Unexpected endemism in the Daphnia longispina complex (Crustacea: Cladocera) in Southern Siberia

A phylogeographic pattern of the trans-Palaearctic littoral water flea Pleuroхus truncatus (O.F. Müller, 1785) (Cladocera: Chydoridae)

Water fleas (Crustacea: Cladocera) are recently regarded as models for phylogeographic studies, but most such publications are concerned the planktonic genera, first of all, Daphnia O.F. Müller. The aim of our article is to study the phylogeographic pattern of a very common littoral chydorid Pleuroxus truncatus (O.F. Müller) based on sequences of two mitochondrial (cytochrome oxidase (COI) and 16S) and two nuclear (18S and 28S) genes. All totality of the sequences could be subdivided into two major clades, A, having a predominantly European distribution with a single exclusion, and B, having a predominantly Asian distribution, but with few populations in European Russia; the clade B is subdivided into three subclades (B1-B3) with a moderate support. Earlier derived phylogroups (subclades B1 and B2) are distributed in south portion of Western Siberia. This pattern is known for previously studied daphniids. Estimations of the major clade (A and B) and subclade differentiation time in P. truncatus based on different methods lie in the interval of ca. 0.01-0.3 Mya. Therefore, the whole revealed pattern is very young, related to Late Pleistocene and more shallow as compared to previously studied daphniids. Probably, the total population of P. truncatus was not so strongly split by the unfavorable conditions during the Pleistocene cold phases.

Branchiopoda (Crustacea: Anostraca and Diplostraca) diversity in Tajik Pamir and plain West and South Tajikistan

Here we attempt to clarify a faunistic composition of branchiopods from southern Tajikistan and the southern part of the Tajik Pamir Plateau (Central Asia) based on samples collected from June 24 to July 6, 2023. In total, 19 species of branchiopods were identified from plain West and South Tajikistan, and 27 species were recorded in Tajik Pamir. Five taxa were newly recorded for the territory of Tajikistan: Chirocephalus cf. bobrinskii (Alcock, 1898), Ceriodaphnia dubia Richard, 1894 s. lat., C. megops Sars, 1862, Ilyocryptus spinifer Herrick, 1882, and Anthalona harti harti Van Damme, Sinev & Dumont, 2011. The previous identifications were corrected for four more taxa. Morphological traits and taxonomic position of several species were discussed in detail, namely two abovementioned anostracan taxa, Eulimnadia behningi Smirnov, 1949 (Spinicaudata), Anthalona harti harti and Coronatella rectangula (Sars, 1861) (Anomopoda). To date, the faunistic list of Tajikistan includes 77 valid branchiopod taxa. Plain Tajikistan is inhabited by both boreal and tropical branchiopod species, what indicates its geographic position on the edge of the Palearctic. Tajik Pamir fauna includes a specific component of alpine species and regional endemics. Complex relief and geographic position of Tajikistan make it prospective for future faunistic, biogeographic and phylogeographic research.

Unexpected high species richness of Bythotrephes Leydig, 1860 (Branchiopoda: Cladocera: Cercopagididae) in subalpine Austrian lakes, with the description of new taxa

The presence of four taxa at the species and subspecies level was revealed based on morphological investigation of a small collection of the representatives of the genus Bythotrephes Leydig, 1860 from Austrian subalpine lakes. The presence of a new species, B. inexpectatus sp. nov. was revealed in two lakes and the presence of a new subspecies, B. longimanus austriacus ssp. nov., in six lakes. Specimens of the population from the Lake Halstättersee, distinguished by the presence of peculiar features, are provisionally assigned to the species B. brevimanus Lilljeborg, 1901 of which the main range is confined to Circumbaltic region. Few morphologically specific specimens from Wolfgangsee could not be accurately identified and therefore assigned to the taxon Bythotrephes sp. requiring further investigation. Previously described taxa from the region, B. styriacus Ischreyt, 1939 and B. longimanus var. carnica Ischreyt, 1939, were considered either required further taxonomic evaluation or having an unclear taxonomic status, respectively. In one lake, the co-occurrence of two species was recorded, which is a rather rare case for the representatives of the genus. The potential reasons for the high species richness of spiny waterfleas in Austrian subalpine lakes and their possible origin are briefly discussed.

Cryptic taxonomic diversity and high-latitude melanism in the glossiphoniid leech assemblage from the Eurasian Arctic

The family Glossiphoniidae is a diverse and widespread clade of freshwater leeches, playing a significant role in functioning of aquatic ecosystems. The taxonomy and biogeography of leeches from temperate, subtropical, and tropical regions attracted much attention of zoologists, while their taxonomic richness and distribution in the Arctic are poorly understood. Here, we present an overview of the Eurasian Arctic Glossiphoniidae based on the most comprehensive occurrence and DNA sequence datasets sampled to date. This fauna contains 14 species, belonging to five genera and three subfamilies. One genus and five species are new to science and described here. The world's northernmost occurrences of glossiphoniids are situated on the Taymyr Peninsula at 72° N, although further records at higher latitudes are expected. Most Arctic leeches are characterized by broad ranges crossing several climatic zones (e.g., Glossiphonia balcanica and G. nebulosa), although the distribution of two new species may be confined to the high-latitude areas. The Taymyr Peninsula with the nearby Putorana Plateau represents the most species-rich area (totally 9 species), while the European Arctic, Iceland, Kolyma Highland, and Chukotka Peninsula house depleted faunas (2-4 species per subregion). Finally, we show that the high-latitude melanism is a common phenomenon in glossiphoniid leeches.

Mitochondrial Lineage Diversity and Phylogeography of Daphnia (Daphnia) (Crustacea: Cladocera) in North-East Russia

The variability of the 12S gene fragment of the mtDNA for taxa belonging to subgenus Daphnia (Daphnia) O.F. Müller, 1776 (Crustacea: Cladocera) in NE Russia is studied, and their phylogenetic analysis performed. We identified (based both on morphological and molecular data) nine species belonging to four species complexes, namely: (A) D. longispina s.l.: (1) D. longispina O.F. Müller, 1776; (2) D. dentifera Forbes, 1893; (3) D. galeata Sars, 1864; (4) D. umbra Taylor, Hebert et Colbourne, 1996; (B) D. cristata s.l.: (5) D. cristata Sars, 1862; (6) D. longiremis Sars, 1862; (C) D. curvirostris s.l.: (7) D. curvirostris Eylmann, 1887; (D) D. pulex s.l.: (8) D. pulex Leydig, 1860; (9) D. middendorffiana Fischer, 1851. Rare arcto-mountainous taxon D. umbra was found in the mountains of the Sakha (Yakutia) Republic for the first time. Species diversity in NE Asia is relatively low, and the most revealed taxa are trans-Beringian. We also performed a phylogeographic analysis of D. dentifera and D. pulex s.l., the two most common species in NE Russia. Our new data allow us to assume that the daphniids of NE Asia have undergone various evolutionary scenarios during the Pleistocene period: survival is within some local refugia, and re-colonization from these areas and from North America through the Beringian land bridge, etc. We agree with previous authors who revealed that the patterns in the studied species groups are relatively recent (of Late Pleistocene or even Holocene age), although the main phylogenetic daphniid lineages (mainly congruent with the biological species) are very old. Our results provide convincing evidence for the hypothesis that NE Russia is a very important source of modern haplotypic diversity for the cladocerans.

Characterization and Comparative Analysis of MicroRNAs in 3 Representative Red Algae

Background

MicroRNA (miRNA) is a key regulator at the gene posttranscriptional regulation level. We have previously identified miRNAs and their putative targets in 3 representative red algae, Chondrus crispus, Galdieria sulphurariais and Porphyridium purpureum.

Objectives

In this study, unique molecular and evolutionary characterization of miRNAs were revealed in the 3 red algae based on the comparative miRNAs profiling.

Materials and Methods

Genome locations of small RNAs (sRNAs), miRNAs and MIRNAs (MIRs) in the 3 red algae were shown by collinearity analysis. Characterization of miRNAs and MIRs were profiled via bioinformatics analysis. Taken MIR156s and miR156s for examples, red algae miRNAs evolutionary features were demonstrated via phylogenetic and evolutionary information analysis. MiRNA targets main inhibition type was validated via performing data statistics and RLM-RACE PCR. Key target genes and their function were predicted by the common Gene Ontolgoy (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis.

Results

Quantity, nucleotide bias and common sequences of miRNAs were analyzed in the 3 red algae. Four typical precursor structures and primary molecular features of red algae miRNAs were profiled. Genome-wide collinearity analysis of sRNAs, miRNAs and MIRs in the 3 red algae was performed to show their distribution and interrelation based on the deep sequencing data. Taken red algae MIR156s for example, their family members and sequences divergence were demonstrated. The whole evolutionary processes of miR156s and pre-miR156s in red algae were steady with negative selected pressure though diverse phylogenetic relationships and evolutionary parameters showed. Through 3 red algae miR156 targets validation, cleavage was validated as their main miRNA targets inhibition type. The common target genes (GO:0009536) enriched significantly for plastid formation will provide important insights for red algal biopigment research. The common KEGG pathways (ko01100) enriched significantly were predicted without a detailed reference metabolic map.

Conclusions

MiRNA plays an essential role in gene expression regulation involved in diverse biological processes of red algae. Comprehensive molecular and evolutionary features of miRNAs in the 3 red algae will provide insights for further utilizing the algae resources at the molecular level.

Crustaceans in the Meiobenthos and Plankton of the Thermokarst Lakes and Polygonal Ponds in the Lena River Delta (Northern Yakutia, Russia): Species Composition and Factors Regulating Assemblage Structures

Information about invertebrates in the low-flow water bodies of northeastern Siberia is far from complete. In particular, little is known about crustaceans—one of the main components of meiobenthic and zooplanktonic communities. An open question is which environmental factors significantly affect the crustaceans in different taxonomic and ecological groups? Based on the data collected on the zooplankton and meiobenthos in the tundra ponds in the southern part of the Lena River Delta, analysis of the crustacean taxocene structure was performed. In total, 59 crustacean species and taxa were found. Five of these are new for the region. The species richness was higher in the large thermokarst lakes than in the small water bodies, and the abundance was higher in small polygonal ponds than in the other water bodies. Variations in the Cladocera assemblages were mainly affected by the annual differences in the water temperature; non-harpacticoid copepods were generally determined by hydrochemical factors; and for Harpacticoida, the macrophyte composition was significant. Three types of the crustacean assemblages characteristic of different stages of tundra lake development were distinguished. The hypothesis that the formation of crustacean taxocenes in the Lena River Delta is mainly determined by two types of ecological filters, temperature and local features of the water body, was confirmed.

Speciation in Daphnia

The microcrustacean Daphnia is arguably one of the most studied zooplankton species, having a well understood ecology, life history, and a relatively well studied evolutionary history. Despite this wealth of knowledge, species boundaries within closely related species in this genus often remain elusive and the major evolutionary forces driving the diversity of daphniids remain controversial. This genus contains more than 80 species with multiple cryptic species complexes, with many closely related species able to hybridize. Here, we review speciation research in Daphnia within the framework of current speciation theory. We evaluate the role of geography, ecology, and biology in restricting gene flow and promoting diversification. Of the 253 speciation studies on Daphnia, the majority of studies examine geographic barriers (55%). While evidence shows that geographic barriers play a role in species divergence, ecological barriers are also probably prominent in Daphnia speciation. We assess the contribution of ecological and nonecological reproductive isolating barriers between closely related species of Daphnia and found that none of the reproductive isolating barriers are restricting gene flow completely. Research on reproductive isolating barriers has disproportionally focused on two species complexes, the Daphnia pulex and Daphnia longispina species complexes. Finally, we identify areas of research that remain relatively unexplored and discuss future research directions that build our understanding of speciation in daphniids.