The chromosomal characteristics, locations and variations of the C-band positive heterochromatin and telomeric DNA sequences were studied in the European grayling karyotype (Thymallus thymallus, Salmonidae) using conventional C-banding, endonucleases digestion banding, silver nitrate (AgNO₃), chromomycin A₃ and 4′,6-diamidino-2-phenylindole staining techniques as well as fluorescence in situ hybridization (FISH) and primed in situ labelling. Original data on the chromosomal distribution of segments resistant to AluI restriction endonuclease and identification of the C-banded heterochromatin presented here have been used to characterize the grayling karyotype polymorphism. Structural and length polymorphism of the chromosome 21 showing a conspicuous heterochromatin block adjacent to the centromere seems to be the result of the deletion and inversion. Two pairs of nuclear organizer regions (NOR)-bearing chromosomes were found to be polymorphic in size and displaying several distinct forms. FISH with telomeric peptide nucleic acid probe enabled recognition of the conservative telomeric DNA sequences. The karyotype of the thymallid fish is thought to experienced numerous pericentric inversions and internal telomeric sites (ITSs) observed at the pericentromeric regions of the six European grayling metacentric chromosomes are likely relics of the these rearrangements. None of the ITS sites matched either chromosome 21 or NOR bearing chromosomes.

Lakes provide different ecosystem services, including those related to tourism and recreation. Sustainable development principles should be respected in lake tourism planning. The aim of this study was to assess the impact of tourism on the lakeshore zone in a typical post-glacial Lakeland in Northern Poland (Central Europe). An explanatory analysis of the distribution of individual spatial factor values was performed using the SHapley Additive exPlanations algorithm (SHAP). In a first step, the aim was to select a Machine Learning model for modelling based on Shapley values. The greater or lesser influence of a given factor on the tourism function was measured for individual lakes. The final results of ensemble modelling and SHAP were obtained by averaging the results of five random repetitions of the execution of these models. The impact of tourism on the lakeshore zone can be much more accurately determined using an indirect method, by analysing the tourism and recreational infrastructure constantly present there. The values of the indices proposed in the study provide indirect information on the number of tourists using the tourist and recreational facilities and are a measure of the impact of tourism on the lakeshore zone. The developed methodology can be applied to the majority of post-glacial lakes in Europe and other regions of the world in order to monitor the threats resulting from shore zone exploitation. Such studies can be an appropriate tool for management and planning by the relevant authorities.

During the last 10 years, the stickleback has emerged as a promising model system in several biological fields. In particular, it is one of the most investigated fish groups by evolutionary biologists, as a model for understanding the genetic and molecular basis in processes of adaptive radiation, microevolution and development, as well as the genetic basis of sex determination. To provide karyological information about stickleback fish we performed cytogenetic analysis of the threespine stickleback (Gasterosteus aculeatus L.) and the ninespine stickleback (Pungitius pungitius L.). Diploid chromosome number in both species equalled 42; however, the chromosome arm numbers were 62 and 70, respectively. In the threespine stickleback, multichromosomal location of silver (AgNO₃) and chromomycin A₃ (CMA₃) positively stained Nucleolar Organizer Regions (Ag/CMA₃-NORs) was observed. The number of silver-stained chromosomes varied among different individuals from two to six. The Ag/CMA₃-NORs covered almost entire short arms of one pair of middle-sized submetacentric chromosome pairs in the ninespine stickleback. In one male, the only Ag-NOR was situated telomerically on the long arm of the Y chromosome. The 5S rDNA clusters were observed on short arms of one pair of subtelocentric chromosomes in the threespine stickleback and four pairs of subtelo-acrocentric chromosomes in the ninespine stickleback of both sexes. Chromosome rearrangements responsible for the stickleback karyotype polymorphisms did not leave any internally located telomeric sequences. The results obtained in two stickleback species are therefore of considerable interest and further karyological studies should be carried out on the other populations of the wide species range in order to provide a more general picture of karyoevolutive trends in Gasterosteidae.