Morphology-based taxonomic re-assessment of the Arctic lamprey, Lethenteron camtschaticum (Tilesius, 1811) and taxonomic position of other members of the genus

The lamprey genusLethenteronCreaser & Hubbs, 1922 is widespread across Eurasia and North America, but the number and distribution of its constituent species is not firmly established. After a morphological examination of extant type material of the currently recognized species and their synonyms,Lethenteron mitsukurii(Hatta, 1901) is resurrected withLe. matsubaraiVladykov & Kott, 1978 as its junior synonym. Amongst nonparasitic speciesLe. reissneri(Dybowski, 1869) andLe. mitsukuriiare confirmed as present in Japan and the former is also present on Sakhalin. An in-depth study of large samples of nonparasitic lamprey adults from Japan and Sakhalin Island is needed to determine whether the lower trunk myomere (< 66) individuals from these areas represent one or more undescribed species, orLe. mitsukurii, orLe. reissneri, or a mixture of these three alternatives. The material from the Anadyr Estuary identified by Berg (1931, 1948) asLampetra japonica kesslerihas been re-identified asLe. camtschaticumand there is no evidence thatLe. kesslerioccurs there.Lethenteron reissneriis reported from the Angara River system, Yenisei River drainage, Russia.Lethenteron alaskenseVladykov & Kott, 1978 is provisionally considered to be a junior synonym ofLe. kessleri(Anikin, 1905).Petromyzon ernstiiDybowski, 1872,Ammocoetes aureusBean, 1881,Petromyzon dentexAnikin, 1905,Lampetra mitsukurii majorHatta, 1911, andLampetra japonica septentrionalisBerg, 1931 are junior synonyms ofPetromyzon marinus camtschaticusTilesius, 1811. A key is provided to adults of the six species recognized as belonging in the genusLethenteron.