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 degrees 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.

BackgroundPreviously, we described the heat shock response in dipteran species belonging to the family Stratiomyidae that develop in thermally and chemically contrasting habitats including highly aggressive ones. Although all species studied exhibit high constitutive levels of Hsp70 accompanied by exceptionally high thermotolerance, we also detected characteristic interspecies differences in heat shock protein (Hsp) expression and survival after severe heat shock. Here, we analyzed genomic libraries from two Stratiomyidae species from thermally and chemically contrasting habitats and determined the structure and organization of their hsp70 clusters.ResultsAlthough the genomes of both species contain similar numbers of hsp70 genes, the spatial distribution of hsp70 copies differs characteristically. In a population of the eurytopic species Stratiomys singularior, which exists in thermally variable and chemically aggressive (hypersaline) conditions, the hsp70 copies form a tight cluster with approximately equal intergenic distances. In contrast, in a population of the stenotopic Oxycera pardalina that dwells in a stable cold spring, we did not find hsp70 copies in tandem orientation. In this species, the distance between individual hsp70 copies in the genome is very large, if they are linked at all. In O. pardalina we detected the hsp68 gene located next to a hsp70 copy in tandem orientation. Although the hsp70 coding sequences of S. singularior are highly homogenized via conversion, the structure and general arrangement of the hsp70 clusters are highly polymorphic, including gross aberrations, various deletions in intergenic regions, and insertion of incomplete Mariner transposons in close vicinity to the 3'-UTRs.ConclusionsThe hsp70 gene families in S. singularior and O. pardalina evolved quite differently from one another. We demonstrated clear evidence of homogenizing gene conversion in the S. singularior hsp70 genes, which form tight clusters in this species. In the case of the other species, O. pardalina, we found no clear trace of concerted evolution for the dispersed hsp70 genes. Furthermore, in the latter species we detected hsp70 pseudogenes, representing a hallmark of the birth-and-death process.

The oldest fossil Diptera are known from the Grès à Voltzia Formation (Upper Buntsandstein) of the northern Vosges Mountains (northeastern France), the age of which is early Anisian (early Middle Triassic). Six monotypic genera assigned to all the major lineages of Diptera (except for the Culicomorpha) were described from these beds based on adults (Krzeminski et al. 1994;Krzeminski & Krzeminska 2003). Immature Diptera also occur in the Grès à Voltzia (ca 30 specimens). Pupae are abundant whereas the larvae are extremely rare. The most numerous and well-preserved pupal type has been assigned to Voltziapupa n. gen. (V. tentata n. sp. and V. cornuta n. sp.). These pupae display plesiomorphic characters combined with possibly derived ones. Among the larvae, Anisinodus crinitus n. gen., n. sp. shows culicomorph features. It represents the earliest Culicomorpha (Chironomoidea inc. fam.) known up to date. The other types of dipteran immatures (six pupal and two larval ones) occurring in the Grès à Voltzia are less well preserved, so that their systematic position is diffi cult to determine and they have been assigned to the Nematocera incertae sedis. These immature Diptera are the fi rst ones recorded from the Triassic. Résumé. La plus ancienne occurence de diptères immatures (Insecta), Triassique Moyen, France.Le plus ancien fossile de diptère est connu de la formation des Grès à Voltzia (Buntsandstein supérieur) du nord des Vosges (nord-est France), dont l'âge correspond à l'Anisien ancien (Triassique Moyen ancien). Six genre monotypiques assignés a toutes les grands groupes de diptères (sauf les culicomorphes) ont été décrits de ces dépôts sous leur seule forme adulte (Krzeminski et al. 1994;Krzeminski & Krzeminska 2003). Des diptères immatures existent aussi dans les Grès à Voltzia (ca 30 spécimens). Les pupes sont abondantes tandis que les larves sont extrèmement rares. Les pupes les plus nombreuses et les mieux préservées ont été attribuées à Voltziapupa n. gen. (V. tentata n. sp. et V. cornuta n. sp.). Ces pupes présentent des caractères plésiomorphes combinés avec d'autres possiblement dérivés. Parmi les larves, Anisinodus crinitus n. gen., n. sp. présente des caractéristiques culicomorphes, ce qui représente le plus ancien culicomorphe connu à ce jour (Chironomoidea inc. fam.). Les autres diptères immatures des Grès à Voltzia (six pupes et deux larves) sont moins bien préservés de telle sorte que leur position systématique est diffi cile à déterminer ce qui mène à les considérer comme des nématocères incertae sedis. Ces diptères immatures sont les premiers connus du Triassique.

BackgroundTransitions in habitats and feeding behaviors were fundamental to the diversification of life on Earth. There is ongoing debate regarding the typical directionality of transitions between aquatic and terrestrial habitats and the mechanisms responsible for the preponderance of terrestrial to aquatic transitions. Snail-killing flies (Diptera: Sciomyzidae) represent an excellent model system to study such transitions because their larvae display a range of feeding behaviors, being predators, parasitoids or saprophages of a variety of mollusks in freshwater, shoreline and dry terrestrial habitats. The remarkable genus Tetanocera (Tetanocerini) occupies five larval feeding groups and all of the habitat types mentioned above. This study has four principal objectives: (i) construct a robust estimate of phylogeny for Tetanocera and Tetanocerini, (ii) estimate the evolutionary transitions in larval feeding behaviors and habitats, (iii) test the monophyly of feeding groups and (iv) identify mechanisms underlying sciomyzid habitat and feeding behavior evolution.ResultsBayesian inference and maximum likelihood analyses of molecular data provided strong support that the Sciomyzini, Tetanocerini and Tetanocera are monophyletic. However, the monophyly of many behavioral groupings was rejected via phylogenetic constraint analyses. We determined that (i) the ancestral sciomyzid lineage was terrestrial, (ii) there was a single terrestrial to aquatic habitat transition early in the evolution of the Tetanocerini and (iii) there were at least 10 independent aquatic to terrestrial habitat transitions and at least 15 feeding behavior transitions during tetanocerine phylogenesis. The ancestor of Tetanocera was aquatic with five lineages making independent transitions to terrestrial habitats and seven making independent transitions in feeding behaviors.ConclusionsThe preponderance of aquatic to terrestrial transitions in sciomyzids goes against the trend generally observed across eukaryotes. Damp shoreline habitats are likely transitional where larvae can change habitat but still have similar prey available. Transitioning from aquatic to terrestrial habitats is likely easier than the reverse for sciomyzids because morphological characters associated with air-breathing while under the water's surface are lost rather than gained, and sciomyzids originated and diversified during a general drying period in Earth's history. Our results imply that any animal lineage having aquatic and terrestrial members, respiring the same way in both habitats and having the same type of food available in both habitats could show a similar pattern of multiple independent habitat transitions coincident with changes in behavioral and morphological traits.

Heat shock protein 70 (Hsp70) is the major player that underlies adaptive response to hyperthermia in all organisms studied to date. We investigated patterns of Hsp70 expression in larvae of dipteran species collected from natural populations of species belonging to four families from different evolutionary lineages of the order Diptera: Stratiomyidae, Tabanidae, Chironomidae and Ceratopogonidae. All investigated species showed a Hsp70 expression pattern that was different from the pattern in Drosophila. In contrast to Drosophila, all of the species in the families studied were characterized by high constitutive levels of Hsp70, which was more stable than that in Drosophila. When Stratiomyidae Hsp70 proteins were expressed in Drosophila cells, they became as short-lived as the endogenous Hsp70. Interestingly, three species of Ceratopogonidae and a cold-water species of Chironomidae exhibited high constitutive levels of Hsp70 mRNA and high basal levels of Hsp70. Furthermore, two species of Tabanidae were characterized by significant constitutive levels of Hsp70 and highly stable Hsp70 mRNA. In most cases, heat-resistant species were characterized by a higher basal level of Hsp70 than more thermosensitive species. These data suggest that different trends were realized during the evolution of the molecular mechanisms underlying the regulation of the responses of Hsp70 genes to temperature fluctuations in the studied families.

The heat shock proteins belonging to the Hsp90 family (Hsp83 in Diptera) play a crucial role in the protection of cells due to their chaperoning functions. We sequenced hsp90 genes from three species of the family Stratiomyidae (Diptera) living in thermally different habitats and characterized by extraordinarily high thermotolerance. The sequence variation and structure of the hsp90 family genes were compared with previously described features of hsp70 copies isolated from the same species. Two functional hsp83 genes were found in the species studied, that are arranged in tandem orientation at least in one of them. This organization was not previously described. Stratiomyidae hsp83 genes share a high level of identity with hsp83 of Drosophila, and the deduced protein possesses five conserved amino acid sequence motifs characteristic of the Hsp90 family as well as the C-terminus MEEVD sequence characteristic of the cytosolic isoform. A comparison of the hsp83 promoters of two Stratiomyidae species from thermally contrasting habitats demonstrated that while both species contain canonical heat shock elements in the same position, only one of the species contains functional GAF-binding elements. Our data indicate that in the same species, hsp83 family genes show a higher evolution rate than the hsp70 family.

One hundred and sixteen species of Chloropidae (Diptera) are recorded in Russian Karelia and Murmansk Province: 112 in Karelia and 44 in Murmansk Province. Twenty-two and seven species are new for Karelia and Murmansk Province, respectively. Calamoncosis oscinella is for the first time reported from Russia and Elachiptera breviscutellata - from European Russia. Pseudogaurax venustus is reinstated as Gaurax venustus. Taxonomic notes are provided on Eribolus nana, Polyodaspis ruficornis, Oscinella vindicata and Cetema simile. The distribution and biological data are given for every species. Point maps are provided for species with at least one exactly known location. The zoogeographical structure of Chloropidae fauna on the examined territories is briefly discussed and compared with other north-European countries.

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