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

分布于东京湾内侧的黄棘鱼(Acanthogobius Flavimanus)和乳叉尾虾(A.lactipe)幼虫分布丰富，其形态特征难以辨别，但根据发生季节的不同而有所区别，前者发生在春季，后者发生在夏季。因此，在本研究中，试图通过遗传特征来鉴定这两个物种的仔鱼。成鱼和仔鱼/幼鱼采自东京湾内侧。通过形态特征对成虫进行了鉴定。此外，利用聚合酶链式反应(PCR)扩增了它们的线粒体DNA细胞色素b基因，并对其进行了RFLP分析，获得了核苷酸序列。另一方面，将幼虫分为春季A型和夏季B型两种类型，并进行了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曲霉属和乳链霉菌的核苷酸序列同源性分别为99.9%和99.9%，因此，A型和B型幼虫分别为各自的种。通过对幼虫形态，特别是黑素细胞分布的详细研究，发现两种幼虫体内的黑素细胞在峡部和身体外侧的分布模式不同，本研究所采用的幼虫采集、幼虫遗传特征鉴定、幼虫详细形态研究等方法可广泛应用于幼虫分类学领域。

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.