No abstract

Trophic resource partitioning is one of the main ecological mechanisms of adaptive radiation. The Garra is a highly specialized periphyton feeder that has widened jaws equipped with a horny cutting scraper. In a river located in the Ethiopian Highlands in East Africa, a diversification of Garra composed of six sympatric ecomorphs which were strikingly diverse in trophic morphology was revealed. A hypothesis on trophic resource partitioning was tested using data on diet composition, gut length, and stable isotopes. The obtained results confirmed the trophic diversification of Garra ecomorphs. Three feeding modes were revealed: (i) periphytonophagy, (ii) mixed periphytonophagy and zoophagy, and (iii) zoophagy. The periphyton feeders had a long gut and were enriched in δ13C values compared to the shorter gut and lowered δ13C values in the zoophagous ecomorphs. Therefore, Garra could respecialize out of its ancestral specialization. This finding does not support the generalists-to-specialists hypothesis on the origin of specializations, and suggests that Liem’s paradox is a more common phenomenon. In the case of specialists, we assume that new ecological opportunities can be ‘visible’ to specialists if they are preceded by relaxed selection constrains that lead to the widening of the ecological/morphological plasticity to jump out of a canalized mode of ancestral specialization.

Trophic resource partitioning is one of the main drivers of adaptive radiation. The evolutionary diversification of large African barbs, the genus Labeobarbus, seems to be related to mouth polymorphism. The chisel-mouthed or scraping phenotype has repeatedly evolved within Labeobarbus. At least five ecomorphs with a scraping mouth morphology were detected in the waters of the Ethiopian Highlands and can be provisionally classified into two groups: (i) “Varicorhinus”-like, and (ii) “Smiling”-like. Previously, all Labeobarbus with a scraping-mouth morphology were considered to be periphyton feeders. Using data on morphology, diet and stable isotope ratios (C and N), we addressed the question: does a scraping-mouth morphology predict feeding on periphyton? Our study revealed that five scraper ecomorphs exhibited three main feeding modes: (i) periphyton-eating, (ii) herbivory–detritivory, and (iii) insectivory. Two cases of the parallel divergence of sympatric ecomorphs with distinct feeding modes (herbivory–detritivory vs. insectivory) were revealed in two geographically isolated basins. A significant difference in δ15N values was detected among sympatric scraper ecomorphs. A periphytonophagous scraper was rich in δ15N values that are comparable with those in sympatric piscivorous fish. This data sheds light on the possibility of the utilization of periphyton as a protein-rich food by fishes.

The article presents data on the mercury content in the muscles of perch Perca fluviatilis (L.) in four large reservoirs of the Vologda region (Kubenskoe and Vozhe lakes, river and lake (Lake Beloe) parts of the Sheksna reservoir) collected during the period 2007–2018. The metal concentration varied widely: from 0,01 mg/kg for perch from Lake Vozhe to 1,51 mg/kg for perch from Lake Kubenskoe. The highest percentage of fish with mercury content exceeding the established SanPiN 2.3.2.1078-01 norms (29,4%) was recorded in perch from Lake Kubenskoe, while the smallest – in fish from Lake Vozhe (5,4%). In fish from the Sheksna reservoir the content of the toxicant in muscles did not go beyond the accepted SanPiN 2.3.2.1078-01 norms. For all perch samples, a statistically significant positive correlation between mercury content and linear-weight characteristics, as well as fish age, was established.

The article presents information about the mercury content in the muscle tissue of the European grayling Thymallus thymallus (L.) in 11 rivers of the Vologda region (Tagazhma, Vozhega, Votcha, Kostyuga, Tiksna, Sheben’ga, Pyrnug, Zemtsovka, Yurmanga, Bol’shaya Rechka and Yontala) for the period of 2011–2015. The average content of toxicant ranged from 0,04 mg/kg in individuals of the river Sheben’ga up to 0,21 mg/kg in the rivers Yurmanga and Bol’shaya Rechka. Four fish noted an excess of the permissible level of sanitary and hygienic standards (SanPiN 2.3.2.1078-01. 2.3.2.) for non-predatory fish species (0,3 mg/kg). Young grayling contains an average of 0,06–0,10 mg/kg mercury in muscle tissue, individuals five to six years old contain 0,26 and 0,27 mg/kg, respectively. A comparison of the level of mercury concentration in the muscle tissue of European grayling with that of other fish species showed that the Hg content does not go beyond the revealed background values for water bodies of the Vologda region.

расПросТранение еВроПейсКого Хариуса на ТерриТории ВологодсКой оБласТи а. с. Комарова Государственный научно-исследовательский институт озерного и речного рыбного хозяйства им. Л. С. Берга, Вологодское отделение, Россия Популяции европейского хариуса бассейна рек Мологи и Суды включены в Красную книгу Вологодской области, статус 3 (VU) -редкий, уязвимый вид. По данным анализа литературных источников, фондовых материалов, опросных сведений, информации интернет-форумов рыбаков и собственных исследований автора, в водных объектах Вологодской области за период с 1855 по 2017 гг. Thymallus thymallus отмечен в 103 реках и 7 озерах. В статье представлен список рек и озер, в которых был зафиксирован европейский хариус, а также карта-схема его распространения на территории Вологодской области. В условиях региона хариус преимущественно обитает в реках длиной до 100 км (80 % от общего количества водотоков, где вид был встречен). Обитание вида в озерах на территории региона (за исключением Онежского озера) современными исследованиями не подтверждено. Настоящая работа наглядно показывает, что использование стандартных методов исследований с привлечением данных опросных сведений и интернет-форумов рыбаков позволяет более эффективно оценить особенности распространения редких видов рыб в регионе. К л ю ч е в ы е с л о в а: европейский хариус; Thymallus thymallus; юго-восточная часть ареала; Красная книга; Вологодская область; реки и озера; карта-схема. A. S. Komarova. DISTRIBUTION OF THE EUROPEAN GRAYLING IN THE VOLOGDA REGION, RUSSIAPopulations of the European grayling in the Mologa and Suda river catchments are included in the Red Data Book of the Vologda Region with the status 3 (VU) -rare, vulnerable species. According to the analysis of the literature, archival materials, interviews and questionnaires, information from online fishermen's forums, and the author's own studies, collectively covering the period from 1855 to 2017, Thymallus thymallus has been reported from 103 rivers and 7 lakes of the Vologda Region. The article presents the list of rivers and lakes where the grayling has been recorded, as well as a schematic map of its distribution in the Vologda Region. In the region, grayling mostly inhabit rivers up to 100 km long (80 % of the total number of watercourses from which the species was reported). The presence of the species in lakes of the region is not confirmed by recent studies (with the exception of Lake Onego). This study demonstrates that the combination of standard research methods with questionnairing and online forums allows for a more efficient assessment of the distribution patterns of rare fish species in the region. K e y w o r d s: European grayling; Thymallus thymallus; South-Eastern part of the range; Red Data Book; Vologda Region; rivers and lakes; map.

Trophic specialization plays a major role in ecological speciation. Multiple adaptive radiations among cyprinid fish of the genus Labeobarbus were recently discovered in riverine environments of the Ethiopian Highlands, East Africa. These radiations contain parallel diversifications of trophic morphology, including thick-lipped or ‘rubberlip’ phenotype, whose trophic function remains largely unexplored. To test the adaptive value of thickened lips, to identify the ecological niche of the thick-lipped ecomorphs, and to test of these ecomorphs are the products of speciation we studied six sympatric pairs of ecomorphs with hypertrophied lips and the normal lip structure from different riverine basins. Trophic morphology, diet, stable isotope (15N and 13C) signatures as well as mtDNA markers and genome-wide SNP variation were analyzed. Our results show that thick-lipped ecomorphs partition trophic resources with generalized ecomorphs in only one half of the examined sympatric pairs despite the pronounced divergence in lip structure. In these thick-lipped ecomorphs that were trophically diverged, the data on their diet along with the elevated 15N values suggest an insectivorous specialization different from the basal omnivorous-detritivouros feeding mode of generalized ecomorphs. Genetic data confirmed an independent and parallel origin of all six lipped ecomorphs. Yet, only one of those six thick-lipped ecomorphs had a notable genetic divergence with sympatric non-lipped ecomorphs based on nuclear SNPs data (FST = 0.21). Sympatric pairs can be sorted by combinations of phenotypic, ecological, and genetic divergence within the speciation continuum from an ecologically non-functional mouth polymorphism via ecologically functional polymorphism to completed speciation via divergent evolution.