Diversity of the genus Bunodera Railliet, 1896 (Trematoda: Allocreadiidae) in the northern part of Eastern Europe and North-eastern Asia, estimated from 28S rDNA sequences, with a description of Bunodera vytautasi sp. nov.

Phylogenetic relationship reconstruction and taxonomical analysis of trematodes of the genus Bunodera was carried out using 28S rDNA partial sequences along with a description and molecular characterisation of a new species, B. vytautasi sp. nov. A new species is reported from the intestine of Pungitius pungitius (Linnaeus, 1758), collected from Magadan Region, Russia. The diagnostic characters of B. vytautasi sp. nov. are the extension of vitelline fields from the oral sucker or posterior edge of the pharynx to the posterior extremity of the body, the confluence of vitelline fields within the forebody, the extension of the cirrus-sac to the posterior third of ventral sucker or further backwards with an outlet beyond the posterior edge of the sucker, and the presence of a unipartite internal seminal vesicle. Both Bayesian and Maximum Likelihood trees shared the same tree topology, in which the genus Bunodera was shown to be monophyletic. Representatives of the genus Bunodera were distributed into three well-supported clades: percid-infecting species (Eurasian species B. luciopercae and B. acerinae and North American B. luciopercae s.l.), gasterosteid-infecting species (amphi-Pacific B. mediovitellata and North American B. inconstans and B. eucaliae) and percid/gasterosteid-infecting species (Asiatic B. vytautasi sp. nov. and North American B. sacculata). Eurasian B. luciopercae and B. acerinae were more closely related to each other than to North American B. luciopercae s.l.

Phylogenetic relationships among European and Asian representatives of the genus Aspidogaster Baer, 1827 (Trematoda: Aspidogastrea) inferred from molecular data.

In the present study, phylogenetic relationships of European and Far Eastern representatives of the genus Aspidogaster Baer, 1827 were analysed: A. conchicola Baer, 1827, A. limacoides Diesing, 1834, A. ijimai Kawamura, 1915 and A. chongqingensis Wei, Huang & Dai, 2001. Based on ITS1-5.8S-ITS2 rDNA sequence data, an obvious differentiation was seen between specimens of A. limacoides sensu stricto from the European part of Russia and A. limacoides sensu Chen et al., 2010 from China (13.7%); the latter parasites were recognized as A. chongqingensis. Aspidogaster chongqingensis was more closely related to A. ijimai than to A. limacoides s. str. Specimens of A. ijimai from the Amur River, Khanka Lake (Russian Far East) and China were grouped into a single clade with low intra specific molecular differentiation (d = 0-0.3%). Specimens of A. conchicola from the European part of Russia, the Russian Far East and China also formed a single distinct clade. Genetic differentiation between European and Chinese samples of this species was two times lower (d = 0.45%) than between Russian Far East and European or Chinese samples (d = 0.96%), suggesting a long-term separate existence of A. conchicola in the Russian Far East.

[Unidirectional Hybridization of Kaluga Acipenser dauricus Georgi, 1775 and Amur Sturgeon Acipenser schrenckii 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 (♀) x Amur sturgeon (♂). This asymmetry could be caused by the large difference in sizes of 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 (♀) x Amur sturgeon (♂)) x 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.

[On the Population Genetic Portrait of Kaluga, Acipenser dauricus Georgi, 1775 Analysis of Sequence Variation in the Mitochondrial DNA Control Region].

The variability of the mtDNA D-loop was examined in kaluga endemic to the Amur River, which is classified as critically endangered by the IUCN Red List of Threatened species. Sequencing of the D-loop fragment (819 bp) in 122 kaluga specimens collected in Lower Amur revealed 27 unique genotypes. The sample was characterized by a relatively low level of haplotypic (0.927) and nucleotide (0.0044) diversity. No considerable deviations from the neutral mutation model of DNA polymorphism were observed. Overall, the mismatch distribution patterns and the results of testing of simple demographic models (sudden demographic expansion and exponential population growth) pointed to a past increase in the number of kaluga sturgeons. According to the Bayesian skyline, the kaluga population doubled over the last two to three thousand years. The number of mature females in the modern kaluga population and the assessment of their long-term effective population size (Nef) are roughly at the same level (about three thousand individuals), which confirms the validity of assigning kaluga to the category of species on the brink of extinction.

THE FIRST RECORD OF DIMEROSACCUS ONCORHYNCHI (TREMATODA: OPECOELIDAE) IN FISHES FROM RIVERS OF PRIMORSKY TERRITORY, RUSSIA, WITH A DISCUSSION ON ITS TAXONOMIC POSITION USING MORPHOLOGICAL AND MOLECULAR DATA.

The opecoelid trematode Dimerosaccus oncorhynchi (Eguchi, 1931) Shimazu, 1980, hitherto known only from the Japanese archipelago, has been found in three species of freshwater salmonid fish (Oncorhynchus masou, Brachymystax tumensis, Salvelinus curilus) from rivers of Primorsky Territory, the Sea of Japan basin, Russia. This is the first record of the parasite in the continental part of Asia. Fishes B. tumensis and S. curilus are new hosts for D. oncorhynchi. The ecological notes, morphological description and drawings of the found trematodes clarifying the morphology of the male reproductive system are given. In the present study phylogenetic relationships of the species D. oncorhynchi with the related taxa were revealed using partial sequences of the 28S rDNA. Obtained results indicate the validity of D. oncorhynchi as the member of the subfamily Opecoelinae, which was closely related to the genus Opecoeloides, a representative of this subfamily.

[Mitochondrial DNA sequence variation, demographic history, and population structure of Amur sturgeon Acipenser schrenckii Brandt, 1869].

The variability of the mtDNA control region (D-loop) was examined in Amur sturgeon endemic to the Amur River. This species is also classified as critically endangered by the IUCN Red List of Threatened species. Sequencing of 796- to 812-bp fragments of the D-loop in 112 sturgeon collected in the Lower Amur revealed 73 different genotypes. The sample was characterized by a high level of haplotypic (0.976) and nucleotide (0.0194) diversity. The identified haplotypes split into two well-defined monophyletic groups, BG (n = 39) and SM (n = 34), differing (HKY distance) on average by 3.41% of nucleotide positions upon an average level of intragroup differences of 0.54 and 1.23%, respectively. Moreover, the haplotypes of the SM groups differed by the presence of a 13-14 bp deletion. Most ofthe samples (66 out of 112) carried BG haplotypes. Overall, the pattern of pairwise nucleotide differences and the results of neutrality tests, as well as the results of tests for compliance with the model of sudden demographic expansion or with the model of exponential growth pointed to a past significant increase in the number of Amur sturgeon, which was most clearly manifested in the analysis of data on the BG haplogroup. The constructed Bayesian skyline plots showed that this growth began about 18 to 16 thousand years ago. At present, the effective size of the strongly reduced (due to overharvesting) population of Amur sturgeon may be equal to or even lower than it was before the beginning of this growth during the Last Glacial Maximum. The presence in the mitochondrial gene pool ofAmur sturgeon of two haplogroups, their unequal evolutionary dynamics, and, judging by scanty data, their unequal representation in the Russian and Chinese parts of the Amur River basin point to the possible existence of at least two distinct populations of Amur sturgeon in the past.