Genome Assembly of a Relict Arabian Species of Daphnia O. F. Müller (Crustacea: Cladocera) Adapted to the Desert Life.

The water flea Daphnia O.F. Müller 1776 (Crustacea: Cladocera) is an important model of recent evolutionary biology. Here, we report a complete genome of Daphnia (Ctenodaphnia) arabica (Crustacea: Cladocera), recently described species endemic to deserts of the United Arab Emirates. In this study, genome analysis of D. arabica was carried out to investigate its genomic differences, complexity as well as its historical origins within the subgenus Daphnia (Ctenodaphnia). Hybrid genome assembly of D. arabica resulted in ~116 Mb of the assembled genome, with an N50 of ~1.13 Mb (BUSCO score of 99.2%). From the assembled genome, in total protein coding, 5374 tRNA and 643 rRNA genes were annotated. We found that the D. arabica complete genome differed from those of other Daphnia species deposited in the NCBI database but was close to that of D. cf. similoides. However, its divergence time estimate sets D. arabica in the Mesozoic, and our demographic analysis showed a great reduction in its genetic diversity compared to other Daphnia species. Interestingly, the population expansion in its diversity occurred during the megadrought climate around 100 Ka ago, reflecting the adaptive feature of the species to arid and drought-affected environments. Moreover, the PFAM comparative analysis highlights the presence of the important domain SOSS complex subunit C in D. arabica, which is missing in all other studied species of Daphnia. This complex consists of a few subunits (A, B, C) working together to maintain the genome stability (i.e., promoting the reparation of DNA under stress). We propose that this domain could play a role in maintaining the fitness and survival of this species in the desert environment. The present study will pave the way for future research to identify the genes that were gained or lost in this species and identify which of these were key factors to its adaptation to the harsh desert environment.

Mitogenomics of Cladocera (Branchiopoda): Marked gene order rearrangements and independent predation roots.

Cladocera (Crustacea: Branchiopoda) is a key group of invertebrates. Despite a long history of phylogenetic research, relationships within this group remain disputed. We here provide new insights based on 15 new mitochondrial genomes obtained from high-throughput sequencing (HTS) and 40 mitogenomes extracted from published HTS datasets. Together with 25 mitogenomes from GenBank, we generated a matrix of 80 mitogenomes, 44 of them belonging to Cladocera. We also obtained a matrix with 168 nuclear orthologous genes to further assess the phylogenetic result from mitogenomes based on published data and one new HTS data ofLeptodora. Maximum likelihood and Bayesian phylogenetic analyses recovered all Branchiopoda orders as monophyletic and supported a sister-group relationship between Anomopoda and Onychopoda, making the taxon Gymnomera paraphyletic and supporting an independent origin of predatory Haplopoda and Onychopoda. The nuclear phylogeny and topological tests also support Gymnomera as paraphyletic, and the nuclear phylogeny strongly supports a sister-group relationship between Ctenopoda and Haplopoda. We provide a fossil-calibrated time tree, congruent with a Carboniferous origin for Cladocera and a subsequent diversification of the crown group of Anomopoda, Onychopoda, and Ctenopoda, at least in the Triassic. Despite their long evolutionary history, non-Cladoceran Branchiopoda exhibited high mitogenome structural stability. On the other hand, 21 out of 24 gene rearrangements occurred within the relatively younger Cladocera. We found the differential base compositional skewness patterns between Daphnia s.s. and Ctenodaphnia, which might be related to the divergence between these taxa. We also provide evidence to support the recent finding that Spinicaudata possesses mitogenomes with inversed compositional skewness without gene rearrangement. Such a pattern has only been reported in Spinicaudata.

A new species of Leydigia Kurz, 1875 (Cladocera: Chydoridae) from Colombia.

A new species of Leydigia Kurz, 1875 (Cladocera: Chydoridae) is described based on the material from Ciénaga Grande de Santa Marta, Magdalena Department, Colombia. L. lourdesae sp. nov. is a member of the subgenus Leydigia (Neoleydigia) Kotov, 2009, having all diagnostic characters of the latter. It could be the closest relative to L. iberica Kotov & Alonso, 2010, having five setae on exopodite III, a unique for the genus character. But new taxon differs from the latter in a series of characters of the head pores, armature of valve ventral margin, postabdomen, antenna I and II, and limbs I-III. We believe that the basal taxa of L. (Neoleydigia) (including L. lourdesae sp. nov.) are remains of an antique pan-continental group, probably of Mesozoic age, partly survived after the mass extinction and represented now by a series of locally distributed taxa in very distant localities of the planet.

Molecular approach to identify sibling species of the Ceriodaphnia cornuta complex (Cladocera: Daphniidae) from Australia with notes on the continental endemism of this group.

Taxonomy of the genus Ceriodaphnia Dana, 1853 (Cladocera: Daphniidae) has been uncertain for a long time, the species richness was often underestimated due to (1) a morphological similarity among the species and (2) their great morphological inter- and intra- populational variability. Support for this conclusion comes from the first analysis of three molecular markers for Australian representatives of this genus, two mitochondrial (COI and 16s) and one nuclear (28s) genes. Sequence analysis indicates the existence of three sibling Australian species belonging to the complex. Further work is required to establish species boundaries and investigate potential morphological diagnoses. Comparison of COI sequences with all other published sequences from the genus Ceriodaphnia revealed no common clades among continents pointing to the regional endemism within this group, which could suggest its Mesozoic differentiation.

Latitudinal patterns in the diversity of two subgenera of the genus Daphnia O.F. Müller (Crustacea: Cladocera: Daphniidae).

Daphnia O.F. Müller (Crustacea: Cladocera: Daphniidae) is an important model in biology. It was concluded earlier that subgenus Daphnia s.str. occurs mainly in the northern hemisphere, subgenus Daphnia (Ctenodaphnia) in the southern hemisphere, which could suggest that: (1) the subgeneric differentiation is correlated with the Laurasia-Gondwanaland subdivision and (2) D. (Ctenodaphnia) is a taxon of Gondwanian origin. Some authors even discussed mechanisms of maintaince of the "ancient subgeneric north-south split", regarding such a pattern as paradoxical. But both molecular clock calculations and fossils of both subgenera from the Jurassic/Cretaceous boundary of Mongolia compromise such ideas and suggest an earlier, Pangaean, differentiation of the subgenera.        We discuss the distribution of Daphnia worldwide based on recent literature. Our analysis covers literature data on all described and on undescribed taxa revealed by genetical methods. Distributional data were associated with five main zones: southern cold (I), southern temperate (II), tropical (III), northern temperate (IV), and northern cold (V) zone. We found no "subgeneric north-south split": the distribution of Daphnia s.str. is dissymmetric between the hemispheres (antipolar), while that of Ctenodaphnia is sub-symmetric (bipolar). We suggest that both patterns are not of Mesozoic, but of Cenozoic origin. Mesozoic differentiation of the subgenera does not contradict a recent origin of the extant species, as found in e.g. Notostraca. A superficially attractive hypothesis about a Gondwanian origin of a taxon (Daphnia (Ctenodaphnia)) therefore did not pass the test of the fossil records. In addition, we agree with the opinion that an antipolar is only a variant of a bipolar pattern, as a result of an extinction in the southern hemisphere, and that these patterns are mid-late Cenozoic instead of Mesozoic.

A new species of the genus Pleuroxus Baird (Cladocera: Anomopoda: Chydoridae) from Jeju Island, South Korea.

A new species of the genus Pleuroxus Baird (Cladocera: Anomopoda: Chydoridae) is described from Jeju Island, South Korea. P. jejuensis sp. nov. is the closest relative of the aduncus-like species from southern hemisphere instead of P. aduncus s. str. It shares with P. wittsteini Studer, 1878 in: (1) brown colour; (2) absence of denticles on postero-ventral portion of valve; (3) unusually short postpore distance; (4) grouped postanal teeth. P. jejuensis sp. nov. differs from P. wittsteini in: (1) smaller postpore distance; (2) submarginal setules on inner side of the posterior valve margin; (3) prominent postero-dorsal angle of the postabdomen; (4) only two postanal teeth in each group; (5) longer proximalmost basal spine of the postabdominal claw; (6) very short accessory seta on limb I. The wittsteini-like chydorines seem to be remnants of an old, pan-continental species group.

An annotated checklist of the Cladocera (Crustacea: Branchiopoda) from India.

Based on a revision of available literature on the Indian Cladocera (Crustacea: Branchiopoda), we present an updated checklist, with taxonomical updates and comments for all taxa recorded since the start of research of this group in the country since 1860. We have listed a total of 137 valid taxa, of which most records belong to species groups that need revision worldwide. The situation in Indian Cladocera taxonomy is, at present, insufficient for realistic conclusions on biodiversity, ecology and biogeography. We list suggestions for an improvement of the current situation.

A new species of the genus Ceriodaphnia Dana, 1853 (Cladocera: Daphnidae) from Eastern Siberia (Russia) that combines morphological features of two species groups.

Taxa of the genus Ceriodaphnia Dana, 1853 (Cladocera: Daphniidae) are ubiquitous in temperate and tropical lakes, and the taxonomy of the genus is confused. Moreover, present keys are often regional and insufficient for the taxonomic assignment of species at a global scale. This communication is aimed at improving our understanding of the C. dubia s.l. species group. We redescribe C. dubia s.l. from Northern Eurasia and describe a new species from Central Yakutia (Eastern Siberia, Russia). In contrast to typical members of the C. dubia group, C. nikolaii sp.nov. has the postabdomen of the parthenogenetic female with preanal margin slightly or strongly projecting and angulated. Moreover, adult males have a pronounced preanal angle and sensory seta of antenna I which is shorter than the longest easthetasc. Our finding challenges current definitions of species groups in Ceriodaphnia. Indeed, a postabdomen shape with a strongly projected preanal angle is characterstic of another group of this genus, namely the C. laticaudata-group. We found a taxon that combines the diagnostic morphological characters of two species groups. Further development of the genus taxonomy must be accompanied by redescriptions of all well-accepted and dubious taxa from their type localities and revisions of populations from other localities of the world.

A new species of Coronatella Dybowski amp; Grochowski, 1984 (Cladocera: Chydoridae) endemic to Jeju Island (Republic of Korea).

Recently particular attention of cladocerologists has focussed on a subtropical-southern temperate zone of the Far East of Eurasia comprising a center of water flea (Crustacea: Cladocera) endemism. Two endemic taxa were described previously from Jeju Island (Republic of Korea), but still the cladocerans of this island are poorly known. The aim of this communication is to describe a new species of Coronatella (Coronatella) Dybowski Grochowski, 1894 (Anomopoda: Chydoridae) and discuss diagnostic characters of this taxon with reference to their diagnostic value in other cladoceran groups. Surprisingly, all characters discriminating C. (C.) jejuana sp. nov. from closest C. (C.) rectangula (Sars, 1862) are from the set suggested for chydorid species delimitation by Nikolai Smirnov more than 50 years ago. Therefore, a search for diagnostic characters of a potentially new taxon could concentrate on just some potentially important structures. However, a program of detailed redescriptions of previously established taxa is necessary for an adequate description of new taxa which are congeners of the former, and such comprehensive work is still in its infancy.

Daphnia japonica sp. nov. (Crustacea: Cladocera) an eastern Palearctic montane species with mitochondrial discordance.

The Daphnia longispina complex (Crustacea: Cladocera) contains several keystone freshwater species such as D. longispina O.F. Müller (D. rosea Sars is a junior synonym), D. galeata Sars, D. cucullata Sars, and D. dentifera Forbes. The complex is common throughout the Holarctic, but there are several geographic regions where local forms have been assigned to European species names based on a superficial morphological resemblance. Here we examine the species status of a form that was previously assigned to D. rosea from a montane bog pond on Honshu, Japan. We used two nuclear non-coding loci (nDNA), mitochondrial sequences (the ND2 protein-coding region) and morphology for evidence. The mitochondrial gene evidence supported the existence of a divergent lineage that is more closely related to D. galeata than to D. dentifera. However, morphology and the nuclear DNA data indicated a lineage that is most closely related to D. dentifera. As our evidence supported the existence of a cohesive divergent lineage, we described a new species, Daphnia japonica sp. nov. Recognition of local and subalpine diversity in this group is critical as ongoing anthropogenic disturbance has been associated with introductions, local extirpations, and hybridization.

A redescription of the Mediterranean endemic cladoceran Daphnia chevreuxi Richard, 1896 (Cladocera: Daphniidae).

The Mediterranean area is a biodiversity and endemism hotspot. Circum-Mediterranean taxa are known among different hydrobionts, including the water fleas. Some Mediterranean endemic cladoceran taxa have been described or redescribed according to modern taxonomical standards, but accurate drawings are missing for others. Here we redescribe the Mediterranean endemic Daphnia chevreuxi Richard, 1896 (Crustacea: Cladocera) and briefly review available data on its distribution and ecology. The species is confirmed to be a typical inhabitant of the temporary ponds of the central Mediterranean area, whereas its populations from the eastern Balkans and the Middle East should be studied in order to check for their actual identity. We conclude that the Mediterranean area is an example of a well-studied region as Cladocera are concerned, but the study of other regions is necessary in order to understand better the cladoceran diversity and distribution patterns in Eurasia.

A new redescription of Daphnia pusilla (Serventy, 1929) (Cladocera: Daphniidae) with emphasis on the thoracic limbs of Daphnia (Ctenodaphnia) Dybowski amp; Grochowski, 1895.

The genus Daphnia O.F. Mller, 1776 (Crustacea: Cladocera) still has a confused taxonomy for several objective and subjective reasons. Still there are many taxa with inadequately described morphology, primarily among the subgenus Daphnia (Ctenodaphnia) Dybowski Grochowski, 1895. We provide a redescription of an Australian endemic taxon Daphnia (Ctenodaphnia) pusilla (Serventy, 1929) according to recent standards of morphological study with special attention to the thoracic limbs. We conclude that main differences between thoracic limbs of the subgenera D. (Ctenodaphnia) and Daphnia s. str. concern the limb I only as it is well-known among the cladocerans of other families. But still only a few species of D. (Ctenodaphnia) have been studied adequately, and efforts to redescribe their morphology need to be continued.

Mesozoic fossils (>145 Mya) suggest the antiquity of the subgenera of Daphnia and their coevolution with chaoborid predators.

BACKGROUND: The timescale of the origins of Daphnia O. F. Mueller (Crustacea: Cladocera) remains controversial. The origin of the two main subgenera has been associated with the breakup of the supercontinent Pangaea. This vicariance hypothesis is supported by reciprocal monophyly, present day associations with the former Gondwanaland and Laurasia regions, and mitochondrial DNA divergence estimates. However, previous multilocus nuclear DNA sequence divergence estimates at < 10 Million years are inconsistent with the breakup of Pangaea. We examined new and existing cladoceran fossils from a Mesozoic Mongolian site, in hopes of gaining insights into the timescale of the evolution of Daphnia. RESULTS: We describe new fossils of ephippia from the Khotont site in Mongolia associated with the Jurassic-Cretaceous boundary (about 145 MYA) that are morphologically similar to several modern genera of the family Daphniidae, including the two major subgenera of Daphnia, i.e., Daphnia s. str. and Ctenodaphnia. The daphniid fossils co-occurred with fossils of the predaceous phantom midge (Chaoboridae). CONCLUSIONS: Our findings indicate that the main subgenera of Daphnia are likely much older than previously known from fossils (at least 100 MY older) or from nuclear DNA estimates of divergence. The results showing co-occurrence of the main subgenera far from the presumed Laurasia/Gondwanaland dispersal barrier shortly after formation suggests that vicariance from the breakup of Pangaea is an unlikely explanation for the origin of the main subgenera. The fossil impressions also reveal that the coevolution of a dipteran predator (Chaoboridae) with the subgenus Daphnia is much older than previously known -- since the Mesozoic.

On the taxonomic status of Oriental populations of the genus Bosminopsis Richard, 1895 (Crustacea: Cladocera).

It is widely accepted among the Cladocera (Crustacea) taxonomists that almost all cosmopolitan taxa are represented by some un-revised complexes of cryptic species. But many macro taxa of the cladocerans are still unrevised. The aim of this work is to analyze the taxonomic status of Oriental populations of the genus Bosminopsis Richard, 1895 (Anomopoda: Bosminidae) based on morphological characters. We have studied populations from India, Myanmar, Cambodia, Thailand, Laos, Vietnam, Philippines, Malaysia and Papua New Guinea and concluded that Oriental populations belong to a single species, Bosminopsis africanus (Daday, 1908), initially described from Africa. Analysis of literature data confirms that is widely distributed through whole Oriental zone. A single large mucro, or the mucro accompanied by an additional small spine in both sexes, is the main trait which differentiates B. africanus from B. zernowi Linko, 1901 distributed in more northern regions of Eurasia.

The Explanatory Effect of a Label: Its Influence on a Category Persists Even If We Forget the Label.

In this study we replicated the explanatory effect of a label which had been found by Giffin et al. (2017). In their experiments, they used vignettes describing an odd behavior of a person based on culturally specific disorders that were unfamiliar to respondents. It turned out that explanations which explain an odd behavior through a person's tendency to behave that way (circulus vitiosus) seemed more persuasive if the disorder was given a label that was used in the explanation. We replicated these results in Experiment 1, and in a follow-up Experiment 2 we examined the familiarity with category information and the evaluation of that category over time (the delay lasted one week). We realized that the label effect persists even when people make judgments based on their recollections about a category. Furthermore, according to a content analysis of the recollections, participants in the label condition remembered more information from the vignettes but tended to forget an artificial label; however, they used other words from the disorder domain instead (like "disease" or "kleptomania"). This allowed us to suggest a new interpretation of this effect: we suppose that in the Giffin et al. (2017) experiments the label did not bring any new features to a category itself, but pointed to a relevant domain instead, so the effect appeared from the activation of areas of knowledge in semantic memory and the application of relevant schema for learning a new phenomenon.

A new species of Bosmina (Liederobosmina) Brték, 1997 (Cladocera: Bosminidae) from high mountain lakes of Colombia.

Insufficient attention has been recently paid by the taxonomists to the family Bosminidae Baird (Crustacea: Cladocera). Here we describe a new species of Bosmina (Liederobosmina) Brték from high mountain water bodies of Colombia which is unique among all bosminids having heavily striated valves. Most probably, this taxon has a narrow distribution area in the Andean high mountains. It is obvious that the Andean highlands must be studied in detail, i.e. using molecular methods, and more new taxa might be detected in the future.

Unexpected mitochondrial lineage diversity within the genus Alonella Sars, 1862 (Crustacea: Cladocera) across the Northern Hemisphere.

Representatives of the genus Alonella Sars (Crustacea: Cladocera: Chydorinae) belong to the smallest known water fleas. Although species of Alonella are widely distributed and often abundant in acidic and mountain water bodies, their diversity is poorly studied. Morphological and genetic approaches have been complicated by the minute size of these microcrustaceans. As a result, taxonomists have avoided revising these species. Here, we present genetic data on Alonella species diversity across the Northern Hemisphere with particular attention to the A. excisa species complex. We analyzed 82 16S rRNA sequences (all newly obtained), and 78 COI sequences (39 were newly obtained). The results revealed at least twelve divergent phylogenetic lineages, possible cryptic species, of Alonella, with different distribution patterns. As expected, the potential species diversity of this genus is significantly higher than traditionally accepted. The A. excisa complex is represented by nine divergent clades in the Northern Hemisphere, some of them have relatively broad distribution ranges and others are more locally distributed. Our results provide a genetic background for subsequent morphological analyses, formal descriptions of Alonella species and detailed phylogeographical studies.

Bosminopsis deitersi (Crustacea: Cladocera) as an ancient species group: a revision.

Water fleas (Crustacea: Cladocera) of the Family Bosminidae have been studied since the founding of paleolimnology and freshwater ecology. However, one species, Bosminopsis deitersi, stands out for its exceptional multicontinental range and broad ecological requirements. Here we use an integrated morphological and multilocus genetic approach to address the species problem in B. deitersi. We analyzed 32 populations of B. deitersi s. lat. Two nuclear and two mitochondrial loci were used to carry out the bGMYC, mPTP and STACEY algorithms for species delimitation. Detailed morphological study was also carried out across continents. The evidence indicated a widely distributed cryptic species in the Old World (Bosminopsis zernowi) that is genetically divergent from B. deitersi s.str. We revised the taxonomy and redescribed the species in this complex. Our sampling indicated that B. zernowi had weak genetic differentiation across its range. A molecular clock and biogeographic analysis with fossil calibrations suggested a Mesozoic origin for the Bosminopsis deitersi group. Our evidence rejects the single species hypothesis for B. deitersi and is consistent with an ancient species group (potentially Mesozoic) that shows marked morphological conservation. The family Bosminidae, then, has examples of both rapid morphological evolution (Holocene Bosmina), and morphological stasis (Bosminopsis).

Priority of Carl Linnaeus as the author of the oldest species of Cladocera (Crustacea: Branchiopoda): Daphnia pulex (Linnaeus, 1758) and Polyphemus pediculus (Linnaeus, 1758).

In taxonomy, it is important to maintain chronological order in taxon naming and understanding. Here, I confirm that according to the rules of Zoological Nomenclature, Carl Linnaeus must be regarded as the author of two common cladoceran taxa, Daphnia pulex (Linnaeus, 1758) and Polyphemus pediculus (Linnaeus, 1758). Both were established in the 10th Edition of "Systema Naturae", the starting point of Zoological Nomenclature. The history of these taxa is described.

A new species of the Daphnia sinevi group (Crustacea: Cladocera: Daphniidae) from Sakhalin Island, Russian Far East.

Daphnia curvirostris species complex is a cladoceran group (Crustacea: Cladocera) with maximum diversity in Eastern Palearctic. To date, several representatives of this complex are known from the Russian Far East. Here we describe a new species of the Daphnia sinevi species group from water bodies of Sakhalin Island. Morphology of its parthenogenetic females is similar to that in D. sinevi from the continental part of Asian Eurasia. However, we found diagnostic traits of D. sakhalinensis sp.nov. in morphology of the second pecten on postabdominal claw, armature of seta 2 on exopodite III, proportions of setae 1/ and 2 length on exopodite V, relative length of male rostrum and structure of the second pecten of male postabdominal claw. This work contributes to our full revision of the D. curvirostris species complex. Separation between continental and Sakhalin populations of D. sinevi group probably happened in Pliocene (about 5 MA) when Sakhalin began to separate from the mainland. However, we cannot exclude a version that populations of D. sakhalinensis sp.nov. appeared as a result of colonization of Sakhalin from the continent and further independent evolution of the island populations.