Instituto de Diversidad y Evolución Austral (IDEAus-CONICET), Puerto Madryn, Chubut, Argentina.
Sección Herpetología, División Zoología Vertebrados, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata (UNLP), La Plata, Buenos Aires, Argentina.
PLoS One. 2020 May 29;15(5):e0233792. doi: 10.1371/journal.pone.0233792. eCollection 2020.
The Argentinian pouched lamprey, classified as Petromyzon macrostomus Burmeister, 1868 was first described in 1867 in De La Plata River, in Buenos Aires, Argentina, and subsequently recorded in several rivers from Patagonia. Since its original description, the validity of P. macrostomus was questioned by several ichthyologists and 36 years after its original discovery it was considered a junior synonym of Geotria australis Gray, 1851. For a long time, the taxonomic status of G. australis has been uncertain, largely due to the misinterpretations of the morphological alterations that occur during sexual maturation, including the arrangement of teeth, size and position of fins and cloaca, and the development of an exceptionally large gular pouch in males. In this study, the taxonomic status of Geotria from across the "species" range was evaluated using both molecular analysis and examination of morphological characteristics.
METHODOLOGY/PRINCIPAL FINDINGS: Phylogenetic and species delimitation analyses based on mitochondrial DNA sequences of Cytochrome b (Cyt b) and Cytochrome C Oxidase Subunit 1 (COI) genes, along with morphological analysis of diagnostic characters reported in the original descriptions of the species were used to assess genetic and morphological variation within Geotria and to determine the specific status of the Argentinian lamprey. These analyses revealed that Geotria from Argentina constitutes a well differentiated lineage from Chilean and Australasian populations. The position of the cloaca and the distance between the second dorsal and caudal fins in sub-adult individuals, and at previous life stages, can be used to distinguish between the two species. In addition, the genetic distance between G. macrostoma and G. australis for the COI and Cyt b mitochondrial genes is higher than both intra- and inter-specific distances reported for other Petromyzontiformes.
CONCLUSIONS/SIGNIFICANCE: Our results indicate that the Argentinian pouched lamprey, found along a broad latitudinal gradient on the south-west Atlantic coast of South America, should be named as Geotria macrostoma (Burmeister, 1868) and not as G. australis Gray 1851, returning to its earliest valid designation in Argentina. Geotria macrostoma can now be considered as the single lamprey species inhabiting Argentinian Patagonia, with distinct local adaptations and evolutionary potential. It is essential that this distinctiveness is recognized in order to guide future conservation and management actions against imminent threats posed by human actions in the major basins of Patagonia.
阿根廷袋鼬鳗，被归类为 Petromyzon macrostomus Burmeister，1868 年于 1867 年首次在阿根廷布宜诺斯艾利斯的拉普拉塔河被描述，随后在巴塔哥尼亚的几条河流中被记录。自最初描述以来，P. macrostomus 的有效性受到几位鱼类学家的质疑，并且在其最初发现 36 年后，它被认为是 Geotria australis Gray，1851 的一个低级同义词。很长一段时间以来，Geotria 的分类地位一直不确定，这主要是由于对性成熟过程中发生的形态变化的误解，包括牙齿排列、鳍和泄殖腔的大小和位置，以及雄性异常大的颈袋的发育。在这项研究中，使用分子分析和形态特征检查评估了 Geotria 在“物种”范围内的分类地位。
方法/主要发现：基于线粒体 DNA 序列的细胞色素 b（Cyt b）和细胞色素 C 氧化酶亚基 1（COI）基因的系统发育和物种界限分析，以及对物种原始描述中报告的诊断特征的形态分析，用于评估 Geotria 内的遗传和形态变异，并确定阿根廷袋鼬鳗的具体地位。这些分析表明，来自阿根廷的 Geotria 与智利和澳大利亚种群形成了一个分化良好的谱系。亚成体和以前生命阶段的泄殖腔位置和第二背鳍与尾鳍之间的距离可以用来区分这两个物种。此外，COI 和 Cyt b 线粒体基因的 G. macrostoma 和 G. australis 之间的遗传距离高于其他 Petromyzontiformes 报告的种内和种间距离。
结论/意义：我们的研究结果表明，在南美洲西南大西洋海岸的广泛纬度梯度上发现的阿根廷袋鼬鳗，应被命名为 Geotria macrostoma（Burmeister，1868），而不是 G. australis Gray 1851，回到它在阿根廷的最早有效命名。Geotria macrostoma 现在可以被认为是栖息在阿根廷巴塔哥尼亚的唯一袋鼬鳗物种，具有明显的地方适应性和进化潜力。必须认识到这种独特性，以便指导未来针对巴塔哥尼亚主要流域人类活动造成的迫在眉睫的威胁而采取的保护和管理行动。
