manzanomaa88@univie.ac.at

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

This January I had the pleasure of visiting the LIIGH – UNAM, at my home city of Querétaro (México), where I was able to talk about the symbiosis research I have done throughout the years and that we now do in the group. I was very impressed with the facilities, students, and the general vibe at the institute. Certainly not the last time I will pay them a visit!

Last week, Pegah Kalatehjari joined the team! Pegah joins us from Iran, with a background in aquaculture, leech biology and reproduction. She will work on the SymBirth project studying symbiont transmission in Placobdella leeches and beyond.

Welcome Pegah!

ESEB 2025 just wrapped up last week. It was a great week of talks, posters, and informal chats about all things evolution. Particularly, it was great to catch up with old friends working at the intersection of symbiosis and evolution. Had a great time talking about our recent work on leeches and their symbionts, and of course, aphids too. Looking forward to next ESEB meeting!

Taking advantage of the trip to China for SMBE 2025, Alejandro visited the group of Jun-Bo Luan (https://www.junboluanlab.com/) at the Shenyang Agricultural University (沈阳农业大学). It was a great visit full of insect symbiosis science, cultural visits, culinary experiences, and a great set of people!

Along with Jun-Bo Luan (https://www.junboluanlab.com/), we organised the Symbiosis symposium at SMBE 2025 (Beijing, China). We were thrilled to see the turnout and the great talks covering bioluminiscent symbiosis in Flashlight fish (Chang Liu), microbiome responses to global warming through meta-analyses (Jingdi Li), Honey bee immune system and their gut microbiome (Shiqi Luo), genomic factors of cytoplasmatic incompatibility in Wolbachia (Yongjun Tan), Arctic sponge species’ microbiomes (Anastasiia Rusanova), evolutionary forces driving Blattabacterium‘s convergent gene losses (Zhuli Cheng), multi-omics of the chemosymbiotic Alviniconcha snails (Hui Wang), and the co-evolution of host and gut bacteria during Honey bee acclimation (Min Tang).

In collaboration with Anouk Willemsen (Uniersity of Vienna), we sequenced high-quality genomes of protists known as hosts of giant viruses (GVs). Matching of codon usage preferences is often used to predict virus-host pairs. Our analyses revealed that in GVs, codon usage alone is a poor predictor of known pairs. Why? well, GVs have complex genomes… They encode few to complete tRNA sets and even genes from the translational machinery (e.g. tRNA–ligases). The host immune system may also play a role, driving viral codon usage away from its own. Moreover, its replication site (nuclear vs. cytoplasmatic) could also play a role. Finally, by analyzing the new amoebal genomes, we discovered viral integrations (potentially from GVs) into some of them, indicating historical infections. Most notably some inserted major capsid proteins seem to potentially encode for intact proteins (work in progress)…

Reference: 10.1101/2024.09.23.614596
*Version of record: 10.1093/gbe/evae271

Very happy the first group project SymBirth: Development of an artificial symbiont’s birth has been funded by the FWF’s 1000 ideas program. This program aims to fund “[…] completely new, high-risk, or particularly original research ideas that go beyond our current scientific understanding. The focus is on seed funding for forward-looking topics that have high transformative potential for science and research.”

In this project, we will study symbiont transmission in the European turtle leech Placobdella costata and related leeches. Using what we learn about this unknown process, we will undertake our ultimate goal of triggering a symbiont replacement event in this species. If accomplished, this project will result in the development of a highly promising model system for the study of the triggering of an obligate symbiotic lifestyle in bacteria.

After many years in the making (and an eternal cycle of adding new data….) our work on the discordance among phylogenomic datasets in is out!

Relationships between subfamilies remain contentious in both mitochondrial and nuclear phylogenies. Topologies obtained with Buchnera appear fully resolved but exhibit some discordance with host phylogenies at deep evolutionary scales and conflict with views on the evolution of aphid morphology. BUT…. further sampling (we had to stop at some point for this study) and sequence-independent analyses, such as male morphology and chromosomal structure, might help piece out some difficult-to-solve/contentious relationships.

This was a great collaboration with friends and work colleagues Emmanuelle Jousselin and Armelle Cœur d’acier (CBGP, france).

Reference: 10.1101/2024.04.12.589189
*Version of record: 10.1093/zoolinnean/zlae098

Pluralibacter now joins the (very) selected group of genera from which obligate nutritional symbionts of leeches have evolved from. As the previously known Providencia, this novel symbiont displays strong genome reduction w/convergent retention of B vitamin biosynthetic pathways. This discovery was surprising, as no change in bacteriome structure is observed (in leeches new symbiont=new bacteriome). Genomic features from the novel symbiont suggest it likely represents a symbiont replacement event, but future work should help clarify symbiont turnover in this leech genus.

This was a great collaboration with friends and work colleagues Alejandro Oceguera Figueroa (IB UNAM, Mexico) and Sebastian Kvist (Naturhistoriska riksmuseet, Sweden).

Reference: 10.1101/2023.12.21.572949
*Version of record: 10.1128/spectrum.04286-23