Bdelloid Research Articles

Biodiversity of Indian Rotifers (Rotifera) with remarks on biogeography and richness in diverse ecosystems

We assess biodiversity status of Rotifera known from India to-date based on our studies from various regions of this country and evaluation of other viable records, and highlight notable features of biogeography and richness. The Indian fauna reveals 434 valid species belonging to 68 genera and 25 families and thus indicates the most biodiverse Rotifera vis-àvis south and Southeast Asia, and records ~25% and ~41% species of global and regional biogeographic interest. It depicts the littoral-periphytic nature, broadly tropical character, the limited reports of cold-water species from the sub-Himalayan and Himalayan latitudes, paucity of the endemics and Bdelloids, and cryptic diversity awaits analyses. The richest diversity and distinct biogeographic identity of Rotifera of Northeast India (NEI) is attributed to location of this region in the ‘Himalayan and Indo-Burmese’ biodiversity hot-spots, ‘Assam gateway’ – the biogeographic corridor, and the ‘Rotiferologist effect’. Regional disparity and spatial heterogeneity of biodiversity elsewhere from India are attributed to the limited sampling, inadequate collections from diverse ecosystems, unidentified species, and paucity of attention on smaller species. The biodiverse rotifer assemblages of the floodplain lakes including Deepor Beel and Loktak Lake, the two Ramsar sites and globally megadiverse ecosystems, are hypothesized to habitat diversity of these ecotones, while ‘Rotifera paradox’ depict speciose constellations per sample. The species-rich small floodplain and urban wetlands focus interest on rotifer diversity in small water bodies. We estimate more diverse Indian Rotifera following analyses of collections from underexplored and unexplored regions and ecosystems, and the bdelloid and sessile rotifers using integrative taxonomic approaches.

Genomic signatures of recombination in a natural population of the bdelloid rotifer Adineta vaga

Sexual reproduction is almost ubiquitous among extant eukaryotes. As most asexual lineages are short-lived, abandoning sex is commonly regarded as an evolutionary dead end. Still, putative anciently asexual lineages challenge this view. One of the most striking examples are bdelloid rotifers, microscopic freshwater invertebrates believed to have completely abandoned sexual reproduction tens of Myr ago. Here, we compare whole genomes of 11 wild-caught individuals of the bdelloid rotifer Adineta vaga and present evidence that some patterns in its genetic variation are incompatible with strict clonality and lack of genetic exchange. These patterns include genotype proportions close to Hardy-Weinberg expectations within loci, lack of linkage disequilibrium between distant loci, incongruent haplotype phylogenies across the genome, and evidence for hybridization between divergent lineages. Analysis of triallelic sites independently corroborates these findings. Our results provide evidence for interindividual genetic exchange and recombination in A. vaga, a species previously thought to be anciently asexual.

Repeated convergent evolution of parthenogenesis in Acariformes (Acari).

The existence of old species‐rich parthenogenetic taxa is a conundrum in evolutionary biology. Such taxa point to ancient parthenogenetic radiations resulting in morphologically distinct species. Ancient parthenogenetic taxa have been proposed to exist in bdelloid rotifers, darwinulid ostracods, and in several taxa of acariform mites (Acariformes, Acari), especially in oribatid mites (Oribatida, Acari). Here, we investigate the diversification of Acariformes and their ancestral mode of reproduction using 18S rRNA. Because parthenogenetic taxa tend to be more frequent in phylogenetically old taxa of Acariformes, we sequenced a wide range of members of this taxon, including early‐derivative taxa of Prostigmata, Astigmata, Endeostigmata, and Oribatida. Ancestral character state reconstruction indicated that (a) Acariformes as well as Oribatida evolved from a sexual ancestor, (b) the primary mode of reproduction during evolution of Acariformes was sexual; however, species‐rich parthenogenetic taxa radiated independently at least four times (in Brachychthonioidea (Oribatida), Enarthronota (Oribatida), and twice in Nothrina (Oribatida), (c) parthenogenesis additionally evolved frequently in species‐poor taxa, for example, Tectocepheus, Oppiella, Rostrozetes, Limnozetes, and Atropacarus, and (d) sexual reproduction likely re‐evolved at least three times from species‐rich parthenogenetic clusters, in Crotonia (Nothrina), in Mesoplophora/Apoplophora (Mesoplophoridae, Enarthronota), and in Sphaerochthonius/Prototritia (Protoplophoridae, Enarthronota). We discuss possible reasons that favored the frequent diversification of parthenogenetic taxa including the continuous long‐term availability of dead organic matter resources as well as generalist feeding of species as indicated by natural variations in stable isotope ratios.

The influence of environmental variables on bdelloid rotifers of the genus Rotaria in Thailand

AbstractThis research investigates the influence of environmental parameters that are known to affect bdelloid rotifer species richness and composition in temperate zones on the genus Rotaria in tropical zone. Our study analysed species richness and composition of the genus Rotaria from 390 samples collected from several types of aquatic habitats in Thailand. Coordinates, elevation, limnological parameters such as water temperature, conductivity, total dissolved solids, salinity, dissolved oxygen and pH were measured. A total of nine species was recorded. Of these, one species, Rotaria macrura (Ehrenberg, 1832), was a new record for Thailand and new to the oriental region, and was a yet undescribed species, Rotaria sp. The species diversity of this genus increased from eight to 10 species. The presence or absence of the genus Rotaria was significantly influenced by dissolved oxygen and habitat type. For the samples where the genus occurred, species richness was not affected by any of the limnological or bioclimatic variables. Differences in species composition were affected only by habitat type. The results support former suggestions that common abiotic parameters do not seem to strongly influence diversity in bdelloids, whereas major ecological differences between habitats influence bdelloid occurrence.

Neurodegeneration-related beta-amyloid as autocatabolism-attenuator in a micro-in vivo system

Investigation of human neurodegeneration-related aggregates of beta-amyloid 1–42 (Aβ42) on bdelloid rotifers is a novel interdisciplinary approach in life sciences. We reapplied an organ size-based in vivo monitoring system, exploring the autocatabolism-related alterations evoked by Aβ42, in a glucose-supplemented starvation model. The experientially easy-to-follow size reduction of the bilateral reproductive organ (germovitellaria) in fasted rotifers was rescued by Aβ42, serving as a nutrient source- and peptide sequence-specific attenuator of the organ shrinkage phase and enhancer of the regenerative one including egg reproduction. Recovery of the germovitellaria was significant in comparison with the greatly shrunken form. In contrast to the well-known neurotoxic Aβ42 (except the bdelloids) with specific regulatory roles, the artificially designed scrambled version (random order of amino acids) was inefficient in autocatabolism attenuation, behaving as negative control. This native Aβ42-related modulation of the ‘functionally reversible organ shrinkage’ can be a potential experiential and supramolecular marker of autocatabolism in vivo.

Genome-wide identification of DNA double-strand break repair genes and transcriptional modulation in response to benzo[α]pyrene in the monogonont rotifer Brachionus spp.

The DNA repair system has evolved from the common ancestor of all life forms and its function is highly conserved within eukaryotes. In this study, to reveal the role of DNA double-strand break repair (DSB) genes in response to benzo[α]pyrene (B[α]P), we first identified DSB genes in relation to homologous recombination and non-homologous end joining events in four Brachionus rotifer spp.: B. calyciflorus, B. koreanus, B. plicatilis, and B. rotundiformis. In all the Brachionus spp., 39 orthologous genes to human DSB repair genes were identified. Furthermore, three genes in B. koreanus, two genes in B. plicatilis, and one gene in B. calyciflorus and B. rotundiformis were present as duplicated genes, indicating that these genes were diversified over speciation in the genus Brachionus. Moreover, we compared DSB repair genes on the gene structures in four monogonont Brachionus rotifers and the bdelloid rotifer Adineta vaga, which possesses highly efficient DNA repair ability. The transcriptional responses of four monogonont Brachionus rotifers in response to B[α]P exposure showed how B[α]P exposure led to DSBs and subsequently recruited DNA DSB repair pathways in the rotifer B. koreanus. Taken together, this study provides a better understanding of the potential role of DSB repair genes in the monogonont rotifer Brachionus spp. in response to B[α]P.

The trouble with Adineta vaga (Davis, 1873): a common rotifer that cannot be identified (Rotifera: Bdelloidea: Adinetidae).

My purpose here is to highlight three long-standing problems in the taxonomy of Adineta vaga (Davis, 1873) and its subspecies: 1. The lack of unique morphological criteria to identify the morphological variant (morphovariant) Davis described; 2. The lack of an evolutionarily meaningful subspecies definition applicable to parthenogenetic bdelloid rotifers; 3. The lack of compliance with the applicable articles of the International Code of Zoological Nomenclature (ICZN; https://tinyurl.com/y8f242an) when subspecies are assigned to A. vaga.

Iron Ladies - How Desiccated Asexual Rotifer Adineta vaga Deal With X-Rays and Heavy Ions?

Space exposure experiments from the last 15 years have unexpectedly shown that several terrestrial organisms, including some multi-cellular species, are able to survive in open space without protection. The robustness of bdelloid rotifers suggests that these tiny creatures can possibly be added to the still restricted list of animals that can deal with the exposure to harsh condition of space. Bdelloids are one of the smallest animals on Earth. Living all over the world, mostly in semi-terrestrial environments, they appear to be extremely stress tolerant. Their desiccation tolerance at any stage of their life cycle is known to confer tolerance to a variety of stresses including high doses of radiation and freezing. In addition, they constitute a major scandal in evolutionary biology due to the putative absence of sexual reproduction for at least 60 million years. Adineta vaga, with its unique characteristics and a draft genome available, was selected by ESA (European Space Agency) as a model system to study extreme resistance of organisms exposed to space environment. In this manuscript, we documented the resistance of desiccated A. vaga individuals exposed to increasing doses of X-ray, protons and Fe ions. Consequences of exposure to different sources of radiation were investigated in regard to the cellular type including somatic (survival assay) and germinal cells (fertility assay). Then, the capacity of A. vaga individuals to repair DNA DSB induced by different source of radiation was investigated. Bdelloid rotifers represent a promising model in order to investigate damage induced by high or low LET radiation. The possibility of exposure both on hydrated or desiccated specimens may help to decipher contribution of direct and indirect radiation damage on biological processes. Results achieved through this study consolidate our knowledge about the radioresistance of A. vaga and improve our capacity to compare extreme resistance against radiation among living organisms including metazoan.

Desiccation does not drastically increase the accessibility of exogenous DNA to nuclear genomes: evidence from the frequency of endosymbiotic DNA transfer

BackgroundAlthough horizontal gene transfer (HGT) is a widely accepted force in the evolution of prokaryotic genomes, its role in the evolution of eukaryotic genomes remains hotly debated. Some bdelloid rotifers that are resistant to extreme desiccation and radiation undergo a very high level of HGT, whereas in another desiccation-resistant invertebrate, the tardigrade, the pattern does not exist. Overall, the DNA double-strand breaks (DSBs) induced by prolonged desiccation have been postulated to open a gateway to the nuclear genome for exogenous DNA integration and thus to facilitate the HGT process, thereby enhancing the rate of endosymbiotic DNA transfer (EDT).ResultsWe first surveyed the abundance of nuclear mitochondrial DNAs (NUMTs) and nuclear plastid DNAs (NUPTs) in five eukaryotes that are highly resistant to desiccation: the bdelloid rotifers Adineta vaga and Adineta ricciae, the tardigrade Ramazzottius varieornatus, and the resurrection plants Dorcoceras hygrometricum and Selaginella tamariscina. Excessive NUMTs or NUPTs were not detected. Furthermore, we compared 24 groups of desiccation-tolerant organisms with their relatively less desiccation-tolerant relatives but did not find a significant difference in NUMT/NUPT contents.ConclusionsDesiccation may induce DSBs, but it is unlikely to dramatically increase the frequency of exogenous sequence integration in most eukaryotes. The capture of exogenous DNA sequences is possible only when DSBs are repaired through a subtype of non-homologous end joining, named alternative end joining (alt-EJ). Due to the deleterious effects of the resulting insertion mutations, alt-EJ is less frequently initiated than other mechanisms.

Bdelloid rotifers (Rotifera, Bdelloidea) of China: diversity and new records.

Bdelloid rotifers are a group of microscopic invertebrates known for their obligate parthenogenesis and exceptional resistance to extreme environments. Their diversity and distributions are poorly studied in Asia, especially in China. In order to better understand the species distribution and diversity of bdelloid rotifers in China, a scientific surveys of habitats was conducted with 61 samples (both terrestrial and aquatic habitats) from 11 provinces and regions of China, ranging from tropics to subtropics with a specific focus on poorly sampled areas (Oriental) during September 2017 to October 2018. A total of 59 morphospecies (including subspecies) were found, of which, thirty-nine morphospecies (including one genus) are new records for China, almost doubling the number of previous records. Four rare morphospecies (Adineta cf. acuticornis Haigh, A. beysunae Örstan, Habrotrocha ligula loxoglotta De Koning and H. serpens Donner) are depicted and redescribed, and an updated checklist of Chinese bdelloids with their location and ecological information is presented. This study provides new data from a large region of China, enriching the knowledge of bdelloid biodiversity, and their global biogeography.

A rapid, simple screening toxicity test using desiccated bdelloid rotifers: Rotifer Activity Inhibition Test (RAIT).

A protocol for an ultra-rapid screening toxicity test is described using the rotifer Philodina acuticornis/roseola. The test can be executed in 30 min starting from the rehydration of desiccated life stages called tuns. Philodina tuns remain viable for years when maintained dry and at low temperature. They are very useful for conducting toxicity tests because the test animals do not require cultivation and are available to initiate tests anytime and anywhere. The swimming/crawling activity of rehydrated Philodina tuns is used as an endpoint to compare activity in control dilution water with inhibition of activity in an environmental sample. The Rotifer Activity Inhibition Test (RAIT) estimates toxicity semi-quantitatively using four toxicity categories: non-toxic, slightly toxic, very toxic, and 100% toxic. As proof of principle, RAIT has been tested on environmental samples from a variety of habitats and RAIT results have been compared with those obtained from traditional toxicity tests with bacteria, algae, Daphnia, and fish. Broad congruence between the effect signals of the rapid RAIT screening test and traditional assays has been found for river surface waters, industrial wastewaters, and sludge leachates from waste water treatment plants. Rotifers are an important group of animals in aquatic and soil food webs, and RAIT is a welcome new method for simple, ultra-rapid, and low-cost toxicity screening with a representative of this ecologically important group.

Descriptions of two new species of Philodina (Rotifera, Bdelloidea), with notes on seven rare bdelloids from Korea.

A taxonomic study on bdelloid rotifers collected from various terrestrial habitats at five different locations in Korea resulted in eight new Korean records and two new species-level taxa, Philodina clypeata n. sp. and P. verrucosa n. sp. Among the eight new Korean records, two species- and three subspecies-level taxa are new to Asia as well. These new Korean records also include seven rare species/subspecies-level taxa with poorly known distributions. Habrotrocha gracilis quadridens Schulte and Macrotrachela zickendrahti seda Donner were rediscovered in Korea 64 and 53 years, respectively, after the original descriptions. Habrotrocha ligula aligula Burger, Macrotrachela insulana Donner, M. petulans Milne, M. pinnigera (Murray), and Philodina parvicalcar De Koning have been reported from two to three countries only including their type localities before the present study. In addition, a partial sequence of mitochondrial cytochrome c oxidase subunit I gene (mtCOX1) for P. verrucosa n. sp. as well as a taxonomic key for the Philodina species recorded from Korea to date are also provided here.

Interactive effects of fish predation and sublethal insecticide concentrations on freshwater zooplankton communities.

Stresses imposed by insecticides and predators are possibly the most rigorous filters to which aquatic organisms are exposed in rivers and lakes associated with agricultural lands. However, their interactive effects on zooplankton communities are still unclear. This study elucidated the zooplankton community response to fish predation, the insecticide chlorpyrifos (CLP), and a combination of both factors, using a 30-day mesocosm experiment. The zooplankton assemblage was influenced by fish presence prior to CLP toxicity. Fish predation reduced microcrustacean density leading to a community dominated by microzooplankton (i.e.: rotifers and copepod nauplii). CLP decreased the species richness in treatments with and without fish, yielding an increase in the abundance of bdelloid rotifers, in the genera Lepadella and Trichocerca. The zooplankton:phytoplankton (<20μm) ratio decreased substantially when the two stressors, fish predation and insecticide toxicity, were combined. Although CLP dissipated relatively rapidly in the aqueous phase and accumulated in sediment and fish tissue, zooplankton richness was unable to recover. A possible explanation for this could be the inhibitory effect of CLP on resting stage hatchings in the sediment. Therefore, the combined effects of fish predation and CLP might influence zooplankton richness, leading to an assemblage dominated by rotifers that appeared to be resistant to both factors, with a limited capability to control phytoplankton growth. Thus, the effects of natural and anthropogenic stressors should be considered together when assessing community dynamics in aquatic ecosystems.

Elucidating the Mechanism of DNA Repair in Bdelloid Rotifers by Using RNAi Knockdown and CRISPR/Cas9 Editing

Genomic DNA regularly becomes damaged by numerous ways, including desiccation, radiation exposure, and during recombination in cell division. Fortunately, cells have DNA repair pathways that seek out and correct damage. The bdelloid rotifer Adineta vaga is an excellent model organism to study DNA repair because it has a highly efficient DNA repair system. Bdelloids can recover from desiccation and return to life by repairing DNA damage endured in the desiccated state. Bdelloids have also been shown to recover from DNA damage caused by massive doses of ionizing radiation. The mechanisms of this miraculous DNA repair in these aquatic invertebrates are unknown. This project explores using RNA interference (RNAi) and CRISPR/Cas9 genome editing as tools to investigate the function of DNA repair genes, MSH6 and MLH1, in bdelloid rotifers. When target genes are knocked down or inactivated, DNA repair in bdelloids should be compromised. For RNAi, two methods were explored. For the “feeding method,” bdelloids were fed strains of E. coli that express double stranded RNA (dsRNA) copies of MLH1 and MSH6. For the “soaking method,” dsRNA copies of MLH1 and MSH6 were synthesized, and bdelloids were transfected with these molecules. The expectation was that ingested or transfected dsRNA would induce RNAi in bdelloid rotifers. Real‐time PCR followed to quantify expression of the target gene and determine if the RNAi knockdown was successful. For the feeding method, an MLH1 knockdown was observed 6–12 hours after feeding, but the effect was absent 24 hours after feeding. For the soaking method, an MSH6 knockdown was only present when rotifers were transfected with 0.2 μg dsRNA and incubated for 48 hours. As an alternative tool for studying gene function, CRISPR/Cas9 genome editing was done to mutate DNA repair genes. For utilizing CRISPR/Cas9, a single guide RNA that targets MLH1 was synthesized and used in a Cas9 in vitro cleavage assay to determine its ability to cut the target sequence. The guide RNA was then combined with Cas9, and these ribonucleoprotein complexes were electroporated into bdelloids. Mutation detection using T7 endonuclease I was then done to identify alterations to the gene sequence. Gene knockdowns using RNAi and gene mutations using CRISPR/Cas9 will provide a reverse genetics approach to identify genes that have a role in bdelloid DNA repair. This could enhance our understanding of similar mechanisms in traditional model systems, which could have implications for biomedical research.Support or Funding InformationThis work was supported by grants from the Hendrix College Odyssey Program and the Hugh Stevens Moseley Undergraduate Research Awards.

Identifying Prospective Genes That Function During DNA Repair in the Bdelloid Rotifer Adineta vaga

The bdelloid rotifer Adineta vaga is a microinvertebrate with a highly efficient DNA repair system that allows individuals to recover from DNA damage caused by desiccation or ionizing radiation. The mechanism behind this remarkable DNA repair in A. vaga is not yet understood. Previous transcriptome sequencing in our lab has identified over 250 genes that are upregulated in response to DNA damage induced by ionizing radiation. These upregulated genes are the strongest candidates for having a role in DNA repair. The objective of this project is to characterize the functions of candidate genes involved in DNA repair in bdelloids and, thereby, establish potential pathways that comprise this mechanism. Three approaches were used to begin to investigate the functions of these candidate DNA repair genes in bdelloids. First, we used real‐time PCR to quantify gene expression of several candidate DNA repair genes during recovery from desiccation. Genes that were upregulated relative to the non‐desiccated control were identified as most likely to have a role in DNA repair as opposed to radiation resistance. Second, we constructed a yeast library of A. vaga proteins for use in yeast two‐hybrid screens against candidate DNA repair proteins. To produce the library, cDNAs representing the full complement of A. vaga proteins were cloned into plasmids that were then transformed into yeast. Yeast strains that each expressed a different candidate DNA repair protein would then be mated with the library to screen for protein‐protein interactions, which would provide evidence for related cellular functions. Third, we developed the molecular tools for using CRISPR/Cas9 genome editing to inactivate candidate genes in A. vaga. In vivo gene knockouts would provide mutant rotifers that could be studied to assess the roles of these genes in DNA repair. Single guide RNAs (sgRNAs) for several genes were created and incubated with the Cas9 enzyme to form sgRNA‐Cas9 complexes. These sgRNA‐Cas9 complexes were shown to successfully cleave their target gene sequences in vitro. To test this method in vivo, these sgRNA‐Cas9 complexes were transfected into A. vaga embryos via electroporation. Genomic DNA was purified from treated rotifers and used in T7 endonuclease I assays to identify subsequent mutations in the target genes. Once perfected, these methods of investigating the roles of candidate genes stand to elucidate the mechanism behind the extraordinary DNA repair in A. vaga.Support or Funding InformationFunding was provided by a Summer Undergraduate Research Fellowship from the Arkansas Department of Higher Education to JTW, and a Hendrix College Faculty Project Grant to AMS.

The Darwin Vermicelli, as Described by Mary Shelley, is a Bdelloid Rotifer

The Darwin Vermicelli, as Described by Mary Shelley, is a Bdelloid Rotifer

Urbanization drives cross-taxon declines in abundance and diversity at multiple spatial scales.

The increasing urbanization process is hypothesized to drastically alter (semi-)natural environments with a concomitant major decline in species abundance and diversity. Yet, studies on this effect of urbanization, and the spatial scale at which it acts, are at present inconclusive due to the large heterogeneity in taxonomic groups and spatial scales at which this relationship has been investigated among studies. Comprehensive studies analysing this relationship across multiple animal groups and at multiple spatial scales are rare, hampering the assessment of how biodiversity generally responds to urbanization. We studied aquatic (cladocerans), limno-terrestrial (bdelloid rotifers) and terrestrial (butterflies, ground beetles, ground- and web spiders, macro-moths, orthopterans and snails) invertebrate groups using a hierarchical spatial design, wherein three local-scale (200m×200m) urbanization levels were repeatedly sampled across three landscape-scale (3km×3km) urbanization levels. We tested for local and landscape urbanization effects on abundance and species richness of each group, whereby total richness was partitioned into the average richness of local communities and the richness due to variation among local communities. Abundances of the terrestrial active dispersers declined in response to local urbanization, with reductions up to 85% for butterflies, while passive dispersers did not show any clear trend. Species richness also declined with increasing levels of urbanization, but responses were highly heterogeneous among the different groups with respect to the richness component and the spatial scale at which urbanization impacts richness. Depending on the group, species richness declined due to biotic homogenization and/or local species loss. This resulted in an overall decrease in total richness across groups in urban areas. These results provide strong support to the general negative impact of urbanization on abundance and species richness within habitat patches and highlight the importance of considering multiple spatial scales and taxa to assess the impacts of urbanizationon biodiversity.

Sequencing of 18S rRNA gene of Bdelloid rotifers and design of the primers for real-time PCR

Three individuals of Bdelloid rotifer (J1, J2 and J3) were isolated from a MBR system in Nagasaki University and one individual of rotifer (J4) in the original seed sludge collected from a wastewater treatment plant for the MBR was isolated. The four rotifer species were able to proliferate in toxic Microcystis cell suspension. The partial sequence of 18S rRNA gene of each isolated rotifer was determined using In-fusion cloning and searched by BLAST. The gene of the four rotifers J1, J2, J3 and J4 showed the same sequence, then the consensus sequence was in the branch of Bdelloid rotifers in the phylogenetic tree. Furthermore, a specific Bdelloid forward primer 55F and reverse primer 395R for real-time PCR was designed based on the consensus sequence for quantitative researches on the Bdelloid rotifers population. We succeeded to quantify the population of a Bdelloid rotifer cultured in toxic Microcystis cell suspension using the new designed primer pairs.

The complex evolutionary history of sulfoxide synthase in ovothiol biosynthesis.

Sulfoxide synthases are enzymes involved in the biosynthesis of small sulfur-containing natural products. Their enzymatic activity represents a unique sulfur transfer strategy in nature that is the insertion of a sulfur atom on the imidazole ring of histidine. To date, only two enzymes are known to carry out this function: the sulfoxide synthase EgtB, involved in the biosynthesis of ergothioneine in fungi and bacteria, and the 5-histidylcysteine sulfoxide synthase OvoA, involved in the biosynthesis of ovothiols, found in the eggs and biological fluids of marine invertebrates, some proteobacteria and protists. In particular, ovothiols, thanks to their unique redox properties, are probably the most intriguing marine sulfur-containing molecules. Although they have long been considered as cellular protective molecules, new evidence suggest that their biological activities and ecological role might be more complex than originally thought. Here, we investigate the evolutionary history of OvoA in Metazoa, reporting its monophyletic ancient origins, which could be traced back to the latest common ancestor of Choanozoa. Nevertheless, we show that OvoA is missing in several major extant taxa and we discuss this patchy distribution in the light of the massive genome reduction events documented in Metazoa. We also highlight two interesting cases of secondary acquisition through horizontal gene transfer, which occurred in hydrozoans and bdelloid rotifers. The evolutionary success of this metabolic pathway is probably ascribable to its role in the maintenance of cellular redox homeostasis, which enables organisms to survive in different environmental niches.

Kynurenic Acid and Its Analogs Are Beneficial Physiologic Attenuators in Bdelloid Rotifers.

The in vivo investigation of kynurenic acid (KYNA) and its analogs is one of the recent exciting topics in pharmacology. In the current study we assessed the biological effects of these molecules on bdelloid rotifers (Philodina acuticornis and Adineta vaga) by monitoring changes in their survival and phenotypical characteristics. In addition to longitudinal (slowly changing) markers (survival, number of rotifers alive and body size index), some dynamic (quickly responding) ones (cellular reduction capacity and mastax contraction frequency) were measured as well. KYNA and its analogs increased longevity, reproduction and growth, whereas reduction capacity and energy-dependent muscular activity decreased conversely. We found that spermidine, a calorie restriction mimetic, exerted similar changes in the applied micro-invertebrates. This characterized systemic profile evoked by the above-mentioned compounds was named beneficial physiologic attenuation. In reference experiments, using a stimulator (cyclic adenosine monophosphate) and a toxin (sodium azide), all parameters changed in the same direction (positively or negatively, respectively), as expected. The currently described adaptive phenomenon in bdelloid rotifers may provide holistic perspectives in translational research.