Diplodiscus Mehrai Pande, 1937 and D. Japonicus (): Morphology of Developmental Stages and Molecular Data.

Specimens of the snails Anisus centrifugops were infected with two types of cercariae relating to the genus Diplodiscus, differing from each other by body and organ sizes were found in a pond in the territory of Vladivostok (Primorsky region, Russia). Further study of their morphology and life cycles allowed us to establish that these flukes belong to Diplodiscus japonicus (Yamaguti, 1936) and D. mehrai Pande, 1937. Morphological and molecular data confirmed the validity of D. japonicus which had previously been synonymized with D. amphichrus Tubangui, 1933 and D. mehrai Pande, 1937.

[Phylogenetic relationships of Amur sturgeon Acipenser schrenckii Brandt, 1869 based on 18S rDNA sequensing data].

The analysis of phylogenetic relationships based on 18S rDNA sequences of Amur sturgeon Acipenser schrenckii Brandt, 1869 with other acipenseriform species was performed in this study. Complete sequences (1746 b. p.) in seven individual clones of A. schrenckii 18S rRNA were determined. Mutation profile of Amur sturgeon 18S rDNA demonstrated high similarity with that of Lake Sturgeon A. fulvescens. Both presumably functional sequence and the specific mutation (insertion of adenine after position 658) of Amur sturgeon 18S rDNA were identified by structural-functional analyses. Phylogenetic reconstructions performed using different methods (NJ, MP, ML and Bayesian) support monophyly of the genus Acipenser and point to: 1) closer relationships Amur sturgeon with sterlet, than Baltic sturgeon, which is in agreement with Artyukhin's eco-morphological classification (Artyukhin, 1995, 2006); 2) sufficiently high differentiation between North-American (A. fulvescens) and Eurasian (A. schrenckii, A. ruthenus and A. sturio) sturgeons.

[Molecular identification and the features of genetic diversity in interspecific hybrids of Amur sturgeon (Acipenser schrenckii x A. baerii, A. baerii x A. schrenckii, A. schrenckii x A. ruthenus, and A. ruthenus x A. schrenckii) based on variability of multilocus RAPD markers].

The method of polymerase chain reaction with random primers (RAPD PCR) was used to identify the progeny of the crosses between three sturgeon species, Amur sturgeon (Acipenser schrenckii Brandt, 1869), Siberian sturgeon (A. baerii Brandt, 1869), and sterlet (A. ruthenus Linnaeus, 1758). Using ten primers, genetic variation in 70 yearlings, produced in seven individual crosses: Acipenser schrenckii x A. schrenckii, A. baerii x A. baerii, A. ruthenus x A. ruthenus, A. schrenckii x A. baerii, A. baerii x A. schrenckii, A. schrenckii x A. ruthenus, and A. ruthenus x A. schrenckii was described and evaluated. It was demonstrated that the samples composed of hybrids from individual crosses were more variable than the samples of parental species. On the other hand, pooled samples of hybrids from two cross directions were genetically less variable than the pooled samples of their parents. The three main features of the hybrid RAPD profiles identified included: (1) preservation of marker DNA fragments of both parents in one genome; (2) presence of specific DNA fragments, absent from both parents; and (3) dependence of the frequency of some DNA fragments from the cross direction. Multidimensional scaling clearly distinguishes in the space of three coordinates the individuals of original species and the hybrid progeny with differentiation in the groups of direct and backcross hybrids. Analysis of relationships (UPGMA and NJ) pointed to substantial differentiation between the species, as well as between the species and hybrid progeny. Close genetic relationships between direct and backcross hybrids were demonstrated. Multilocus RAPD markers in association with statistical methods are considered to be the useful tool for discrimination of interspecific hybrids of sturgeon. Possible reasons for the differences in the hybrid RAPD profiles are discussed.

[Discrimination of interspecific hybrids in natural populations of Amur sturgeon fishes using multilocus RAPD-PCR markers].

RAPD-PCR analysis of 46 individuals of sturgeons from Amur River has been carried out. Genetic status of Amur sturgeon Acipenser schrenckii Brandt, 1869 and kaluga Huso dauricus Georgi, 1775 native populations has been estimated. Genetic evidences of hybrid origin for two phenotypical hybrids were obtained; estimations of genetic distances between species and hybrids appeared to be at interspecific level. The exact test for differentiation of populations (Exact test) and multidimensional scaling (MDS) analysis were estimated to be the most effective for species and hybrid discrimination, respectively. According to data obtained populations of sturgeon fishes which inhabit Amur River maintained an essential level of genetic variability; the presence of hybrids is regarded as one of risk factors. Multilocus RAPD-PCR markers admit as the convenient and reliable tool for genetic monitoring of Amur River sturgeons to preserve their gene pool.