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Thanks to the European Reference Genome Atlas initiative (ERGA) and their Biodiversity Genomics Europe project (BGE), a reference genome for the European pond turtle leech Placobdella costata (Müller, 1846) has been sequenced and assembled to chromosome level!

P. costata is just one of two Palearctic representatives of its genus, with recent cryptic diversity uncovered by molecular analyses. This specific leech was collected by collaborator Clemens Grosser in Germany, and belongs to the so-called “C4” species cluster. Like other blood-feeding glossiphoniids, it hosts a nutritional symbiont in specialised organs called bacteriomes. This reference genome will be of great value to different lines of research including

• the evolution of new organs (such as the bacteriome), body parts (such as a proboscis), and biological traits (such as parental care)
• disentangle the host-microbe interactions between this leech and its nutritional symbiont
• unravelling cryptic diversity within P. costata
• the exploration of novel putative anticoagulants

This work included invaluable contributions from the Welcome Sanger Institute‘s Tree of Life programme, the Leibniz Institute for the Analysis of Biodiversity Change, and a bunch of staff and collaborators of the ERGA initiative and BGE project.

Reference: 10.12688/openreseurope.24522.1
*Version of record: 10.12688/openreseurope.24522.1

This last week, Anna Doblhofer (Bachelor student at the University of Vienna) joined the group for her Bachelor internship. Anna will be taking over barcoding of leeches we have collected and received from different sites and identifying the symbionts some are suspected to carry.

Along with Anna Michalik & Piotr Łukasik (Jagiellonian University), we will embark on a large-scale collaborative project funded by the Austrian Science fund (Austria) and the National Science Centre (Poland) through the Weave initiative, which funds research collaborations across European borders. Within this project, we will explore potential pathogens carried by hemipteran insects (namely aphids, psyllids, and true hoppers) and the the interaction of these with facultative symbiont strains. We will carry out high-throughput analyses of thousands of samples in order to infer symbiont composition as well as identify potential pathogenic taxa carried by the sampled insects. We will then perform functional and genomic characterisation of selected insect populations. Finally, we will approach the experimental validation of inferred positive/negative interactions between pathogens and the co-occurring facultative symbionts. We expect the results of this project will uncover hidden pathogen diversity, clarify how microbial partners shape disease spread, and provide a foundation for predicting pathogen emergence and developing innovative strategies to mitigate vector-borne plant diseases.

We will soon(ish) be advertising several position, including PhD positions in both Kraków and Vienna.

FWF: 10.55776/PIN1203225

NCN: 2025/59/I/NZ9/03691

In a collaboration with Anouk Willemsen and led by Dominik (VEE lab), we reconstructed high-quality genomes from diverse Waste-water treatment plants (61 novel nucleocytoviruses, 15 virophages and 14 polinton-like viruses). We aimed to study interactions among the players in this complex ecosystems. Through a multi-layered network analysis (looking at gene sharing, co-occurrence, and integration), we demonstrate nucleocytoviruses mediate the centrality of key interaction-hubs, and entities associated with NCVs strongly coincide with more central positions… meaning that while NCVs themselves do not rank among the most central (neither by degree or betweenness), NCV-connected microbial contigs assume dramatically elevated centrality compared to both unconnected microbes and the NCVs themselves. So, NCVs are key mediators of interaction.

Reference: 10.64898/2026.05.21.726523

Aphids typically rely on the obligate symbiont Buchnera, but several lineages have acquired additional co-obligate symbionts, most commonly Serratia symbiotica. Through phylogenetic analyses, we found that a clade of Cinara aphids shows strict co-speciation between aphids and both endosymbionts.To our surprise, both bacterial lineages show similar substitution rates, contrasting what we have observed in, for example, Leafhopper’s symbiotic systems (Nasuia and Sulcia). Genome variations within and between aphid species indicate strong purifying selection acting on both symbionts… AND no evidence of relaxed selection on protein-coding genes shared between Buchnera and Serratia, suggesting that the presence of Serratia does not exacerbate genome erosion in Buchnera even on redundant metabolic genes! Thus, we show that these symbionts have co-evolved under comparable selective constraints and demographic events at least within this clade of Cinara species, that originated ~25 Million years ago.

This work was the result of a collaboration stated a while ago at the Biology Centre for Population Management (CBGP, INRAE, France) with Emmanuelle Jousselin and Armelle Coeur d’acier and led by then PhD student Jess Rouïl.

Reference: 10.64898/2026.05.09.722923

This last week, I had the pleasure to attend the annual “Microbiology day“, a meeting from the Nouvelle-Aquitaine region in France, as a keynote speaker, spreading the word on bacterial symbioses in leeches. This meeting brings together the academic and industrial sector of the region working in the broader topic of microbiology. We heard from topics regarding viral infections in plants, microbiological solutions to crops and soils, antimicrobial peptides, and more. It was very enjoyable running into old friends and making new ones as well as getting to know an emblematic French city, Bordeaux.

After a long hiatus, we are back in Slovenia! This past week Pegah and I went to the University of Ljubljana to join long-term collaborator Peter Trontelj and Maria Kolesnykova (М. Колесникова) in a sampling trip under the umbrella of our FWF SymBirth project. We visited a couple of known plus new sites and managed to sample some glossiphoniids, erpobdellids, and piscicolids to use in our sutdy on symbiont transmission in leeches. I also had the opportunity to present our past and current work on leech symbioses across leeches at the Ecology & Evolution Doctoral Seminar Series. Thanks Peter and Maria for being great hosts! very much looking forward to the next trip.

This week I was lucky to have been invited to talk at the Institute of Integrative Biology (IBZ) Seminar Series by the Vorburger’s group (Evolutionary Ecology). Got to talk about my favourite topics: aphids, leeches, and their symbionts. It was very fun to interact with people from the group and the larger Institute, discussing the exciting science talking place there. Thanks to Gioacomo, Georgia, Dominic, and Christoph for being great hosts!

Pegah was just awarded a Mobility Fellowship from the University of Vienna! This fellowship will enable Pegah to visit the “leech lab” at Kyoto University (Japan) led by Dr. Takafumi Nakano. During her visit she aims to gain insight into the microbial symbioses of three Japanese leeches: Hirudo nipponia, Placobdella okai, and Torix tagoi. Through her stay, we also aim to establish a formal collaboration between out two groups and gain important data for planning joint projects on the symbioses present in these organisms.

Thanks to the European Reference Genome Atlas initiative (ERGA) and their Biodiversity Genomics Europe project (BGE), a reference genome for the historical European southern medicinal leech Hirudo verbana Carena, 1820 has been sequenced and assembled to chromosome level!

This specific leech was collected in Vienna, where it should not naturally occur, likely representing an historical introduction into an artificial pond. This so-called “medicinal” leech was erroneously treated for a long time as a colouration type/form H. medicinalis L. 1758, but now is one of several recognised European species (along with H. troctina and H. orientalis). Historically, it has been, and still is, widely used and trafficked for medicinal and pseudo-medicinal purposes. This reference genome will be of great value to different lines of research including

• the study of genomic evolution in the Hirudo genus
• unravelling cryptic diversity within the morphospecies H. verbana
• the exploration of novel putative anticoagulants
• the establishment, maintenance, and cross-talk between the leech host and its symbionts.

This work included invaluable contributions from the Welcome Sanger Institute‘s Tree of Life programme, the Leibniz Institute for the Analysis of Biodiversity Change, and a bunch of staff and collaborators of the ERGA initiative and BGE project.

Reference: 10.12688/openreseurope.21672.1
*Version of record: 10.12688/openreseurope.21672.2