Louse flies holding on mammals' hair: Comparative functional morphology of specialized attachment devices of ectoparasites (Diptera: Hippoboscoidea)

Hippoboscidae and Nycteribiidae of the dipteran superfamily Hippoboscoidea are obligate ectoparasites, which feed on the blood of different mammals. Due to their limited flight capability, the attachment system on all tarsi is of great importance for a secure grasp onto their host and thus for their survival. In this study, the functional morphology of the attachment system of two hippoboscid species and two nycteribiid species was compared in their specificity to the host substrate. Based on data from scanning electron microscopy and confocal laser scanning microscopy, it was shown that the attachment systems of both Hippoboscidae and Nycteribiidae (Hippoboscoidea) differ greatly from that of other calyptrate flies and are uniform within the respective families. All studied species have an attachment system with two monodentate claws and two pulvilli. The claws and pulvilli of the Hippoboscidae are asymmetric, which is an adaptation to the fur of even-toed ungulates (Artiodactyla). The fur of these mammals possesses both, thinner woolen and thicker coat hair; thus, the asymmetry of the attachment system of the hippoboscid species enables a secure attachment to all surfaces of their hosts. The claws and pulvilli of the nyceribiid species do not show an asymmetry, since the fur of their bat (Chiroptera) hosts consists of hairs with the same thickness. The claws are important for the attachment to mammals' fur, because they enable a secure grip by mechanical interlocking of the hairs through the claws. Additionally, well-developed pulvilli are able to attach on thicker hairs of Artiodactyla or on smooth substrates such as the skin

Phylogeography in an "oyster" shell provides first insights into the genetic structure of an extinct Ostrea edulis population

The historical phylogeography of Ostrea edulis was successfully depicted in its native range for the first time using ancient DNA methods on dry shells from museum collections. This research reconstructed the historical population structure of the European flat oyster across Europe in the 1870s-including the now extinct population in the Wadden Sea. In total, four haplogroups were identified with one haplogroup having a patchy distribution from the North Sea to the Atlantic coast of France. This irregular distribution could be the result of translocations. The other three haplogroups are restricted to narrow geographic ranges, which may indicate adaptation to local environmental conditions or geographical barriers to gene flow. The phylogenetic reconstruction of the four haplogroups suggests the signatures of glacial refugia and postglacial expansion. The comparison with present-day O. edulis populations revealed a temporally stable population genetic pattern over the past 150 years despite large-scale translocations. This historical phylogeographic reconstruction was able to discover an autochthonous population in the German and Danish Wadden Sea in the late nineteenth century, where O. edulis is extinct today. The genetic distinctiveness of a now-extinct population hints at a connection between the genetic background of O. edulis in the Wadden Sea and for its absence until today

Direct long-read RNA sequencing identifies a subset of questionable exitrons likely arising from reverse transcription artifacts

Resistance to CD19-directed immunotherapies in lymphoblastic leukemia has been attributed, among other factors, to several aberrant CD19 pre-mRNA splicing events, including recently reported excision of a cryptic intron embedded within CD19 exon 2. While “exitrons” are known to exist in hundreds of human transcripts, we discovered, using reporter assays and direct long-read RNA sequencing (dRNA-seq), that the CD19 exitron is an artifact of reverse transcription. Extending our analysis to publicly available datasets, we identified dozens of questionable exitrons, dubbed “falsitrons,” that appear only in cDNA-seq, but never in dRNA-seq. Our results highlight the importance of dRNA-seq for transcript isoform validation