Bogutskaya Nina G, Stefanov Tihomir, Naseka Alexander M
Naturhistorisches Museum Wien, Burgring 7, Vienna 1010, Austria Naturhistorisches Museum Wien Vienna Austria.
National Museum of Natural History, 1 Tsar Osvoboditel Blvd, 1000 Sofia, Bulgaria National Museum of Natural History Sofia Bulgaria.
Zookeys. 2019 Feb 27(825):105-122. doi: 10.3897/zookeys.825.32434. eCollection 2019.
The Danube delta gudgeon, , has been considered to be extinct because there were no reliable recent observations. The latest record confirmed by a voucher specimen dating from 1992. We report here on a specimen of collected in 2016 in the Bulgarian sector of the Danube main stream using a bottom drift net at a depth of 8 m. The species determination is supported by morphological examination including discriminant and cluster analyses in comparison with three syntypes and five non-type specimens of , samples of the species complex and . most clearly differs from both and by proportional measurements (caudal peduncle depth, head width, eye horizontal diameter, and interorbital width), from also by the number of scales above and below the lateral line (6 and 4, respectively, (vs. commonly 5 and 3), and from , also by 8½ branched dorsal-fin rays (vs. 7½) and the vertebral caudal region longer than the abdominal vertebral region (abdominal+caudal vertebrae 19+21 or 20+21, vs. commonly 20+20 or variants with a caudal region shorter than the abdominal one). The possibility that represents a deep-water cophenotype of either or , cannot be excluded. The new record demonstrates that is still extant in the lower Danube but may be restricted to greater depths in the main channel and the deltaic branches.
多瑙河三角洲 gudgeon（学名未给出），曾被认为已灭绝，因为近期没有可靠观测记录。最新记录由一份可追溯至1992年的凭证标本证实。我们在此报告2016年在多瑙河主流保加利亚段8米深处使用底拖网采集到的一份该物种标本。物种鉴定得到形态学检查的支持，包括与三个模式标本和五个非模式标本、该物种复合体样本及其他相关样本进行判别分析和聚类分析。该物种与其他相关物种相比，在比例测量（尾柄深度、头宽、眼水平直径和眶间宽度）方面与两者差异明显，在侧线上下鳞片数量上（分别为6和4，而通常为5和3）与另一物种不同，在背鳍分支鳍条数量上（8½对7½）以及尾椎区域长于腹椎区域（腹椎 + 尾椎为19 + 21或20 + 21，而通常为20 + 20或尾椎区域短于腹椎区域的变体）也与另一物种不同。不能排除该物种代表另一物种深水表型的可能性。新记录表明该物种在多瑙河下游仍然存在，但可能仅限于主河道和三角洲分支的较深水域。
