The gut microbiota of Cystidicola farionis parasitizing the swim bladder of the nosed charr morph Salvelinus malma complex in Lake Kronotskoe (Kamchatka, Russia)

Using the approach of sequencing the V3–V4 region of the 16S rRNA gene, we have analyzed the bacterial diversity associated with the gut and “body” (other parts of nematode after dissection: cuticle, epidermis and longitudinal muscles, etc) of Cystidicola farionis parasitizing the swim bladder of different morphotypes of the nosed charr. Comparisons of the gut microbiota of nematodes with their “body” has revealed that the associated microbiota are closely related to each other. Taxonomic analysis indicated that the relative abundances of the dominant nematode-associated bacteria varied with individual fish. The common dominant microbiota of the gut and “body” of nematodes were represented by Aeromonas, Pseudomonas, Shewanella, and Yersinia, while the associated microbiota of the swim bladder of the nosed charr was dominated by Acinetobacter, Cetobacterium, Pajaroellobacter, Paracoccus, Pseudomonas, Shewanella. By comparing the associated microbiota of nematode parasitizing the different morphotypes of the nosed charr the difference in richness estimates (number of OTU’s and Chao1) were revealed between the N1g and N2 morphs.

Occurrence of sympatric charr groups, Salvelinus, Salmonidae, in the lakes of Kamchatka: a legacy of the last glaciations

Six postglacial lakes were studied along both sides of the Kamchatka central mountain range, Russia. Pairs of local morphotypes of species of Arctic charrs, Salvelinus spp., have previously been described from the southernmost lakes while the fish fauna of the four northernmost lakes was studied here for the first time. Phenotypic data support the division of Kamchatkan lacustrine charrs into two groups according to the number of gill rakers and pyloric caeca, as well as snout-dorsal and snout-ventral distances (MANOVA, P < 0·001). These groups respectively correspond to phenotypes commonly referred to as Salvelinus malma and Salvelinus taranetzi. To clarify the identity of these groups, D-loop and cytochrome b (cytb) region sequences were analysed. Haplotype network analysis of mtDNA shows the salmonids inhabiting four lakes on the south and north are phylogenetically close to either Beringian S. malma or to S. taranetzi from the Chukotka and Kolyma River basins (the mean ± s.e. pairwise per cent sequence divergence is 0·006 ± 0·001). Phenotype-genotype discordance suggests that mitochondrial introgression between species has occurred in the two smallest lakes (<0·5 km² ) in the central part of the peninsula. Identical haplotypes of D-loop and cytb regions were found for the populations of S. taranetzi from the most distant southern and northern lakes, indicating all lakes were colonized by both species simultaneously after the last glacial maximum. Salvelinus taranetzi may have colonized the Kamchatka peninsula from one or both of two different source regions: the Arctic Beringia and the northern coast of the Okhotsk Sea.

[PARASITES FAUNA OF THE LAKE KRONOTSKOE CHARRS (SALVELINUS), KAMCHATKA]

The new data on the parasites fauna of the Lake Kronotskoe sympatric charr forms (genus Salvelinus (Nilsson) Richardson, 1836) is presented. Parasites fauna of Bigmouth and Smallmouth charr forms are described for the first time. The information about Longhead charr, Nosed charr and White charr parasites is added. 29 species of parasites from 9 classes were found: Oligohymenophorea, Myxosporea, Monogenea, Trematoda, Cestoda, Nematoda, Acantocephala, Crustacea and Hirudinea. Longhead charr was the most intensively infected by Proteocephalus longicollis (Zeder, 1800) (abundance 306.0) and Neoechinorhynchus salmonis Ching, 1984 (abundance 230.0). White charr was mostly infected by Crepidostomum Braun, 1900 (abundance 242.2) and P. longicollis (abundance 183.4). Nosed charr group that feed on gammarids was infected mostly by Crepidostomum spp. (abundance 3461.3), Cyathocephalus truncatus (Pallas, 1781) (abundance 179.9) and Cystidicola farionis Fisher, 1798 (abundance 169.0); while Chironomidae consumers group was infected mostly by Diplostomum Nordmann, 1832 (abundance 62.3) and Phyllodistomum umblae (Fabricius, 1780) (abundance 27.3). Bigmouth charr was infected mostly by P. longicollis (abundance 17.0) and Eubolhrium salvelini Schrank, 1790 (abundance 11.0), Smallmouth charr form — by P. longicollis (abundance 67.0) and Diplostomum sp. (abundance 64.2). Sympatric flock of charrs form the Lake Kronotskoe (Kamchatka) is the most polymorphic for the genus Salvelinus in Eurasia. According to the parasitological analysis this flock consists six ecological forms.

Structure of "species flocks" in fishes: Channels of the splanchnocranium divergence in endemic lacustrine benthivorous charrs (Salvelinus, Salmonidae, Teleostei) in Lake Kronotskoye, Kamchatka

The structure of splanchnocranium bones has been studied in four endemic benthivorous charrs (the genus Salvelinus) from Lake Kronotskoe (Kamchatka). It has been found that, according to the whole set of characters of the splanchnocranium structure, the most expressed differences are observed between specialized forms, nosed and largemouth charrs, inhabiting different biotopes of the lake. Differences between small-mouth and white charrs are less pronounced, and the species are characterized by generalized features of the structure of jaws. It can be suggested that, in addition to diverse feeding preferences within a feeding niche, an extremely high diversity of charrs in Lake Kronotskoe is due to a complex geomorphological structure of the water system. Thus, the "species flock" comprising a complex set of diverse benthivorous morphotypes has been formed and exists in Lake Kronotskoe. Charrs from Lake Kronotskoe are a representative example of sympatric speciation by way of formation of new forms differing from each other in morphological, ecological, and trophic features.

[Preliminary data on variation of four microsatellite loci in Pacific herring Clupea pallasii]

Variation of microsatellite loci Cpa 10, Cpa 113, Cpa4, and Cpa7 was for the first time examined in Pacific-type herring Clupea pallasii from the White Sea (CI. pallasii marisalbi), the Kara Sea (CI. pallasii suworowi), the Sea of Okhotsk, and Lake Nerpich'e, Kamchatka Bay, northwestern Pacific (CI. pallasiipallasii). All loci exhibitedhigh genetic diversity. The estimates of expected heterozygosity varied from 41.5 to 95.6% (mean, 82%). The level of pairwise genetic differentiation Fst at all microsatellite loci varied from 0.005 to 0.076 (0.019, on average) and t was statistically significant (P < 0.05) in most of the pairs of herring samples. Estimates of genetic differentiation among the herring of one subspecies were lower than between the groups belonging to different subspecies.

[Postspawning survival in lacustrine sock-eyed salmon Oncorhynchus nerka Walb]

The state of gonads, age, structure of scales, and size of specimens of the resident lacustrine form of sock-eyed salmon--kokanee Onchorhynchus nerka--are analyzed. In stocked, previously fishless, lakes, there are specimens that have survived spawning and have remained active for a year or several years. No evidence was found of the possibility of repeated spawning. Thus, such fish do not belong to the spawning stock of the population, and their ecological function is not clear.