Daria S. Bedulina

Temperature influences the performance of marine ectotherms, and understanding species' thermal responses is key to predicting climate change impacts. This study investigated seasonal acclimatization effects on the thermal tolerance of the common periwinkle Littorina littorea. Snails were collected in winter and summer on the North Sea Island of Helgoland and exposed to gradually increasing temperatures (1.5 °C/h from the sampling temperature, 10-16 °C to 34 °C). Behavioral responses (antenna extension and movement onset) were assessed at target temperatures (10/16, 22, 25, 28, 31, and 34 °C), alongside cellular responses measured via activity of catalase (CAT), Hsp70 content and ¹H NMR-based metabolite profiling. Both winter and summer groups showed delayed behavioral responses above 22 °C, indicating a similar behavioral breakpoint temperature across seasons. Metabolite data revealed temperature-dependent changes only in the winter group, with elevated succinate, glutathione, glutamine and propionate levels at 28 °C, indicating anaerobic metabolism and onset of critical thermal limits. While the upper suboptimal temperature appeared similar between groups (22 °C), the upper critical temperature (Tc) was detected only in the winter group (28 °C). Summer snails had significantly higher baseline Hsp70 levels and slightly higher CAT activities, indicating enhanced cellular protection in conjunction with a seasonal shift in Tc. Overall, the results show that seasonal acclimatization alters acute thermal responses in L. littorea and behavioral metrics are confirmed as valuable sublethal indicators for assessing heat tolerance in marine invertebrates.

The vast global freshwater biodiversity hotspot Lake Baikal is located in a region with extremely cold winters and warm summers. Although conditions in winter with low water temperatures and relative scarcity of food may seem unfavorable for reproduction, Baikal is inhabited by a major endemic winter-reproducing amphipod species complex. We analyzed sex-specific seasonal proteome dynamics in a common representative species of this complex, Eulimnogammarus verrucosus, sampled in the field in fall, winter, and summer 2019/20. Especially female proteomes were dominated by sampling time point-specific hallmarks of reproduction-related processes and events, particularly related to formation of the eggs and embryo development. Proteome characteristics indicated that processes requiring the supply of external resources tend to take place at times of higher food availability before and after the winter: Thus, formation of the eggs in female E. verrucosus starts already in summer and juveniles hatch from eggs in spring; in winter, processes supplied by stored resources take place, such as embryo development in the egg fueled by the egg yolk. Adjustments of the amphipods of both sexes to environmental winter conditions were reflected by abundance changes of enzymes of the digestive system, indicating a response to seasonal diet changes, and of enzymes involved in RNA biosynthesis and protein folding, possibly related to decreasing water temperatures. The here analyzed proteomes reveal a strategy of a cold-adapted amphipod to deal with the unique and extreme environmental conditions of Baikal, directed to pace and timing of the resource depending, reproduction-related processes in relation to environmental parameters.

Lake Baikal in eastern Siberia is the deepest and (by volume) largest lake on Earth. Among the most ancient lakes, it is home to thousands of endemic species. Lake Baikal is well‐known for its water purity, especially its dominant deep‐water layers, which consist of pristine, drinking‐quality water and is inhabited by unique endemics with enormous biodiversity. But some coastal sites of this giant lake (mainly localized in isolated shallow bays and littoral zones close to settlements and industrial sites) are suffering from an environmental crisis that threatens the water's quality and the ecosystem it supports. As part of the global ecosystem, Lake Baikal is already facing significant impacts from global climate change, which, in turn, increase the risks and consequences of local anthropogenic effects. Although the lake is protected by federal law, human activities are nevertheless having a growing negative impact on its ecosystem. Political, economic, and social factors result in cascading natural consequences in water quality, coastal sustainability, pollution sinks, water level management, forest maintenance, fire control and biodiversity. While Lake Baikal is a UNESCO World Heritage Site, known and valued around the world, it remains vulnerable to worsening threats that must be addressed if humanity is to preserve this unique ecosystem and its endemic species into the future.This article is categorized under: Water and Life > Stresses and Pressures on Ecosystems Water and Life > Conservation, Management, and Awareness Science of Water > Water Quality Engineering Water > Planning Water

Purpose Studies of proteins expressed in the morphological structures of the parasite are necessary for elucidating the biological functions of unknown proteins and understanding the molecular basis of parasitism. The research aim was to investigate the spatial distribution of major proteins in scolex, immature and gravid proglottids of Triaenophorus nodulosus and Triaenophorus crassus. Methods Protein extracts of worm body parts were analyzed using two-dimensional difference gel electrophoresis (DIGE) and mass spectrometry. Results Comparison of the protein repertoire of the adult worm and the encysted plerocercoid revealed differences between the worm body parts, life stages and parasite species. The content of proteins associated with the cytoskeleton and musculature (actin, myosin regulatory light chain, and tropomyosin 2) decreased with distance from the scolex. Mature proglottids were rich in transforming growth factor-beta-induced protein, propionyl-CoA carboxylase, glutamate dehydrogenase and beta-tubulin. Interspecific variation in T. nodulosus and T. crassus was found in the content of the myosin, paramyosin, the major vault protein and an uncharacterized secreted protein TRINITY_DN24645. Differential expression of TRINITY_DN24645, paramyosin and tropomyosin 2 was found between plerocercoids and adult worms. Conclusion The present study provides the first characteristics of the spatial distribution of the major proteins of T. crassus and T. nodulosus. Comparison of the protein composition of plerocercoids and adult parasites indicates a significant similarity in the proteomic organization of Triaenophorus sp. in the second intermediate and final hosts. The gradual change in the morphological organization of tapeworms in the longitudinal direction coincided with the expression of some structural and metabolic proteins.

Background: Lake Baikal is one of the oldest freshwater lakes and has constituted a stable environment for millions of years, in stark contrast to small, transient bodies of water in its immediate vicinity. A highly diverse endemic endemic amphipod fauna is found in one, but not the other habitat. We ask here whether differences in stress response can explain the immiscibility barrier between Lake Baikal and non-Baikal faunas. To this end, we conducted exposure experiments to increased temperature and the toxic heavy metal cadmium as stressors.Results: Here we obtained high-quality de novo transcriptome assemblies, covering mutiple conditions, of three amphipod species, and compared their transcriptomic stress responses. Two of these species,Eulimnogammarus verrucosusandE. cyaneus, are endemic to Lake Baikal, while the HolarcticGammarus lacustrisis a potential invader.Conclusions: Both Baikal species possess intact stress response systems and respond to elevated temperature with relatively similar changes in their expression profiles.G. lacustrisreacts less strongly to the same stressors, possibly because its transcriptome is already perturbed by acclimation conditions.

The ancient Lake Baikal is characterized by an outstanding diversity of endemic faunas with more than 350 amphipod species and subspecies. We determined the genetic diversity within the endemic littoral amphipod species Eulimnogammarus verrucosus, E. cyaneus and E. vittatus and investigated whether within those species genetically separate populations occur across Lake Baikal. Gammarus lacustris from water bodies in the Baikal area was examined for comparison. Genetic diversities within a species were determined based on fragments of cytochrome c oxidase I (COI) and for E. verrucosus additionally of 18S rDNA. Highly location-specific haplogroups of E. verrucosus and E. vittatus were found at the southern and western shores of Baikal that are separated by the Angara River outflow; E. verrucosus from the eastern shore formed a further, clearly distinct haplotype cluster possibly confined by the Selenga River and Angarskiy Sor deltas. The genetic diversities within these haplogroups were lower than between the different haplogroups. Intraspecific genetic diversities within E. verrucosus and E. vittatus with 13 and 10%, respectively, were similar to interspecies differences indicating the occurrence of cryptic, morphologically highly similar species; for E. verrucosus this was confirmed with 18S rDNA. The haplotypes of E. cyaneus and G. lacustris specimens were with intraspecific genetic distances of 3 and 2%, respectively, more homogeneous indicating no or only recent disruption of gene flow of E. cyaneus across Baikal and recent colonization of water bodies around Baikal by G. lacustris. Our finding of separation of subgroups of Baikal endemic amphipods to different degrees points to a species-specific ability of dispersal across areas with adverse conditions and to potential geographical dispersal barriers in Lake Baikal.

Heat shock proteins/cognates 70 are chaperones essential for proper protein folding. This protein family comprises inducible members (Hsp70s) with expression triggered by the increased concentration of misfolded proteins due to protein-destabilizing conditions, as well as constitutively expressed cognate members (Hsc70s). Previous works on non-model amphipod species Eulimnogammarus verrucosus and Eulimnogammarus cyaneus, both endemic to Lake Baikal in Eastern Siberia, have only revealed a constitutively expressed form, expression of which was moderately further induced by protein-destabilizing conditions. Here we describe heat-inducible hsp70s in these species. Contrary to the common approach of using sequence similarity with hsp/hsc70 of a wide spectrum of organisms and some characteristic features, such as absence of introns within genes and presence of heat shock elements in their promoter areas, the present study is based on next-generation sequencing for the studied or related species followed by differential expression analysis, quantitative PCR validation and detailed investigation of the predicted polypeptide sequences. This approach allowed us to describe a novel type of hsp70 transcripts that overexpress in response to heat shock. Moreover, we propose diagnostic sequence features of this Hsp70 type for amphipods. Phylogenetic comparisons with different types of Hsp/Hsc70s allowed us to suggest that the hsp/hsc70 gene family in Amphipoda diversified into cognate and heat-inducible paralogs independently from other crustaceans. Thus, the cognate and inducible hsp70 types in distant taxa may not be recognized by sequence similarity.