Identification of fish larvae collected from Tokyo Bay based on genetic biology

东东湾中部分布丰富的黄棘虾蛄（Acanthogobius flavimanus）和laactipes虾蛄（A. lactipes），其幼虫的形态特征难以识别；然而，它们的发生季节是不同的，前者发生在春天，后者发生在夏天。因此，在本研究中，试图通过遗传性状来鉴定这两个物种的幼虫。在东京湾内部采集成鱼和幼鱼。通过形态特征对成虫进行鉴定。利用聚合酶链反应（PCR）扩增线粒体DNA细胞色素b基因，采用RFLP法进行分析，得到其核苷酸序列。将幼虫分为春季A型和夏季B型两种类型，并进行与成虫相同的遗传分析。结果表明，这些幼虫的核苷酸序列与黄斑拟蚊和紫斑拟蚊的核苷酸序列匹配度分别为99.9%；因此，A型和B型幼虫被鉴定为各自的种类。详细的形态学研究，特别是对黑素细胞分布的研究表明，这两种幼虫在峡部和身体外侧的黑素细胞分布模式不同。本研究采用的幼虫采集、幼虫遗传特征鉴定和幼虫详细形态研究等方法可广泛应用于幼虫分类领域。

Larvae of two gobiids, Acanthogobius flavimanus and A. lactipes, distributed and abundant in the inner part of Tokyo Bay, are difficult to be identified by their morphological characters ; however, they are distinguished each other by their occurrence seasons, the former occurring in Spring and the latter in Summer. Therefore, in this study, larvae of both the species were tried to be identified by the genetic characters.Adult fish and larvae/juveniles were collected from the inner part of Tokyo Bay. The adults were identified by their morphological characters. Furthermore, their cytochrome b gene of mitochondrial DNA, amplified by using the polymerase chain reaction (PCR), was analyzed by RFLP method, and the nucleotide sequences were obtained.The larvae were, on the other hand, divided into two types, Type A occurred in Spring and Type B in Summer, and the same genetic analyses were done as in the adults. Consequently, 99.9% of nucleotide sequences of these larvae were matched with those of A. flavimanus and A. lactipes, respectively; therefore, Type A and B larvae were identified to be the respective species. Detailed study on morphology, especially melanophore distribution of these larvae, revealed that the distribution patterns of melanophores on the isthmus and lateral part of body were different between these two species.The methods performed in this study such as larval collection, larval identification by genetic characters and detailed morphological studies of larvae can be applied widely to the field of larval taxonomy.