Brown bullhead Ameiurus nebulosus — new fish species for Russia

The native habitat of the brown bullhead Ameiurus nebulosus is located in the eastern part of North America. This species was introduced in Europe, Southwestern Asia and New Zealand. It was supposed that it entered Russia from the southwest and now inhabits some water bodies at the border with Ukraine and Belarus. Information about bullheads in Russia was searched for in scientific editions and angler’s blogs. Anglers’ reports have been verified by survey and fishing. It turned out that brown bullheads did in fact appear in Russia, but not where they were expected: they were found by the city of Saint Petersburg on the Karelian Isthmus, i.e., on the territory between Lake Ladoga and the Gulf of Finland of the Baltic Sea. They inhabit at least three lakes. This invasion resulted from release by unauthorized individuals. The revealed habitats are linked by brooks with the river systems of the Baltic Sea Basin. The following spread of the brown bullhead is possible due to intentional releases and natural processes.

Morphometric and genetic evidence for cryptic diversity in Gyrodactylus (Monogenea) infecting non-native European populations of Ameiurus nebulosus and A. melas

Gyrodactylid parasites were observed on non-native populations of North-American freshwater catfishes, Ameiurus nebulosus and Ameiurus melas (Siluriformes: Ictaluridae), at several sites in the Elbe River basin, Czech Republic, Europe. Using a combination of morphological and genetic analyses, the parasites infecting A. nebulosus were determined to be Gyrodactylus nebulosus, a North American parasite co-introduced to Europe along with its Ameiurus fish hosts. Subtle morphometrical differences, as well as seasonal variations, were observed among parasites collected from A. nebulosus and A. melas. The host-related variation was further supported through genetic analysis of the partial 18S rDNA, ITS1-5.8S-ITS2 and COI, showing 0.2, 3.0 and 4.8% divergence, respectively. Consistent genetic differences indicated there were two distinct genotypes. Subtle morphological differences associated with the shape of sickle toe, anchor root and ventral bar membrane, according to host species, also supported the description of a new cryptic species, Gyrodactylus melas n. sp., infecting A. melas. Multivariate morphometrical analysis of haptoral hard parts showed significant differences between the anchor lengths of G. nebulosus and G. melas n. sp. However, the measurements of the haptoral hard structures partially overlapped between species, limiting the usage of these parameters for species delineation.