Designation of a lectotype for Siberian lamprey Lethenteron kessleri (Anikin, 1905) (Petromyzotiformes: Petromyzontidae)

The conservator of the Zoological Museum of Imperial Tomsk University V.P. Anikin described the Siberian lamprey, Lethenteron kessleri (Anikin, 1905), after studying 16 adult specimens from the Tom’ River and the mouth of the Kirgizka River. In the original description, he did not designate a holotype. Due to Article 73.2 of the International Code of Zoological Nomenclature (ICZN), all these specimens are syntypes. In order to identify a lectotype, we studied all suitable specimens of the Siberian lamprey from the collections of the Zoological Museum (ZM TSU) and the Department of Ichthyology and Hydrobiology of National Research Tomsk State University (DIH TSU). As a result, we found eight lampreys, only two of which belong to the type series. We compared these specimens with those described in articles by B.G. Johansen (1935) and A.M. Naseka & C.B. Renuard (2020). In accordance with Articles 74.1 and 74.7 of the ICZN, we designated a specimen from the ZM TSU (No. 3698) as the lectotype for the Siberian lamprey, L. kessleri (Anikin, 1905). This lamprey specimen is in satisfactory condition and corresponds to the characteristics of the type series by date, locality of capture, and measurements. We measured the lectotype (See Table 1) with an electronic caliper, counted teeth of the oral disc using a stereoscopic microscope and described the color in the preservative. Additionally, we determined the sex of this specimen with micro-computed tomography (See Fig. 1). We also designated another specimen from the DIH TSU (No. 3699) as a paralectotype because of its unsatisfactory condition. Below we present the measurements and features of the lectotype. Designation of the lectotype Lethenteron kessleri (Anikin, 1905). ZM TSU, No. 3698 (No. 8 in Iogansen, 1935b) (See Figs. 1A-1C), Russia, Tomsk Province, Tomsk, mouth of the Kirgizka River near Tomsk, the Tom’ River system, the Ob’ River drainage, the Kara Sea basin, the Arctic Ocean basin, 02.10.1900. Coll.: V.P. Anikin. Description of lectotype Lethenteron kessleri (Anikin, 1905). Color of lectotype in preservative: plain beige. Adult male (See Fig. 2): snout length - 9.6 mm, eye length - 3.6 mm, postocular length - 5.1 mm, prebranchial length - 20.3 mm, branchial length - 17.4 mm, branchial depth - 9.3 mm, prenostril length - 11.2 mm, trunk length - 92 mm, total length - 188 mm, interocular width - 7.2 mm, disc length - 8.3 mm, trunk depth -10.8 mm, first dorsal fin length - 30.4 mm, first dorsal fin depth - 5.4 mm, second dorsal fin length is impossible to measure, second dorsal fin depth - 4 mm, tail length - 52 mm, caudal fin length is impossible to measure, interbranchial opening length -0.65 mm, tail depth at junction of second dorsal and caudal fins - 2.2 mm, maximum depth of caudal fin is impossible to measure, tail depth at maximum depth of caudal fin is impossible to measure. Teeth: 21 anterior teeth, supraoral lamina with 2 unicuspid teeth, infraoral lamina with 6 teeth: 2 bicuspid lateral teeth, 4 unicuspid intercalar teeth, 26 posterial teeth, 2 left anterior endolateral bicuspid teeth and one left anterior unicuspid endolateral tooth; 3 right anterior endolateral bicuspid teeth. Number of trunk myomeres - 69. The second dorsal fin and caudal fin are in poor condition; it is impossible to measure three associated characteristics. The article contains 2 Figures, 22 References. The Authors declare no conflict of interest.

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