Promiscuous specialists : Host specificity patterns among generalist louse flies

Ectoparasites such as louse flies (Diptera: Hippoboscidae) have tendency for host specialization, which is driven by adaptation to host biology as well as competition avoidance between parasites of the same host. However, some louse fly species, especially in genera attacking birds, show wide range of suitable hosts. In the presented study, we have surveyed the current status of bird specific louse flies in Finland to provide comprehensive host association data to analyse the ecological requirements of the generalist species. A thorough sampling of 9342 birds, representing 134 species, recovered 576 specimens of louse flies, belonging to six species: Crataerina hirundinis, C. pallida, Ornithomya avicularia, O. chloropus, O. fringillina and Ornithophila metallica. Despite some overlapping hosts, the three Ornithomya species showed a notable pattern in their host preference, which was influenced not only by the host size but also by the habitat and host breeding strategy. We also provide DNA barcodes for ten Finnish species of Hippoboscidae, which can be used as a resource for species identification as well as metabarcoding studies in the future.Peer reviewe

TFAM knockdown-triggered mtDNA-nucleoid aggregation and a decrease in mtDNA copy number induce the reorganization of nucleoid populations and mitochondria-associated ER-membrane contacts

The correct organization of mitochondrial DNA (mtDNA) in nucleoids and the contacts of mitochondria with the ER play an important role in maintaining the mitochondrial genome distribution within the cell. Mitochondria-associated ER membranes (MAMs) consist of interacting proteins and lipids located in the outer mitochondrial membrane and ER membrane, forming a platform for the mitochondrial inner membrane-associated genome replication factory as well as connecting the nucleoids with the mitochondrial division machinery. We show here that knockdown of a core component of mitochondrial nucleoids, TFAM, causes changes in the mitochondrial nucleoid populations, which subsequently impact ER-mitochondria membrane contacts. Knockdown of TFAM causes a significant decrease in the copy number of mtDNA as well as aggregation of mtDNA nucleoids. At the same time, it causes significant upregulation of the replicative TWNK helicase in the membrane-associated nucleoid fraction. This is accompanied by a transient elevation of MAM proteins, indicating a rearrangement of the linkage between ER and mitochondria triggered by changes in mitochondrial nucleoids. Reciprocal knockdown of the mitochondrial replicative helicase TWNK causes a decrease in mtDNA copy number and modifies mtDNA membrane association, however, it does not cause nucleoid aggregation and considerable alterations of MAM proteins in the membrane-associated fraction. Our explanation is that the aggregation of mitochondrial nucleoids resulting from TFAM knockdown triggers a compensatory mechanism involving the reorganization of both mitochondrial nucleoids and MAM. These results could provide an important insight into pathological conditions associated with impaired nucleoid organization or defects of mtDNA distribution.publishedVersionPeer reviewe

Spatial adjustment of bioenergetics, a possible determinant of contractile adaptation and development of contractile failure

Cardiomyocytes depend on mitochondrial oxidative phosphorylation (OXPHOS) for energy metabolism, which is facilitated by the mitochondrial electron transfer system (ETS). In a series of thermogenic redox reactions, electrons are shuttled through the ETS to oxygen as the final electron acceptor. This electron transfer is coupled to proton translocation across the inner mitochondrial membrane, which itself is the main driving force for ATP production. Oxygen availability is thus a prerequisite for ATP production and consequently contractility. Notably, cardiomyocytes are exceptionally large cells and densely packed with contractile structures, which constrains intracellular oxygen distribution. Moreover, oxygen must pass through layers of actively respiring mitochondria to reach the ones located in the innermost contractile compartment. Indeed, uneven oxygen distribution was observed in cardiomyocytes, suggesting that local ATP supply may also vary according to oxygen availability. Here, we discuss how spatial adjustment of bioenergetics to intracellular oxygen fluctuations may underlie cardiac contractile adaptation and how this adaptation may pose a risk for the development of contractile failure

Replication fork rescue in mammalian mitochondria

Replication stalling has been associated with the formation of pathological mitochondrial DNA (mtDNA) rearrangements. Yet, almost nothing is known about the fate of stalled replication intermediates in mitochondria. We show here that replication stalling in mitochondria leads to replication fork regression and mtDNA double-strand breaks. The resulting mtDNA fragments are normally degraded by a mechanism involving the mitochondrial exonuclease MGME1, and the loss of this enzyme results in accumulation of linear and recombining mtDNA species. Additionally, replication stress promotes the initiation of alternative replication origins as an apparent means of rescue by fork convergence. Besides demonstrating an interplay between two major mechanisms rescuing stalled replication forks - mtDNA degradation and homology-dependent repair - our data provide evidence that mitochondria employ similar mechanisms to cope with replication stress as known from other genetic systems.Peer reviewe

Systoechus laevifrons (Loew, 1855) new to Finland and the Western Palearctic region (Diptera, Bombyliidae)

Systoechus laevifrons (Loew, 1855) (Diptera, Bombyliidae) is recorded from Finland. Having previously been known only from Eastern Siberia and the Russian Far East, the species is new to the Western Palearctic region. All verifiable previous records of Systoechus gradatus (Wiedemann in Meigen, 1820) from Finland proved to be misdentifications of Systoechus laevifrons. S. gradatus is here deleted from the national checklist of Finnish species. Systoechus laevifrons inherits the national red list status (CR) previously given to S. gradatus. Based on museum material, the historical range of Systoechus laevifrons in Finland covers most of the southern and middle parts of the country, but records are very sparse and scattered, with only five known localities. In the 21st century Systoechus laevifrons has only been found at two localities in Finland (Säkylä and Taipalsaari). Both are army artillery practice grounds on sandy soils. In 2021, at least twenty adults were seen nectaring primarily on Solidago virgaurea at the Säkylä site. In addition to the species record, we provide a partial DNA barcode analysis of the northern Holarctic Systoechus species as well as an updated key to the identification of the European species, and discuss the biology and distribution of Systoechus laevifrons.Peer reviewe

Origins and wanderings of the Finnish hunting spitzes.

Deducing the evolutionary histories of dog breeds can be challenging due to convergent traits and frequent admixture. In this report, we have explored the relationships of indigenous Finnish hunting spitz breeds among other northern Eurasian hunting breeds using commercially available SNP analysis (the MyDogDNA panel test). We find that Nordic hunting breeds Finnish Spitz, Nordic Spitz and the Karelian Bear Dog, as well as the reindeer herding Lapphund and Lapponian herder are all closely related and have common origins with the northeastern Eurasian Laika breeds, rather than with other Scandinavian Spitz breeds, such as Elkhounds and Swedish Vallhund. By tracing admixture events and direction of gene flow, we also elucidate the complex interactions between the breeds and provide new insight into the history of Swedish Elkhound and Russian-European Laika. The findings, together with an analysis of genetic differentiation between the populations, not only help to understand the origins of the breeds but also provide interesting possibilities to revive genetic diversity, lost during the breeding history, by backcrossing breeds to their hypothetical ancestry

Geographic variation in tachinid <i>COI</i> sequences.

<p>(A) The northern Finnish (map locations 1–2) <i>Microsoma exiguum</i> (Meigen) belong to a different BIN cluster than the specimens from southern Finland, Central Europe (map locations 3–6) and Mediterranean France (map location 7). Note that the specimens from Provence represent a different haplogroup than the Central European ones, although the difference is not enough to split the BIN. Similar differentiation was not observed for (B) <i>Tachina fera</i> (L.), (C) <i>Mintho rufiventris</i> (Fallén), <i>Thriarthria setipennis</i> (Fallén) and (D) <i>Cylindromyia brassicaria</i> (Fabricius) collected from the same locations. Example species: Male <i>Microsoma exiguum</i>, Friedberg, Germany. Scale bar: 1% sequence difference.</p

Possible taxonomic conflicts within tachinid genera.

<p>(A) <i>Kirbya moerens</i> (Meigen) is embedded within the <i>COI</i> sequences of the closely related <i>Wagneria</i>, whereas the other Voriini genera form their own clusters. <i>Voria</i> is thought only to be represented by <i>V</i>. <i>ruralis</i> (Fallén) in the Palearctic. However, the <i>COI</i> of a specimen from S-Agean Greece differs significantly (by 4.91%) from the northern European examples and could represent a species of its own. Similar to <i>Kirbya–Wagneria</i> case, also (B) <i>Billaea–Dinera</i> and (C) <i>Phorocera–Parasetigena</i> have mixed <i>COI</i> clusters. Example species: Male <i>Billaea kolomyetzi</i>, Ruokolahti, Finland. Scale bar: 2% sequence difference.</p