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Background. Diapause is an important component of insect life cycle which ensures synchronization of reproduction and development with local seasonal climate. Genetic bases of this synchronization are particularly important for the analysis of biological invasions. Materials and methods. We investigated photoperiodic induction of diapause in hybrids between two populations of Harmonia axyridis (Pallas): autochthonous population from Irkutsk (Siberia) which shows a strong induction of diapause by short days and invasive population from Sochi (the Caucasus) which exhibits very weak photoperiodic induction of diapause. Results. Reciprocal crosses showed that the strong photoperiodic induction of diapause is dominant and the effects of male and female genotypes on progeny phenotype are equal.

The amphipod Gmelinoides fasciatus from Lake Baikal is an example of a species being introduced into a number of water bodies in Russia, including the water system of North-west Russia, to expand food reserves of commercial fish. The interest in this crustacean has been attributed to its successful adaptation and expanding habitat area in the region. In order to assess the role of genetic mechanisms in adaptation to new conditions the frequency of chromosomal aberrations (ChA) at anaphase and telophase stages of mitosis in G. fasciatus embryos from six local populations of Lake Baikal and two invasive populations of the Gulf of Finland, originating from natural habitats were studied in two sequential years. The average level of ChA varied slightly between 0.95% in the samples collected in Lake Baikal and 2.9% in those from the Gulf of Finland. A significant increase in the frequency of ChA was found at two sites in Lake Baikal in 2015 and at two locations in the Gulf of Finland in 2016. First information on G. fasciatus chromosome number and constitution acquired by means of molecular cytogenetic techniques is presented and discussed. The results enable us to suggest this amphipod as a sensitive model to study possible mechanisms of biological adaptation and at the same time as a natural bioindicator of the environmental state.

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