA . 我们使用现场水样和实时 PCR 测量成功地收集并扩增了我们研究区的 A. dux eDNA。A. dux eDNA 在冬季检测到，但在夏季未检测到，反映了该地区 A. dux 观察的历史记录。