The First Data on Harpacticoid Copepod Diversity of the Deep-Water Zone of Lake Baikal (Siberia, Russia)

Lake Baikal (LB) is the only freshwater ancient lake on Earth where animals inhabit all bathymetric zones down to the deepest sites (approximately 1640 m). However, there is very little data on the composition of their abyssal harpacticoid fauna. On the basis of the samples collected in LB in 2010–2017 at a depth of 270–1632 m, analysis of the fauna composition and species diversity of harpacticoids in the deep-water zone is presented. Studies were conducted in all parts of the lake, including areas of a hydrothermal, oil–methane seeps, and mud volcanoes. Nineteen Baikal endemic morphological species of the genera Bryocamptus, Attheyella, and Moraria (Baikalomoraria) were found. A brief description of the taxa morphology is presented. The genus Bryocamptus was the richest by species number at the studied sites, and Bryocamptus smirnovi Borutzky was the most frequent. The most diverse (8 species) was the fauna of the Saint Petersburg methane seep. Studies have shown that the taxonomic diversity of harpacticoid copepods in the deep-water zone of LB is lower than in its littoral zone. According to two non-parametric species estimators (Chao 2 and Jackknife 1), a 1.5-fold increase of species richness of harpacticoids of the LB abyssal is expected

Data from: Conquest of the deep, old and cold: an exceptional limpet radiation in Lake Baikal

Lake Baikal is the deepest, oldest and most speciose ancient lake in the world. The lake is characterized by high levels of molluscan species richness and endemicity, including the limpet family Acroloxidae with 25 endemic species. Members of this group generally inhabit the littoral zone, but have been recently found in the abyssal zone at hydrothermal vents and oil-seeps. Here, we use mitochondrial and nuclear data to provide a first molecular phylogeny of the Lake Baikal limpet radiation, and to date the beginning of intra-lacustrine diversification. Divergence time estimates suggest a considerably younger age for the species flock compared with lake age estimates, and the beginning of extensive diversification is possibly related to rapid deepening and cooling during rifting. Phylogenetic relationships and divergence time estimates do not clearly indicate when exactly the abyssal was colonized but suggest a timeframe coincident with the formation of the abyssal in the northern basin (Middle to Late Pleistocene)

Keyhole into a Lost World: The First Purely Freshwater Species of the Ponto-Caspian Genus Clathrocaspia (Caenogastropoda: Hydrobiidae)

The species of the Ponto-Caspian gastropod genus Clathrocaspia Lindholm, 1930 have been recorded so far from the Caspian Sea Basin only from marine waters, whereas they inhabit the estuarine areas as well as the purely freshwater environments in the Azov–Black Sea Basin. This genus has recently been assessed as putatively extinct in the Caspian Sea. A new purely freshwater species Clathrocaspia laevigata sp. n. from the water-flows of the Samur River delta in Dagestan, Russia, is described. A morphological comparison of the new species with C. brotzkajae (Starobogatov in Anistratenko & Prisjazhnjuk, 1992) from the Caspian Sea and C. knipowitschii (Makarov, 1938) inhabiting the Azov–Black Sea Basin shows their overall similarity. The major difference is that C. laevigata sp. n. almost completely lacks the reticulate teleoconch sculpture, whereas it is well-developed in all known Clathrocaspia species. The molecular data revealed probable sister relationships between the new species and C. knipowitschii. All Dagestan populations are ecologically and spatially isolated from the open sea and and are very locally restricted. We suggest to consider newly described snail species as retained in a pure freshwater refuge located in the coastal area of the Caspian Sea. The discovery of such a refuge sheds more light on the origin, current state and the future of the unique Ponto-Caspian aquatic biota under global change and increasing anthropogenic impact

Supplementary data

Supplementary data includes the RAxML phylogram for the concatenated dataset (16S rRNA, 28S rRNA, COI and H3), the BEAST input xml file and the BEAST MCC tree file. For details see the electronic supplementary material of the article