Morphological variation of oocytes of initial phases of vitellogenesis in two forms of Baikal grayling <Emphasis Type="Italic">Thymallus baicalensis</Emphasis> (Thymallidae)

The variation of oocytes of initial phases of vitellogenesis in two forms of Baikal grayling Thymallus baicalensis was studied. The dependence of their diameter on the size-age indices of females, as well as differences in the sizes of oocytes between the studied forms, was established. Comparison of oocytes of identical forms of development revealed that oocytes of the white grayling during termination of the phase of cytoplasm vacuolization and at the beginning of the phase of yolk accumulation have a smaller diameter of the cell, of the nucleus, respectively, and of yolk granules and a greater, with respect to cell diameter, size of vacuoli. The revealed differences of morphological characteristics of oocytes of initial phases of vitellogenesis in combination with the well-known, stably smaller (by a factor of 1.5) size of mature eggs of the white Baikal grayling that matures at a later age at larger sizes indicate a profound adaptive diversification in the course of development of the reproductive system of both forms.     

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.     

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.     

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.     

Biological and morphological characteristic of the Arctic grayling Thymallus arcticus (Thymallidae) from Alpine Lakes of the basin of the upper reaches of the Angara River

Specific morphological and biological features of the populations of the Arctic grayling Thymallus arcticus from lakes Urunge Nur, Mongosha, Sadaiskoe, and Gusinoe situated in the Upper Sayan Mountains in the sources of the Oka and Kitoi rivers (the basin of the upper reaches of Angara) that have been not studied previously are considered. The results of the multivariate analysis indicated the uniformity of all samples by 12 meristic characters. Graylings of the studied lakes are similar to graylings from the Angara and Nizhnyaya Tunguska rivers and the Irkutsk Reservoir, as well as to the Baikal grayling T. a. baicalensis in body coloration and pattern of the dorsal fin. The samples studied and T. a. baicalensis considerably differ in the above characters from populations inhabiting the basin of the upper reaches of the Ob that belong to the nominative subspecies T. a. arcticus. The differences established between the Angara-Yenisei and the Upper Ob graylings give grounds to doubt the justification of including them into one taxon, T. a. arcticus. The same is evidenced by the results of molecular-genetic studies of graylings from the Palearctic (Froufe et al., 2005). The data obtained indicate the necessity of ascertaining the boundaries of the ranges of different forms of graylings in the Angara-Yenisei and Ob basins and of the revision of their taxonomic status. Populations inhabiting the Angara and Yenisei rivers, except their sources and the section of the lower reaches, should be assigned to the Baikal subspecies, T. a. baicalensis. Graylings from different lakes in the upper reaches of Oka and Kitoi differ in their linear-weight indices. The indices of growth are highest where they occupy a dominant position. Their food in the summer consists mainly of the larval and imaginal stages of amphibiotic and aerial-terrestrial insects. Only in Lake Urunge Nur do graylings of elder age groups use fish of other species for food. The extreme conditions of habitation of the grayling in Lake Gol’tsovoe are the cause of food deficiency, which determines its dwarfism.     

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.     

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.     

General patterns of sexual dimorphism in graylings (Thymallus), with a comparison to other salmonid species

Among fishes, salmonids (family Salmonidae) have attracted a great deal of research attention focused on sexual dimorphism and associated selective forces. Most of this research has been directed toward anadromous and mostly semelparous salmon and trout (Oncorhynchus, Salmo), and comparatively little is known about intersexual variability in strictly iteroparous freshwater salmonids. We examined a comprehensive data set of 28 linear morphometric characters in 11 of 15 currently recognised species of grayling (Thymallinae, Thymallus), a genus consisting of iteroparous species only, to identify general patterns of intersexual morphological variability. Overall, we found that all grayling species show common sex-specific traits particularly relating to size dimensions of the dorsal, anal, pelvic and pectoral fins. Although the magnitude of sexual dimorphism differed among species, there was no significant phylogenetic signal associated with these differences across the genus. These results are discussed in terms of the assumed selection pressures driving sexual dimorphism in graylings and are compared to existing knowledge in Salmonidae as a whole where similarities and differences with both Salmoninae and Coregoninae exist. The present study provides the first detailed genus-wide comparison of sexually dimorphic phenotypic characters in graylings, and highlights the need for more large-scale comparative studies in multiple salmonid species to better understand general macroevolutionary trends among this important group of freshwater fishes.

     

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.     

Genetic differentiation of Arctic charr <Emphasis Type="Italic">Salvelinus alpinus</Emphasis> complex from Transbaikalia revealed by microsatellite markers

Variation at eight microsatellite loci was studied in Arctic charr Salvelinus alpinus complex from five Transbaikalian mountain lakes. Samples from three lakes included two sympatric charr forms (dwarf and small) differing in trophic specialization, morphology and life cycle parameters. Sympatric forms were genetically closer to each other than to charr from other lakes which evidences their independent origin in each of these lakes as the result of sympatric speciation. In each lake, gene pools of sympatric forms were segregated to a different degree (estimates of F _ST varying from 0.030–0.184 and those of ρ _ST varying from 0.119–0.359). Hierarchical analysis of allelic frequencies variance (AMOVA) in Arctic charr from Lake Baikal, the Vitim, and the Olekma basins showed that variation among and within these basins accounted for 19.5% of the interpopulational variance each. In the AMOVA design, investigating differences among sympatric forms in three lakes these differences accounted for 7.1% of the total variance.     

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.     

Comparative analysis of respiratory activity in the wild type strain of <Emphasis Type="Italic">Neurospora crassa</Emphasis> and its photoreceptor complex mutants

Cell respiratory activity of protoplasts obtained from the wild type of Neurospora crassa and photoreceptor complex WCC—white collar 1 (wc-1) and white collar 2 (wc-2)—mutants of Neurospora crassa strains was investigated. Respiration inhibition by KCN in the presence of 25 mM succinate was similar in all strains and did not exceed 83–85% against control. The significant induction of KCN-resistant respiratory pathway occurred under 1% glucose oxidation in wc-1 and wc-2 mutants if compared with the wild type strains. The inhibitors of the main (cytochrome) pathway of electron transfer in mitochondria—1 mM KCN and antimycin A (4 μg/ml)—blocked the respiration rate of the protoplasts from N. crassa wild type by 75%, while the cell respiration of wc-1 and wc-2 strains was suppressed by approximately 50%. The specific inhibitor of alternative oxidase—10 mM salicylhydroxamic acid (SHAM)—in combination with the blockers of mitochondrial electron transfer chain caused the total suppression of respiratory activity of protoplasts in all studied strains. It is supposed that an increase of KCN-resistance in WCC mutants under glucose oxidation is connected with alternative oxidase activation as the result of failure in reception and signal transduction of active oxygen species.     

New data on biology of the pearlfish <Emphasis Type="Italic">Maurolicus imperatorius</Emphasis> (Sternopthychidae) from the Emperor Seamount Chain

The pearlfish Maurolicus imperatorius occurs above seamounts of the Emperor Seamount Chain between 30°–40° N and 168°–176° E. It forms dense aggregations at the daytime in the upper mesopelagial above the ground and disperses in the dark period of the day in the surficial layer. Judged by maturation dynamics of gonads, the spawning of this species occurs from January until April with the maximum in March. Catches of this species are characterized by expressed seasonal dynamics of size composition. Juveniles appear in catches in the end of spring-the beginning of summer. The maximum recorded SL is 68 mm. Among large fish, females dominate. The part of females is maximum in winter and minimum in spring. The age of fish with AC 46–63 mm is 265–420 days. The growth rate is abruptly retarded at the fourth month of life when the length 40–45 mm is attained. Life duration of most fish does not exceed 1.5 years, though some specimens may attain the age of two years. It is supposed that the presence of another species—M. japonicus—on the Emperor Seamount Chain may result from passive transfer in the Kuroshio waters.     

Subcellular localization of Cd in the root cells of<Emphasis Type="Italic">Allium sativum</Emphasis> by electron energy loss spectroscopy

The ultrastructural investigation of the root cells ofAllium sativum L. exposed to three different concentrations of Cd (100 (AM, 1 μM and 10 mM) for 9 days was carried out. The results showed that Cd induced several significant ultrastructural changes — high vacuolization in cytoplasm, deposition of electron-dense material in vacuoles and nucleoli and increment of disintegrated organelles. Data from electron energy loss spectroscopy (EELS) revealed that Cd was localized in the electron-dense precipitates in the root cells treated with 10 mM Cd. High amounts of Cd were mainly accumulated in the vacuoles and nucleoli of cortical cells in differentiating and mature root tissues. The mechanisms of detoxification and tolerance of Cd are briefly explained.     

Development of skeleton elements in juvenile dwarf and small sympatric forms of <Emphasis Type="Italic">Salvelinus alpinus</Emphasis> complex from Lake Davatchan (Transbaikalia)

The development of skeleton elements was studied in prolarvae, larvae, and fry of two morphologically different forms of the Arctic char Salvelinus alpinus complex—small plankton-eating and dwarf (having a seasonal change of plankton and benthic feeding)—that sympatrically inhabit Lake Davatchan (Transbaikalia). According to genetic data, these forms diverged in this lake from a specialized lacustrine ecotype of char and reached reproductive isolation. Comparative analysis revealed similarity in the shape of anlagen and transitive states of cranial bones. In prolarvae and larvae of the dwarf form, the onset of similar morphological states of skeleton elements occurs at a smaller body length than in fish of the small form. Differences in the development of serial skeleton structures (teeth, gill rakers, fin rays, centra, and scales), heterochronies of timing of appearance and rate of differentiation of skeleton elements were found. It is suggested that these differences resulted from the ecological differentiation of the two forms according to spawning grounds that became local habitats of larvae and fry (sublittoral and hypolimnion). The initial divergence could be caused by the presence in the lake of two (autumn and spring-summer) peaks of numbers of food organisms.     

Characteristics of histopathological changes in organs of banded catfish <Emphasis Type="Italic">Pelteobagrus fulvidraco</Emphasis> (Bagridae) from the Amur River basin

The most frequently occurring pathological changes in the inner organs of banded catfish Pelteobagrus fulvidraco from the Amur basin, including those caused by parasites, are described. Eleven species of parasites are recorded. In gills of individuals from different areas, parasite occurrence varied from 7 (Lake Bolon) to 64% (bays of Bolshoi Ussuri Island), and in the liver tissue they varied from 7 (Lake Bolon) to 16% (Sindinskaya channel). Helminths cause moderate local changes in the liver, which manifests itself in the growth of connective tissue, incapsulation, and aggregation of pigmented macrophages around the capsule. Without relation to parasites, numerous changes were found in the liver: hepatocyte vacuolization (in some cases, focal), hypertrophy of some hepatocytes and an increase in their nuclei (polymorphism), karyopyknosis and diffuse necrosis of hepatocytes (in some cases, focal), edema of the liver, proliferation of bile ducts, and accumulation of pigments in melanomacrophyte centers and in proper hepatocytes. Hepatocyte necrosis—the most important indicator of the toxic impact of pollutants—was recorded in 44–50% of individuals from different areas of the Amur basin. In kidneys, vacuolization and hypertrophy of nephrocytes, coarse granularity of their cytoplasm, and karyopyknosis and necrosis of nephrocytes are observed. Rarely occurring changes in the kidneys include crystallury and proliferation of epithelium of ureters of unclear etiology. Some fish have pathological changes in two to three organs simultaneously.     

On Intraspecies Forms of the Mongolian grayling (<Emphasis Type="Italic">Thymallus brevirostris</Emphasis>Kessl.) from Hoton Nur Lake (Western Mongolia)

Morphological and ecological traits of the Mongolian grayling Thymallus brevirostrisfrom Hoton Nur Lake are investigated with consideration of the assumption for a possible presence in this species of two morpho-ecological forms. The data on growth, feeding, sex, and age composition are presented. Plastic and meristic characters, distribution of fish in the water body, and feeding are analyzed. Within the age range of 3+ to 6+, in the population there are two groups of specimens differing in growth rate, diet, and some plastic characters of the head. These two groups may be designated as “predatory” and “benthos-feeding” forms. The predatory form lacks specimens of junior age groups; the benthos_feeding form lacks specimens older than seven years. Validity of these morpho-ecological groups is discussed.     

Population differences in early life‐history traits in grayling

In this paper we test population differences in early life‐history traits in three grayling Thymallus thymallus populations. The grayling shared ancestors some 80–90 years ago. We performed common‐garden experiments at three temperatures (mimicking population‐specific summer temperatures), and measured survival and growth rates during early development. We found significant additive genetic variance in size (length and yolk‐sac volume) measured at hatching, swim‐up and termination of the experiment, and significantly different reaction norms for growth rate and survival during the period of first feeding. In general, each population did best at the temperature experienced in nature. These differences in early life‐history traits suggest that natural selection has resulted in local adaptation in a time period of 13–18 generations.     

Reproductive characteristics of free-livingCalomys venustus (Rodentia, Muridae)

Calomys venustus showed a cyclic seasonal pattern of reproductive activity characterized by a period of repose and a variable length of the period of sexual activity between August—September to May—June. The study was done from 1983 to 1999. During this time the population density increased from October—November to the end of autumn and sharply decreased in winter. Three peaks in rate of pregnancy were recognized in the breeding period: spring, summer and late summer. The average litter size was different among the three peaks in rate of pregnancy. The reproductive pattern had a peak at the beginning of the spring produced by overwintering animals, and another peak in summer-autumn caused by the reproductive activity of young born in the same period in which they breed. The spring cohort exhibited the greatest breeding contribution suggesting that this cohort is principally responsible for the yearly peak in abundance.     

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.