Molecular characterization of Moenkhausia (Pisces: Characiformes) populations with different lateral line developmental levels

ABSTRACT The genera Hemigrammus and Moenkhausia have been traditionally diagnosed mainly by the former having lateral line completely pored whereas the latter having a lateral line with a few pored scales. Those features have been used to diagnose species of both genera in the upper Paraná River floodplain. Specimens with the diagnostic features of Moenkhausia bonita, collected in the upper Paraná River floodplain, exhibited different developmental levels of the lateral line, making it difficult to distinguish them from specimens of Hemigrammus sp. We analyzed the gene encoding cytochrome C oxidase I (COI) and intron 1 of the nuclear gene S7 to investigate the genetic similarities between the called Hemigrammus marginatus and M. bonita and to confirm their identities. Molecular sequences of other Moenkhausia species were analyzed for genus delimitation tests. The results reveal genetic similarities of M. bonita specimens with different developmental levels of the lateral line, and also distinguish between M. bonita and Hemigrammus sp. Species delimitation tests revealed that specimens from the upper Paraná River floodplain were M. bonita and were distinct from other Moenkhausia species. The developmental level of the lateral line is not a consistent characteristic that distinguishes between Moenkhausia and Hemigrammus species.

摘要
传统分类学中，半线脂鲤属（Hemigrammus）与莫氏脂鲤属（Moenkhausia）的鉴别主要依据侧线特征：前者侧线完全穿孔，后者侧线仅具少量穿孔鳞。该特征曾被用于巴拉那河上游泛滥平原中这两个属的物种鉴定。
在巴拉那河上游泛滥平原采集的、带有美丽莫氏脂鲤（Moenkhausia bonita）鉴别特征的标本，其侧线发育程度存在差异，导致难以与半线脂鲤属未定种（Hemigrammus sp.）标本区分。
本研究通过扩增并分析细胞色素C氧化酶亚基I（COI）编码基因与核基因S7的第一内含子序列，探究了所谓"边半线脂鲤（Hemigrammus marginatus）"与美丽莫氏脂鲤（M. bonita）的遗传相似性，以确认二者的分类身份。同时纳入其他莫氏脂鲤属物种的分子序列开展属级物种界定实验。
研究结果显示，侧线发育程度存在差异的美丽莫氏脂鲤标本间具有遗传相似性，同时明确了美丽莫氏脂鲤与半线脂鲤属未定种的分类界限。物种界定实验结果表明，采自巴拉那河上游泛滥平原的标本确为美丽莫氏脂鲤，且与其他莫氏脂鲤属物种存在显著分化。本研究证实，侧线发育程度并非区分莫氏脂鲤属与半线脂鲤属物种的可靠特征。