Expedition onboard the RV “G.Yu. Vereshchagin” from 11 to 21 August 2026

The primary objective of the research expedition conducted from 11 to 21 August 2026 on board the RV “G.Yu. Vereshchagin” was to investigate the deep-water fauna of Lake Baikal and to employ new methods in studying the taxonomic diversity, speciation, and ecological well-being of the lake’s deep-water fish.

The expedition was carried out within the framework of the state projects “The influence of abiotic factors of Lake Baikal and adjacent areas of East Siberia on the adaptation and biodiversity of aquatic organisms at the level of ecological, biochemical, and molecular genetic characteristics,” No. FWSR-2026-0015 (headed by A.P. Fedotov) and “Evolutionary and functional genomics of species, populations, and communities of aquatic organisms in freshwater ecosystems,” No. FWSR-2026-0003 (headed by D.Yu. Shcherbakov).

Twenty successful deep-water trawls were conducted during the expedition, and a representative volume of material (samples) was collected concerning abyssal and pelagic species of cottoid fish inhabiting various areas and basins of Lake Baikal. The maximum trawling depth was 1433 m. Divers collected live specimens near the Maloye More Strait and Sagan-Khushun Cape for experiments to be conducted aboard the research vessel.

The expedition primarily aimed to investigate adaptations of benthic sculpins to inhabit depths exceeding 500 m (down to 1600 m)–in comparison with deep-water pelagic and bottom coastal species–and to evaluate the effectiveness of biomarkers such as sensory systems, cytometric blood parameters, and differential expression of genes responsible for adaptative responses, telomere length, and telomerase activity.

Tissues from six key organ systems (brain, gills, liver, kidney, intestine, and muscles) were taken from the collected fish to study adaptations at various levels. The tissues were fixed in ethanol, TRIzol, and liquid nitrogen for different types of analysis.

Additionally, experiments were conducted directly aboard the research vessel using Baikal water and maintaining the required temperature–to study the effects of abiotic stress factors, including elevated temperature and salinity, as well as their combined impact. Experiments were performed for the first time on the deep-water endemic species, Asprocottus platycephalus, involving simultaneous water sampling to test a non-invasive method for analyzing environmental RNA and DNA.

Overall, ~ 2500 samples of key tissues were fixed for different types of analysis.

During the expedition, amphipods were sampled at nine stations in the northern, central, and southern basins of Lake Baikal at depths ranging from 123 to 1433 m. At least 15 species of large amphipods of the families Acanthogammaridae, Eulimnogammaridae, and Pallaseidae were collected. These species were examined for parasitic amphipods of the family Pachyschesidae. The percentage of parasitic amphipod infection was calculated for each species at each sampling site (at least 50 specimens), ranging from 1.8 to 26%.

The collected samples of parasitic amphipods and their hosts were fixed in a 70% ethanol solution for further species identification by morphological characteristics. DNA was extracted from some collected specimens, and the parasite and host specimens were photographed in detail. The resulting high-molecular-weight preparations are suitable for various types of molecular analysis, including PCR, routine Senger sequencing (nucleotide sequence determination), and high-throughput sequencing on the Illumina platform, etc.

This work will update and expand data on parasite amphipod infection in large, deep-water Baikal amphipods of the family Pachyschesidae. The sequence fragments of the mitochondrial (COX1) and nuclear (18S rRNA gene) genomes of deep-water Baikal amphipod species (both parasites and hosts) are suitable for molecular identification of these species, enabling the reconstruction of evolutionary history of parasitism in amphipods of the family Pachyschesidae.

A demonstration trawl and sampling of specimens of Lake Baikal’s deep-water fauna were conducted for the participants of the “Baikal-Evolution” Floating University aboard the RV “Akademik V.A. Koptyug”.