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Mitochondrial DNA transmission in the hybridization and introgression zone of Mytilus edulis and M.Trossulus in the Baltic and Danish straits

100%

Kijewski T. , Wenne R.

Folia Malacologica

2000

tom 08

nr 4

Analysis of population and taxonomical structure of Atlantic cod, Gadus morhua (Actinopterygii: Gadiformes: Gadidae) from the Baltic Sea with use of microsatellite DNA

80%

Kijewska A. , Wiecaszek B. , Kijewski T.

Acta Ichthyologica et Piscatoria

2011

tom 41

nr 4

Background. Substantial declines in biomass of Atlantic cod, Gadus morhua L., one of the most valuable commercial fish species in the north Atlantic (including the Baltic Sea), has been observed in recent decades. A comprehensive understanding of the population structure contributes to proper management and conservation of genetic resources. We attempted to answer the question whether there exists differentiation among localized samples, and if so, whether this separation is large enough to warrant the recognition of distinct clades in cod as well as whether these distinct clades correspond to traditionally described regions of spawning and nursery areas or even stocks. Materials and methods. Six microsatellites were used for finding differentiation between four sampling areas of G. morhua) from the Baltic Sea (Puck Bay, Bay of Gdańsk, Pomeranian Bay, and Øresund) and two from the north-eastern Atlantic (North Sea and Barents Sea). Genetic differences among localities were estimated with FST using Weir and Cockerham’s estimator θ. Genetic distances among samples were calculated and visualized by multidimensional scaling using XLStat (Addinsoft). Results. There is a statistically supported structure pattern among sampling localities from the Baltic Sea. One of them is related to the population from the Barents Sea, second is mixing with cod migrating from the North Sea. Conclusion. The level of heterozygosity and slight heterozygote deficiency suggest that, in case of all samples, we observed an isolation processes that could be an effect of withering or weakening the migrations between separate breeding stocks. This effect is most apparent for the most eastern populations from the Puck Bay and the Gulf of Gdańsk.

Distribution of ascaridoid nematodes (Nematoda: Chromadorea: Ascaridoidea) in fish from the Barents Sea

70%

Najda K. , Kijewska A. , Kijewski T. , Plauška K. , Rokicki J.

Oceanological and Hydrobiological Studies

2018

tom Vol. 47, No. 2

128--139

The Ascaridoidea are parasites with heteroxenous life cycles. The study shows that fish can be paratenic, intermediate, or final hosts for parasites, and parasitic fauna reflects the feeding behavior of the hosts. Each species of parasites has also different environmental preferences and host specificity. Parasitic nematodes of fish representing Pleuronectidae, Gadidae, Sebastidae, and Macrouridae were studied. Worms were collected separately from different infection sites: stomach, intestine, liver and body cavity. Nematodes were identified using both morphological and molecular methods (PCR-RFLP). Six nematode species were recorded: Anisakis simplex s.s., Contracaecum osculatum A, B, and C. osculatum C (s.s.), Hysterothylacium aduncum and Pseudoterranova bulbosa. Anisakis simplex s.s. was the most numerous nematode species of all catches combined. Differences in parasite species composition were related to the depth and location of sampling areas. In the fish from deep waters, the abundance of A. simplex s.s. decreased compared to fish from shallow waters and P. bulbosa was the dominant species. Ascaridoid species have specific preferences regarding the impact on various internal organs of fish, which is reflected in their abundance. The presence of Ascaridoidea in the Barents Sea is associated with the distribution of hosts and varying food preferences related to the age of fish. The abundance of parasites varied between different host species.

Random forest assessment of correlation between environmental factors and genetic differentiation of populations: Case of marine mussels Mytilus

61%

Kijewski T. , Zbawicka M. , Strand J. , Kautsky H. , Kotta J. , Ratsep M. , Wenne R.

Oceanologia

2019

tom 61

nr 1