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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. [ABSTRACT FROM AUTHOR]

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. Several teleost groups display secondary loss of the stomach. Analyses of genotypic convergence among agastric fishes showed that four genes, slc26a9, kcne2, cldn18a, and vsig1, are co-deleted or pseudogenized in most agastric fishes. [ABSTRACT FROM AUTHOR]

Zacco platypus is an endemic colorful freshwater minnow that is intensively distributed in East Asia. In this study, two adult female individuals collected from Haihe River basin were used for karyotypic study and genome sequencing, respectively. The karyotype formula of Z. platypus is 2N = 48 = 18 M + 24SM/ST + 6 T. We used PacBio long-read sequencing and Hi-C technology to assemble a chromosome-level genome of Z. platypus. As a result, an 814.87 Mb genome was assembled with the PacBio long reads. Subsequently, 98.64% assembled sequences were anchored into 24 chromosomes based on the Hi-C data. The chromosome-level assembly contained 54 scaffolds with a N50 length of 32.32 Mb. Repeat elements accounted for 52.35% in genome, and 24,779 protein-coding genes were predicted, with 92.11% were functionally annotated with the public databases. BUSCO analysis yielded a completeness score of 96.5%. This high-quality genome assembly provides valuable resources for future functional genomic research, comparative genomics, and evolutionary studies of genus Zacco. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. Major dams are found to disrupt platypus gene flow and dispersal, with higher genetic differentiation found across dams than along similar stretches of undammed rivers, indicating that they act as significant barriers to platypus movement. [ABSTRACT FROM AUTHOR]

Growth characteristic features of the blue king crab Paralithodes platypus inhabiting the northern part of the Sea of Okhotsk has been analyzed. The samples were collected in the course of the trap-recapture surveys in the northeastern part of the Sea of Okhotsk (Shelikhov Gulf) in 2013–2015, in the northwestern part of the Sea of Okhotsk (west of the Lisyansky Peninsula) in 2012–2015, and near the Shantar Islands in 2011–2015. The Bertalanffy equation was used to describe growth features of groups of blue crab males and females with different age. This equation was obtained using the ELEFAN dimensional distribution method, which was optimized by a genetic algorithm using the R software environment. Analysis of growth patterns under different environmental conditions allowed us to assess the adaptive abilities of blue king crab. According to the data, males from the Shelikhov Gulf reach the maximal carapace width CWinf = 171.4 mm, which is larger than CWinf of the males from the Lisyansky Peninsula (152.5 mm) and from Shantar Islands (130.6 mm). A similar growth pattern has been observed in females. The maximal CWinf for femailes was 145.9 mm for Shelikhov Gulf, 128.3 mm for Lisyansky Peninsula, and 115.7 mm for Shantar Islands. Growth rates were significantly higher for crabs from the Shelikhov Gulf than for crabs from the northwestern part of the Sea of Okhotsk, where habitat conditions are less favorable for blue king crab. [ABSTRACT FROM AUTHOR]

This document, titled "The IR Platypus," is a letter published in the journal CardioVascular & Interventional Radiology. The author reflects on a conversation with a Mexican colleague about the challenges and unique nature of their work in Interventional Radiology (IR). They compare IR to the peculiar platypus, highlighting the dichotomy between their role as radiologists and their surgical-like practice. The author expresses frustration with the lack of understanding and recognition of their profession, emphasizing the importance of validation from their peers and the medical community. They also mention a recent discovery about the platypus that brings them solace. The document concludes with funding and conflict of interest declarations. [Extracted from the article]

A midwater fish species, duckbill barracudina Magnisudis atlantica, was recorded as a prey item for Chinook salmon Oncorhynchus tshawytscha at high seas for the first time. The prey-to-predator size ratio of this occurrence is evidence that salmon can feed upon bigger prey than considered before. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Wild fish show consistent behavioral differences, e.g., personalities among populations, whereas the possible relationships between personality and environmental conditions have seldom been systemically examined. We aimed to test whether the personality of wild-caught fish was affected by the biotic (food resources and predation) and abiotic (temperature, dissolved oxygen level, and flow velocity) conditions of natural habitats. Six populations of pale chub (Zacco platypus) were sampled along a river longer than 1000 km, and environmental conditions and personality characteristics, such as boldness, activity, and sociability, were measured. Personality variables could be reduced to two factors by principal component analysis, boldness, and sociability factors, with the former factor having more variation among and within populations. Individuals from populations with higher food availability (plankton density) and flow velocity generally showed higher boldness factor scores, possibly due to the better energy status of higher food abundance or the low water transparency and hence decreased predation risk and fast-flow lifestyle of populations with higher water velocity populations. All populations showed high sociability as group-living species, which was positively correlated with only the phytoplankton biomass, possibly due to decreased intraspecific competition in habitats with abundant food resources. The correlations among personality variables were population-dependent, as individuals who moved more had a shorter distance to the stimulus shoal (i.e., increased shoaling tendency) within high-predation populations, whereas individuals who moved more spent less time in shoals within low-predation populations. The results suggest that alterations in habitat conditions can result in divergent natural selection that favors a particular personality; thus, human-induced alterations in habitat conditions may shape the personality of individual fish. [ABSTRACT FROM AUTHOR]

Platypuses (Ornithorhynchus anatinus) inhabit the permanent rivers and creeks of eastern Australia, from north Queensland to Tasmania, but are experiencing multiple and synergistic anthropogenic threats. Baseline information of health is vital for effective monitoring of populations but is currently sparse for mainland platypuses. Focusing on seven hematology and serum chemistry metrics as indicators of health and nutrition (packed cell volume (PCV), total protein (TP), albumin, globulin, urea, creatinine, and triglycerides), we investigated their variation across the species' range and across seasons. We analyzed 249 unique samples collected from platypuses in three river catchments in New South Wales and Victoria. Health metrics significantly varied across the populations' range, with platypuses from the most northerly catchment, having lower PCV, and concentrations of albumin and triglycerides and higher levels of globulin, potentially reflecting geographic variation or thermal stress. The Snowy River showed significant seasonal patterns which varied between the sexes and coincided with differential reproductive stressors. Male creatinine and triglyceride levels were significantly lower than females, suggesting that reproduction is energetically more taxing on males. Age specific differences were also found, with juvenile PCV and TP levels significantly lower than adults. Additionally, the commonly used body condition index (tail volume index) was only negatively correlated with urea, and triglyceride levels. A meta-analysis of available literature revealed a significant latitudinal relationship with PCV, TP, albumin, and triglycerides but this was confounded by variation in sampling times and restraint methods. We expand understanding of mainland platypuses, providing reference intervals for PCV and six blood chemistry, while highlighting the importance of considering seasonal variation, to guide future assessments of individual and population condition. [ABSTRACT FROM AUTHOR]

The platypus is a semi-aquatic mammal, endemic to freshwater habitats of eastern Australia. There are gaps in the understanding of platypus movement behaviour within river systems, including spatial and temporal organization of individuals. We tracked movements of 12 platypuses on the regulated Snowy and Mitta Mitta Rivers for up to 12-months, the longest continuous tracking of platypus using acoustic telemetry. Platypuses remained relatively localized, occupying 0.73–8.45 km of river over 12 months, consistent with previous tracking studies over shorter periods. Males moved further than females, and larger males had higher cumulative movements, suggesting a possible relationship to metabolic requirements. Platypuses moved greater distances on the Mitta Mitta River, possibly associated with impacts of altered flow regimes to their macroinvertebrate diet. Increased movements and diurnal activity during winter were primarily driven by males, possibly attributable to breeding behaviours, rather than increased costs of winter foraging. Evidence for relatively small movements has implications for declining populations, given areas of localised declines are unlikely to be supplemented by migrating platypuses, especially when dispersal is restricted by dam walls. Understanding platypus movement behaviour is pertinent for their conservation, as water resource development and habitat modification continue to reduce connectivity between populations across their distribution. [ABSTRACT FROM AUTHOR]

Habitat use and diet composition of invasive smallmouth bass, Micropterus dolomieu, Japanese dace, Pseudaspius hakonensis, and pale chub, Opsariichthys platypus, were studied for two years in the Middle Chikuma River, Nagano, Japan. Habitat use of dace and chub overlapped both years but showed differences from smallmouth bass. Additionally, smallmouth bass habitat use differed greatly between years, as young smallmouth bass were found in uncharacteristically fast flowing habitat in 2018 and predominantly in more typical slow flowing habitat in 2019. This use of fast flowing habitat in 2018 appears to be influenced by the high overall fish density, especially for smallmouth bass. Diet composition, studied in 2018, overlapped significantly between the three species in riffle habitat and overlap became less significant in run and pool habitat where smallmouth bass fed increasingly on fish prey. We therefore suggest that the interactions between smallmouth bass and dace and chub shift from predominantly predation in slow flowing habitat to resource competition in faster flowing habitat. [ABSTRACT FROM AUTHOR]

Predators can have strong impacts on prey populations, with cascading effects on lower trophic levels. Although such effects are well known in aquatic ecosystems, few studies have explored the influence of predatory aquatic mammals, or whether the same predator has similar effects in contrasting systems. We investigated the effects of platypus (Monotremata: Ornithorhynchus anatinus) on its benthic invertebrate prey, and tested predictions that this voracious forager would more strongly affect invertebrates—and indirectly, epilithic algae—in a mesotrophic lake than in a dynamic stream ecosystem. Hypotheses were tested using novel manipulative experiments involving platypus-exclusion cages. Platypuses had strongly suppressive effects on invertebrate prey populations, especially detritivores and omnivores, but weaker or inconsistent effects on invertebrate taxon richness and composition. Contrary to expectation, predation effects were stronger in the stream than the lake; no effects were found on algae in either ecosystem due to weak effects of platypuses on herbivorous invertebrates. Platypuses did not cause redistribution of sediment via their foraging activities. Platypuses can clearly have both strong and subtle effects on aquatic food webs that may vary widely between ecosystems and locations, but further research is needed to replicate our experiments and understand the contextual drivers of this variation. [ABSTRACT FROM AUTHOR]

The genus Chloromyxum (Myxozoa: Myxosporea: Bivalvulida) is defined as having ridged or smooth bivalvular myxospores containing four polar capsules, with/without caudal filaments. Currently containing more than 140 nominal species, this genus is reasonably speciose with myxospores of unique but heterogeneous morphology. Recent phylogenetic studies have demonstrated its polyphyletic nature. During our myxosporean survey of freshwater fish, a new coelozoic myxosporean species, Chloromyxum trilineatum n. sp., was detected in the gall bladder of the pale chub, Zacco platypus (Cypriniformes: Cyprinidae), which originated from central Japan. Spores were subspherical, measuring 8.5–9.1 (8.8) μm in length, 7.6–8.2 (8.0) μm in width, and 6.8–7.8 (7.4) μm in thickness (n = 20). The valvular surface was smooth and three or four distinct ridges ran parallel to the suture line. Four almost equal polar capsules, 2.9–3.8 (3.3) μm in length and 1.6–2.4 (2.0) μm in width, assembled at the apical part of the spores. The partial nucleotide sequence of the 18S ribosomal RNA gene, 2014 bp in length, was closest to that of morphologically distinct Chloromyxum ellipticum, infecting the gall bladder of grass carp (Ctenopharyngodon idella) in China with 96.99% (1673/1725) identity and three insertion/deletion (indel) sites, followed by Chloromyxum legeri, infecting the gall bladder of common carp (Cyprinus carpio) in the Czech Republic with 89.97% (1803/2004) identity and 14 indel sites. Other myxosporean species, including Chloromyxum spp. from the gall bladder or urinary system of freshwater and marine fish, were phylogenetically distant from the present species. [ABSTRACT FROM AUTHOR]

We evaluated the effects of wastewater effluents on pale chub (Zacco platypus) in a contaminated stream by integrating genotoxic, oxidative stress, histological, and physiological biomarkers. The metal pollution index indicated higher pollution loads at downstream sites (DS1 and DS2) compared with the upstream reference site. Significantly higher nuclear abnormality confirmed the existence of genotoxicity (p < 0.05) at downstream sites. Antioxidant activity (catalase and glutathione S-transferase) and lipid peroxidation levels in livers of Z. platypus were also significantly higher at the DS1 site (p < 0.05). The liver somatic index was also influenced, with abnormal histological alterations in the liver, possibly caused by heavy metal accumulation (Cd, Co, Cr, Mn, Ni, and Pb). The integrated biomarker response value was the highest at DS1 (13.74) followed by DS2 (1.94), indicating that wastewater effluents had the potential to cause adverse effects on Z. platypus inhabiting receiving stream. [ABSTRACT FROM AUTHOR]

Individual olfactory sensory neurons express a single odorant receptor gene from either class I genes residing in a single cluster on a single chromosome or class II genes spread over multiple clusters on multiple chromosomes. Here, we identify an enhancer element for mouse class I genes, the J element, that is conserved through mammalian species from the platypus to humans. The J element regulates most class I genes expression by exerting an effect over ~ 3 megabases within the whole cluster. Deletion of the trans J element increases the expression frequencies of class I genes from the intact J allele, indicating that the allelic exclusion of class I genes depends on the activity of the J element. Our data reveal a long-range cis-regulatory element that governs the singular class I gene expression and has been phylogenetically preserved to retain a single cluster organization of class I genes in mammals. [ABSTRACT FROM AUTHOR]

The ambrosia beetle Platypus quercivorus (Coleoptera: Platypodidae) is a vector of the pathogenic fungi, Raffaelea quercivora (Ophiostomatales: Ophiostomataceae), which causes Japanese oak wilt disease. Previous studies have shown that the beetle displays positive phototactic behavior; however, the adaptive significance of this behavior remains unclear. We postulated that positive phototaxis is necessary to allow the beetle to fly skyward immediately after emergence from a tree, and that this taxis changes following a certain period of flight. The present study aimed to clarify the changes in phototactic behavior of P. quercivorus before and after flight by using individual beetles emerging from the trunk of a Quercus crispula (Fagales: Fagaceae) tree that was attacked in 2014. The response of 60 beetles to light was tested ten times each, before and after flight in a flight mill. A generalized linear mixed model was constructed to predict the probability of positive phototaxis of P. quercivorus before and after flight. A best-fit model showed that the probability of positive phototaxis was lower after flight than before. The results suggest that positive phototaxis of P. quercivorus is decreased after flight. [ABSTRACT FROM AUTHOR]

To investigate the phylogeography of the Japanese pale chub Opsariichthys platypus, we examined the genetic differentiation, phylogenetic relationships, and historical demography using mitochondrial cytochrome b gene sequences of 788 O. platypus from 124 localities throughout the Japanese Archipelago. Molecular phylogenetic analyses revealed that Japanese O. platypus is divided into three major clades (western Japan: WJ; eastern Japan: EJ; and Kyushu: KY), and that among these clades, KY is remarkably differentiated from the others. The distribution of the EJ and KY clades clearly reflects their respective geographical ranges: the EJ and KY clades are restricted to the eastern region of the Ibuki-Suzuka Mountains in central Honshu and northern Kyushu, respectively. In contrast to the EJ and KY clades, the WJ clade is widely distributed throughout the Japanese Archipelago, including areas where O. platypus is not naturally distributed (e.g., northern part of Honshu, southern Kyushu, and Tokunoshima). In addition, nearly all the WJ haplotypes in the non-indigenous regions were the same as or similar to the haplotypes in Lake Biwa, and the WJ haplotypes in the distribution ranges of the EJ and KY clades were also same as or similar to those of Lake Biwa, indicating that the distribution of WJ clade had been the result of inadvertent releases in conjunction with releases of Plecoglossus altivelis from Lake Biwa. The estimated divergence time indicated that each clade was formed during or before the Pleistocene, and mismatch distribution test suggested the occurrence of the population expansion in three clades and the time since expansion was 120,000-226,000 years. This study demonstrates that O. platypus exhibits clear genetic differentiation among regional populations, and that range expansion following divergence caused by uplifting of mountains is important for distribution and genetic structuring of O. platypus. In addition, artificial introductions of non-indigenous populations have proceeded throughout the Japanese Archipelago, indicating ongoing loss of the genetic features due to introductions or introgression. Further efforts should be made toward a comprehensive understanding of the current state of introductions of non-indigenous O. platypus populations and the potential influence of invasive populations, including loss of genetic diversity. [ABSTRACT FROM AUTHOR]

It is generally held that the right and left middle ears of mammals are acoustically isolated from each other, such that mammals must rely on neural computation to derive sound localisation cues. There are, however, some unusual species in which the middle ear cavities intercommunicate, in which case each ear might be able to act as a pressure-difference receiver. This could improve sound localisation at lower frequencies. The platypus Ornithorhynchus is apparently unique among mammals in that its tympanic cavities are widely open to the pharynx, a morphology resembling that of some non-mammalian tetrapods. The right and left middle ear cavities of certain talpid and golden moles are connected through air passages within the basicranium; one experimental study on Talpa has shown that the middle ears are indeed acoustically coupled by these means. Having a basisphenoid component to the middle ear cavity walls could be an important prerequisite for the development of this form of interaural communication. Little is known about the hearing abilities of platypus, talpid and golden moles, but their audition may well be limited to relatively low frequencies. If so, these mammals could, in principle, benefit from the sound localisation cues available to them through internally coupled ears. Whether or not they actually do remains to be established experimentally. [ABSTRACT FROM AUTHOR]

For over two centuries, the platypus ( Ornithorhynchus anatinus) has been constructed and categorized in multiple ways. An unprecedented mélange of anatomical features and physiological functions, it long remained a systematic quandary. Nevertheless, since 1797, naturalists and biologists have pursued two recurring obsessions. Investigations into platypus reproduction and lactation have focused attention largely upon females of the species. Despite its apparent admixture of avian, reptilian and mammalian characters, the platypus was soon placed as a rudimentary mammal - primitive, naïve and harmless. This article pursues a different taxonomic trajectory, concentrating on a specifically male anatomical development: the crural spur and venom gland on the hind legs. Once the defining characteristic of both the platypus and echidna ( Tachyglossus aculeatus), by 1830 this sexed spur had been largely dismissed as inactive and irrelevant. For a creature regularly depicted as a biological outlier, the systematic and evolutionary implications of platypus poison have remained largely overlooked. In Australia, however, sporadic cases of 'spiking' led to consistent homologies being remarked between the platypus crural system and the venom glands of snakes. As with its reproductive reliance upon eggs, possession of an endogenous poison suggested significant reptilian affinities, yet the platypus has rarely been classed as an advanced reptile. Indeed, ongoing uncertainty regarding the biological purpose of the male's spur has ostensibly posed a directional puzzle. As with so many of its traits, however, platypus poison has been consistently described as a redundant remnant, rather than an emergent feature indicating evolutionary advance. [ABSTRACT FROM AUTHOR]

Geographically isolated populations of freshwater fish have been introduced into conspecific native populations. One of the most representative cases is the pale chub Zacco platypus. The pale chub of Lake Biwa in western Japan has been inadvertently introduced to other waters with the release of game fish. Because they are not clearly discriminated from other populations by their morphological characteristics, the morphological detection of the colonization is not possible. Hence, a genetic analysis of fish collected from rivers of the Kanto Plain in eastern Japan, where the introduction was made, was conducted. The haplotype variety of the mitochondrial gene cytochrome b of the fish revealed the presence of two major groups of haplotypes. We concluded that one of the groups was introduced from western Japan, especially Lake Biwa, and the other was native to the Kanto Plain. The haplotypes from western Japan were established in all of the rivers studied and occurred together with the native haplotypes in the rivers within the original distribution range of the species. The allelic composition of microsatellite loci indicated that fish from the two different sources were well admixed through hybridization in the populations of the rivers of the Kanto Plain. [ABSTRACT FROM AUTHOR]

Dispersal patterns can have a major impact on the dynamics and viability of populations, and understanding these patterns is crucial to the conservation and management of a species. In this study, patterns of sex-biased dispersal and waterway/overland dispersal are investigated in the endemic Australian platypus, Ornithorhynchus anatinus, a semi-aquatic monotreme. Analyses of over 750 individuals from south-eastern Australia at 13 microsatellite loci and two mitochondrial genes, cytochrome b and cytochrome oxidase subunit II, provide genetic insight into dispersal patterns. For the first time, platypuses of western Victoria are shown to be genetically distinct from other populations of the mainland. Despite distinct morphological differentiation either side of the Great Dividing Range, populations remain genetically similar between coastal and inland areas suggesting gene flow is likely to occur across these ranges. Landscape genetic analyses indicate variability in dispersal patterns between Victorian and Tasmanian platypuses with a greater avoidance of overland travel indicated in Victoria compared to Tasmania. Females appear to remain within their natal area or return to breed, maintaining greater genetic structure in maternally inherited mitochondrial DNA in comparison to nuclear DNA and sharing genetic similarity within a short river distance (i.e. ≤1.4 km). The results of this study provide a valuable spatial framework for the management of wild platypus populations within south-eastern Australia and a baseline for future monitoring of populations that are likely to be impacted by environmental and anthropogenic change. [ABSTRACT FROM AUTHOR]

Passive electroreception is a sensory modality in many aquatic vertebrates, predominantly fishes. Using passive electroreception, the animal can detect and analyze electric fields in its environment. Most electric fields in the environment are of biogenic origin, often produced by prey items. These electric fields can be relatively strong and can be a highly valuable source of information for a predator, as underlined by the fact that electroreception has evolved multiple times independently. The only mammals that possess electroreception are the platypus ( Ornithorhynchus anatinus) and the echidnas (Tachyglossidae) from the monotreme order, and, recently discovered, the Guiana dolphin ( Sotalia guianensis) from the cetacean order. Here we review the morphology, function and origin of the electroreceptors in the two aquatic species, the platypus and the Guiana dolphin. The morphology shows certain similarities, also similar to ampullary electroreceptors in fishes, that provide cues for the search for electroreceptors in more vertebrate and invertebrate species. The function of these organs appears to be very similar. Both species search for prey animals in low-visibility conditions or while digging in the substrate, and sensory thresholds are within one order of magnitude. The electroreceptors in both species are innervated by the trigeminal nerve. The origin of the accessory structures, however, is completely different; electroreceptors in the platypus have developed from skin glands, in the Guiana dolphin, from the vibrissal system. [ABSTRACT FROM AUTHOR]

Peptide isomerase catalyses the post-translational isomerisation of the l- to the d-form of an amino acid residue around the N/ C-termini of substrate peptides. To date, some peptide isomerases have been found in a limited number of animal secretions and cells. We show here that papaya extracts have weak peptide isomerase activity. The activity was detected in each 30-100 kDa fraction of the flesh and the seed extracts of unripe and ripe papaya fruit. The definitive activity was confirmed in the ripe papaya extracts, but even then it was much less active than that of the other peptide isomerases previously reported. The activity was markedly inhibited by methanol, and partly so by amastatin and diethyl pyrocarbonate. This is the first report of peptide isomerase activity in a plant and suggests that perhaps every living organism may have some peptide isomerase activity. [ABSTRACT FROM AUTHOR]

The living monotremes (platypus and echidnas) are distinguished from therians as well as each other in part by the unusual structure of the thalamus in each. In particular, the platypus has an enlarged ventral posterior (VP) nucleus reflecting the great behavioural importance of trigeminosensation and electroreception. The embryological collections of the Museum für Naturkunde in Berlin were used to analyse the development of the dorsal thalamus and ventral thalamus (prethalamus) in both species. Prosomeric organization of the forebrain emerged at 6 mm crown-rump length (CRL), but thalamic neurogenesis did not commence until about 8-9 mm CRL. Distinctive features of the dorsal thalamus in the two species began to emerge after hatching (about 14-15 mm CRL). During the first post-hatching week, dense clusters of granular cells aggregated to form the VP of the platypus, whereas the VP complex of the echidna remained smaller and divided into distinct medial and lateral divisions. At the end of the first post-hatching week, the thalamocortical tract was much larger in the platypus than the echidna. The dorsal thalamus of the platypus is essentially adult-like by the sixth week of post-hatching life. The similar appearance of the dorsal thalamus in the two species until the time of hatching, followed by the rapid expansion of the VP in the platypus, is most consistent with ancestral platypuses having undergone changes in the genetic control of thalamic neurogenesis to produce a large VP for trigeminal electroreception after the divergence of the two lineages of monotreme. [ABSTRACT FROM AUTHOR]

Isolations were made to determine the fungal symbionts colonizing Platypus quercivorus beetle galleries of dead or dying Quercus laurifolia, Castanopsis cuspidata, Quercus serrata, Quercus crispula, and Quercus robur. For these studies, logs from oak wilt-killed trees were collected from Kyoto Prefecture, Japan. Fungi were isolated from the: (1) entrances of beetle galleries, (2) vertical galleries, (3) lateral galleries, and (4) the larval cradle of P. quercivorus in each host tree. Among the fungus colonies which appeared on YM agar plates, 1,219 were isolated as the representative isolates for fungus species inhabiting in the galleries based on their cultural characteristics. The validity of the visual classification of the fungus colonies was checked and if necessary properly corrected using microsatellite-primed PCR fingerprints. The nucleotide sequence of the D1/D2 region of the large subunit nuclear rRNA gene detected 38 fungus species (104 strains) of which three species, i.e., Candida sp. 3, Candida kashinagacola (both yeasts), and the filamentous fungus Raffaelea quercivora were isolated from all the tree species. The two yeasts were most prevalent in the interior of galleries, regardless of host tree species, suggesting their close association with the beetle. A culture-independent method, terminal restriction fragment length polymorphism (T-RFLP) analysis was also used to characterize the fungus flora of beetle galleries. T-RFLP patterns showed that yeast species belonging to the genus Ambrosiozyma frequently occurred on the gallery walls along with the two Candida species. Ours is the first report showing the specific fungi inhabiting the galleries of a platypodid ambrosia beetle. [ABSTRACT FROM AUTHOR]

striking example of the power of chromosome painting has been the resolution of the male platypus karyotype and the pairing relationships of the chain of ten sex chromosomes. We have extended our analysis to the nine sex chromosomes of the male echidna. Cross-species painting with platypus shows that the first five chromosomes in the chain are identical in both, but the order of the remainder are different and, in each species, a different autosome replaces one of the five X chromosomes. As the therian X is homologous mainly to platypus autosome 6 and echidna 16, and as SRY is absent in both, the sex determination mechanism in monotremes is currently unknown. Several of the X and Y chromosomes contain genes orthologous to those in the avian Z but the significance of this is also unknown. It seems likely that a novel testis determinant is carried by a Y chromosome common to platypus and echidna. We have searched for candidates for this determinant among the many genes known to be involved in vertebrate sex differentiation. So far fourteen such genes have been mapped, eleven are autosomal in platypus, two map to the differential regions of X chromosomes, and one maps to a pairing segment and is likewise excluded. Search for the platypus testis-determining gene continues, and the extension of comparative mapping between platypus and birds and reptiles may shed light on the ancestral origin of monotreme sex chromosomes. [ABSTRACT FROM AUTHOR]

The platypus, Ornithorhynchus anatinus is a unique, iconic mammal endemic to Australia. Despite being listed as 'common' throughout its range, platypus abundance is poorly understood. Dependence on aquatic habitats in Australia renders this species potentially vulnerable to a variety of processes including drought, climate change and habitat loss. To assist with understanding population processes, 180 individuals from Tasmania and Victoria were characterised across thirteen microsatellite loci. Large genetic differences were evident between Tasmanian and Victorian O. anatinus. Within Tasmania, high levels of allelic diversity were detected with genetic differentiation identified among some populations. Similarly, allelic diversity was high within Victorian platypuses, along with significant genetic differentiation among populations. The large genetic differences found between Tasmanian and mainland platypuses indicate long-term isolation and it is likely that the lack of past/present catchment connectedness contributes to differentiation found between populations within these regions. Understanding patterns of genetic differentiation within and between catchments will help guide future conservation management decisions for platypus. [ABSTRACT FROM AUTHOR]

Natural killer (NK) cell receptors belong to two unrelated, but functionally analogous gene families: the immunoglobulin superfamily, situated in the leukocyte receptor complex (LRC) and the C-type lectin superfamily, located in the natural killer complex (NKC). Here, we describe the largest NK receptor gene expansion seen to date. We identified 213 putative C-type lectin NK receptor homologs in the genome of the platypus. Many have arisen as the result of a lineage-specific expansion. Orthologs of OLR1, CD69, KLRE, CLEC12B, and CLEC16p genes were also identified. The NKC is split into at least two regions of the genome: 34 genes map to chromosome 7, two map to a small autosome, and the remainder are unanchored in the current genome assembly. No NK receptor genes from the LRC were identified. The massive C-type lectin expansion and lack of Ig-domain-containing NK receptors represents the most extreme polarization of NK receptors found to date. We have used this new data from platypus to trace the possible evolutionary history of the NK receptor clusters. [ABSTRACT FROM AUTHOR]

We present a draft genome sequence of the platypus, Ornithorhynchus anatinus. This monotreme exhibits a fascinating combination of reptilian and mammalian characters. For example, platypuses have a coat of fur adapted to an aquatic lifestyle; platypus females lactate, yet lay eggs; and males are equipped with venom similar to that of reptiles. Analysis of the first monotreme genome aligned these features with genetic innovations. We find that reptile and platypus venom proteins have been co-opted independently from the same gene families; milk protein genes are conserved despite platypuses laying eggs; and immune gene family expansions are directly related to platypus biology. Expansions of protein, non-protein-coding RNA and microRNA families, as well as repeat elements, are identified. Sequencing of this genome now provides a valuable resource for deep mammalian comparative analyses, as well as for monotreme biology and conservation. [ABSTRACT FROM AUTHOR]

We have examined the organization of the pretectal area in two monotremes (the short beaked echidna— Tachyglossus aculeatus, and the platypus— Ornithorhynchus anatinus) and compared it to that in the Wistar strain rat, using Nissl staining in conjunction with enzyme histochemistry (acetylcholinesterase and NADPH diaphorase) and immunohistochemistry for parvalbumin, calbindin, calretinin and non-phosphorylated neurofilament protein (SMI-32 antibody). We were able to identify distinct anterior, medial, posterior (now called tectal gray) and olivary pretectal nuclei as well as a nucleus of the optic tract, all with largely similar topographical and chemoarchitectonic features to the homologous regions in therian mammals. The positions of these pretectal nuclei correspond to the distributions of retinofugal terminals identified by other authors. The overall size of the pretectum in both monotremes was found to be at least comparable in size, if not larger than, the pretectum of representative therian mammals of similar brain and body size. Our findings suggest that the pretectum of these two monotreme species is comparable in both size and organization to that of eutherian mammals, and is more than just an undifferentiated area pretectalis. The presence of a differentiated pretectum with similar chemoarchitecture to therians in both living monotremes lends support to the idea that the stem mammal for both prototherian and therian lineages also had a differentiated pretectum. This in turn indicates that a differentiated pretectum appeared at least 125 million years ago in the mammalian lineage and that the stem mammal for proto- and eutherian lineages probably had similar pretectal nuclei to those identified in its descendants. [ABSTRACT FROM AUTHOR]

Abstract??The presence of the pale chubZacco platypus(Japanese name,Oikawa) in Taiwan has been suggested to be a result of its inadvertent introduction from Lake Biwa in Japan in the 1980s in conjunction with the Japanese Ayu,Plecoglossus altivelis altivelis, which was released several times into the Tamsui River to restock the extinct Ayu population of Taiwan. However, it is also possible thatZ. platypusis native to Taiwan and has not been previously described for reasons of its narrow range. Knowledge of the colonizing history ofZ. platypusis of considerable importance because it provides insight into the evolutionary process and, hence, impacts management decisions regarding this species in Taiwan. A portion of the mitochondrial D-loop was sequenced for 77 specimens from five populations ofZ. platypusfrom Japan and Taiwan. A total of 22 haplotypes were identified, and nucleotide divergence among haplotypes ranged from 0.20% to 2.82%. Haplotype diversity was high in all populations examined, with a range from 0.718 in the Tagiri River population to 0.909 in the Lake Biwa population. Phylogenetic and statistical parsimony analyses of the molecular data revealed a close genetic relationship between Taiwanese and JapaneseZ. platypusand supported the previous report that the TaiwaneseZ. platypusoriginated in Lake Biwa in Japan. [ABSTRACT FROM AUTHOR]

The duck-billed platypus is an extraordinary mammal. Its chromosome complement is no less extraordinary, for it includes a system in which ten sex chromosomes form an extensive meiotic chain in males. Such meiotic multiples are unprecedented in vertebrates but occur sporadically in plant and invertebrate species. In this paper, we review the evolution and formation of meiotic multiples in plants and invertebrates to try to gain insights into the origin of the platypus meiotic multiple. We describe the meiotic hurdles that translocated mammalian chromosomes face, which make longer chains disadvantageous in mammals, and we discuss how sex chromosomes and dosage compensation might have affected the evolution of sex-linked meiotic multiples. We conclude that the evolutionary conservation of the chain in monotremes, the structural properties of the translocated chromosomes and the highly accurate segregation at meiosis make the platypus system remarkably different from meiotic multiples in other species. We discuss alternative evolutionary models, which fall broadly into two categories: either the chain is the result of a sequence of translocation events from an ancestral pair of sex chromosomes (Model I) or the entire chain came into being at once by hybridization of two populations with different chromosomal rearrangements sharing monobrachial homology (Model II). [ABSTRACT FROM AUTHOR]

Complementary DNAs encoding immunoglobulin light chains were isolated from two monotreme species, Ornithorhynchus anatinus (duckbill platypus) and Tachyglossus aculeatus (echidna). The sequences of both the variable and constant regions of these clones had greater similarity to IGK than to other light chain classes and phylogenetic analyses place them squarely within the mammalian IGK group, establishing them as monotreme IGK homologues. The constant region sequences of all clones were essentially identical within each species and, along with Southern blot results, the data are consistent with a single IGKC in each species. The expressed IGKV repertoires from both platypus and echidna were randomly sampled and there appear to be at least four platypus and at least nine echidna IGKV subgroups. The IGKV subgroups are highly divergent within species, in some cases sharing as little as 57% nucleotide identity. Two of the IGKV subgroups are present in both species, so there is some degree of overlap in the germline repertoires of these two monotremes. Overall the complexity seen in platypus and echidna IGK light chains is comparable with that of other mammals considered to have high levels of germline diversity and is in contrast to what has been found so far for monotreme IGL. [ABSTRACT FROM AUTHOR]

We measured the energy requirements of platypuses foraging, diving and resting in a swim tank using flow-through respirometry. Also, walking metabolic rates were obtained from platypuses walking on a conventional treadmill. Energy requirements while foraging were found to depend on water temperature, body weight and dive duration and averaged 8.48 W kg–1. Rates for subsurface swimming averaged 6.71 W kg–1. Minimal cost of transport for subsurface swimming platypuses was 1.85 J N–1m–1 at a speed of 0.4 m s–1. Aerobic dive limit of the platypus amounted to 59 s. Metabolic rate of platypuses resting on the water surface was minimal with 3.91 W kg–1 while minimal RMR on land was 2.08 W kg–1. The metabolic rate for walking was 8.80 W kg–1 and 10.56 W kg–1 at speeds of 0.2 m s–1 and 0.3 m s–1, respectively. A formula was derived, which allows prediction of power requirements of platypuses in the wild from measurements of body weight, dive duration and water temperature. Platypuses were found to expend energy at only half the rate of semiaquatic eutherians of comparable body sizes during both walking and diving. However, costs of transport at optimal speed were in line with findings for eutherians. These patterns suggest that underwater locomotion of semiaquatic mammals have converged on very similar efficiencies despite differences in phylogeny and locomotor mode. [ABSTRACT FROM AUTHOR]

To study the emergence of the major subfamilies of serine proteases during vertebrate evolution, we present here the primary structure of four serine proteases expressed in the spleen of a monotreme, the platypus, Ornithorhynchus anatinus. Partial cDNA clones for four serine proteases were isolated by a PCR-based strategy. This strategy is based on the high level of sequence identity between various members of the large gene family of trypsin-related serine proteases, over two highly conserved regions, those of the histidine and the serine of the catalytic triad. The partial cDNA clones were used to isolate full-length or almost full-length cDNA clones for three of these proteases from a platypus spleen cDNA library. By phylogenetic analysis, these three clones were identified as being the platypus homologues of human coagulation factor X, neutrophil elastase, and a protease distantly related to the T-cell granzymes. The remaining partial clone was found to represent a close homologue of human complement factor D (adipsin). The isolation of these four clones shows that several of the major subfamilies of serine proteases had evolved as separate subfamilies long before the radiation of the major mammalian lineages of today, the monotremes, the marsupials, and the placental mammals. Upon comparison of the corresponding proteases of monotremes and eutherian mammals, the coagulation and complement proteases were shown to display a higher degree of conservation compared to the hematopoietic proteases N-elastase and the T-cell granzymes. This latter finding indicates a higher evolutionary pressure to maintain specific functions in the complement and coagulation enzymes compared to many of the hematopoietic serine proteases. [ABSTRACT FROM AUTHOR]

SUMMARY::Interspecific relationships between ayu Plecoglossus altivelis and pale chub Zacco platypus were examined in experimental streams where ayu, pale chub or both species were stocked. Ayu predominantly employed algal feeding in areas with rapid currents, whereas pale chub were omnivorous, exhibiting feeding behavior towards algae and other objects which were drifting in the currents or fell onto the water surface in areas with slow currents. Both ayu and pale chub attacked conspecifics with larger fish tending to be dominant. Pale chub never attacked ayu, but ayu occasionally attacked pale chub that invaded their territory, regardless of their body size. When ayu was present, pale chub employed algal feeding less frequently and snapped at an object on the water surface more frequently. The feeding behavior and habitat use of ayu also differed between streams where pale chub were present or absent in some periods. However, ayu and pale chub growth rates were not negatively affected by the presence of one another, presumably due to the flexible habitat use and feeding behavior of the omnivorous pale chub. [ABSTRACT FROM AUTHOR]

The relative frequencies of endocrine cells and peptidergic nerve elements in the proximal small intestine of the adult platypus were studied by immunohistochemistry. Six kinds of endocrine cells - serotonin (5-HT)-, somatostatin-, gastrin-, motilin-, cholecystokinin (CCK) and bovine pancreatic polypeptide (BPP)-immunoreactive cells - were identified in this study. These endocrine cells were found most frequently in the intestinal glands, in moderate numbers in the tubular ducts and were infrequent in the surface folds. 5-HT-immunoreactive cells were most numerous, somatostatin-, gastrin-, motilin and BPP-immunoreactive cells were moderately numerous, whereas CCK-immunoreactive cells were rare. Five kinds of neuropeptides: substance P, vasoactive intestinal polypeptide (VIP), gastrin releasing peptide (GRP), somatostatin and leuenkephalin, were detected in the intramural nerve elements. Substance P-, VIP and GRP-immunoreactive nerve fibers were found most frequently in the lamina propria mucosae of the surface folds. The relationships between the possible functions of the peptides and amine detected in this study as well as the characteristic structure of the digestive tract of the adult platypus are discussed. [ABSTRACT FROM AUTHOR]

The amino acid sequences of the α-lactalbumins of the echidna, Tachyglossus aculeatus, and the platypus, Ornithorhynchus anatinus, were compared with each other and with those of 13 eutherian and 3 marsupial species. Phylogenetic parsimony analyses, in which selected mammalian lysozymes were used as outgroups, yielded trees whose consensus indicated that the two monotremes are sister taxa to marsupials and eutherians and that the latter two clades are each other's closest relatives. The data do not support the notion of a Marsupionta (monotreme–marsupial) clade. Pairwise comparison between the α-lactalbumins yielded maximum-likelihood distances from which divergence dates were estimated on the basis of three calibration points. The distance data support the view that the echidna and platypus lineages diverged from their last common ancestor at least 50 to 57 Ma (million years ago) and that monotremes diverged from marsupials and eutherian mammals about 163 to 186 Ma. [ABSTRACT FROM AUTHOR]

The vertebrate mitochondrial genome is highly conserved in size and gene content. Among the chordates there appears to be one basic gene arrangement, but rearrangements in the mitochondrial gene order of the avian lineages have indicated that the mitochondrial genome may be more variable than once thought. Different gene orders in marsupials and eutherian mammals leave the ancestral mammalian order in some doubt. We have investigated the mitochondrial gene order in the platypus ( Ornithorhynchus anatinus), a representative of the third major group of mammals, to determine which mitochondrial gene arrangement is ancestral in mammals. We have found that the platypus mtDNA conforms to the basic chordate gene arrangement, common to fish, amphibians, and eutherian mammals, indicating that this arrangement was the original mammalian arrangement, and that the unusual rearrangements observed in the avians and marsupials are probably lineage-specific. [ABSTRACT FROM AUTHOR]

Anorganic unerupted developing teeth and airdired erupted teeth of the platypus ( Ornithorhynchus anatinus) were examined in a scanning electron microscope and in a tandem scanning reflected light microscope. Typically mammalian developing fronts of enamel and dentine were identified in the anorganic unerupted specimens. The developing teeth were particularly small and fragile and the enamel elusive and difficult to examine in the normal way for morphological detail. Prepared fractured surfaces of unerupted specimens revealed preferentially oriented crystallite groups in the enamel generally perpendicular to the developing front and a highly globular, mineralized pattern in the dentine with fine diameter, sparsely distributed dentinal tubules. Although optically homogeneous, the enamel of both developing and mature teeth displayed well-defined incremental lines, radial clefts, crystallite domains of variable size and outline, and fine tubules when examined by high contrast, back-scattered electron imaging. The enamel is prismatic only in part; well-formed, regular prisms not being a primary feature of platypus enamel. This can be related to the variability inherent in the developing surface and the thinness of the enamel layer. No surface was found which could be confidently identified as cementum; those developing surfaces not covered by enamel displaying small calcospherites which elsewhere marked the outer aspect of the dentine. [ABSTRACT FROM AUTHOR]

Two diploid platypus cell lines, designated Oa-1F and Oa-2F, have been derived from the toe webs of two females. The development and growth characteristics of the lines are described and G-banded karyotypes presented (the first reported for the platypus). The availability of these lines will greatly facilitate chromosome and gene mapping studies of the platypus and permit the extension of comparative studies of mammalian chromosome and genome evolution to the monotremes. [ABSTRACT FROM AUTHOR]

Twelve compound microsatellite loci were isolated from the ambrosia beetle Platypus quercivorus. Every locus was polymorphic among 50 individuals from two localities, with two to six alleles per locus, without linkage disequilibrium. The observed and expected heterozygosities ranged from 0.140 to 0.740 and from 0.255 to 0.731, respectively. These markers will be available for population genetic studies and parentage analysis of this beetle. [ABSTRACT FROM AUTHOR]

The article highlights several studies which have revealed that the mixture of mammalian and reptilian characteristics of the platypus are reflected at the genomic level. It relates that genomic sequencing of platypus genome shows that the X and Y chromosomes of the platypus have extensive homology to bird sex chromosomes, but unrelated to the sex chromosomes of other mammals. It notes that the studies also provide new evolutionary insights into the diversity and function of small RNAs.

The article reports on the discovery concerning the study of the draft sequence of the platypus genome conducted by researcher Wesley Warren of Washington University in St Louis, Missouri. The study revealed reptilian and mammalian elements found in the platypus genome and provides more evidence for its place in animal evolution. Moreover, the structure of the platypus genome has brought out new clues to how mammals evolved. According to Warren, the analysis is beginning to align these strange features with genetic innovation.

Focuses on the report of an Australian Aboriginal legend that the platypus is the offspring of a duck and a water-rat, with a duck-like bill and webbed toes, but four feet and fur like a rat. Classification of platypus according to phylogenetic studies; Studies conducted of platypus male reproductive cells undergoing meiosis.

Discusses research being done on the chromosome system of platypuses. Reference to a study by Frank Grützner and colleagues published in the same issue; Number of pairs of sex chromosomes obtained from platypuses; Use of chromosome painting and comparative genetics to determine chromosome arrangement; Features of platypus chromosomes.