manzanomaa88@univie.ac.at

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

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!