Finding a new form of the grayling Thymallus arcticus (thymallidae) in the basin of lake baikal

A dwarf form of the Arctic grayling Thymallus arcticus, inhabiting a group of small lakes at the origin of the Yakchii stream, which flows into the Verkhnyaya Angara River (basin of Lake Baikal), has been found in the northeastern watershed of the Baikal and Lena basins. The form is similar to upper Lena populations in body coloration and the pattern of dorsal fin. Our comparison by meristic characters indicated that the grayling of the Yakchii Lakes is more similar to the fish from Kutima River (basin of the upper courses of the Lena River) than to the black Baikal grayling T. arcticus baicalensis. The presence in Lake Baikal of a population similar to upper Lena graylings may have three causes: (1) possible drainage from Baikal to the pra-Lena via ancient valleys of the Barguzin and the Upper Angara; (2) appearance of transit zones as a result of glacial or tectonic events during the periods of watershed development between the Baikal and Lena basins; (3) the upper Lena grayling could be an endemic of the Baikal basin which was replaced by graylings penetrating from the Yenisei basin and remained in the form of relic populations in the upper courses of certain tributaries of the northern and northeastern parts of Lake Baikal.     

Graylings of Baikal Lake basin (Thymallus, Thymallidae): Diversity of forms and their taxonomic status

The morphological characters, molecular-genetic features, and patterns of the dorsal fin in different subspecies and forms of Arctic grayling Thymallus arcticus populating Lake Baikal and its tributaries, Irkutsk Reservoir, and Lake Khubsugul have been studied. Three groups are discernable. The first includes the white and black Baikal graylings T. a. baicalensis, as well as the western Siberian T. a. arcticus; the second group is represented by the Kosogol grayling T. a. nigrescens, and the third is composed of T. arcticus ssp. from the Yakchii lakes (the Verkhnyaya Angara basin) with a phenotype close to graylings populating the upper reaches of the Lena River. All of them are distinguished by some morphological characters, elements of the dorsal fin pattern, and by body coloration. The populations of black Baikal graylings are genetically uniform, and their distinctions from white Baikal graylings are insignificant, which agrees with the absence of a considerable divergence of these forms by a complex of meristic characters. It is assumed that in the black and white Baikal graylings the exchange by genetic information has either ceased quite recently, or persists, although, insignificantly. Some genetic remoteness of the west Siberian grayling from Irkutsk Reservoir and Nizhnyaya Tunguska, closely related to the Baikal grayling, is recorded. The formation of the Khubsugul subspecies is possibly a result of the contact of grayling populations during the rearrangements of the river system in the last glaciation period in the upper reaches of Yenisei and Selenga in Mongolia. The habitation in the Baikal system of the Upper Lena graylings indicates a connection between the Lena and Baikal basins in the past. The results of a multivariate analysis of meristic characters and the sequences of mitochondrial DNA confirm the conclusion made by Svetovidov (1931, 1936), concerning the absence of grounds to assign a species status to the Baikal forms.     

New data on the distribution of the Upper Lena form of grayling (Thymallidae) in the basin of Lake Baikal and its taxonomic status

The habitation of the Upper Lena form of grayling in the upper reaches of the Tiya (the northwestern tributary of Lake Baikal) and Barguzin rivers, where Baikal grayling Thymallus baicalensis Dyb. also occurs, was established. The listed forms can be diagnosed from the body coloration, dorsal fin pattern, combination of meristic characters, as well as by molecular-genetic methods. The sympatric habitation of the Upper Lena and Baikal graylings in the northern tributaries of Baikal, considerable phenotypic and genetic differences, as well as the absence of individuals with intermediate characters, make it possible to consider them as independent species. The results indicate the need to revise the intraspecies structure of the Arctic grayling T. arcticus (Pall.) and the entire genus Thymallus. The localization of populations of the Upper Lena grayling in the upper reaches of Baikal tributaries testifies to its possible penetration of the Baikal basin by means of temporary river catchments that formed in the past and which are probable at present at watersheds with the Lena River. A wider distribution of this form is apparently hindered by the pressure of aboriginal species.     

A new species of grayling <Emphasis Type="Italic">Thymallus svetovidovi</Emphasis> sp. nova (Thymallidae) from the Yenisei basin and its position in the genus <Emphasis Type="Italic">Thymallus</Emphasis>

The Upper Yenisei grayling Thymallus svetovidovi sp. nova that inhabits the headwaters of the Yenisei River in Mongolia is described. From the other representatives of the genus Thymallus, the species differs in the elements of body coloration, dorsal fin pattern, some morphometric characters, and genetic characteristics. Besides this species, most of the Yenisei basin is inhabited by Baikal grayling T. baicalensis Dyb., and its low reaches, by the Arctic grayling T. arcticus (Pall.).     

On the diversity and taxonomic status of graylings (Thymallus Thymallidae) from the Lena River

Two forms of graylings were distinguished in the Lena River, which differ in body coloration, the shape and pattern of the dorsal fin, and biological characteristics. With respect to these traits, the forms are divided between the upper and lower Lena. The first inhabits most of the basin, from the upper courses to the lower reaches, whereas the second inhabits the Lena delta and the adjacent arctic rivers and their tributaries. Comparative analysis of meristic traits revealed their low appropriateness for diagnosing Lena lineages as well as grayling populations inhabiting other northern rivers of Siberia. The body and fin coloration in the upper Lena form significantly differ from that found in forms and subspecies of graylings from the basins of the other rivers in the ranges of Eastern Siberian, Kamchatka, and Alaska. The lower Lena form should be classified with the Eastern Siberian subspecies T. arcticus pallasii and is closer to the populations of graylings from the rivers Anabar and Yana, and the rivers of the Chukot Peninsula and Alaska, and the upper courses of the Missouri. These results are supported by analysis of the mitochondrial DNA of graylings throughout the Paleoarctic. Further studies of these lineages and phylogenetic relationships between Arctic lineages are necessary for the final determination of the taxonomic status of the upper Lena form.     

New host species and new distribution areas of <Emphasis Type="Italic">Salmincola lavaretus</Emphasis> (Copepoda: Lernaeopodidae): A parasite of coregonid fishes of Siberia

Data on the infestation of certain fish species by the parasitic copepod Salmincola lavaretus are presented for the first time. The infested fish species included Bauntovsky whitefish (Coregonus baunti), an endemic species from the Maloye and Bolshoye Kapylyushi lakes; Siberian whitefish (C. pidschian) and Siberian cisco (C. sardinella) from Bolshoye Kapylyushi Lake and Baunt Lake, which belong to the Tsypo-Tsypikan lake system (the Lena River basin, Transbaikalia); and Teletsky whitefish (C. lavaretus natio smitti) from Teletskoe Lake (the Ob River basin). Previously, S. lavaretus had been described as a parasite of Baikal omul (C. migratorius) and Baikal whitefish (C. baicalensis) from Baikal. The taxons of S. longimanus complex (S. longimanus, S. l. sibirica, S. svetlanovi, and S. lavaretus)—parasites of nasal fossae of grayling and coregonid fishes—were registered in the lakes of the Lake Baikal basin (Lake Baikal and Khovsgol Lake), the Lena River, the Yenisei and the Ob rivers (the largest rivers of the Arctic zoogeographic province), and the Kobdo River (the Western Mongolian province). It was assumed that S. longimanus complex is more widely distributed in the water bodies of the Arctic zoogeographic province of the Palearctic.     

Comparative analysis of oocyte growth in two forms of Baikal grayling <Emphasis Type="Italic">Thymallus baicalensis</Emphasis> (Thymallidae)

Size characteristics of oocytes of the elder generation of the end of previtollogenesis, as well as of the beginning and middle of the phase of cytoplasm vacuolization in two forms of Baikal grayling Thymallus baicalensis were studied. In each form, the dependence of oocyte parameter on the age and size of females is traced. During the studied phases of development—at the termination of the period of previtellogenesis and at the proper beginning of the period of vitellogenesis—oocytes of the white and black graylings have similar sizes; cytoplasm vacuolization in white grayling proceeds less actively. It was established that differences in the diameter of mature ovicells in the black and white Baikal graylings result from dissimilar rate of accumulation of trophic substances in the oocytes of the given forms of this species and are determined by differences in the rate of growth of oocytes during the formation in them of yolk inclusions.     

Graylings (Thymallidae) of water bodies in western Mongolia: Morphological and genetic diversity

Morphological characters, the pattern on the dorsal fin, some biological parameters, and variations of mtDNA control region were studied in graylings of the upper reaches of the Khovd River (western Mongolia). Obtained results demonstrated that grayling of this part of the river was presented by great (predatory) and small (benthophagous) forms of Mongolian grayling Thymallus brevirostris. The last form was erroneously equated to Arctic grayling Thymallus arcticus. However, genetic unity of great and small forms, homogeneity by meristic characters, and similarity in varying the color of scales and pattern on the dorsal fin attest their belonging to the same species. Water bodies of the Central Asian basin are also populated with populations of Mongolian grayling with mixed type of feeding and signs of external structure, which are typical for both forms in a different degree.     

Age and growth comparisons of Hovsgol grayling (Thymallus nigrescens Dorogostaisky, 1923), Baikal grayling (T. baicalensis Dybowski, 1874), and lenok (Brachymystax lenok Pallas, 1773) in lentic and lotic habitats of Northern Mongolia

Despite concern over the conservation status of many Mongolian salmonids and the importance of their ecological role in Mongolia's aquatic ecosystems, little is known about their basic biology. Hovsgol grayling (Thymallus nigrescens) is endemic to Lake Hovsgol, Mongolia and listed as endangered on the Mongolian Red List. Baikal grayling (T. baicalensis) and lenok (Brachymystax lenok) are found in lakes and rivers throughout the Selenge drainage. A detailed study of the age and growth of these three salmonids was conducted based on 1,682 samples collected from July 2006 to July 2013 in Lake Hovsgol, its outlet the Eg River, and one of the Eg's largest tributaries, the Uur River. Our results suggest that Hovsgol grayling in particular can reach a much older maximum age (17 years in our samples) than previously believed based on aging from scales. Female Hovsgol grayling were heavier at a given length than their male counterparts. Lenok had a greater average length‐at‐age in Lake Hovsgol compared to the rivers and greater weight‐at‐length in the warmer Uur River than in the Eg; female lenok from the rivers had a greater average length‐at‐age than their male counterparts. This study provides critical new information for the management and conservation of these threatened salmonid species in Mongolia.     

A comparative analysis of the Far Eastern grayling species Thymallus tugarinae and Thymallus grubii flavomaculatus based on the data from mitochondrial DNA cytochrome b gene sequencing

Nucleotide sequences of a fragment of mitochondrial DNA cytochrome b gene were obtained from two species of graylings that inhabit the Russian Far East, viz., Thymallus tugarinae and T. grubii flavomaculatus. A phylogenetic analysis of four Thymallus species, whose relationships have been poorly studied, was performed on these new data as well as on several sequences from the NCBI GenBank sequence database. The rate of genetic divergence between the Far Eastern graylings Thymallus tugarinae and T. g. flavomaculatus corresponded to that between European (T. thymallus) and Arctic (T. arcticus) graylings. Moreover, single nucleotide substitutions that result in alterations of the amino-acid structure of protein products (non-synonymic mutations) were revealed between sequences of the cytochrome b gene in the Far Eastern grayling species. The topology of phylogenetic trees, which was composed by means of Bayesian analysis and the maximum parsimony method, showed four independent phylogenetic lineages of graylings. In addition, the phylogenetic relationships between T. tugarinae and T. g. flavomaculatus were supported statistically. The obtained data indicated that Far Eastern graylings T. tugarinae and T. g. flavomaculatus are distinct species and confirmed that they belong to different phylogenetic lineages, as found earlier.     

Biological features of Low Amur grayling Thymallus tugarinae (Salmoniformes: Thymallidae): 2. Growth

We present the results of analysis of the group growth of the Low Amur grayling Thymallus tugarinae from 18 rivers of the Low Amur basin, tributaries of the Bureya and Ussuri rivers. We made use of the published data on the fishes of Sakhalin Island. The dwarf and fast-growing forms are not revealed among the investigated groups of this species. The parameters of growth of the Low Amur grayling in the investigated rivers are different, which is determined by the different conditions of feeding migration connected with the geographical location of the streams, their hydrological features, density of populations, etc. The anthropogenic factor influence is essential. Growth rate of T. tugarinae is lower compared with the other Amur species of graylings.     

Transformation of Baikal sponges (family Lubomirskiidae) after penetration into the Angara River

Genetic and morphological analysis of endemic sponges of the Lubomirskiidae family from Lake Baikal and the upper reaches of the Angara River was performed. Various sponge species acquired a number of similar morphological traits after the transition from the lake into the river. These traits enabled an increase of sponge skeleton strength under the conditions of elevated hydrodynamic activity. The changes significantly impeded morphology-based species identification of Angara sponges. Phylogenetic analysis of ITS regions and noncoding mitochondrial DNA fragments confirmed that the Angara sponges belonged to the Baikalian Lubomirskiidae family and demonstrated the polyphyletic origin of the sponges. The use of combined molecular and morphological data allowed for the clustering of some sponge samples into groups that corresponded to individual species. The absence of genetic isolation between the Baikalospongia intermedia and Lubomirskia baicalensis species was demonstrated, whereas the B. intermedia profundalis subspecies was well separated from B. intermedia. This finding pointed to the necessity of further studies for the clarification of the taxonomic status of this subspecies.     

A new subspecies of the amur grayling Thymallus grubii flavomaculatus ssp. nova (Thymallidae)

A new subspecies of the Amur grayling is described, the yellow-spotted grayling Thymallus grubii flavomaculatus ssp. n. populating the upper reaches of large tributaries of the Lower Amur basin and some rivers flowing to the Tatar Strait, the Sea of Okhotsk, and the Sea of Japan. From nominative subspecies T. g. grubii populating the basin in the upper reaches of the Amur and from other representatives of the genus Thymallus, this subspecies differs in the dorsal fin pattern whose principal trait is a yellow spot on the last two-five interray membranes, in the body coloration, and in some morphological characters. The yellow-spotted grayling in the upper reaches of tributaries sympatrically coexists with the Lower Amur grayling Thymallus sp. No specimens with intermediate characters are found. The sympatric forms spawn at different times, thus being isolated reproductively. Isolation of the yellow-spotted grayling as a subspecies of the Amur grayling T. grubii is confirmed by the results of molecular-genetic investigations.     

Materials on the flora of diatoms (Centrophyceae) from lakes of the Baikal Region and Transbaikalia

The species composition of Centrophyceae (Bacillariophyta) in the phytoplankton of nine lakes in the Baikal Region and Transbaikalia was studied using electron microscopy (SEM) methods. Nineteen species and varieties of Centrophyceae were recorded; Aulacoseira distans var. septentrionalis and Cyclotella arctica were registered in this region for the first time. Aulacoseira baicalensis, Cyclotella minuta, and Stephanodiscus inconspicuus were also found in the studied lakes and attributed to being endemic to Lake Baikal.     

Seismosensory system of the Lower Amur rayling <Emphasis Type="Italic">Thymallus tugarinae</Emphasis> (Thymallidae) from the Anyui River

Data on specific features of the seismosensory system of the Lower Amur grayling Thymallus tugarinae from the Anyui River (basin of the Lower Amur) are provided. According to the number of openings in canals of the seismosensory system, individuals from the middle course significantly differ from graylings from the lower course in greater values of interpopulation diversity and fluctuating asymmetry. According to the number of pores of canals of the seismosensory system, the Lower Amur grayling differs from the East Siberian T. arcticus pallasi, Kamchatka T. a. mertensii, and Alaska T. a. signifer graylings.     

Comparative biology and management of Arctic and European grayling (Salmonidae,Thymallus)

Summary The biological and ecological features of Arctic grayling (Thymallus arcticus) relevant to its management and enhancement are reviewed over its range in North America as well as in Asia, and are compared with those for the European grayling (Thymallus thymallus). Populations of both species have declined in some areas where angling pressure has been severe and where major alterations of their habitats have occurred. But native populations of Arctic grayling have been extirpated in eastern parts of its North American range, and nearly so in south-western parts, whereas the range of European grayling has been extended, especially in the United Kingdom and in Finland, by introduction. Furthermore, in contrast to the Arctic grayling, the European grayling, in Scandinavia at least, seems to have been less severely affected by impoundment of rivers and lakes for hydroelectric generation, perhaps because it has been able to successfully reproduce in large rivers below dams, especially those where fluctuation in water level is small.The success of various grayling management and enhancement practices, including hatchery culture and stocking, angling restrictions, spawning and rearing facilities, competitor and predator control, stream habitat restoration, lake and stream fertilization, and invertebrate prey introduction, are evaluated and compared for both species.     

Heavy metal content and response of the blood system of Siberian dace <Emphasis Type="Italic">Leuciscus leuciscus baicalensis</Emphasis> (Cypriniformes,Cyprinidae) under anthropogenic impact

Chemical, hematological, and immunological characteristics of the Siberian dace Leuciscus baicalensis from different areas of Lake Baikal basin were first determined. It was established that the most considerable changes in hemopoesis, cellular, and humoral links of immunity were in individuals with a high content of heavy metals in the liver from populations inhabiting the Selenga River downstream the Ulan Ude Industrial Center and the Selenga Pulp-and-Cardboard Plant. Changes in immunohematological responses of L. leusiscus baicalensis from Cherkalov Bay of Lake Baikal proceeded within the adaptive possibilities of the species and indicated the development of compensatory reactions in response to the accumulation of heavy metals in the body. The results obtained make it possible to assert that Chivurkuiskii Bay of Baikal may serve as a control polygon during monitoring of immunobiological states of fish populations from Baikal basin.     

New species of grayling <Emphasis Type="Italic">Thymallus tugarinae</Emphasis> sp. nova (Thymallidae) from the Amur River Basin

Data on a new species, low Amur grayling Thymallus tugarinae sp. nova, inhabiting tributaries of the lower and middle current of the Amur River, are presented. This species has been earlier equated with the Amur grayling T. grubii, described by Dybowski (1869) from the rivers Onon and Ingoda (the Upper Amur Basin). The new species differs from other representatives of the genus in the body coloration, the pattern on the upper fin, and certain morphological characters. On most of the Amur Basin, the grayling from the Lower Amur is sympatric with T. grubii and in its tributary Bureya River, also with the Bureya grayling T. burejensis. Individuals with intermediate traits are unknown, pointing to reproductive isolation. These data are supported by the results of molecular-genetic analysis (Froufe et al., 2003, 2005; Knizhin et al., 2004).     

Biological specific features of the Lower Amur grayling Thymallus tugarinae (Salmoniformes: Thymallidae): 1. Age composition

We consider age composition of samples of the Lower Amur grayling Thymallus tugarinae inhabiting water bodies of the lower and middle course of the Amur and several rivers of the northwestern part of Sakhalin Island and the southern coast of the Sea of Okhotsk. Age composition of the Lower Amur grayling from the studied samples is not similar because of several reasons. In rivers of the Amur basin, the species has a maximal age of 6+.     

Finding of the subarctic leeches, Acanthobdella peledina and Cystobranchus mammillatus, in the Lake Baikal basin and the reasons for their absence in Lake Baikal itself]

Acanthobdella peledina was first found in the basin of Lake Baikal on the fluvial form of the Balkal grayling Thymallus arcticus baicalensis and Coregonus lavaretus pidschian from the Upper Angara. Cystobranchus mammillatus, a parasite of burbot, is widely distributed in the tributaries of Baikal. The absence of these subarctic leeches from Baikal itself is explained by their rheophily.