Convergent gene losses and pseudogenizations in multiple lineages of stomachless fishes.

The regressive evolution of independent lineages often results in convergent phenotypes. Several teleost groups display secondary loss of the stomach, and four gastric genes, atp4a, atp4b, pgc, and pga2 have been co-deleted in agastric (stomachless) fish. Analyses of genotypic convergence among agastric fishes showed that four genes, slc26a9, kcne2, cldn18a, and vsig1, were co-deleted or pseudogenized in most agastric fishes of the four major groups. kcne2 and vsig1 were also deleted or pseudogenized in the agastric monotreme echidna and platypus, respectively. In the stomachs of sticklebacks, these genes are expressed in gastric gland cells or surface epithelial cells. An ohnolog of cldn18 was retained in some agastric teleosts but exhibited an increased non-synonymous substitution when compared with gastric species. These results revealed novel convergent gene losses at multiple loci among the four major groups of agastric fish, as well as a single gene loss in the echidna and platypus.

Taxonomic changes for Neotropical pinhole borer ambrosia beetles (Coleoptera: Curculionidae: Platypodinae).

Stephen L. Wood re-defined Platypus such that its members are native to realms outside of the Americas and transferred most Neotropical species out of that genus. I have come across 44 species that still remain, though, and these are treated here. In total, I report 49 new generic assignments, 30 of which are transfers out of Platypus. I propose 22 new synonymies, eight of which are Platypus species that are synonymized with previously transferred species. Six Neotropical species are left in Platypus, for reasons detailed in the text. These taxonomic acts affect the compositions of eight of the 11 Neotropical genera of core Platypodinae. The following species are transferred from Platypus Herbst, 1793: Cenocephalus dubiosus (Schedl, 1933) comb. nov., Cenocephalus neotruncatus (Schedl, 1972) comb. nov.; Costaroplatus barbosai (Schedl, 1972) comb. nov., Costaroplatus devius (Schedl, 1976) comb. nov., Costaroplatus mixtus (Schedl, 1976) comb. nov., Costaroplatus roppai (Schedl, 1978) comb. nov.; Epiplatypus bicaudatulus (Schedl, 1935) comb. nov., Epiplatypus carduus (Schedl, 1936) comb. nov., Epiplatypus complanus (Schedl, 1967) comb. nov., Epiplatypus grandiporus (Schedl, 1961) comb. nov., Epiplatypus insculptus (Schedl, 1967) comb. nov., Epiplatypus macroporus (Chapuis, 1865) comb. nov., Epiplatypus perforans (Schedl, 1961) comb. nov., Epiplatypus propinquus (Schedl, 1959) comb. nov., Epiplatypus quadrispinatus (Chapuis, 1865) comb. nov., Epiplatypus sallei (Chapuis, 1865) comb. nov., Epiplatypus sequius (Schedl, 1935) comb. nov.; Euplatypus detectus (Schedl, 1976) comb. nov., Euplatypus erraticus (Schedl, 1972) comb. nov., Euplatypus longulus (Chapuis, 1865) comb. nov., Euplatypus perplexus Bright, 1972 comb. nov., Euplatypus rugosifrons (Schedl, 1933) comb. nov., Euplatypus vexans (Schedl, 1972) comb. nov.; Megaplatypus asperatus (Schedl, 1976) comb. nov., Megaplatypus carinifer (Schedl, 1970), Megaplatypus durus (Schedl, 1936) comb. nov., Megaplatypus eversus (Wood, 1971) comb. nov., Megaplatypus gagates (Schedl, 1976) comb. nov., Megaplatypus irrepertus (Schedl, 1936) comb. nov., Megaplatypus lineaticornis (Schedl, 1936) comb. nov., Megaplatypus paramonovi (Schedl, 1972) comb. nov., Megaplatypus schedli (Wood, 1966) comb. nov., Megaplatypus vafer (Schedl, 1972) comb. nov.; Teloplatypus caligatus (Schedl, 1972) comb. nov. Costaroplatus bidens (Schedl, 1970) comb. nov. and Costaroplatus darlingtoni (Reichardt, 1965) comb. nov. are transferred from Megaplatypus Wood, 1993. Costaroplatus vonfaberi (Reichardt, 1962) comb. nov. is transferred from Platyphysus Wood, 1993. Epiplatypus striatus (Chapuis, 1865) comb. nov., Megaplatypus contextus (Schedl, 1963) comb. nov., Megaplatypus decorus (Schedl, 1936) comb. nov. and Megaplatypus dignatus (Schedl, 1936) comb. nov. are removed from Euplatypus Wood, 1993. Epiplatypus ornatus (Schedl, 1936) comb. nov. is transferred from Teloplatypus Wood, 1993. Euplatypus jamaicensis Bright, 1972 comb. nov., Megaplatypus discolor (Blandford, 1896) comb. nov., Teloplatypus brasiliensis (Nunberg, 1959) comb. nov., Teloplatypus nudus (Schedl, 1936) comb. nov. and Teloplatypus pernudus (Schedl, 1936) comb. nov. are transferred from Epiplatypus Wood, 1993. Costaroplatus ornatus (Schedl, 1936) comb. nov., is transferred from Cenocephalus Chapuis, 1865. Megaplatypus acutidens (Blandford, 1895) comb. nov. and Megaplatypus despectus (Schedl, 1971) comb. nov. are transferred from Tesserocerus Saunders, 1837. New synonymies are proposed as follows: Cenocephalus rugicollis Schedl, 1952 (= Cenocephalus epistomalis Wood, 1966 syn. nov.); Tesserocerus forcipatus Schedl, 1972 (= Platypus aplanatus Schedl, 1976 syn. nov.); Tesserocerus retusus Gurin-Mneville, 1838 (= Tesserocerus guerini ssp. montanus Schedl, 1960 syn. nov.); Tesserocerus simulatus Schedl, 1936 (= Platypus bilobus Schedl, 1961 syn. nov.); Tesserocerus spinax Blandford, 1896 (= Tesserocephalus forficula Schedl, 1936 syn. nov.); Costaroplatus carinulatus (Chapuis, 1865) (= Platypus umbrosus Schedl, 1936 syn. nov.); Costaroplatus shenefelti Nunberg (1963) (= Platypus abditulus Wood, 1966 syn. nov.); Costaroplatus vonfaberi (Reichardt, 1962) (= Platypus convexus Schedl, 1972 syn. nov.); Epiplatypus sallei (Chapuis, 1865) (= Platypus quadricaudatulus Schedl, 1934 syn. nov. and = Platypus filaris Wood, 1971 syn. nov.); Euplatypus longulus (Chapuis, 1865) (= Platypus dimidiatus Chapuis, 1865 syn. nov. = Platypus mulsanti Chapuis, 1865 syn. nov. and = Platypus pseudolongulus Schedl, 1963 syn. nov. ); Megaplatypus acutidens (Blandford, 1895) (= Tesserocerus alternantes Schedl, 1977 syn. nov.); Megaplatypus durus (Schedl, 1936) (= Platypus arcuatus Schedl, 1976 syn. nov.); Megaplatypus fuscus (Chapuis, 1865) (= Platypus marginatus Chapuis, 1865 syn. nov., = Platypus granarius Schedl, 1952 syn. nov., and = Platypus obsitus Schedl, 1976 syn. nov.); Megaplatypus irrepertus (Schedl, 1936) (= Platypus sulcipennis Schedl, 1976 syn. nov.); Neotrachyostus abbreviatus (Chapuis, 1865) (= Platypus concavus Chapuis, 1865 syn. nov.); Teloplatypus enixus (Schedl, 1936) (= Platypus interponens Schedl, 1978 syn. nov.); Teloplatypus ratzeburgi (Chapuis, 1865) (= Platypus pallidipennis Blandford, 1896 syn. nov.). Platypus simpliciformis Wood, 1966 had been transferred by Wood (1993) to both Megaplatypus and Euplatypus by mistake; I propose keeping it in Megaplatypus. Six Neotropical species are left in the genus Platypus with the status incertae sedis: Platypus armatus Chapuis, 1865; Platypus dorsalis Schedl, 1972; Playpus quadrilobus Blandford, 1895; Platypus squamifer Schedl, 1963; Platypus subaequalispinosus Schedl, 1936; and Platypus trispinosus Chapuis, 1965. These taxonomic changes prepare the foundations for future revisionary work on the American Platypodinae.

Comparative genomics of monotremes provides insights into the early evolution of mammalian epidermal differentiation genes.

The function of the skin as a barrier against the environment depends on the differentiation of epidermal keratinocytes into highly resilient corneocytes that form the outermost skin layer. Many genes encoding structural components of corneocytes are clustered in the epidermal differentiation complex (EDC), which has been described in placental and marsupial mammals as well as non-mammalian tetrapods. Here, we analyzed the genomes of the platypus (Ornithorhynchus anatinus) and the echidna (Tachyglossus aculeatus) to determine the gene composition of the EDC in the basal clade of mammals, the monotremes. We report that mammal-specific subfamilies of EDC genes encoding small proline-rich proteins (SPRRs) and late cornified envelope proteins as well as single-copy EDC genes such as involucrin are conserved in monotremes, suggesting that they have originated in stem mammals. Monotremes have at least one gene homologous to the group of filaggrin (FLG), FLG2 and hornerin (HRNR) in placental mammals, but no clear one-to-one pairwise ortholog of either FLG, FLG2 or HRNR. Caspase-14, a keratinocyte differentiation-associated protease implicated in the processing of filaggrin, is encoded by at least 3 gene copies in the echidna. Our results reveal evolutionarily conserved and clade-specific features of the genetic regulation of epidermal differentiation in monotremes.

ePlatypus: an ecosystem for computational analysis of immunogenomics data.

MOTIVATION: The maturation of systems immunology methodologies requires novel and transparent computational frameworks capable of integrating diverse data modalities in a reproducible manner. RESULTS: Here, we present the ePlatypus computational immunology ecosystem for immunogenomics data analysis, with a focus on adaptive immune repertoires and single-cell sequencing. ePlatypus is an open-source web-based platform and provides programming tutorials and an integrative database that helps elucidate signatures of B and T cell clonal selection. Furthermore, the ecosystem links novel and established bioinformatics pipelines relevant for single-cell immune repertoires and other aspects of computational immunology such as predicting ligand-receptor interactions, structural modeling, simulations, machine learning, graph theory, pseudotime, spatial transcriptomics, and phylogenetics. The ePlatypus ecosystem helps extract deeper insight in computational immunology and immunogenomics and promote open science. AVAILABILITY AND IMPLEMENTATION: Platypus code used in this manuscript can be found at github.com/alexyermanos/Platypus.

Body distribution and ecotoxicological effect of nanoplastics in freshwater fish, Zacco platypus.

The increased consumption of plastics worldwide, has led to the emergence of nanoplastics as important environmental pollutants. Despite the presence of nanoplastics in aquatic environments, their effects on ecosystems remain largely unexplored due to the analysis complexity. This study investigated the organ accumulation and toxic effects of 50 nm polystyrene nanoplastics (PS-NPs) in Zacco platypus (Z. platypus; also known as pale chub fish) using pyrolyzer-gas chromatography-mass spectrometry (Pyr-GC/MS). PS-NPs accumulated in Z. platypus' brain, digestive tract, branchia, and liver, causing changes at cellular level. Over a 14-day exposure, the accumulated PS-NPs led to observable changes in fish behavior (e.g., Total traveled distance and maximum velocity). In addition, the oxidative stress in each organ of Z. platypus increased as the exposure concentration of PS-NPs increased. This study shows that accumulation of nanoplastics in fish, resulting in behavioral changes and biochemical toxicity. As the pattern of change magnifies with exposure time and concentration, from a long-term perspective, the influence of nanoplastics on aquatic ecosystems become evident. This underscores the urgency for continuous research into the potential risks of nanoplastics in aquatic ecosystems.

Comparative genomics of the T cell receptor µ locus in marsupials and monotremes.

T cells are a primary component of the vertebrate adaptive immune system. There are three mammalian T cell lineages based on their T cell receptors (TCR). The αß T cells and γδ T cells are ancient and found broadly in vertebrates. The more recently discovered γµ T cells are uniquely mammalian and only found in marsupials and monotremes. In this study, we compare the TCRµ locus (TRM) across the genomes of two marsupials, the gray short-tailed opossum and Tasmanian devil, and one monotreme, the platypus. These analyses revealed lineage-specific duplications, common to all non-eutherian mammals described. There is conserved synteny in the TRM loci of both marsupials but not in the monotreme. Our results are consistent with an ancestral cluster organization which was present in the last common mammalian ancestor which underwent lineage-specific duplications and divergence among the non-eutherian mammals.

Dynamic Evolution of Retroviral Envelope Genes in Egg-Laying Mammalian Genomes.

Independently acquired envelope (env) genes from endogenous retroviruses have contributed to the placental trophoblast cell-cell fusion in therian mammals. Egg-laying mammals (monotremes) are an important sister clade for understanding mammalian placental evolution, but the env genes in their genomes have yet to be investigated. Here, env-derived open reading frames (env-ORFs) encoding more than 400 amino acid lengths were searched in the genomes of two monotremes: platypus and echidna. Only two env-ORFs were present in the platypus genome, whereas 121 env-ORFs were found in the echidna genome. The echidna env-ORFs were phylogenetically classified into seven groups named env-Tac1 to -Tac7. Among them, the env-Tac1 group contained only a single gene, and its amino acid sequence showed high similarity to those of the RD114/simian type D retroviruses. Using the pseudotyped virus assay, we demonstrated that the Env-Tac1 protein utilizes echidna sodium-dependent neutral amino acid transporter type 1 and 2 (ASCT1 and ASCT2) as entry receptors. Moreover, the Env-Tac1 protein caused cell-cell fusion in human 293T cells depending on the expression of ASCT1 and ASCT2. These results illustrate that fusogenic env genes are not restricted to placental mammals, providing insights into the evolution of retroviral genes and the placenta.

Transcriptome and computational approaches highlighting the molecular regulation of Zacco platypus induced by mesocosm exposure to common disinfectant chlorine.

Chlorine (Cl2) is a disinfectant often used in swimming pools and water treatment facilities. However, it is released into aquatic ecosystems, where it may harm non-targeted organisms. Here, we performed a mesocosm experiment exposing Zacco platypus (Z. platypus) to biocide Cl2 for 30 days (30 d) at two days' time points 15 days (15 d) and 30 d samples were collected. Here, Z. platypus was exposed to a sublethal concentration (0.1 mg/L) of Cl2, and comparative transcriptomics analyses were performed to determine their response mechanisms at the molecular level. According to RNA sequencing of the whole-body transcriptome, 860 and 1189 differentially expressed genes (DEGs) were identified from the 15 d and 30 d responses to Cl2, respectively. After enrichment analysis of GO (Gene Ontology) functions and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways, identified DEGs were demonstrated to be associated with a variety of functions, including "ion binding and transmembrane transporters". Cl2 also induced oxidative stress in Z. platypus by increasing the levels of reactive oxygen species (ROS) while decreasing the catalase (CAT) content and the levels of solute carrier family 22 member 11 (slc22a11), Caspase-8 (casp-8), inducible nitric oxide synthase (NOS2), cytosolic phospholipase A2 gamma (PLA2G4). However, Z. platypus still allows recovery during stress suspension by increasing the expression levels of solute carrier family proteins. The GO and KEGG annotation results revealed that the expression of DEGs were related to the detoxification process, immune response, and antioxidant mechanism. Additionally, protein-protein interaction networks (PPI) and cytoHubba analyses identified sixteen hub genes and their interaction. These findings elucidate the regulation of various DEGs and signaling pathways in response to Cl2 exposure, which will improve our knowledge and laid foundation for further investigation of the toxicity of Cl2 to Z. platypus.

First monotreme from the Late Cretaceous of South America.

Monotremata is a clade of egg-lying mammals, represented by the living platypus and echidnas, which is endemic to Australia, and adjacent islands. Occurrence of basal monotremes in the Early Cretaceous of Australia has led to the consensus that this clade originated on that continent, arriving later to South America. Here we report on the discovery of a Late Cretaceous monotreme from southern Argentina, demonstrating that monotremes were present in circumpolar regions by the end of the Mesozoic, and that their distinctive anatomical features were probably present in these ancient forms as well.

Na+/Cl- cotransporter 2 is not fish-specific and is widely found in amphibians, non-avian reptiles, and select mammals.

Solute carrier 12 (Slc12) is a family of electroneutral cation-coupled chloride (Cl-) cotransporters. Na+/K+/2Cl- (Nkcc) and Na+/Cl- cotransporters (Ncc) belong to the Nkcc/Ncc subfamily. Human and mouse possess one gene for the Na+/Cl- cotransporter (ncc gene: slc12a3), whereas teleost fishes possess multiple ncc genes, slc12a3 (ncc1) and slc12a10 (ncc2), in addition to their species-specific paralogs. Amphibians and squamates have two ncc genes: slc12a3 (ncc1) and ncc3. However, the evolutionary relationship between slc12a10 and ncc3 remains unresolved, and the presence of slc12a10 (ncc2) in mammals has not been clarified. Synteny and phylogenetic analyses of vertebrate genome databases showed that ncc3 is the ortholog of slc12a10, and slc12a10 is present in most ray-finned fishes, coelacanths, amphibians, reptiles, and a few mammals (e.g., platypus and horse) but pseudogenized or deleted in birds, most mammals, and some ray-finned fishes (pufferfishes). This shows that slc12a10 is widely present among bony vertebrates and pseudogenized or deleted independently in multiple lineages. Notably, as compared with some fish that show varied slc12a10 tissue expression profile, spotted gar, African clawed frog, red-eared slider turtle, and horse express slc12a10 in the ovaries or premature gonads. In horse tissues, an unexpectedly large number of splicing variants for Slc12a10 have been cloned, many of which encode truncated forms of Slc12a10, suggesting that the functional constraints of horse slc12a10 are weakened, which may be in the process of becoming a pseudogene. Our results elaborate on the evolution of Nkcc/Ncc subfamily of Slc12 in vertebrates.NEW & NOTEWORTHY slc12a10 is not a fish-specific gene and is present in a few mammals (e.g., platypus and horse), non-avian reptiles, amphibians, but was pseudogenized or deleted in most mammals (e.g., human, mouse, cat, cow, and rhinoceros), birds, and some ray-finned fishes (pufferfishes).

Attention and platypuses.

This perspective piece discusses a set of attentional phenomena that are not easily accommodated within current theories of attentional selection. We call these phenomena attentional platypuses, as they allude to an observation that within biological taxonomies the platypus does not fit into either mammal or bird categories. Similarly, attentional phenomena that do not fit neatly within current attentional models suggest that current models are in need of a revision. We list a few instances of the "attentional platypuses" and then offer a new approach, that we term dynamically weighted prioritization, stipulating that multiple factors impinge onto the attentional priority map, each with a corresponding weight. The interaction between factors and their corresponding weights determines the current state of the priority map which subsequently constrains/guides attentional allocation. We propose that this new approach should be considered as a supplement to existing models of attention, especially those that emphasize categorical organizations. This article is categorized under: Psychology > Attention Psychology > Perception and Psychophysics Neuroscience > Cognition.

The rare genus Myoplatypus (Coleoptera: Curculionidae: Platypodinae): three new species, new reports, and first records for South America.

We describe three new species of Myoplatypus Wood, 1993: from Peru, Myoplatypus petrovi Kirkendall new species; from Honduras, M. quadricornis Kirkendall new species; from Nicaragua (M. nicaraguensis Kirkendall new species). We transfer Platypus biprorus Blandford, 1896 and Platypus sicarius Wood, 1971 into Myoplatypus, and we synonymize Platypus querceus Wood, 1971 with M. biprorus. The net result of these actions is a genus comprising nine tropical and one temperate American species. Males of all species are illustrated by photographs and a key to all species is provided. The collections reported here include the first South American records of Myoplatypus, a genus hitherto known only from North and Central America. Most Myoplatypus species are known from just one or a few collections and none of the tropical species are very widespread; only five tropical species have any known hosts (Quercus [Fagaceae] for three of them). The paucity of specimens could be because of peculiarities of biology that lead to them being under-collected (such as restriction to high elevations), but it also could be that they are narrow endemics, in which case these pinhole borer species deserve conservation attention. Nosotros describimos tres nuevas especies de Myoplatypus Wood, 1993: de Per, Myoplatypus petrovi Kirkendall espcie nueva; de Honduras, M. quadricornis Kirkendall espcie nueva; de Nicaragua, M. nicaraguensis Kirkendall espcie nueva. Platypus biprorus Blandford, 1896 y Platypus sicarius Wood, 1971 se transfieren a Myoplatypus, y Platypus querceus Wood, 1971 se sinonimiza con M. biprorus Blandford. El resultado neto de estas acciones es un gnero que consiste en nueve espcies tropicales y una templada. Los machos de todas las especies estn ilustrados con fotografas y se da una clave para todas las especies. Las colecciones reportadas aqu incluyen los primeros registros sudamericanos de Myoplatypus, un gnero hasta ahora conocido solo en Amrica del Norte y Amrica Central. La mayora de las especies de Myoplatypus se conocen a partir de solo una o unas pocas colecciones y ninguna de las especies tropicales est muy extendida; slo cinco especies tropicales tienen hospedadores conocidos (tres de ellos son robles). La escasez de especmenes podra deberse a algunas peculiaridades de la biologa que los llevan a una recoleccin insuficiente (como la restriccin a grandes alturas), pero tambin podra ser que sean endmicos estrechos, en cuyo caso estas especies de barrenadores merecen atencin de conservacin.

Fragmentation by major dams and implications for the future viability of platypus populations.

The evolutionarily unique platypus (Ornithorhynchus anatinus) has experienced major declines and extinctions from a range of historical and recent interacting human-mediated threats. Although spending most of their time in the water, platypuses can move over land. Nevertheless, uncertainties remain whether dams are barriers to movement, thus limiting gene flow and dispersal, essential to evolution and ecology. Here we examined disruption of gene flow between platypus groups below and above five major dams, matched to four adjacent rivers without major dams. Genetic differentiation (FST) across dams was 4- to 20-fold higher than along similar stretches of adjacent undammed rivers; FST across dams was similar to differentiation between adjacent river systems. This indicates that major dams represent major barriers for platypus movements. Furthermore, FST between groups was correlated with the year in which the dam was built, increasing by 0.011 every generation, reflecting the effects of these barriers on platypus genetics. This study provides evidence of gene flow restriction, which jeopardises the long-term viability of platypus populations when groups are fragmented by major dams. Mitigation strategies, such as building of by-pass structures and translocation between upstream and downstream of the dam, should be considered in conservation and management planning.

Transcriptional Responses of Stress-Related Genes in Pale Chub (Zacco platypus) Inhabiting Different Aquatic Environments: Application for Biomonitoring Aquatic Ecosystems.

Pale chub (Zacco platypus) is a dominant species in urban rivers and reservoirs, and it is used as an indicator to monitor the effects of environmental contaminants. Gene responses at the molecular level can reflect the health of fish challenged with environmental stressors. The objective of this study was to identify correlations between water quality factors and the expression of stress-related genes in Z. platypus from different lake environments (Singal and Juam Lakes). To do so, transcriptional responses of genes involving cellular homeostasis (heat-shock protein 70, HSP70; heat-shock protein 90, HSP90), metal detoxification (metallothionein, MT), and antioxidation (superoxide dismutase, SOD; catalase, CAT) were analyzed in the gill and liver tissues of Z. platypus. HSP70, HSP90, and MT genes were overall upregulated in Z. platypus from Singal Lake, which suffered from poorer water quality than Juam Lake. In addition, gene responses were significantly higher in Singal Lake outflow. Upregulation of HSP70, HSP90, and MT was significantly higher in Z. platypus gills than in the liver tissue. In addition, integrated biomarker response and heatmap analysis determined correlations between expression of biomarker genes or water quality factors and sampling sites of both lakes. These results suggest that stress-related genes used as multiple biomarkers may reflect spatial characteristics and water quality of different lake environments, and they can be used for biomonitoring and ecological risk assessment.

Functional Diversity and Evolution of Bitter Taste Receptors in Egg-Laying Mammals.

Egg-laying mammals (monotremes) are a sister clade of therians (placental mammals and marsupials) and a key clade to understand mammalian evolution. They are classified into platypus and echidna, which exhibit distinct ecological features such as habitats and diet. Chemosensory genes, which encode sensory receptors for taste and smell, are believed to adapt to the individual habitats and diet of each mammal. In this study, we focused on the molecular evolution of bitter taste receptors (TAS2Rs) in monotremes. The sense of bitter taste is important to detect potentially harmful substances. We comprehensively surveyed agonists of all TAS2Rs in platypus (Ornithorhynchus anatinus) and short-beaked echidna (Tachyglossus aculeatus) and compared their functions with orthologous TAS2Rs of marsupial and placental mammals (i.e., therians). As results, the agonist screening revealed that the deorphanized monotreme receptors were functionally diversified. Platypus TAS2Rs had broader receptive ranges of agonists than those of echidna TAS2Rs. While platypus consumes a variety of aquatic invertebrates, echidna mainly consumes subterranean social insects (ants and termites) as well as other invertebrates. This result indicates that receptive ranges of TAS2Rs could be associated with feeding habits in monotremes. Furthermore, some orthologous receptors in monotremes and therians responded to ß-glucosides, which are feeding deterrents in plants and insects. These results suggest that the ability to detect ß-glucosides and other substances might be shared and ancestral among mammals.

Activation of Xist by an evolutionarily conserved function of KDM5C demethylase.

XX female and XY male therian mammals equalize X-linked gene expression through the mitotically-stable transcriptional inactivation of one of the two X chromosomes in female somatic cells. Here, we describe an essential function of the X-linked homolog of an ancestral X-Y gene pair, Kdm5c-Kdm5d, in the expression of Xist lncRNA, which is required for stable X-inactivation. Ablation of Kdm5c function in females results in a significant reduction in Xist RNA expression. Kdm5c encodes a demethylase that enhances Xist expression by converting histone H3K4me2/3 modifications into H3K4me1. Ectopic expression of mouse and human KDM5C, but not the Y-linked homolog KDM5D, induces Xist in male mouse embryonic stem cells (mESCs). Similarly, marsupial (opossum) Kdm5c but not Kdm5d also upregulates Xist in male mESCs, despite marsupials lacking Xist, suggesting that the KDM5C function that activates Xist in eutherians is strongly conserved and predates the divergence of eutherian and metatherian mammals. In support, prototherian (platypus) Kdm5c also induces Xist in male mESCs. Together, our data suggest that eutherian mammals co-opted the ancestral demethylase KDM5C during sex chromosome evolution to upregulate Xist for the female-specific induction of X-inactivation.

Using DNA metabarcoding as a novel approach for analysis of platypus diet.

Platypuses (Ornithorhynchus anatinus) forage for macroinvertebrate prey exclusively in freshwater habitats. Because food material in their faeces is well digested and mostly unidentifiable, previous dietary studies have relied on cheek pouch assessments and stable isotope analysis. Given DNA metabarcoding can identify species composition from only fragments of genetic material, we investigated its effectiveness in analysing the diet of platypuses, and to assess variation across seasons and sexes. Of the 18 orders and 60 families identified, Ephemeroptera and Diptera were the most prevalent orders, detected in 100% of samples, followed by Trichoptera, Pulmonata, and Odonata (86.21% of samples). Caenidae and Chironomidae were the most common families. Diptera had a high average DNA read, suggesting it is an important dietary component that may have been underestimated in previous studies. We found no variation in diet between sexes and only minimal changes between seasons. DNA metabarcoding proved to be a highly useful tool for assessing platypus diet, improving prey identification compared to cheek pouch analysis, which can underestimate soft-bodied organisms, and stable isotope analysis which cannot distinguish all taxa isotopically. This will be a useful tool for investigating how platypus prey diversity is impacted by habitat degradation as a result of anthropogenic stressors.