The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
P. Bonifazi - One of the best experts on this subject based on the ideXlab platform.
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Nautilus Recent Results
Recent Developments in General Relativity Genoa 2000, 2020Co-Authors: V. Fafone, P. Astone, P. Bonifazi, G. Federici, Lina Quintieri, I. Modena, M. Visco, Arturo Moleti, M. Bassan, R. TerenziAbstract:The resonant-mass gravitational wave detector Nautilus, operated by the ROG collaboration at the INFN Frascati National Laboratories, is in continuous data taking since June 1998 with peak sensitivity of \( h \simeq 3 \cdot 10^{ - 22} Hz^{ - {1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} \). It has recently proven to be capable of recording signals due to the passage of cosmic rays. The results of the latest coincidence analyses between the Nautilus data and the cosmic ray signals measured by detectors located above and below Nautilus are reported.
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detection of high energy cosmic rays with the resonant gravitational wave detectors Nautilus and explorer
Astroparticle Physics, 2008Co-Authors: P. Astone, V. Fafone, P. Bonifazi, E. Coccia, M Bassan, S Dantonio, D Babusci, G Cavallari, G GiordanoAbstract:Abstract The cryogenic resonant gravitational wave detectors Nautilus and EXPLORER, made of an aluminum alloy bar, can detect cosmic ray showers. At temperatures above 1 K, when the material is in the normal-conducting state, the measured signals are in good agreement with the expected values based on the cosmic rays data and on the thermo-acoustic model. When Nautilus was operated at the temperature of 0.14 K, in superconductive state, large signals produced by cosmic ray interactions, more energetic than expected, were recorded. The Nautilus data in this case are in agreement with the measurements done by a dedicated experiment on a particle beam. The biggest recorded event was in EXPLORER and excited the first longitudinal mode to a vibrational energy of ∼670 K, corresponding to ∼360 TeV absorbed in the bar. Cosmic rays can be an important background in future acoustic detectors of improved sensitivity. At present, they represent a useful tool to verify the gravitational wave antenna performance.
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Recent results of Nautilus
AIP Conference Proceedings, 2001Co-Authors: P. Astone, V. Fafone, P. Bonifazi, M. Bassan, P. Carelli, E. Coccia, S. D'antonio, Andrea Carlo Marini, E. Mauceli, Y. MinenkovAbstract:Nautilus started its second run of continuous data taking in june 1998. The measured strain sensitivity at the two resonances is 410−22/Hz over a bandwidth of 1 Hz and better than 310−20/Hz over a band of about 25 Hz, with a duty cycle mainly limited by cryogenic operations. A summary of the most recent results obtained with the Nautilus data is given.
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energetic cosmic rays observed by the resonant gravitational wave detector Nautilus
Physics Letters B, 2001Co-Authors: Pia Astone, V. Fafone, P. Bonifazi, G. Federici, P. Carelli, E. Coccia, Andrea Carlo Marini, M Bassan, S Dantonio, G MazzitelliAbstract:Abstract Cosmic-ray showers interacting with the resonant mass gravitational wave antenna Nautilus have been detected. The experimental results show large signals at a rate much greater than expected. The largest signal corresponds to an energy release in Nautilus of 87 TeV. We note that a resonant mass gravitational wave detector used as particle detector has characteristics different from the usual particle detectors, and it could detect new features of cosmic rays.
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search for coincident excitation of the widely spaced resonant gravitational wave detectors explorer Nautilus and niobe
Astroparticle Physics, 1999Co-Authors: P. Astone, V. Fafone, P. Bonifazi, P. Carelli, E. Coccia, M Bassan, D G Blair, C Cosmelli, L Febo, S FrascaAbstract:We report the search for coincidences among three resonant mass detectors: EXPLORER at CERN and Nautilus in Frascati of the Rome group and NIOBE in Perth of the UWA group. The three detectors have a sensitivity for short bursts of GW in the h ≈ 10−18 range, about one thousand times better in energy than Weber's original detectors. The analysis is based on the comparison of candidate event lists recorded by the detectors in the period December 1994 through October 1996. The events have been obtained by applying a pulse detection filter to the raw data and using a predetermined threshold. Due to the different periods of data taking it was not possible to search for triple coincidences. We searched for coincidences between EXPLORER and Nautilus during the years 1995 and 1996 for a total time coverage of 1372 hours and between EXPLORER and NIOBE in 1995 for a coverage of 1362 hours. The results have been: a weak indication of a coincidence excess with respect to the accidental ones between EXPLORER and Nautilus and no coincidence excess between EXPLORER and NIOBE.
Peter D Ward - One of the best experts on this subject based on the ideXlab platform.
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genomic signatures of evolution in Nautilus an endangered living fossil
Molecular Ecology, 2017Co-Authors: Peter D Ward, Neil H. Landman, David J Combosch, Sarah Lemer, Gonzalo GiribetAbstract:Living fossils are survivors of previously more diverse lineages that originated millions of years ago and persisted with little morphological change. Therefore, living fossils are model organisms to study both long-term and ongoing adaptation and speciation processes. However, many aspects of living fossils evolution and their persistence in the modern world remain unclear. Here, we investigate three major aspects of the evolutionary history of living fossils: cryptic speciation, population genetics, and effective population sizes; using members of the genera Nautilus and AlloNautilus as classic examples of true living fossils. For this, we analyzed genome-wide ddRAD-Seq data for all six currently recognized nautiloid species throughout their distribution range. Our analyses identified three major allopatric Nautilus clades: a South Pacific clade, subdivided into three subclades with no signs of admixture between them; a Coral Sea clade, consisting of two genetically distinct populations with significant admixture; and a widespread Indo-Pacific clade, devoid of significant genetic substructure. Within these major clades we detected five Nautilus groups, which likely correspond to five distinct species. With the exception of Nautilus macromphalus, all previously described species are at odds with genome-wide data, testifying to the prevalence of cryptic species among living fossils. Detailed FST analyses further revealed significant genome-wide and locus-specific signatures of selection between species and differentiated populations, which is demonstrated here for the first time in a living fossil. Finally, approximate Bayesian computation (ABC) simulations suggested large effective population sizes, which may explain the low levels of population differentiation commonly observed in living fossils. This article is protected by copyright. All rights reserved.
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a revisited phylogeography of Nautilus pompilius
Ecology and Evolution, 2016Co-Authors: Lauren E Vandepas, Gregory Jeff Barord, Frederick D Dooley, Billie J Swalla, Peter D WardAbstract:The cephalopod genus Nautilus is considered a “living fossil” with a contested number of extant and extinct species, and a benthic lifestyle that limits movement of animals between isolated seamounts and landmasses in the Indo-Pacific. Nautiluses are fished for their shells, most heavily in the Philippines, and these fisheries have little monitoring or regulation. Here, we evaluate the hypothesis that multiple species of Nautilus (e.g., N. belauensis, N. repertus and N. stenomphalus) are in fact one species with a diverse phenotypic and geologic range. Using mitochondrial markers, we show that Nautiluses from the Philippines, eastern Australia (Great Barrier Reef), Vanuatu, American Samoa, and Fiji fall into distinct geographical clades. For phylogenetic analysis of species complexes across the range of Nautilus, we included sequences of Nautilus pompilius and other Nautilus species from GenBank from localities sampled in this study and others. We found that specimens from Western Australia cluster with samples from the Philippines, suggesting that interbreeding may be occurring between those locations, or that there is limited genetic drift due to large effective population sizes. Intriguingly, our data also show that Nautilus identified in other studies as N. belauensis, N. stenomphalus, or N. repertus are likely N. pompilius displaying a diversity of morphological characters, suggesting that there is significant phenotypic plasticity within N. pompilius.
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Nautilus biology systematics and paleobiology as viewed from 2015
Swiss Journal of Palaeontology, 2016Co-Authors: Peter D Ward, Frederick D Dooley, Gregory Jeff BarordAbstract:The natural history of the nautilid genus Nautilus, composed of a controversial number of extinct and extant species, has been the subject of scientific scrutiny for centuries. While a great research effort lasting from the mid-1970s to 1990s contributed vast amounts of new information concerning the evolutionary history, current diversity, mode of life, and ecological position in its habitats took place, since that time there has been far less concentrated research, and most of that has concerned the diversity and genetic distance of isolated populations using genetic techniques. In spite of the reprinting of one of the two 1987 books examining aspects of Nautilus biology, the only new field-based work on Nautilus until recently has been the important, Ph.D. thesis conducted by Andrew Dunstan on the isolated, seamount inhabiting Nautiluses living on Osprey Reef, Australia. In this contribution we attempt to integrate Dunstan’s important new work with other, post-2010 research so as to update our current understanding of the evolutionary history (based on fossil as well as modern genetic work), characteristic habitats, mode of life, and physiology so as to give a 2015 perspective on those aspects of the natural history of Nautilus that are of paleobiological relevance.
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comparative population assessments of Nautilus sp in the philippines australia fiji and american samoa using baited remote underwater video systems
PLOS ONE, 2014Co-Authors: Gregory Jeff Barord, Frederick D Dooley, Andrew J Dunstan, Anthony S Ilano, Karen N Keister, Heike Neumeister, Thomas G Preuss, Shane D Schoepfer, Peter D WardAbstract:The extant species of Nautilus and AlloNautilus (Cephalopoda) inhabit fore-reef slope environments across a large geographic area of the tropical western Pacific and eastern Indian Oceans. While many aspects of their biology and behavior are now well-documented, uncertainties concerning their current populations and ecological role in the deeper, fore-reef slope environments remain. Given the historical to current day presence of Nautilus fisheries at various locales across the Pacific and Indian Oceans, a comparative assessment of the current state of Nautilus populations is critical to determine whether conservation measures are warranted. We used baited remote underwater video systems (BRUVS) to make quantitative photographic records as a means of estimating population abundance of Nautilus sp. at sites in the Philippine Islands, American Samoa, Fiji, and along an approximately 125 km transect on the fore reef slope of the Great Barrier Reef from east of Cairns to east of Lizard Island, Australia. Each site was selected based on its geography, historical abundance, and the presence (Philippines) or absence (other sites) of Nautilus fisheries The results from these observations indicate that there are significantly fewer Nautiluses observable with this method in the Philippine Islands site. While there may be multiple possibilities for this difference, the most parsimonious is that the Philippine Islands population has been reduced due to fishing. When compared to historical trap records from the same site the data suggest there have been far more Nautiluses at this site in the past. The BRUVS proved to be a valuable tool to measure Nautilus abundance in the deep sea (300–400 m) while reducing our overall footprint on the environment.
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vertical distribution and migration patterns of Nautilus pompilius
PLOS ONE, 2011Co-Authors: Andrew J Dunstan, Peter D Ward, Justin N MarshallAbstract:Vertical depth migrations into shallower waters at night by the chambered cephalopod Nautilus were first hypothesized early in the early 20th Century. Subsequent studies have supported the hypothesis that Nautilus spend daytime hours at depth and only ascend to around 200 m at night. Here we challenge this idea of a universal Nautilus behavior. Ultrasonic telemetry techniques were employed to track eleven specimens of Nautilus pompilius for variable times ranging from one to 78 days at Osprey Reef, Coral Sea, Australia. To supplement these observations, six remotely operated vehicle (ROV) dives were conducted at the same location to provide 29 hours of observations from 100 to 800 meter depths which sighted an additional 48 individuals, including five juveniles, all deeper than 489 m. The resulting data suggest virtually continuous, nightly movement between depths of 130 to 700 m, with daytime behavior split between either virtual stasis in the relatively shallow 160–225 m depths or active foraging in depths between 489 to 700 m. The findings also extend the known habitable depth range of Nautilus to 700 m, demonstrate juvenile distribution within the same habitat as adults and document daytime feeding behavior. These data support a hypothesis that, contrary to previously observed diurnal patterns of shallower at night than day, more complex vertical movement patterns may exist in at least this, and perhaps all other Nautilus populations. These are most likely dictated by optimal feeding substrate, avoidance of daytime visual predators, requirements for resting periods at 200 m to regain neutral buoyancy, upper temperature limits of around 25°C and implosion depths of 800 m. The slope, terrain and biological community of the various geographically separated Nautilus populations may provide different permutations and combinations of the above factors resulting in preferred vertical movement strategies most suited for each population.
Bruce M Paterson - One of the best experts on this subject based on the ideXlab platform.
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stereotypic founder cell patterning and embryonic muscle formation in drosophila require Nautilus myod gene function
Proceedings of the National Academy of Sciences of the United States of America, 2007Co-Authors: Yikang Rong, Bruce M PatersonAbstract:Nautilus is the only MyoD-related gene in Drosophila. Nautilus expression begins around stage 9 at full germ-band extension in a subset of mesodermal cells organized in a stereotypic pattern in each hemisegment. The muscle founder cell marker Duf-LacZ, produced by the enhancer trap line rP298LacZ, is coexpressed in numerous Nautilus-positive cells when founders first appear. Founders entrain muscle identity through the restricted expression of transcription factors such as S59, eve, and Kr, all of which are observed in subsets of the Nautilus expressing founders. We inactivated the Nautilus gene using homology-directed gene targeting and Gal4/UAS regulated RNAi to determine whether loss of Nautilus gene activity affected founder cell function. Both methods produced a range of defects that included embryonic muscle disruption, reduced viability and female sterility, which could be rescued by hsp70-Nautilus cDNA transgenes. Our results demonstrate Nautilus expression marks early founders that give rise to diverse muscle groups in the embryo, and that Nautilus gene activity is required to seed the correct founder myoblast pattern that prefigures the muscle fiber arrangement during embryonic development.
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rna interference demonstrates a role for Nautilus in the myogenic conversion of schneider cells by daughterless
Developmental Biology, 2000Co-Authors: Gabriele H Marchler, Kirsten Edington, Ilene Karschmizrachi, Bruce M PatersonAbstract:Abstract Schneider SL2 cells activate the myogenic program in response to the ectopic expression of daughterless alone, as indicated by exit from the cell cycle, syncytia formation, and the presence of muscle myosin fibrils. Myogenic conversion can be potentiated by the coexpression of DMEF2 and Nautilus with daughterless. In RT-PCR assays Schneider cells express two mesodermal markers, Nautilus and DMEF2 mRNAs, as well as very low levels of daughterless mRNA but no twist. Full-length RT-PCR products for Nautilus and DMEF2 encode immunoprecipitable proteins. We used RNA-i to demonstrate that both endogenous Nautilus expression and DMEF2 expression are required for the myogenic conversion of Schneider cells by daughterless. Coexpression of twist blocks conversion by daughterless but twist dsRNA has no effect. Our results indicate that Schneider cells are of mesodermal origin and that myogenic conversion with ectopic expression of daughterless occurs by raising the levels of daughterless protein sufficiently to allow the formation of Nautilus/daughterless heterodimers. The effectiveness of RNA-i is dependent upon protein half-life. Genes encoding proteins with relatively short half-lives (10 h), such as Nautilus or HSF, are efficiently silenced, whereas more stable proteins, such as cytoplasmic actin or β -galactosidase, are less amenable to the application of RNA-i. These results support the conclusion that Nautilus is a myogenic factor in Drosophila tissue culture cells with a functional role similar to that of vertebrate MyoD. This is discussed with regard to the in vivo functions of Nautilus.
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targeted disruption of gene function in drosophila by rna interference rna i a role for Nautilus in embryonic somatic muscle formation
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Leonie Misquitta, Bruce M PatersonAbstract:The expression of the MyoD gene homolog, Nautilus (nau), in the Drosophila embryo defines a subset of mesodermal cells known as the muscle “pioneer” or “founder” cells. These cells are thought to establish the future muscle pattern in each hemisegment. Founders appear to recruit fusion-competent mesodermal cells to establish a particular muscle fiber type. In support of this concept every somatic muscle in the embryo is associated with one or more Nautilus-positive cells. However, because of the lack of known (isolated) Nautilus mutations, no direct test of the founder cell hypothesis has been possible. We now have utilized toxin ablation and genetic interference by double-stranded RNA (RNA interference or RNA-i) to determine both the role of the Nautilus-expressing cells and the Nautilus gene, respectively, in embryonic muscle formation. In the absence of Nautilus-expressing cells muscle formation is severely disrupted or absent. A similar phenotype is observed with the elimination of the Nautilus gene product by genetic interference upon injection of Nautilus double-stranded RNA. These results define a crucial role for Nautilus in embryonic muscle formation. The application of RNA interference to a variety of known Drosophila mutations as controls gave phenotypes essentially indistinguishable from the original mutation. RNA-i provides a powerful approach for the targeted disruption of a given genetic function in Drosophila.
E. Coccia - One of the best experts on this subject based on the ideXlab platform.
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EXPLORER and Nautilus: Present status
The Tenth Marcel Grossmann Meeting, 2020Co-Authors: P. Astone, I. Modena, Arturo Moleti, M. Bassan, P. Carelli, E. Coccia, Y. Minenkov, C Cosmelli, G. V. Pallottino, G. PizzellaAbstract:We report on the present status of the resonant gravitational waves detectors EXPLORER and Nautilus operated by the ROG collaboration at CERN and at the INFN Prascati National Laboratories respectively. EXPLORER has been operating in continuous data taking for three years. Nautilus during 2002 underwent a partial overhaul of its read-out electronics. The results obtained since May 2003 show a considerable improvement in the performances of the apparatus. Both the detectors exhibit an unprecedented useful bandwidth: in over 30 Hz their spectral sensitivities are better than 10~/ \/Hz with a duty cycle only limited by cryogenic operations.
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detection of high energy cosmic rays with the resonant gravitational wave detectors Nautilus and explorer
Astroparticle Physics, 2008Co-Authors: P. Astone, V. Fafone, P. Bonifazi, E. Coccia, M Bassan, S Dantonio, D Babusci, G Cavallari, G GiordanoAbstract:Abstract The cryogenic resonant gravitational wave detectors Nautilus and EXPLORER, made of an aluminum alloy bar, can detect cosmic ray showers. At temperatures above 1 K, when the material is in the normal-conducting state, the measured signals are in good agreement with the expected values based on the cosmic rays data and on the thermo-acoustic model. When Nautilus was operated at the temperature of 0.14 K, in superconductive state, large signals produced by cosmic ray interactions, more energetic than expected, were recorded. The Nautilus data in this case are in agreement with the measurements done by a dedicated experiment on a particle beam. The biggest recorded event was in EXPLORER and excited the first longitudinal mode to a vibrational energy of ∼670 K, corresponding to ∼360 TeV absorbed in the bar. Cosmic rays can be an important background in future acoustic detectors of improved sensitivity. At present, they represent a useful tool to verify the gravitational wave antenna performance.
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Recent results of Nautilus
AIP Conference Proceedings, 2001Co-Authors: P. Astone, V. Fafone, P. Bonifazi, M. Bassan, P. Carelli, E. Coccia, S. D'antonio, Andrea Carlo Marini, E. Mauceli, Y. MinenkovAbstract:Nautilus started its second run of continuous data taking in june 1998. The measured strain sensitivity at the two resonances is 410−22/Hz over a bandwidth of 1 Hz and better than 310−20/Hz over a band of about 25 Hz, with a duty cycle mainly limited by cryogenic operations. A summary of the most recent results obtained with the Nautilus data is given.
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energetic cosmic rays observed by the resonant gravitational wave detector Nautilus
Physics Letters B, 2001Co-Authors: Pia Astone, V. Fafone, P. Bonifazi, G. Federici, P. Carelli, E. Coccia, Andrea Carlo Marini, M Bassan, S Dantonio, G MazzitelliAbstract:Abstract Cosmic-ray showers interacting with the resonant mass gravitational wave antenna Nautilus have been detected. The experimental results show large signals at a rate much greater than expected. The largest signal corresponds to an energy release in Nautilus of 87 TeV. We note that a resonant mass gravitational wave detector used as particle detector has characteristics different from the usual particle detectors, and it could detect new features of cosmic rays.
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search for coincident excitation of the widely spaced resonant gravitational wave detectors explorer Nautilus and niobe
Astroparticle Physics, 1999Co-Authors: P. Astone, V. Fafone, P. Bonifazi, P. Carelli, E. Coccia, M Bassan, D G Blair, C Cosmelli, L Febo, S FrascaAbstract:We report the search for coincidences among three resonant mass detectors: EXPLORER at CERN and Nautilus in Frascati of the Rome group and NIOBE in Perth of the UWA group. The three detectors have a sensitivity for short bursts of GW in the h ≈ 10−18 range, about one thousand times better in energy than Weber's original detectors. The analysis is based on the comparison of candidate event lists recorded by the detectors in the period December 1994 through October 1996. The events have been obtained by applying a pulse detection filter to the raw data and using a predetermined threshold. Due to the different periods of data taking it was not possible to search for triple coincidences. We searched for coincidences between EXPLORER and Nautilus during the years 1995 and 1996 for a total time coverage of 1372 hours and between EXPLORER and NIOBE in 1995 for a coverage of 1362 hours. The results have been: a weak indication of a coincidence excess with respect to the accidental ones between EXPLORER and Nautilus and no coincidence excess between EXPLORER and NIOBE.
Neil H. Landman - One of the best experts on this subject based on the ideXlab platform.
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Nautilus The Biology and Paleobiology of a Living Fossil, Reprint with additions
2020Co-Authors: W. Bruce Saunders, Neil H. LandmanAbstract:Nautilus Studies—The First Twenty-Two Centuries -- Nautilus Studies—The First Twenty-Two Centuries -- The Ancestry of the Genus Nautilus -- The Ancestry of the Genus Nautilus -- Nautilus and Its Distribution -- The Species of Nautilus -- Geographic Distribution of Nautilus Shells -- Genetic Variation and Phylogeny in Nautilus -- Morphological Variation in Nautilus from Papua New Guinea -- Biometrie Analysis of Nautilus pompilius from the Philippines and the Fiji Islands -- Biomineralization and Systematic Implications -- Ecology -- Ecology, Distribution, and Population Characteristics of Nautilus -- Incidence and Kinds of Epizoans on the Shells of Live Nautilus -- On the Habitat of Nautilus pompilius in Tanon Strait (Philippines) and the Fiji Islands -- Predation on Nautilus -- Physiology -- The Central Nervous System -- The Sense Organs of Nautilus -- Visual Behavior and Visual Sensitivity of Nautilus pompilius -- A Possible Function of the Iris Groove of Nautilus -- Histology of the Long Digital Tentacles -- The Functional Morphology of the Tentacle Musculature of Nautilus pompilius -- The Circulatory System -- The Excretory System of Nautilus -- Respiratory Physiology -- Mouth Part Histology and Morphology -- Metabolism -- Energy Metabolism of Nautilus Swimming Muscles -- Oxygen Conformity and Metabolic Arrest in Nautilus -- Ventilation and Oxygen Extraction by Nautilus -- Reproduction and Growth -- Reproduction and Embryology of Nautilus -- Development of the Embryonic Shell of Nautilus -- Growth and Longevity of Nautilus -- Adolescent Growth and Maturity in Nautilus -- The Shell and Its Architecture -- Nautilus Shell Architecture -- Ultrastructure of the Nautilus Shell -- Swimming and Buoyancy -- Locomotion of Nautilus -- Nautilus Shell Hydrostatics -- Buoyancy in Nautilus -- Aquarium Maintenance -- Collection and Aquarium Maintenance of Nautilus -- Experience with Aquarium Rearing of Nautilus in Japan -- A Small, Closed Aquarium System for Nautilus.
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genomic signatures of evolution in Nautilus an endangered living fossil
Molecular Ecology, 2017Co-Authors: Peter D Ward, Neil H. Landman, David J Combosch, Sarah Lemer, Gonzalo GiribetAbstract:Living fossils are survivors of previously more diverse lineages that originated millions of years ago and persisted with little morphological change. Therefore, living fossils are model organisms to study both long-term and ongoing adaptation and speciation processes. However, many aspects of living fossils evolution and their persistence in the modern world remain unclear. Here, we investigate three major aspects of the evolutionary history of living fossils: cryptic speciation, population genetics, and effective population sizes; using members of the genera Nautilus and AlloNautilus as classic examples of true living fossils. For this, we analyzed genome-wide ddRAD-Seq data for all six currently recognized nautiloid species throughout their distribution range. Our analyses identified three major allopatric Nautilus clades: a South Pacific clade, subdivided into three subclades with no signs of admixture between them; a Coral Sea clade, consisting of two genetically distinct populations with significant admixture; and a widespread Indo-Pacific clade, devoid of significant genetic substructure. Within these major clades we detected five Nautilus groups, which likely correspond to five distinct species. With the exception of Nautilus macromphalus, all previously described species are at odds with genome-wide data, testifying to the prevalence of cryptic species among living fossils. Detailed FST analyses further revealed significant genome-wide and locus-specific signatures of selection between species and differentiated populations, which is demonstrated here for the first time in a living fossil. Finally, approximate Bayesian computation (ABC) simulations suggested large effective population sizes, which may explain the low levels of population differentiation commonly observed in living fossils. This article is protected by copyright. All rights reserved.
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taphonomy of backshore versus deep marine collected Nautilus macromphalus conchs new caledonia
PALAIOS, 2015Co-Authors: Barbara Seuss, Royal H Mapes, Daniel I Hembree, Max Wisshak, Neil H. LandmanAbstract:Abstract The extant Nautilus nowadays exclusively lives in the Indo-Pacific Ocean along the slopes of coral reefs, mainly in water depths of 300–400 m. It possesses a complex gas-liquid combined system to regulate its buoyancy in the water column. After death this system is lost and the shells become either positively or negatively buoyant and float for some time or respectively sink to the seafloor where taphonomic processes strongly influence the shell’s condition. A major process in taphonomy is bioerosion. We present herein a detailed study of the influence of taphonomic pathways on bioerosion in backshore collected and deep-water dredged Nautilus shells from the New Caledonia region. Some bioerosion of Nautilus shells may take place during life but most occurs after death and deposition of the shell. The ichnocoenosis found in the shells collected in backshore settings indicates that these shells were positively buoyant after the death of the animals and were initially deposited in a nearshore enviro...
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syn vivo bioerosion of Nautilus by endo and epilithic foraminiferans new caledonia and vanuatu
PLOS ONE, 2015Co-Authors: Barbara Seuss, Royal H Mapes, Max Wisshak, Neil H. LandmanAbstract:A variety of syn-vivo bioerosion traces produced by foraminiferans is recorded in shells of Nautilus sampled near New Caledonia and Vanuatu. These are two types of attachment scars of epilithic foraminiferans and two forms of previously undescribed microborings, a spiral-shaped and a dendritic one, both most likely being the work of endolithic 'naked' foraminiferans. Scanning electron microscopy of epoxy-resin casts of the latter revealed that these traces occur in clusters of up to many dozen individuals and potentially are substrate-specific. The foraminiferan traces are the sole signs of bioerosion in the studied Nautilus conchs, and neither traces of phototrophic nor other chemotrophic microendoliths were found. While the complete absence of photoautotrophic endoliths would be in good accordance with the life habit of Nautilus, which resides in aphotic deep marine environments and seeks shallower waters in the photic zone for feeding only during night-time, the absence of any microbial bioerosion may also be explained by an effective defence provided by the nautilid periostracum. Following this line of reasoning, the recorded foraminiferan bioerosion traces in turn would identify their trace makers as being specialized in their ability to penetrate the periostracum barrier and to bioerode the shell of modern Nautilus.
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evolutionary radiation of present day Nautilus and alloNautilus
American Malacological Bulletin, 2011Co-Authors: James Bonacum, Royal H Mapes, Neil H. Landman, Matthew M White, Aliciajeannette White, Justin IrlamAbstract:Abstract: The extensive fossil record of coiled nautiloids indicates that they comprised a diverse assemblage of species in ancient oceans. Today they are represented by the genera Nautilus Linnaeus, 1758 and AlloNautilus Ward and Saunders, 1997, inhabiting reef systems throughout the Indo-Pacific region. Some individual populations of Nautilus show subtle differences in shell morphologies, and these morphological differences may be used to diagnose different species. An alternative view is that these differences are simply geographically localized, morphological variants within the broadly distributed taxon generally referred to as Nautilus pompilius Linnaeus, 1758. Here we present a hypothesis for the phylogeny of present-day Nautilus and AlloNautilus using molecular characters from two mitochondrial gene regions, 16S rDNA and Cytochrome Oxidase c subunit I. Populations of N. pompilius in Indonesia (Ambon Strait), the Philippines, Vanuatu (New Hebrides Islands), Papua New Guinea, Carter Reef and Osprey ...
