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Horizontal transfer of transposable elements (TEs) is an important mechanism contributing to genetic diversity and innovation. Bats (order Chiroptera) have repeatedly been shown to experience horizontal transfer of TEs at what appears to be a high rate compared with other mammals. We investigated the occurrence of horizontally transferred (HT) DNA transposons involving bats. We found over 200 putative HT elements within bats; 16 transposons were shared across distantly related mammalian clades, and 2 other elements were shared with a fish and two lizard species. Our results indicate that bats are a hotspot for horizontal transfer of DNA transposons. These events broadly coincide with the diversification of several bat clades, supporting the hypothesis that DNA transposon invasions have contributed to genetic diversification of bats.

Horizontal transfer of transposable elements (TEs) is an important mechanism contributing to genetic diversity and innovation. Bats (order Chiroptera) have repeatedly been shown to experience horizontal transfer of TEs at what appears to be a high rate compared with other mammals. We investigated the occurrence of horizontally transferred (HT) DNA transposons involving bats. We found over 200 putative HT elements within bats; 16 transposons were shared across distantly related mammalian clades, and 2 other elements were shared with a fish and two lizard species. Our results indicate that bats are a hotspot for horizontal transfer of DNA transposons. These events broadly coincide with the diversification of several bat clades, supporting the hypothesis that DNA transposon invasions have contributed to genetic diversification of bats.

Horizontal transfer of transposable elements (TEs) is an important mechanism contributing to genetic diversity and innovation. Bats (order Chiroptera) have repeatedly been shown to experience horizontal transfer of TEs at what appears to be a high rate compared with other mammals. We investigated the occurrence of horizontally transferred (HT) DNA transposons involving bats. We found over 200 putative HT elements within bats; 16 transposons were shared across distantly related mammalian clades, and 2 other elements were shared with a fish and two lizard species. Our results indicate that bats are a hotspot for horizontal transfer of DNA transposons. These events broadly coincide with the diversification of several bat clades, supporting the hypothesis that DNA transposon invasions have contributed to genetic diversification of bats.

Horizontal transfer of transposable elements (TEs) is an important mechanism contributing to genetic diversity and innovation. Bats (order Chiroptera) have repeatedly been shown to experience horizontal transfer of TEs at what appears to be a high rate compared with other mammals. We investigated the occurrence of horizontally transferred (HT) DNA transposons involving bats. We found over 200 putative HT elements within bats; 16 transposons were shared across distantly related mammalian clades, and 2 other elements were shared with a fish and two lizard species. Our results indicate that bats are a hotspot for horizontal transfer of DNA transposons. These events broadly coincide with the diversification of several bat clades, supporting the hypothesis that DNA transposon invasions have contributed to genetic diversification of bats.

Horizontal transfer of transposable elements (TEs) is an important mechanism contributing to genetic diversity and innovation. Bats (order Chiroptera) have repeatedly been shown to experience horizontal transfer of TEs at what appears to be a high rate compared with other mammals. We investigated the occurrence of horizontally transferred (HT) DNA transposons involving bats. We found over 200 putative HT elements within bats; 16 transposons were shared across distantly related mammalian clades, and 2 other elements were shared with a fish and two lizard species. Our results indicate that bats are a hotspot for horizontal transfer of DNA transposons. These events broadly coincide with the diversification of several bat clades, supporting the hypothesis that DNA transposon invasions have contributed to genetic diversification of bats.

Egg-laying mammals (monotremes) are a sister Glade of therians (placental mammals and marsupials) and a key Glade 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 beta-glucosides, which are feeding deterrents in plants and insects. These results suggest that the ability to detect beta-glucosides and other substances might be shared and ancestral among mammals.

Egg-laying mammals (monotremes) are a sister Glade of therians (placental mammals and marsupials) and a key Glade 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 beta-glucosides, which are feeding deterrents in plants and insects. These results suggest that the ability to detect beta-glucosides and other substances might be shared and ancestral among mammals.

To monitor biodiversity effectively, accurate and sensitive detection methods that can be implemented over large spatial scales are required. It has been demonstrated that environmental DNA (eDNA) sampling can be a valid alternative to many traditional sampling methods. This thesis explored the data and conclusions which could be drawn from eDNA sampling regimes across large spatial scales for individual species and communities, answering key questions on species occupancy and detection method sensitivity. Adaptations of site occupancy-detection models (SODM) are used throughout. First, I investigated the relative sensitivity of single- and multi-species detection methods using a consistent methodological framework across multiple datasets with different study designs. I used SODM to evaluate how the molecular method used impacted the probability that a species was detected. I found that qPCR was generally more sensitive at detecting target species but that different methodological decisions impacted its sensitivity. Second, I used eDNA sampling to conduct an extensive platypus occupancy survey across 37% of the species’ estimated distribution. Using a systematic study design, I demonstrated that correlates of platypus occupancy could be revealed using this efficient survey method. I found that platypuses were less likely to occupy sites in areas with a high proportion of surrounding agricultural land or grasslands and were more likely to occupy sites with increased runoff, less zero-flow days, and suitable banks for burrowing. Third, the 2019/2020 mega-fires impacted south-eastern Australia severely. My pre-fire eDNA data provided the opportunity to investigate if platypus occupancy was impacted by this large-scale event. I developed a SODM extension to incorporate a Before-After Control-impact (BACI) design. After surveying 118 sites in three time periods (pre-fire, 2020 and 2021), I found that platypus occupancy was not significantly impacted by the presence of f

Egg-laying mammals (monotremes) are a sister Glade of therians (placental mammals and marsupials) and a key Glade 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 beta-glucosides, which are feeding deterrents in plants and insects. These results suggest that the ability to detect beta-glucosides and other substances might be shared and ancestral among mammals.

Egg-laying mammals (monotremes) are a sister Glade of therians (placental mammals and marsupials) and a key Glade 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 beta-glucosides, which are feeding deterrents in plants and insects. These results suggest that the ability to detect beta-glucosides and other substances might be shared and ancestral among mammals.

[Resumo]: A electrorrecepción pasiva é unha modalidade sensorial que fai uso da recepción de impulsos eléctricos para localizar ás presas, así como para situarse no espazo. É unha capacidade restrinxida a animais acuáticos, tales como peixes e anfibios, os cales durante a súa evolución desenvolveron receptores sensoriais denominados electrorreceptores (situados na pel) para detectar os campos eléctricos externos. No taxón dos peixes (e, máis concretamente, nos elasmobranquios) esta habilidade está moi estendida. Sen embargo, os monotremas son os únicos mamíferos coñecidos que a posúen. Dentro deste grupo, destacarase ao ornitorrinco semiacuático (Ornithorhynchus anatinus). Neste traballo realízase unha revisión bibliográfica para describir os mecanismos electrorreceptivos dos tiburóns e ornitorrincos, co obxectivo de poder establecer unhas similitudes e/ou diferenzas entre ambos. Para isto, analízanse aspectos como o número de electrorreceptores e a súa distribución, a súa orixe e evolución, os procesos de detección e integración do sinal eléctrico, así como as posibles adaptacións do comportamento para a utilización desta información electrosensorial. Estas características estúdanse mediante a análise de experimentos levados a cabo por distintos autores dende que foi descrita a electrorrecepción pasiva por primeira vez., [Resumen]: La electrorrecepción pasiva es una modalidad sensorial que hace uso de la recepción de impulsos eléctricos para localizar a las presas, así como para situarse en el espacio. Es una capacidad restringida a animales acuáticos, tales como peces y anfibios, los cuales durante su evolución desarrollaron receptores sensoriales denominados electrorreceptores (situados en la piel) para detectar los campos eléctricos externos. En el taxón de los peces (y, más concretamente, en elasmobranquios) esta habilidad está muy extendida. Sin embargo, los monotremas son los únicos mamíferos conocidos que la poseen. Dentro de este grupo, se destaca al ornitorrinco semiacuático (Ornithorhynchus anatinus). En este trabajo se realiza una revisión bibliográfica para describir los mecanismos electrorreceptivos de los tiburones y ornitorrincos, con el objetivo de poder establecer unas similitudes y/o diferencias entre ambos. Para esto, se analizan aspectos como el número de electrorreceptores y su distribución, su origen y evolución, los procesos de detección e integración de la señal eléctrica, así como las posibles adaptaciones del comportamiento para la utilización de esta información electrosensorial. Estas características se estudian mediante el análisis de experimentos llevados a cabo por distintos autores desde que fue descrita la electrorrecepción por primera vez., [Abstract]: Passive electroreception is a sensory modality that makes use of the reception of electrical impulses to locate prey, as well as to position itself in space. It is a capability restricted to aquatic animals, such as fish and amphibians, which during their evolution developed sensory receptors called electroreceptors (located in the skin) to detect external electric fields. In the fish taxon (and, more specifically, in elasmobranchs) this ability is widespread. However, monotremes are the only mammals known to possess it. Within this group, the semi – aquatic platypus (Ornithorhynchus anatinus) stands out. In this work, a bibliographic review is carried out to describe the electroreceptive mechanisms of sharks and platypuses, with the aim of establishing similarities and/or differences between them. For this purpose, aspects such as the number of electroreceptors and their distribution, their origin and evolution, the processes of detection and integration of the electrical signal, as well as the possible behavioral adaptations for the use of this electrosensory information are analyzed. These characteristics are studied by analyzing experiments carried out by different authors since electroreception was first described.

Egg-laying mammals (monotremes) are the only extant mammalian outgroup to therians (marsupial and eutherian animals) and provide key insights into mammalian evolution1,2. Here we generate and analyse reference genomes of the platypus (Ornithorhynchus anatinus) and echidna (Tachyglossus aculeatus), which represent the only two extant monotreme lineages. The nearly complete platypus genome assembly has anchored almost the entire genome onto chromosomes, markedly improving the genome continuity and gene annotation. Together with our echidna sequence, the genomes of the two species allow us to detect the ancestral and lineage-specific genomic changes that shape both monotreme and mammalian evolution. We provide evidence that the monotreme sex chromosome complex originated from an ancestral chromosome ring configuration. The formation of such a unique chromosome complex may have been facilitated by the unusually extensive interactions between the multi-X and multi-Y chromosomes that are shared by the autosomal homologues in humans. Further comparative genomic analyses unravel marked differences between monotremes and therians in haptoglobin genes, lactation genes and chemosensory receptor genes for smell and taste that underlie the ecological adaptation of monotremes.

Mast cells (MCs) are inflammatory cells primarily found in tissues in close contact with the external environment, such as the skin and the intestinal mucosa. They store large amounts of active components in cytoplasmic granules, ready for rapid release. The major protein content of these granules is proteases, which can account for up to 35 % of the total cellular protein. Depending on their primary cleavage specificity, they can generally be subdivided into chymases and tryptases. Here we present the extended cleavage specificities of two such proteases from the platypus. Both of them show an extended chymotrypsin-like specificity almost identical to other mammalian MC chymases. This suggests that MC chymotryptic enzymes have been conserved, both in structure and extended cleavage specificity, for more than 200 million years, indicating major functions in MC-dependent physiological processes. We have also studied a third closely related protease, originating from the same chymase locus whose cleavage specificity is closely related to the apoptosis-inducing protease from cytotoxic T cells, granzyme B. The presence of both a chymase and granzyme B in all studied mammals indicates that these two proteases bordering the locus are the founding members of this locus.

Mast cells (MCs) are inflammatory cells primarily found in tissues in close contact with the external environment, such as the skin and the intestinal mucosa. They store large amounts of active components in cytoplasmic granules, ready for rapid release. The major protein content of these granules is proteases, which can account for up to 35 % of the total cellular protein. Depending on their primary cleavage specificity, they can generally be subdivided into chymases and tryptases. Here we present the extended cleavage specificities of two such proteases from the platypus. Both of them show an extended chymotrypsin-like specificity almost identical to other mammalian MC chymases. This suggests that MC chymotryptic enzymes have been conserved, both in structure and extended cleavage specificity, for more than 200 million years, indicating major functions in MC-dependent physiological processes. We have also studied a third closely related protease, originating from the same chymase locus whose cleavage specificity is closely related to the apoptosis-inducing protease from cytotoxic T cells, granzyme B. The presence of both a chymase and granzyme B in all studied mammals indicates that these two proteases bordering the locus are the founding members of this locus.

Mast cells (MCs) are inflammatory cells primarily found in tissues in close contact with the external environment, such as the skin and the intestinal mucosa. They store large amounts of active components in cytoplasmic granules, ready for rapid release. The major protein content of these granules is proteases, which can account for up to 35 % of the total cellular protein. Depending on their primary cleavage specificity, they can generally be subdivided into chymases and tryptases. Here we present the extended cleavage specificities of two such proteases from the platypus. Both of them show an extended chymotrypsin-like specificity almost identical to other mammalian MC chymases. This suggests that MC chymotryptic enzymes have been conserved, both in structure and extended cleavage specificity, for more than 200 million years, indicating major functions in MC-dependent physiological processes. We have also studied a third closely related protease, originating from the same chymase locus whose cleavage specificity is closely related to the apoptosis-inducing protease from cytotoxic T cells, granzyme B. The presence of both a chymase and granzyme B in all studied mammals indicates that these two proteases bordering the locus are the founding members of this locus.

Platypuses are evolutionarily and morphologically unique, making them one of the world’s most iconic animals. Due to their cryptic, nocturnal nature, they are notoriously difficult to study in the wild, limiting knowledge of their distribution, ecology, and behaviour, hindering effective assessments of decline and status. Recently, studies have suggested declines resulting from a range of threats, but despite their distribution overlapping Australia’s most regulated rivers, the impacts of dams remains relatively unstudied. In my thesis, I aimed to address specific knowledge gaps for platypuses, assessing potential past and present distribution, the impact of dams, and their movement behaviours. Chapter one highlights ongoing species declines and provides insight into the life history of the platypus. In my second chapter, I compiled the most comprehensive database on the distribution and abundance of platypus, which allowed me to identify potential declines in range and number. The inclusion of historical data highlighted how shifting baselines have changed perspectives on platypus abundance, impacting perceptions on the magnitude of decline. For Chapters 3 – 5, I examined impacts of large dams and river regulation by surveying upstream and downstream of dams, and on adjacent unregulated rivers, and tracked movement of platypuses downstream of dams. In Chapter 3 I examined population dynamics, finding populations downstream of dams with significantly altered flow regimes had lower abundances and densities of platypuses than above dams, while the opposite was true for rivers where flow regimes had been improved. In Chapter 4, movement tracking highlighted interactions among individuals in a localised pool and revealed no detrimental impacts of an environmental flow on the Snowy River. Long-term movement analysis on regulated rivers in Chapter 5 suggested platypus have restricted movements, with implications for declining populations, given areas of decline are unlike

Mast cells (MCs) are inflammatory cells primarily found in tissues in close contact with the external environment, such as the skin and the intestinal mucosa. They store large amounts of active components in cytoplasmic granules, ready for rapid release. The major protein content of these granules is proteases, which can account for up to 35 % of the total cellular protein. Depending on their primary cleavage specificity, they can generally be subdivided into chymases and tryptases. Here we present the extended cleavage specificities of two such proteases from the platypus. Both of them show an extended chymotrypsin-like specificity almost identical to other mammalian MC chymases. This suggests that MC chymotryptic enzymes have been conserved, both in structure and extended cleavage specificity, for more than 200 million years, indicating major functions in MC-dependent physiological processes. We have also studied a third closely related protease, originating from the same chymase locus whose cleavage specificity is closely related to the apoptosis-inducing protease from cytotoxic T cells, granzyme B. The presence of both a chymase and granzyme B in all studied mammals indicates that these two proteases bordering the locus are the founding members of this locus.

Umberto Eco’s A Theory of Semiotics has a notion of sign which Eco himself seems to have overlooked or omitted, not only through this book´s pages, but also along those of Kant and the Platypus. In my opinion, this omission has prevented Eco from satisfactorily solving most of the semiotic problems posed in both works by him. Thus, this paper starts by tackling some contradictions in that notion of sign to later apply the conclusions to those aforementioned semiotic problems in an attempt to find correct solutions for them., El Tratado de Semiótica General posee una noción de signo que el mismo Umberto Eco parece haber olvidado u omitido tanto a lo largo de aquellas páginas como en las de Kant y el Ornitorrinco. Según mi juicio, esa omisión no le ha permitido a Eco resolver satisfactoriamente muchos de los problemas semióticos que plantea en ambas obras. Por ende, comienzo este artículo salvando algunas contradicciones de aquella noción de signo para luego aplicarlas a esos problemas semióticos y así intentar arribar a su resolución satisfactoria.

Umberto Eco’s A Theory of Semiotics has a notion of sign which Eco himself seems to have overlooked or omitted, not only through this book´s pages, but also along those of Kant and the Platypus. In my opinion, this omission has prevented Eco from satisfactorily solving most of the semiotic problems posed in both works by him. Thus, this paper starts by tackling some contradictions in that notion of sign to later apply the conclusions to those aforementioned semiotic problems in an attempt to find correct solutions for them., El Tratado de Semiótica General posee una noción de signo que el mismo Umberto Eco parece haber olvidado u omitido tanto a lo largo de aquellas páginas como en las de Kant y el Ornitorrinco. Según mi juicio, esa omisión no le ha permitido a Eco resolver satisfactoriamente muchos de los problemas semióticos que plantea en ambas obras. Por ende, comienzo este artículo salvando algunas contradicciones de aquella noción de signo para luego aplicarlas a esos problemas semióticos y así intentar arribar a su resolución satisfactoria.

Mast cells (MCs) are inflammatory cells primarily found in tissues in close contact with the external environment, such as the skin and the intestinal mucosa. They store large amounts of active components in cytoplasmic granules, ready for rapid release. The major protein content of these granules is proteases, which can account for up to 35 % of the total cellular protein. Depending on their primary cleavage specificity, they can generally be subdivided into chymases and tryptases. Here we present the extended cleavage specificities of two such proteases from the platypus. Both of them show an extended chymotrypsin-like specificity almost identical to other mammalian MC chymases. This suggests that MC chymotryptic enzymes have been conserved, both in structure and extended cleavage specificity, for more than 200 million years, indicating major functions in MC-dependent physiological processes. We have also studied a third closely related protease, originating from the same chymase locus whose cleavage specificity is closely related to the apoptosis-inducing protease from cytotoxic T cells, granzyme B. The presence of both a chymase and granzyme B in all studied mammals indicates that these two proteases bordering the locus are the founding members of this locus.

The transient receptor potential vanilloid 1 (TRPV1) ion channel is a prototypical molecular sensor for noxious heat in mammals. Its role in sustained heat response remains poorly understood, because rapid heat-induced desensitization (Dh) follows tightly heat-induced activation (Ah). To understand the physiological role and structural basis of Dh, we carried out a comparative study of TRPV1 channels in mouse (mV1) and those in platypus (pV1), which naturally lacks Dh. Here we show that a temperature-sensitive interaction between the N- and C-terminal domains of mV1 but not pV1 drives a conformational rearrangement in the pore leading to Dh. We further show that knock-in mice expressing pV1 sensed heat normally but suffered scald damages in a hot environment. Our findings suggest that Dh evolved late during evolution as a protective mechanism and a delicate balance between Ah and Dh is crucial for mammals to sense and respond to noxious heat.

The end-Permian mass extinction (EPME) led to reorganization of marine predatory communities, through introduction of air-breathing top predators, such as marine reptiles. We report two new specimens of one such marine reptile, Eretmorhipis carrolldongi, from the Lower Triassic of Hubei, China, revealing superficial convergence with the modern duckbilled platypus (Ornithorhynchus anatinus), a monotreme mammal. Apparent similarities include exceptionally small eyes relative to the body, snout ending with crura with a large internasal space, housing a bone reminiscent of os paradoxum, a mysterious bone of platypus, and external grooves along the crura. The specimens also have a rigid body with triangular bony blades protruding from the back. The small eyes likely played reduced roles during foraging in this animal, as with extant amniotes (group containing mammals and reptiles) with similarly small eyes. Mechanoreceptors on the bill of the animal were probably used for prey detection instead. The specimens represent the oldest record of amniotes with extremely reduced visual capacity, utilizing non-visual cues for prey detection. The discovery reveals that the ecological diversity of marine predators was already high in the late Early Triassic, and challenges the traditional view that the ecological diversification of marine reptiles was delayed following the EPME.

The end-Permian mass extinction (EPME) led to reorganization of marine predatory communities, through introduction of air-breathing top predators, such as marine reptiles. We report two new specimens of one such marine reptile, Eretmorhipis carrolldongi, from the Lower Triassic of Hubei, China, revealing superficial convergence with the modern duckbilled platypus (Ornithorhynchus anatinus), a monotreme mammal. Apparent similarities include exceptionally small eyes relative to the body, snout ending with crura with a large internasal space, housing a bone reminiscent of os paradoxum, a mysterious bone of platypus, and external grooves along the crura. The specimens also have a rigid body with triangular bony blades protruding from the back. The small eyes likely played reduced roles during foraging in this animal, as with extant amniotes (group containing mammals and reptiles) with similarly small eyes. Mechanoreceptors on the bill of the animal were probably used for prey detection instead. The specimens represent the oldest record of amniotes with extremely reduced visual capacity, utilizing non-visual cues for prey detection. The discovery reveals that the ecological diversity of marine predators was already high in the late Early Triassic, and challenges the traditional view that the ecological diversification of marine reptiles was delayed following the EPME.

The transient receptor potential vanilloid 1 (TRPV1) ion channel is a prototypical molecular sensor for noxious heat in mammals. Its role in sustained heat response remains poorly understood, because rapid heat-induced desensitization (Dh) follows tightly heat-induced activation (Ah). To understand the physiological role and structural basis of Dh, we carried out a comparative study of TRPV1 channels in mouse (mV1) and those in platypus (pV1), which naturally lacks Dh. Here we show that a temperature-sensitive interaction between the N- and C-terminal domains of mV1 but not pV1 drives a conformational rearrangement in the pore leading to Dh. We further show that knock-in mice expressing pV1 sensed heat normally but suffered scald damages in a hot environment. Our findings suggest that Dh evolved late during evolution as a protective mechanism and a delicate balance between Ah and Dh is crucial for mammals to sense and respond to noxious heat.

All biology only makes sense when seen in the light of evolution, and this is especially true for the nervous system.

My dissertation is about the fascinating Australian mammals, platypus and echidna milk components function and milk production. I have investigated the platypus and echidna milk proteins and miRNAs that involved in protection or development of the immature monotreme hatchlings, and investigated the hormonal control of monotreme milk production.

Monotremes (platypus and echidna) are the descendants of the oldest ancestor of all extant mammals distinguished from other mammals by mode of reproduction. Monotremes lay eggs following a short gestation period and after an even briefer incubation period, altricial hatchlings are nourished over a long lactation period with milk secreted by nipple-less mammary patches located on the female's abdomen. Milk is the sole source of nutrition and immune protection for the developing young until weaning. Using transcriptome and mass spectrometry analysis of milk cells and milk proteins, respectively, a novel Monotreme Lactation Protein (MLP) was identified as a major secreted protein in milk. We show that platypus and short-beaked echidna MLP genes show significant homology and are unique to monotremes. The MLP transcript was shown to be expressed in a variety of tissues; however, highest expression was observed in milk cells and was expressed constitutively from early to late lactation. Analysis of recombinant MLP showed that it is an N-linked glycosylated protein and biophysical studies predicted that MLP is an amphipathic, α-helical protein, a typical feature of antimicrobial proteins. Functional analysis revealed MLP antibacterial activity against both opportunistic pathogenic Staphylococcus aureus and commensal Enterococcus faecalis bacteria but showed no effect on Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Salmonella enterica. Our data suggest that MLP is an evolutionarily ancient component of milk-mediated innate immunity absent in other mammals. We propose that MLP evolved specifically in the monotreme lineage supporting the evolution of lactation in these species to provide bacterial protection, at a time when mammals lacked nipples.

X chromosome inactivation in eutherian mammals has been thought to be tightly controlled, as expected from a mechanism that compensates for the different dosage of X-borne genes in XX females and XY males. However, many X genes escape inactivation in humans, inactivation of the X in marsupials is partial, and the unrelated sex chromosomes of monotreme mammals have incomplete and gene-specific inactivation of X-linked genes. The bird ZW sex chromosome system represents a third independently evolved amniote sex chromosome system with dosage compensation, albeit partial and gene-specific, via an unknown mechanism (i.e. upregulation of the single Z in females, down regulation of one or both Zs in males, or a combination). We used RNA-fluorescent in situ hybridization (RNA-FISH) to demonstrate, on individual fibroblast cells, inactivation of 11 genes on the chicken Z and 28 genes on the X chromosomes of platypus. Each gene displayed a reproducible frequency of 1Z/1X-active and 2Z/2X-active cells in the homogametic sex. Our results indicate that the probability of inactivation is controlled on a gene-by-gene basis (or small domains) on the chicken Z and platypus X chromosomes. This regulatory mechanism must have been exapted independently to the non-homologous sex chromosomes in birds and mammals in response to an over-expressed Z or X in the homogametic sex, highlighting the universal importance that (at least partial) silencing plays in the evolution on amniote dosage compensation and, therefore, the differentiation of sex chromosomes.

The semi-aquatic platypus, Ornithorhynchus anatinus, is endemic to Australia. It is widespread throughout waterways along the east coast of Australia with a distribution extending as far north as Cooktown in Queensland to Tasmania in the south. The platypus is one of the last extant monotremes and the only member of its family. Consequently, it is of great evolutionary significance. In addition, its status as an Australian icon and a flagship species make the platypus worthy of conservation attention. This study aims to increase our knowledge of the population ecology and genetics of the species. I investigate the variation that exists among platypus populations, both morphologically and genetically. Large variation in body size is detected throughout the species’ entire geographic range and even across a relatively small geographic scale. Bergmann’s cline is shown to exist in the species with larger body size evident in the cooler regions to the south. Variability inconsistent with this latitudinal cline was shown to exist, however, with significant variation in platypus body size detected either side of the Great Dividing Range on the mainland. Associations with rainfall variables revealed larger-sized individuals were typically found in lower rainfall environments. This variation in body size reveals some clear associations with environmental variables worthy of further investigation. Following the isolation of thirteen microsatellite loci and sequencing of two partial mitochondrial DNA (mtDNA) genes, significant genetic differentiation was detected among platypus populations of southeastern Australia. Tasmanian individuals revealed clear genetic divergence from mainland individuals displaying a high frequency of unique microsatellite alleles and a minimum of 2.9% sequence divergence at mtDNA sequences. On the mainland, western Victoria was shown to be genetically divergent from the rest of the state with further genetic partitioning evident among regions of New

To trace the emergence of modern IgA isotypes during vertebrate evolution we have studied the immunoglobulin repertoire of a model monotreme, the platypus. Two highly divergent IgA-like isotypes (IgA1 and IgA2) were identified and their primary structures were determined from full-length cDNAs. A comparative analysis of the amino acid sequences for IgA from various animal species showed that the two platypus IgA isotypes form a branch clearly separated from their eutherian (placental) counterparts. However, they still conform to the general structure of eutherian IgA, with a hinge region and three constant domains. This indicates that the deletion of the second domain and the formation of a hinge region in IgA did occur very early during mammalian evolution, more than 166 million years ago. The two IgA isotypes in platypus differ in primary structure and appear to have arisen from a very early gene duplication, possibly preceding the metatherian eutherian split. Interestingly, one of these isotypes, IgA1, appears to be expressed in only the platypus, but is present in the echidna based on Southern blot analysis. The platypus may require a more effective mucosal immunity, with two highly divergent IgA forms, than the terrestrial echidna, due to its lifestyle, where it is exposed to pathogens both on land and in the water.

The platypus epididymal proteome is being studied because epididymal proteins are essential for male fertility in mammals and it is considered that knowledge of the epididymal proteome in an early mammal would be informative in assessing the convergence and divergence of proteins that are important in the function of the mammalian epididymis. Few of the epididymal proteins that have been identified in eutherian mammals were found in platypus caudal epididymal fluid, and the major epididymal proteins in the platypus (PXN-FBPL, SPARC and E-OR20) have never been identified in the epididymis of any other mammal.

The platypus epididymal proteome is being studied because epididymal proteins are essential for male fertility in mammals and it is considered that knowledge of the epididymal proteome in an early mammal would be informative in assessing the convergence and divergence of proteins that are important in the function of the mammalian epididymis. Few of the epididymal proteins that have been identified in eutherian mammals were found in platypus caudal epididymal fluid, and the major epididymal proteins in the platypus (PXN-FBPL, SPARC and E-OR20) have never been identified in the epididymis of any other mammal.

The platypus epididymal proteome is being studied because epididymal proteins are essential for male fertility in mammals and it is considered that knowledge of the epididymal proteome in an early mammal would be informative in assessing the convergence and divergence of proteins that are important in the function of the mammalian epididymis. Few of the epididymal proteins that have been identified in eutherian mammals were found in platypus caudal epididymal fluid, and the major epididymal proteins in the platypus (PXN-FBPL, SPARC and E-OR20) have never been identified in the epididymis of any other mammal.

BACKGROUND Sex-determining systems have evolved independently in vertebrates. Placental mammals and marsupials have an XY system, birds have a ZW system. Reptiles and amphibians have different systems, including temperature-dependent sex determination, and XY and ZW systems that differ in origin from birds and placental mammals. Monotremes diverged early in mammalian evolution, just after the mammalian clade diverged from the sauropsid clade. Our previous studies showed that male platypus has five X and five Y chromosomes, no SRY, and DMRT1 on an X chromosome. In order to investigate monotreme sex chromosome evolution, we performed a comparative study of platypus and echidna by chromosome painting and comparative gene mapping. RESULTS Chromosome painting reveals a meiotic chain of nine sex chromosomes in the male echidna and establishes their order in the chain. Two of those differ from those in the platypus, three of the platypus sex chromosomes differ from those of the echidna and the order of several chromosomes is rearranged. Comparative gene mapping shows that, in addition to bird autosome regions, regions of bird Z chromosomes are homologous to regions in four platypus X chromosomes, that is, X1, X2, X3, X5, and in chromosome Y1. CONCLUSION Monotreme sex chromosomes are easiest to explain on the hypothesis that autosomes were added sequentially to the translocation chain, with the final additions after platypus and echidna divergence. Genome sequencing and contig anchoring show no homology yet between platypus and therian Xs; thus, monotremes have a unique XY sex chromosome system that shares some homology with the avian Z.

Antibodies are a central part of the immune defense system, and a large variability in their specificity is needed in order to be able to react against all possible foreign substances we may encounter during our lives. In this thesis, results are presented from investigations into how an egg-laying mammal, the Australian duck-billed platypus (Ornithorhynchus anatinus) creates antibody variability. Our results show that despite the lack of many V gene families the antibody repertoire in the platypus seems to be well developed. A long and highly variable complementarity-determining region (CDR) 3 compensates for the limited germline diversity. Interestingly, the presence of additional cysteine residues in the CDRs may form stabilizing disulfide bridges in the antigen binding loops and thereby increasing the affinity of the antibody-antigen interaction. Although the immune system is necessary for survival, it must be strictly controlled since it may otherwise over-react and cause more harm than benefits. Allergies and autoimmune diseases are examples of such over-reactions by the immune system. Allergies are increasing in the western world and have become one of the main medical issues of the 21st century. IgE is the central mediator in atopic allergies such as hay fever, eczema and asthma; it is therefore a prime target in the development of allergen-independent preventative treatments. Here we present results from several studies of a novel vaccine strategy aimed at reducing the levels of IgE antibodies. The vaccine results in the induction of anti-IgE antibodies, and the skin reactivity upon allergen challenge was significantly reduced in vaccinated animals. Our results suggest that active immunization against IgE has the potential to become a therapeutic method for humans. In addition, an evaluation of possible adjuvants that could be used as immune stimulators and thus help break self-tolerance at the time of vaccination is presented.

Antibodies are a central part of the immune defense system, and a large variability in their specificity is needed in order to be able to react against all possible foreign substances we may encounter during our lives. In this thesis, results are presented from investigations into how an egg-laying mammal, the Australian duck-billed platypus (Ornithorhynchus anatinus) creates antibody variability. Our results show that despite the lack of many V gene families the antibody repertoire in the platypus seems to be well developed. A long and highly variable complementarity-determining region (CDR) 3 compensates for the limited germline diversity. Interestingly, the presence of additional cysteine residues in the CDRs may form stabilizing disulfide bridges in the antigen binding loops and thereby increasing the affinity of the antibody-antigen interaction. Although the immune system is necessary for survival, it must be strictly controlled since it may otherwise over-react and cause more harm than benefits. Allergies and autoimmune diseases are examples of such over-reactions by the immune system. Allergies are increasing in the western world and have become one of the main medical issues of the 21st century. IgE is the central mediator in atopic allergies such as hay fever, eczema and asthma; it is therefore a prime target in the development of allergen-independent preventative treatments. Here we present results from several studies of a novel vaccine strategy aimed at reducing the levels of IgE antibodies. The vaccine results in the induction of anti-IgE antibodies, and the skin reactivity upon allergen challenge was significantly reduced in vaccinated animals. Our results suggest that active immunization against IgE has the potential to become a therapeutic method for humans. In addition, an evaluation of possible adjuvants that could be used as immune stimulators and thus help break self-tolerance at the time of vaccination is presented.

Antibodies are a central part of the immune defense system, and a large variability in their specificity is needed in order to be able to react against all possible foreign substances we may encounter during our lives. In this thesis, results are presented from investigations into how an egg-laying mammal, the Australian duck-billed platypus (Ornithorhynchus anatinus) creates antibody variability. Our results show that despite the lack of many V gene families the antibody repertoire in the platypus seems to be well developed. A long and highly variable complementarity-determining region (CDR) 3 compensates for the limited germline diversity. Interestingly, the presence of additional cysteine residues in the CDRs may form stabilizing disulfide bridges in the antigen binding loops and thereby increasing the affinity of the antibody-antigen interaction. Although the immune system is necessary for survival, it must be strictly controlled since it may otherwise over-react and cause more harm than benefits. Allergies and autoimmune diseases are examples of such over-reactions by the immune system. Allergies are increasing in the western world and have become one of the main medical issues of the 21st century. IgE is the central mediator in atopic allergies such as hay fever, eczema and asthma; it is therefore a prime target in the development of allergen-independent preventative treatments. Here we present results from several studies of a novel vaccine strategy aimed at reducing the levels of IgE antibodies. The vaccine results in the induction of anti-IgE antibodies, and the skin reactivity upon allergen challenge was significantly reduced in vaccinated animals. Our results suggest that active immunization against IgE has the potential to become a therapeutic method for humans. In addition, an evaluation of possible adjuvants that could be used as immune stimulators and thus help break self-tolerance at the time of vaccination is presented.

Antibodies are a central part of the immune defense system, and a large variability in their specificity is needed in order to be able to react against all possible foreign substances we may encounter during our lives. In this thesis, results are presented from investigations into how an egg-laying mammal, the Australian duck-billed platypus (Ornithorhynchus anatinus) creates antibody variability. Our results show that despite the lack of many V gene families the antibody repertoire in the platypus seems to be well developed. A long and highly variable complementarity-determining region (CDR) 3 compensates for the limited germline diversity. Interestingly, the presence of additional cysteine residues in the CDRs may form stabilizing disulfide bridges in the antigen binding loops and thereby increasing the affinity of the antibody-antigen interaction. Although the immune system is necessary for survival, it must be strictly controlled since it may otherwise over-react and cause more harm than benefits. Allergies and autoimmune diseases are examples of such over-reactions by the immune system. Allergies are increasing in the western world and have become one of the main medical issues of the 21st century. IgE is the central mediator in atopic allergies such as hay fever, eczema and asthma; it is therefore a prime target in the development of allergen-independent preventative treatments. Here we present results from several studies of a novel vaccine strategy aimed at reducing the levels of IgE antibodies. The vaccine results in the induction of anti-IgE antibodies, and the skin reactivity upon allergen challenge was significantly reduced in vaccinated animals. Our results suggest that active immunization against IgE has the potential to become a therapeutic method for humans. In addition, an evaluation of possible adjuvants that could be used as immune stimulators and thus help break self-tolerance at the time of vaccination is presented.

Antibodies are a central part of the immune defense system, and a large variability in their specificity is needed in order to be able to react against all possible foreign substances we may encounter during our lives. In this thesis, results are presented from investigations into how an egg-laying mammal, the Australian duck-billed platypus (Ornithorhynchus anatinus) creates antibody variability. Our results show that despite the lack of many V gene families the antibody repertoire in the platypus seems to be well developed. A long and highly variable complementarity-determining region (CDR) 3 compensates for the limited germline diversity. Interestingly, the presence of additional cysteine residues in the CDRs may form stabilizing disulfide bridges in the antigen binding loops and thereby increasing the affinity of the antibody-antigen interaction. Although the immune system is necessary for survival, it must be strictly controlled since it may otherwise over-react and cause more harm than benefits. Allergies and autoimmune diseases are examples of such over-reactions by the immune system. Allergies are increasing in the western world and have become one of the main medical issues of the 21st century. IgE is the central mediator in atopic allergies such as hay fever, eczema and asthma; it is therefore a prime target in the development of allergen-independent preventative treatments. Here we present results from several studies of a novel vaccine strategy aimed at reducing the levels of IgE antibodies. The vaccine results in the induction of anti-IgE antibodies, and the skin reactivity upon allergen challenge was significantly reduced in vaccinated animals. Our results suggest that active immunization against IgE has the potential to become a therapeutic method for humans. In addition, an evaluation of possible adjuvants that could be used as immune stimulators and thus help break self-tolerance at the time of vaccination is presented.

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., Addresses: Hellman L, Univ Uppsala, Biomed Ctr, Dept Cell & Mol Biol, Box 596, S-75124 Uppsala, Sweden. Univ Uppsala, Biomed Ctr, Dept Cell & Mol Biol, S-75124 Uppsala, Sweden. Univ Tasmania, Sch Biomed Sci, Launceston, Tas, Australia.

Electroreceptor organs and mechanoreceptor organs located in the bill skin of the platypus are used by the animal to locate prey items, underwater, with eyes and ears closed. The precise manner in how these senses aid the platypus to locate food is not yet known. In this study we provide data on the activity of cortical neurons in the bill representation of SI when stimulated electrically, mechanically, and concurrently. Within the SI bill representation, there are alternating stripes of cortex that represent purely mechanical inputs, and combined electrical and mechanical inputs. Generally, the bimodal units responded more vigorously to electrical stimulation and had very small dynamic ranges, usually saturating within 20 μV cm-1 of threshold. Latencies to electrical or mechanical stimulation were around 25 ms, but were significantly reduced for concurrent stimulation. Combined with the previously reported observation that the receptive fields of bimodal neurons within cortical modules were the same, and that thresholds varied considerably, the observation of limited dynamic range suggests a mechanism for localization of stimuli. A model is developed wherein the relative activation of a module is dependent on its proximity to the source.

Back caption: New York Zoological Park (Bronx Zoo) / The duck-billed platypus / One of the great curiosities of the animal world--a mammal that lays eggs. Outside its native Australia and Tasmania, it has been exhibited only in the Bronx Zoo.