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Hybridization and polyploidization are important evolutionary processes whose impacts range from the alteration of gene expression and phenotypic variation to the triggering of asexual reproduction. We investigated fishes of the Cobitis taenia-elongatoides hybrid complex, which allowed us to disentangle the direct effects of both processes, due to the co-occurrence of parental species with their diploid and triploid hybrids. Employing morphological, ecological, and RNAseq approaches, we investigated the molecular determinants of hybrid and polyploid forms. In contrast with other studies, hybridization and polyploidy induced relatively very little transgressivity. Instead, Cobitis hybrids appeared intermediate with a clear effect of genomic dosing when triploids expressed higher similarity to the parent contributing two genome sets. This dosage effect was symmetric in the germline (oocyte gene expression), interestingly though, we observed an overall bias toward C. taenia in somatic tissues and traits. At the level of individual genes, expression-level dominance vastly prevailed over additivity or transgressivity. Also, trans-regulation of gene expression was less efficient in diploid hybrids than in triploids, where the expression modulation of homoeologs derived from the "haploid" parent was stronger than those derived from the "diploid" parent. Our findings suggest that the apparent intermediacy of hybrid phenotypes results from the combination of individual genes with dominant expression rather than from simple additivity. The efficiency of cross-talk between trans-regulatory elements further appears dosage dependent. Important effects of polyploidization may thus stem from changes in relative concentrations of trans-regulatory elements and their binding sites between hybridizing genomes. Links between gene regulation and asexuality are discussed., (© The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.)

The aim of the study was to verify whether the use of heparin as an anticoagulant can affect the results of genome size measurements using a flow cytometer. The values obtained by measuring blood samples with different concentrations of heparin were compared. The differences observed were highly significant, suggesting that the results of previous comparative studies, or those determining individual polyploidy, may need reinterpretation. We anticipate that our findings will increase the accuracy of flow cytometric analysis and will be useful for further surveys of genome size undertaken using blood samples. [ABSTRACT FROM AUTHOR]

Three species of loaches (Cobitis L., 1758) were collected and examined for endohelminths from North Bulgaria. The most common was the trematode Allocreadium transversale (Rudolphi, 1802), which is reported for the first time in Bulgaria. Measurements and figures as well as host-species and locality details are presented. Allocreadium transversale was recorded from all three loach species: Cobitis elongatoides, C. elongata and C. strumicae, the last two being new host records for A. transversale. In addition, metacercariae of Clinostomum complanatum (Rudolphi, 1814) and one unidentified nematode were found. The helminth fauna of loach was quite depauperate, the factors of which have to be elucidated. [ABSTRACT FROM AUTHOR]

Loaches (genus Cobitis ) in Slovakian tributaries (Danube River Basin) are represented by diploid-polyploid hybrid complexes of C. elongatoides and C. tanaitica . Uniquely, their coexistence is made possible by the presence of polyploid (mainly triploid) females that are sexually dependant on diploid male sperm (donors) for gynogenesis. Information on the spatial distribution of Cobitis with of differing ploidy remains relatively scarce. The main aim of this study, therefore, was to identify in ploidy in the species preferred microhabitat. Overall, 345 Cobitis were recorded in Rivers Okna and Ondava (Danube Basin) between 2011 and 2015, with 316 diploid and triploid individuals detected by flow cytometry examined were studied for the microhabitat preferences with the using the point sample method. The sex ratio differed significantly between localities, while diploid-polyploid ratio not. Moreover, each of ploidy-sex forms (i.e. diploid male, diploid female, triploid female) showed a preference for a specific substrate composition, velocity, depth and distance from the bank at both localities. Mixed effect linear models identified clear differences in fine substrate between seasons for individuals from the River Okna. Similarly, non-metric multidimensional scaling detected differences in environmental variables preference for both diploid and triploid forms. These finding indicate specific spatial and temporal microhabitat preference for diploid (sexual donors) and triploid (asexuals) C. elongatoides × C. tanaitica when coexisting as mixed a population. [ABSTRACT FROM AUTHOR]

Background. Many of Cobitis subpopulations exist as diploid-polyploid hybrid complexes where polyploid gynogenetic females act as "sperm parasites" of diploid individuals. In addition to sexual strategy, the life history of such individuals is also affected by their growth performance. In order to elucidate unknown aspects of the Cobitis hybrid complexes we decided to identify differences in the annual size increments between individuals representing different ploidy and sex, and to compare the condition factor expressed by length-weight (L-W) relation within the same ploidy and sex groups. Material and methods. In total, 158 specimens representing Cobitis elongatoides (Băcescu et Mayer, 1969) × Cobitis tanaitica (Băcescu et Mayer, 1969) hybrid complex were caught in August and September 2014, of which 132 were analysed. The fish were caught in the Okna River (Danube River basin), Slovakia. Sex was determined based on externally visible morphological features or based on microscopic observation of the gonads. Ploidy level was determined by means of flow cytometry on fin clips taken from each specimen. Age was estimated based on the total number of annuli visible on vertebrae. All statistical models were performed in the R statistical environment. Results. Sex ratio varied within age classes, with 3+ fish primarily composed of females and, 4+ fish mostly triploid. Maximum back-calculated lengths for diploid females were obtained up to 3+, and for the 4+ age group for triploid. L-W relations for adult males and females also differed significantly, but did not vary between diploid and triploid females. There were differences in at specific body lengths for Cobitis with different ploidy level. Diploid males were characterised by short annual age and length increments during the first two years of life. Annual increments in diploid females were highest overall though their frequency decreased after the reaching the fourth year of life (3+). On the contrary, annual increments in triploid females were the lowest within all groups until their fourth year, thought their frequency in the oldest age group (4+). Conclusion. In our study, we first confirmed that yearly increments and maximal age of Cobitis individuals are affected by different ploidy. Contrary, the L-W relations of gutted diploid and triploid females did not differ and they were affected only by sex. We suggest that the intensity of growth is more affected by ploidy, while the L-W of Cobitis is determined by intensity of feeding and stage of gonad development at the local conditions during season. Therefore, in the future studies of Cobitis growth and condition parameters the ploidy level of individuals should also be considered. [ABSTRACT FROM AUTHOR]