Unidirectional hybridization of kaluga <Emphasis Type="Italic">Acipenser dauricus</Emphasis> Georgi, 1775 and Amur sturgeon <Emphasis Type="Italic">Acipenser schrenckii</Emphasis> Brandt, 1869, inferred from the mitochondrial DNA genotyping of their natural hybrids

In 2009 through 2011, among 730 individuals of kaluga and Amur sturgeon collected in the lower reaches of the Amur River and the Amursky Liman, 17 morphologically intermediate individuals (hybrids) with the body length of 56 to 202 cm (median, 81 cm) were identified, including 11 individuals (4.6%) found in 2009, three individuals (1.6%) found in 2010, and three individuals (1.1%), in 2011. In 16 hybrids, 819 bp of the mtDNA control regions were sequences and 11 haplotypes were identified. Since all these haplotypes were from the mtDNA lineages of kaluga, it was concluded that hybridization occurred in one direction, kaluga (♀) × Amur sturgeon (♂). This asymmetry could be caused by the large size differences between these species. Since the earlier examined morphologically typical Amur sturgeons showed the absence of alien haplotypes (Shedko et al., 2015), the absence of the mtDNA introgression is claimed. This can be caused by low viability or sterility of the backcross females (kaluga (♀) × Amur sturgeon (♂)) × Amur sturgeon (♂). The samples of hybrids and typical kaluga individuals demonstrated no differences in the frequency spectra of the mtDNA haplotypes. However, haplotype and nucleotide diversity in the first sample was somewhat higher than in the second one (0.950 versus 0.927 and 0.0054 versus 0.0044, respectively). The data obtained will be useful for population monitoring of kaluga and Amur sturgeon, Amur River endemics, which are classified as critically endangered by the IUCN Red List of Threatened Species.     

New records of the chaetiferous leech-like annelid Paracanthobdella livanowi (Epshtein, 1966) (Annelida: Clitellata: Acanthobdellida) from Kamchatka, Russia

Acanthobdellidans are unique in their organisation and phylogenetic relationships due to having transitional characters that combine features of oligochaetous and achaetous annelids. Alongside the relatively well-studied Acanthobdella peledina Grube, 1851, there is another member of the group, Paracanthobdella livanowi (Epshtein, 1966), with five rows of chaetae and an anterior sucker. It appears that the anterior sucker is weakly developed in small juveniles but acquires a deep cavity in adults. Smaller individuals of P. livanowi can be distinguished from A. peledina, which does not possess an anterior sucker, by the varying breadth of their chaetae. The mid-body segment consists of two doubled annuli in juveniles and is quadri-annulate in large individuals. In Kamchatka freshwaters, hosts of P. livanowi mostly include Salvelinus spp. and more rarely Gasterosteus aculeatus, Oncorhynchus mykiss and O. kisutch. New information on the distribution and the biology of P. livanowi is presented.     

Phylogeny of salmonids (Salmoniformes: Salmonidae) and its molecular dating: Analysis of nuclear RAG1 gene

The phylogenetic relationships among 26 species of salmonid fishes (family Salmonidae) were studied using the RAG1 gene as phylogenetic marker. No unambiguous relationships between thymalllins, coregonins, and salmonins it was possible to establish. It seems likely, that divergence of these lineages took place during rather short time interval (about 3 to 4 million years). The thymallins are thought to be the first separated lineage. The genera of the subfamily Salmoninae form two distinct monophyletic groups, represented by (1) Brachymystax and Hucho and (2) Salmo, Parahucho, Salvelinus, Parasalmo and Oncorhynchus. Ancestral forms of these two evolutionary lineages could diverge at the Oligocene-Miocene boundary (about 24 million years ago). It is suggested that diversification of the main lineages within the second group was rather rapid, and took place in middle Miocene (about 19?C16 million years ago). Moreover, the lineages of Salvelinus, Parasalmo and Oncorhynchus were the latest to diverge. It seems likely that divergence of the Prosopium and Coregonus ancestral lineages occurred during the same time interval.     

Is the Khanka Sawbelly <Emphasis Type="Italic">Hemiculter lucidus</Emphasis> (Cyprinidae) able to reproduce by gynogenesis?

The Khanka Sawbelly Hemiculter lucidus is characterized by a significant prevalence of females in catches of mature fish. By means of RAPD-analysis using 12 primers and karyological investigations, the assumption on the presence of a unisexual gynogenetic form in this species was checked. With consideration of the obtained data, the assumption on gynogenetic reproduction is rejected. Other causes of the shift in sex ratio towards females are discussed.     

Phylogeography of the eight-barbel loach <Emphasis Type="Italic">Lefua nikkonis</Emphasis> (Cypriniformes: Nemacheilidae): how important were straits in northern Japan as biogeographical barriers?

Many straits in the Japanese archipelago have been proposed as biogeographical boundaries, but there is disagreement regarding their importance as historic barriers against dispersal of terrestrial and freshwater taxa. Mitochondrial DNA haplotype and phylogenetic analyses of Lefua nikkonis, a primary freshwater fish inhabiting northern Japan and descendent from Siberia, revealed that the species is genetically structured within its geographic range, but that two major haplotypes are widely distributed across the Ishikari Lowland of Hokkaido Island as well as across the Tsugaru Strait between Hokkaido and Honshu Islands, two well-known biogeographical boundaries of northern Japan. The two major haplotypes were separated from each other by only one mutational step, and many other haplotypes, including those endemic to the region south of these barriers, have diverged from the major haplotypes, suggesting rapid range expansion and local differentiation. Divergence-time estimates, based on vicariance of the Honshu endemic congener L. echigonia via uplift of the Central Highlands, demonstrated that the southward dispersal of L. nikkonis from Hokkaido Island to Honshu Island occurred less than 0.08–0.19 Mya, suggesting that a land bridge emerged at the Tsugaru Strait during the Riss glaciation. Given that other freshwater taxa crossed the strait earlier (during the Middle Pleistocene), it is likely that land bridges in the strait have repeatedly emerged. The fact that L. nikkonis invaded only the northern part of Honshu, and that many other freshwater species also have the limit of their distribution ranges in this area as well, indicates that a faunal transition zone might persist even without the Tsugaru Strait. Thus, straits and lowlands in northern Japan are likely to have been less important as dispersal barriers to freshwater taxa than is currently thought.     

The validation of specific status of the sakhalin sturgeon <Emphasis Type="Italic">Acipenser mikadoi</Emphasis> (Acipenseridae) in the light of recent genetic and morphological data

The comparative morphological study in different Acipenseriform species demonstrates that there are only two morphological features combining the kaluga and the great sturgeon and separating them from other sturgeons, namely the shape of a mouth and the manner attaching of gill membranes to isthmus in adult specimens; whereas many morphological characters are different in these species. The relations of morphological similarity/distinction among different sturgeon species and polyphyletic origin of genus Huso revealed by both molecular and cytogenetic studies presume the restoration of initial taxonomic states for the great sturgeon and kaluga as members of the same genus Acipenser, namely A. huso and A. dauricus.     

The revision of the validity of genus <Emphasis Type="Italic">Huso</Emphasis> (Acipenseridae) based on recent morphological and genetic data with particular reference to the Kaluga <Emphasis Type="Italic">H. dauricus</Emphasis>

The comparative morphological study in different Acipenseriform species demonstrates that there are only two morphological features combining the kaluga and the great sturgeon and separating them from other sturgeons, namely the shape of a mouth and the manner attaching of gill membranes to isthmus in adult specimens; whereas many morphological characters are different in these species. The relations of morphological similarity/distinction among different sturgeon species and polyphyletic origin of genus Huso revealed by both molecular and cytogenetic studies presume the restoration of initial taxonomic states for the great sturgeon and kaluga as members of the same genus Acipenser, namely A. huso and A. dauricus.     

Mitochondrial DNA divergence in populations of the tapeworm Diphyllobothrium nihonkaiense and its phylogenetic relationship with Diphyllobothrium klebanovskii

Diphyllobothrium nihonkaiense [Y. Yamane, H. Kamo, G. Bylund, J.P. Wilkgren. Diphyllobothrium nihonkaiense sp. nov (Cestoda: Diphyllobothriidae)- revised identification of Japanese broad tapeworm. Shimane J Med Sci 1986;10:29-48.] and Diphyllobothrium klebanovskii [I.V. Muratov, P.S. Posokhov. Causative agent of human diphyllobothriasis - Diphyllobothrium klebanovskii sp. n. Parazitologiia. 1988;22:165-170.] are two major species of human diphyllobothriasis in Japan and Far East Russia, respectively, but their taxonomical relationship remains unclear. In this study, we analysed the DNA sequences of 16 clinical isolates of D. nihonkaiense from Japanese people, 3 isolates of D. klebanovskii from a bear in Kamchatka, and 4 clinical isolates of D. klebanovskii from native Udygeyci people in Russia, as well as 4 plerocercoids from Oncorhynchus spp. 18S rDNA and internal transcribed spacer 1 (ITS1) sequences from D. nihonkaiense and D. klebanovskii showed a high level of similarity, indicating synonymy of the two species. Analyses of mitochondrial DNA (mtDNA) sequence polymorphisms in the cox1 and nad3 genes of D. nihonkaiense (D. klebanovskii) revealed two deeply divergent lineages, A and B, with genetic distances (Kimura-2 parameter) of 0.018-0.022. Furthermore, the distinct monophyletic groupings of cox1 haplotypes corresponded to the distinct monophyletic groupings of nad3 haplotypes. The two lineages were neither distinguished by morphological features nor defined by the localities of the samples. These results suggest that the two morphologically cryptic lineages have diverged and coexisted over a long period of time.     

On the systematics and phylogeography of eight-barbel loaches of the genus Lefua (Cobitoidea: Nemacheilidae): mtDNA typing of L. pleskei

Comparative analysis of own sequence data for the mtDNA control region (926 to 928 bp) from eight-barbel loaches inhabiting eight localities in the Amur River basin (4) and the Sea of Japan (4) and the GeneBank/NCBI data for the Lefua individuals from the other regions of East Asia showed that eight-barbel loaches from Primorskii krai water basins were marked by a specific group of mtDNA haplotypes. This finding is considered as supporting the species status of L. pleskei. Genetic distances within L. pleskei are small (on average 0.35%) and close to those within L. nikkonis (on average 0.48%). The distances between this species pair are the least (on average 2.15%) among all other pairs compared. In MP, ML, and Bayesian trees, L. pleskei and L. nikkonis haplotypes formed a common clade with high statistically significant support. In all tree variants, L. costata mtDNA haplotypes were located out of the group of interest. A clade consisting of highly diverged lineages of Lefua sp. and L. echigonia haplotypes occupied a basal position. The mtDNA haplotypes of L. pleskei and L. costata from the Amur River basin were evolutionary young and derived from the haplotypes found in these species from the Sea of Japan (L. pleskei) or the Yellow Sea (L. costata) basins. It is thereby suggested that both species rather recently migrated into the Amur River system. According to the molecular clock data, basal diversification of the eight-barbel loach lineages took place at the end of middle Miocene (about 11 to 12 Myr ago), while divergence of L. pleskei and L. nikkonis ancestral forms probably occurred approximately, 5 Myr ago. Since all main lineages of eight-barbel loaches were found in the Sea of Japan basin (continental coastline and the islands), the divergence order and dispersal patterns of the Lefua species might have been largely determined by the geological development pattern of this water body and the adjacent territories.