The platypus (Ornithorhynchus anatinus) is a semi-aquatic monotreme that occupies a high trophic position in the freshwater ecosystems of eastern mainland Australia and Tasmania. Platypuses are continuously exposed to anthropogenic contaminants including perfluorooctane sulfonate (PFOS). This study examined PFOS concentrations in the livers of deceased platypuses (eight wild; one captive) that were opportunistically collected across NSW over a two- and a half-year period. There was a large variation in PFOS concentrations, ranging from < 1 µg/kg to 1200 µg/kg. This study presents the first report of PFOS contamination in platypuses, revealing their PFOS levels are broadly similar to those found in river otters (Lutra canadensis) and lower than those in American mink (Mustela vison), both which occupy similar ecological niches in freshwater systems. This study raises concerns about the impact of PFOS on platypus health.

Heteromorphic sex chromosomes (XY or ZW) present problems of gene dosage imbalance between sexes and with autosomes. A need for dosage compensation has long been thought to be critical in vertebrates. However, this was questioned by findings of unequal mRNA abundance measurements in monotreme mammals and birds. Here, we demonstrate unbalanced mRNA levels of X genes in platypus males and females and a correlation with differential loading of histone modifications. We also observed unbalanced transcripts of Z genes in chicken. Surprisingly, however, we found that protein abundance ratios were 1:1 between the sexes in both species, indicating a post-transcriptional layer of dosage compensation. We conclude that sex chromosome output is maintained in chicken and platypus (and perhaps many other non therian vertebrates) via a combination of transcriptional and post-transcriptional control, consistent with a critical importance of sex chromosome dosage compensation.

Platypuses are the world\'s most evolutionarily distinct mammal and have several host-specific ecto- and endoparasites. With platypus populations declining, consideration should also be given to preserving these high conservation priority parasites alongside their charismatic host. A disease risk analysis (DRA) was performed for a platypus conservation translocation, using a modified streamlined methodology that incorporated a parasite conservation framework. DRA frameworks rarely consider parasite conservation. Rather, parasites are typically considered myopically in terms of the potential harm they may cause their host. To address this, a previously proposed parasite conservation framework was incorporated into an existing streamlined DRA methodology. Incorporation of the two frameworks was achieved readily, although there is opportunity for further refinement of this process. This DRA is significant as it is the first performed for any monotreme species, and implements the emerging approach of balancing the health and disease risk of the host with parasite conservation.

The enzymatic breakdown and regulation of food passage through the vertebrate antral stomach and pyloric sphincter (antropyloric region) is a trait conserved over 450 million years. Development of the structures involved is underpinned by a highly conserved signalling pathway involving the hedgehog, bone morphogenetic protein and Wingless/Int-1 (Wnt) protein families. Monotremes are one of the few vertebrate lineages where acid-based digestion has been lost, and this is consistent with the lack of genes for hydrochloric acid secretion and gastric enzymes in the genomes of the platypus (Ornithorhynchus anatinus) and short-beaked echidna (Tachyglossus aculeatus) . Furthermore, these species feature unique gastric phenotypes, both with truncated and aglandular antral stomachs and the platypus with no pylorus. Here, we explore the genetic underpinning of monotreme gastric phenotypes, investigating genes important in antropyloric development using the newest monotreme genomes (mOrnAna1.pri.v4 and mTacAcu1) together with RNA-seq data. We found that the pathway constituents are generally conserved, but surprisingly, NK3 homeobox 2 (Nkx3.2) was pseudogenized in both platypus and echidna. We speculate that the unique sequence evolution of Grem1 and Bmp4 sequences in the echidna lineage may correlate with their pyloric-like restriction and that the convergent loss of gastric acid and stomach size genotypes and phenotypes in teleost and monotreme lineages may be a result of eco-evolutionary dynamics. These findings reflect the effects of gene loss on phenotypic evolution and further elucidate the genetic control of monotreme stomach anatomy and physiology.

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.

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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.

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.

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.

Egg-laying mammals (monotremes) are considered \"primitive\" due to traits such as oviparity, cloaca, and incomplete homeothermy, all of which they share with reptiles. Two groups of monotremes, the terrestrial echidna (Tachyglossidae) and semiaquatic platypus (Ornithorhynchidae), have evolved highly divergent characters since their emergence in the Cenozoic era. These evolutionary differences, notably including distinct electrosensory and chemosensory systems, result from adaptations to species-specific habitat conditions. To date, very few studies have examined the visual adaptation of echidna and platypus. In the present study, we show that echidna and platypus have different light absorption spectra in their dichromatic visual sensory systems at the molecular level. We analyzed absorption spectra of monotreme color opsins, long-wavelength sensitive opsin (LWS) and short-wavelength sensitive opsin 2 (SWS2). The wavelength of maximum absorbance (λmax) in LWS was 570.2 in short-beaked echidna (Tachyglossus aculeatus) and 560.6 nm in platypus (Ornithorhynchus anatinus); in SWS2, λmax was 451.7 and 442.6 nm, respectively. Thus, the spectral range in echidna color vision is ~ 10 nm longer overall than in platypus. Natural selection analysis showed that the molecular evolution of monotreme color opsins is generally functionally conserved, suggesting that these taxa rely on species-specific color vision. In order to understand the usage of color vision in monotremes, we made 24-h behavioral observations of captive echidnas at warm temperatures and analyzed the resultant ethograms. Echidnas showed cathemeral activity and various behavioral repertoires such as feeding, traveling, digging, and self-grooming without light/dark environment selectivity. Halting (careful) behavior is more frequent in dark conditions, which suggests that echidnas may be more dependent on vision during the day and olfaction at night. Color vision functions have contributed to dynamic adaptations and dramatic ecological changes during the ~ 60 million years of divergent monotreme evolution. The ethogram of various day and night behaviors in captive echidnas also contributes information relevant to habitat conservation and animal welfare in this iconic species, which is locally endangered.