Larvae of related Diptera species from thermally contrasting habitats exhibit continuous up-regulation of heat shock proteins and high thermotolerance

A population of Stratiomys japonica, a species belonging to the family Stratiomyidae (Diptera), common name ‘soldier flies’, occurs in a hot volcanic spring, which is apparently among the most inhospitable environments for animals because of chemical and thermal conditions. Larvae of this species, which naturally often experience temperatures more than 40 °C, have constitutively high concentrations of the normally inducible heat-shock protein Hsp70, but very low level of corresponding mRNA. Larvae of three other species of the same family, Stratiomys singularior, Nemotelus bipunctatus and Oxycera pardalina, are confined to different type semi-aquatic habitats with contrasting thermal regime. However, all of them shared the same pattern of Hsp70 expression. Interestingly, heat-shock treatment of S. japonica larvae activates heat-shock factor and significantly induces Hsp70 synthesis, whereas larvae of O. pardalina, a species from constant cold environment, produce significantly less Hsp70 in response to heat shock. Adults of the four species also exhibit lower, but detectable levels of Hsp70 without heat shock. Larvae of all species studied have very high tolerance to temperature stress in comparison with other Diptera species investigated, probably representing an inherent adaptive feature of all Stratiomyidae enabling successful colonization of highly variable and extreme habitats.     

Combined manifestations of natural foci in the territory of the Vologda province

Based on epizootological and epidemiological investigations in the Vologda province since 1958 till 2000, the combined territorial and temporal manifestations of natural foci of diseases was revealed. A natural focus occupies a complex of biotopes, and in different time the focus is activated in different areas, such as a river plain, marsh, meadow-field, and forest. Most commonly an activation of the natural focus appears in a border zone of three biotopes, namely, a forest, meadow-field, and river plain. A dependence of activation of various natural foci upon local climate conditions and fluctuations of micromammalian host number are considered.