Grażyna Furgała-Selezniow

Pericentromeric location of the telomeric DNA sequences on the European grayling chromosomes

AbstractThe 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.

Feeding habits of larval Eurasian perch, Perca fluviatilis (Percidae)

Abstract Feeding during the development of Eurasian perch (Perca fluviatilis) larvae was studied in situ in cylindrical cages. Initially perch larvae were maintained in cages, 0.2 mm of mesh size. The initial stocking density was 7 000 larvae per cage. Fish were fed with Zooplankton and after 17 days were transplanted to cages with a larger mesh size (1.2 mm). Development was observed for additional 17 days. Larval survival was about 25% and 65% for the initial and secondary rearing, respectively. Perch larvae ate initially rotifers and later ate nauplii and copepodites. Cladocera was the dominant food item in the diet of perch at the conclusion of our observations.

Chromosomal location of Ag/CMA3-NORs, 5S rDNA and telomeric repeats in two stickleback species

Abstract 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.

The morphological, histological and cytogenetic characteristics of goldfish Carassius auratus (L.) × common carp Cyprinus carpio (L.) hybrids

Morphology of hybrids between the goldfish (Carassius auratus) and common carp (Cyprinus carpio) are studied by biometric and meristic methods. Additionally, histological analyses concerning gonads as well as genetic characteristics of chromosomes are performed. Studied hybrids were morphologically very similar to a goldfish but possessed one pair of reduced posterior barbels. Most meristic and biometric indices had intermediate values when compared to parental species. Histological study showed that investigated hybrids produce gonads with germ cells. All studied males had gonads at the same stage of maturity (III stage). By contrast, female gonads were in various stages of development – from sexually immature to post-spawning stage. Karyotype characteristics were assessed in terms of chromosomes number, fundamental arm number and location of nucleolus organizer regions (NOR). The data obtained were compared with baseline karyotypes of species used for hybridization, based on information from the literature. The diploid chromosome number of studied hybrids equaled 2n = 100, NF = 152. Ag-NORs were localized on the short arms of two to three submetacentric chromosomes. Additionally, one to two supernumerary (B) chromosomes were also found, which is a typical phenomenon for interspecific hybrids, especially between cyprinid fish species.