Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 51
Filtrar
Mais filtros










Intervalo de ano de publicação
1.
ACS Biomater Sci Eng ; 7(10): 4819-4827, 2021 10 11.
Artigo em Inglês | MEDLINE | ID: mdl-34541853

RESUMO

Mollusk shells generally consist of several macro-layers with different microstructures. To explore the specific role that different macro-layers play in the overall mechanical properties of shells, the microstructures, hardness distribution, and three-point bending behavior in the deep-sea Nautilus shell were investigated. It is found that the shell presents a hierarchical structure comprising three layers in thickness, that is, the outer, middle, and inner layers, which exhibit homogeneous, prismatic, and nacreous structures, respectively. Among them, the homogeneous structure in the outer layer is harder, which is beneficial for the shell to enhance resistance to wear and perforation. Furthermore, both the bending strength and fracture energy for group Up (loading from outer to inner surfaces) are far higher than those for group Down (loading from inner to outer surfaces), indicating that the inner nacreous layer is not only stronger but also tougher. Cracks tend to deflect at the interfaces in nacreous structure, and nacreous structure is thereby more resistant to breakage. Hence, the nacreous structure in the inner layer could protect the shell from breaking catastrophically in the deep sea with high pressure. In brief, the combination of a harder outside layer and a tougher inside layer provides an effective protective structure for the deep-sea shell, and the excellent environment adaptability of Nautilus shell can thus be interpreted in terms of its ingenious microstructure arrangement.


Assuntos
Nácar , Nautilus , Exoesqueleto , Animais , Resistência à Flexão , Moluscos
2.
Sci Rep ; 11(1): 17114, 2021 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-34429487

RESUMO

Assessing the taxonomic importance of the suture line in shelled cephalopods is a key to better understanding the diversity of this group in Earth history. Because fossils are subject to taphonomic artifacts, an in-depth knowledge of well-preserved modern organisms is needed as an important reference. Here, we examine the suture line morphology of all known species of the modern cephalopods Nautilus and Allonautilus. We applied computed tomography and geometric morphometrics to quantify the suture line morphology as well as the conch geometry and septal spacing. Results reveal that the suture line and conch geometry are useful in distinguishing species, while septal spacing is less useful. We also constructed cluster trees to illustrate the similarity among species. The tree based on conch geometry in middle ontogeny is nearly congruent with those previously reconstructed based on molecular data. In addition, different geographical populations of the same species of Nautilus separate out in this tree. This suggests that genetically distinct (i.e., geographically isolated) populations of Nautilus can also be distinguished using conch geometry. Our results are applicable to closely related fossil cephalopods (nautilids), but may not apply to more distantly related forms (ammonoids).


Assuntos
Exoesqueleto/anatomia & histologia , Nautilus/classificação , Filogenia , Animais , Fósseis/anatomia & histologia , Nautilus/anatomia & histologia
3.
Nat Ecol Evol ; 5(7): 927-938, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33972735

RESUMO

Nautilus is the sole surviving externally shelled cephalopod from the Palaeozoic. It is unique within cephalopod genealogy and critical to understanding the evolutionary novelties of cephalopods. Here, we present a complete Nautilus pompilius genome as a fundamental genomic reference on cephalopod innovations, such as the pinhole eye and biomineralization. Nautilus shows a compact, minimalist genome with few encoding genes and slow evolutionary rates in both non-coding and coding regions among known cephalopods. Importantly, multiple genomic innovations including gene losses, independent contraction and expansion of specific gene families and their associated regulatory networks likely moulded the evolution of the nautilus pinhole eye. The conserved molluscan biomineralization toolkit and lineage-specific repetitive low-complexity domains are essential to the construction of the nautilus shell. The nautilus genome constitutes a valuable resource for reconstructing the evolutionary scenarios and genomic innovations that shape the extant cephalopods.


Assuntos
Nautilus , Animais , Biomineralização , Genoma , Humanos , Nautilus/genética
4.
World Neurosurg ; 151: 117, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33989820

RESUMO

A variety of recently introduced devices have allowed more complex aneurysms to be rendered for endovascular embolization. Tiny and sophisticated implants are nowadays designed to provide further either temporary or permanent remodeling of the wide-necked aneurysms and improve coil occlusion rates.1-4 Such improvements in the technical armamentarium include the Woven EndoBridge (Sequent Medical, California, USA), the Medina Embolic Device (Medtronic, Irvine, California, USA), The Contour Neurovascular System (Cerus Endovascular, Fremont, California, USA), and pCONUS 2 HPC (Phenox, GmbH, Bohum, Germany).5-7 Intrasaccular neck bridging is a conceptually new technique descending from the theoretical combination of intrasaccular flow diversion and temporary-stent assisted coiling.8 The Nautilus (EndoStream Medical, Tel Aviv, Israel) is an intrasaccular bridging device that offers complete neck reconstruction in coil embolization of wide-neck cerebral aneurysms. It has been granted a CE mark by the European Union. The detachable intrasaccular implant comprises flexible and "tornado-like"-shaped Nitinol-based layers. The device is compatible with a standard microcatheter with minimal 0.0165″ inner diameter and is fully radiopaque and fully resheathable. The device's intrasaccular nature and the fact that it does not harbor any intraluminal satellite parts suggest that the implant can be safely used in both unruptured and ruptured case scenarios without the need for dual antiplatelet therapy. This is what we consider a great advantage of the proposed technique over the alternative options of intrasaccular and intraluminal flow diversion. This technical video (Video 1) demonstrates the successful obliteration of a complex posterior communicating artery aneurysm with Nautilus-assisted endovascular coiling. To our knowledge, this is the first technical video demonstrating an in-vivo and step-by-step implementation of this novel device.


Assuntos
Aneurisma Roto/cirurgia , Artérias/cirurgia , Aneurisma Intracraniano/cirurgia , Nautilus , Animais , Prótese Vascular/efeitos adversos , Embolização Terapêutica/métodos , Procedimentos Endovasculares/métodos , Humanos
5.
Clin Exp Nephrol ; 24(10): 971-972, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32592079

RESUMO

We report a 71-year-old woman who presented with unilateral flank pain and sepsis. A computed tomographic (CT) scan demonstrated left-sided hydronephrosis. Subsequent percutaneous nephrotomy drainage showed pus-like material, confirming the diagnosis of pyonephrosis. The ureteral stricture was caused by previous radiation injury for cervical cancer in this ESRD patient who was on chronic dialysis for years. In our case, the grade IVB hydronephrosis is a result of an extremely atrophic kidney, pyonephrosis, and ureteral stricture. The CT section of pyonephrosis in an extremely atrophic kidney resembles a sagittal section of a Nautilus shell, as the shell corresponds to the diffusely thinned renal cortex.


Assuntos
Rim/diagnóstico por imagem , Pionefrose/diagnóstico por imagem , Idoso , Animais , Atrofia/complicações , Feminino , Dor no Flanco/etiologia , Humanos , Hidronefrose/etiologia , Rim/patologia , Nautilus , Pionefrose/complicações , Sepse/etiologia , Tomografia Computadorizada por Raios X , Obstrução Ureteral/complicações
6.
Zootaxa ; 4564(2): zootaxa.4564.2.5, 2019 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-31716504

RESUMO

Seven species of chirostyloidean squat lobsters are reported from the Galapagos Rift zone and Galapagos platform: Eumunida subsolanus n. sp. (Eumunididae), Heteroptychus galapagos n. sp., H. nautilus n. sp. (Chirostylidae), Uroptychus bellus Faxon, 1893, U. compressus n. sp., U. occidentalis Faxon, 1893 (Chirostylidae), and Sternostylus defensus (Benedict, 1902) (Sternostylidae). All new species are described and illustrated, and the two species previously known from the Galapagos Islands, Uroptychus bellus and U. occidentalis, are re-illustrated from respective lectotypes, herein designated, since both original descriptions were only brief. Both the species of Heteroptychus and Eumunida subsolanus are the first representatives of their respective genera in the eastern Pacific and the latter is also the first record for the family Eumunididae in the region.


Assuntos
Anomuros , Decápodes , Nautilus , Animais , Equador , Ilhas
7.
Sci Rep ; 9(1): 15411, 2019 10 28.
Artigo em Inglês | MEDLINE | ID: mdl-31659206

RESUMO

Molluscan eyes exhibit an enormous range of morphological variation, ranging from tiny pigment-cup eyes in limpets, compound eyes in ark clams and pinhole eyes in Nautilus, through to concave mirror eyes in scallops and the large camera-type eyes of the more derived cephalopods. Here we assess the potential of non-destructive micro-computed tomography (µ-CT) for investigating the anatomy of molluscan eyes in three species of the family Solariellidae, a group of small, deep-sea gastropods. We compare our results directly with those from traditional histological methods applied to the same specimens, and show not only that eye microstructure can be visualised in sufficient detail for meaningful comparison even in very small animals, but also that µ-CT can provide additional insight into gross neuroanatomy without damaging rare and precious specimens. Data from µ-CT scans also show that neurological innervation of eyes is reduced in dark-adapted snails when compared with the innervation of cephalic tentacles, which are involved in mechanoreception and possibly chemoreception. Molecular tests also show that the use of µ-CT and phosphotungstic acid stain do not prevent successful downstream DNA extraction, PCR amplification or sequencing. The use of µ-CT methods is therefore highly recommended for the investigation of difficult-to-collect or unique specimens.


Assuntos
Evolução Biológica , Olho/diagnóstico por imagem , Olho/inervação , Caramujos/anatomia & histologia , Microtomografia por Raio-X , Animais , Nautilus/anatomia & histologia
8.
Integr Zool ; 14(6): 561-575, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30811879

RESUMO

Fossil cephalopods are frequently encrusted by epibionts; however, determining whether encrustation occurred prior to or post-mortem to the host, and whether the final environment of deposition corresponds to the habitat of encrustation is complex. The present paper describes cirripede epibionts, their calcareous bases and their attachment scars on 6 post-mortem shells of Nautilus macromphalus, collected from deep water off New Caledonia. The cirripedes have left both cemented calcareous bases of Hexelasma and scars associated with bioerosion and discoloration produced by verrucomorph barnacles. Live cirripedes included a Metaverruca recta, with articulated opercular plates and organic tissue (on a shell that had been exposed on the sea floor for at least 150 years), and specimens of Hexelasma velutinum, one of which was partly attached to an internal surface of a shell. The disposition of verrucomorphs indicates that most Nautilus shells were colonized post-mortem rather than during a floating stage. However, as cirripedes are known to have colonized living Nautilus, some Hexelasma, preserved only as calcareous eroded bases, may represent specimens that settled on a living Nautilus. The degree of bioerosion and discoloration induced by verrucomorph barnacles varies according to the surface preservation of Nautilus shells, with deeper and discolored traces preserved on old and degraded shells. Traces made by verrucomorphs described here are ellipsoidal and a new ichnotaxon, Anellusichnus ellipticus, is proposed to accommodate them. Importantly, verrucomorphs and other cirripede taxa with membranous bases that were attached to pristine shells may not leave any substantial scars, and, thus, will be difficult to detect in the fossil record.


Assuntos
Exoesqueleto , Crustáceos/classificação , Nautilus , Animais , Crustáceos/fisiologia , Nova Caledônia , Oceano Pacífico
9.
J Aquat Anim Health ; 30(3): 175-178, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29862571

RESUMO

The correct diagnosis and treatment of disease in chambered nautiluses Nautilus pompilius are difficult. The basic morphology and natural behaviors of the species tend to mask the initial onset of a disease or infection, and by the time it is observable, mortality usually occurs. A single specimen of chambered nautilus at the Museum of Nature South Tyrol, Italy, exhibited symptoms of an infection, including mucus production, abnormal buoyancy, irregular hood appearance, and inconsistent tentacle movement. Soon after, tetracycline hydrochloride was administered in bath form at 25 mg/L in seawater daily for 30 min over six consecutive days. The specimen regained normal buoyancy after the fifth day. After the 6-d treatment, the specimen regained all normal behaviors and appearance within 2 weeks. More than 1 year after treatment, the specimen was exhibiting normal behaviors with no adverse reactions. When administered soon after symptoms of an infection were observed, tetracycline was effective at halting the progression of symptoms and led to the full recovery of the chambered nautilus.


Assuntos
Antibacterianos/uso terapêutico , Nautilus/efeitos dos fármacos , Tetraciclina/uso terapêutico , Animais , Feminino , Nautilus/microbiologia
10.
Mol Ecol ; 26(21): 5923-5938, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28872211

RESUMO

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 fossil 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 analysed genomewide 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 genomewide 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 suggest large effective population sizes, which may explain the low levels of population differentiation commonly observed in living fossils.


Assuntos
Especiação Genética , Genética Populacional , Nautilus/classificação , Animais , Teorema de Bayes , Nautilus/genética , Filogenia , Densidade Demográfica , Transcriptoma
11.
Sci Rep ; 7(1): 7500, 2017 08 08.
Artigo em Inglês | MEDLINE | ID: mdl-28790422

RESUMO

The human inner ear has an intricate spiral shape often compared to shells of mollusks, particularly to the nautilus shell. It has inspired many functional hearing theories. The reasons for this complex geometry remain unresolved. We digitized 138 human cochleae at microscopic resolution and observed an astonishing interindividual variability in the shape. A 3D analytical cochlear model was developed that fits the analyzed data with high precision. The cochlear geometry neither matched a proposed function, namely sound focusing similar to a whispering gallery, nor did it have the form of a nautilus. Instead, the innate cochlear blueprint and its actual ontogenetic variants were determined by spatial constraints and resulted from an efficient packing of the cochlear duct within the petrous bone. The analytical model predicts well the individual 3D cochlear geometry from few clinical measures and represents a clinical tool for an individualized approach to neurosensory restoration with cochlear implants.


Assuntos
Ducto Coclear/anatomia & histologia , Modelos Estatísticos , Osso Petroso/anatomia & histologia , Gânglio Espiral da Cóclea/anatomia & histologia , Lâmina Espiral/anatomia & histologia , Ligamento Espiral da Cóclea/anatomia & histologia , Exoesqueleto/anatomia & histologia , Exoesqueleto/ultraestrutura , Animais , Autopsia , Variação Biológica Individual , Ducto Coclear/fisiologia , Ducto Coclear/ultraestrutura , Audição/fisiologia , Humanos , Imageamento Tridimensional/instrumentação , Imageamento Tridimensional/métodos , Modelos Anatômicos , Nautilus/anatomia & histologia , Nautilus/ultraestrutura , Osso Petroso/fisiologia , Gânglio Espiral da Cóclea/fisiologia , Gânglio Espiral da Cóclea/ultraestrutura , Lâmina Espiral/fisiologia , Lâmina Espiral/ultraestrutura , Ligamento Espiral da Cóclea/fisiologia , Ligamento Espiral da Cóclea/ultraestrutura
12.
PLoS One ; 12(7): e0179811, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28727800

RESUMO

Averaged demographic data from previously unfished populations of Nautilus and Allonautilus (Cephalopoda) provide a baseline to determine if a population is undisturbed and in "equilibrium" or is in "disequilibrium" as a result of fishery pressure. Data are available for previously undisturbed local nautiloid populations in Papua New Guinea, Australia, Indonesia, Fiji, Palau, American Samoa, New Caledonia and Vanuatu (total n = 2,669 live-caught, tagged and released animals). The data show that unfished populations average ~75% males and ~74% mature animals. By contrast, unpublished, anecdotal and historical records since 1900 from the heavily fished central Philippines have shown a persistent decline in trap yields and a change in demographics of N. pompilius. By 1979, a sample of fished live-caught animals (n = 353) comprised only ~28% males and ~27% mature animals. Continued uncontrolled trapping caused collapse of the fishery and the shell industry has moved elsewhere, including Indonesia. In addition, we show that estimated rates of population decline are offered by unpublished tag-release records in unfished Palau. These data show that patterns of trap yields and demographic differences between fished and unfished populations in relative age class and sex ratios can indicate disequilibria wrought by fisheries pressure that can render local populations inviable. Given adequate samples (n ≥100 live-caught animals), a threshold of <50% males and mature animals in fished populations should signal the need to initiate curative conservation initiatives. The current trajectory of uncontrolled nautiloid fisheries can only mean trouble and possibly extinction of local populations of this ancient, iconic molluscan lineage.


Assuntos
Cefalópodes , Conservação dos Recursos Naturais , Pesqueiros , Distribuição Animal , Animais , Austrália , Feminino , Masculino , Nautilus , Ilhas do Pacífico , Dinâmica Populacional
13.
J Hum Evol ; 97: 1-16, 2016 08.
Artigo em Inglês | MEDLINE | ID: mdl-27457541

RESUMO

In this paper, we describe worked and pigment-stained Nautilus shell artefacts recovered from Jerimalai, Timor-Leste. Two of these artefacts come from contexts dating to between 38,000 and 42,000 cal. BP (calibrated years before present), and exhibit manufacturing traces (drilling, pressure flaking, grinding), as well as red colourant staining. Through describing more complete Nautilus shell ornaments from younger levels from this same site (>15,900, 9500, and 5000 cal. BP), we demonstrate that those dating to the initial occupation period of Jerimalai are of anthropogenic origin. The identification of such early shell working examples of pelagic shell in Island Southeast Asia not only adds to our growing understanding of the importance of marine resources to the earliest modern human communities in this region, but also indicates that a remarkably enduring shell working tradition was enacted in this area of the globe. Additionally, these artefacts provide the first material culture evidence that the inhabitants of Jerimalai were not only exploiting coastal resources for their nutritional requirements, but also incorporating these materials into their social technologies, and by extension, their social systems. In other words, we argue that the people of Jerimalai were already practicing a developed coastal adaptation by at least 42,000 cal. BP.


Assuntos
Arqueologia , Nautilus , Animais , Fósseis , Humanos , Tecnologia , Timor-Leste
14.
PLoS One ; 11(4): e0153890, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27100183

RESUMO

Nautilus is often used as an analogue for the ecology and behavior of extinct externally shelled cephalopods. Nautilus shell grows quickly, has internal growth banding, and is widely believed to precipitate aragonite in oxygen isotope equilibrium with seawater. Pieces of shell from a wild-caught Nautilus macromphalus from New Caledonia and from a Nautilus belauensis reared in an aquarium were cast in epoxy, polished, and then imaged. Growth bands were visible in the outer prismatic layer of both shells. The thicknesses of the bands are consistent with previously reported daily growth rates measured in aquarium reared individuals. In situ analysis of oxygen isotope ratios using secondary ion mass spectrometry (SIMS) with 10 µm beam-spot size reveals inter- and intra-band δ18O variation. In the wild-caught sample, a traverse crosscutting 45 growth bands yielded δ18O values ranging 2.5‰, from +0.9 to -1.6 ‰ (VPDB), a range that is larger than that observed in many serial sampling of entire shells by conventional methods. The maximum range within a single band (~32 µm) was 1.5‰, and 27 out of 41 bands had a range larger than instrumental precision (±2 SD = 0.6‰). The results from the wild individual suggest depth migration is recorded by the shell, but are not consistent with a simple sinusoidal, diurnal depth change pattern. To create the observed range of δ18O, however, this Nautilus must have traversed a temperature gradient of at least ~12°C, corresponding to approximately 400 m depth change. Isotopic variation was also measured in the aquarium-reared sample, but the pattern within and between bands likely reflects evaporative enrichment arising from a weekly cycle of refill and replacement of the aquarium water. Overall, this work suggests that depth migration behavior in ancient nektonic mollusks could be elucidated by SIMS analysis across individual growth bands.


Assuntos
Exoesqueleto/química , Exoesqueleto/crescimento & desenvolvimento , Nautilus/crescimento & desenvolvimento , Isótopos de Oxigênio/química , Oxigênio/química , Animais , Espectrometria de Massas
15.
Zootaxa ; 3963(1): 55-73, 2015 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-26249392

RESUMO

Few animals are treasured by zoologists more than Nautilus, and Nautilus pompilius Linnaeus, 1758, the type species of the genus, in particular. However, the type series of this species has not been studied in great detail. According to the rules of zoological nomenclature the type series consists of all the specimens included by the author in the new nominal taxon at the time of description (whether directly or by bibliographic reference), and any evidence, published or unpublished, may be taken into account to determine what specimens are included. The type series of Nautilus pompilius includes specimens in the Linnean Society of London, the University Museum in Uppsala, and specimens figured by pre-Linnaean authors indicated by reference by Linnaeus (1758). One specimen in London and four specimens in Uppsala, which are still extant, are likely to have been known to Linnaeus at the time when he prepared the 10th Edition of Systema Naturae (Linnaeus 1758), although none of these specimens was specifically mentioned by him. Even though it is widely believed that Linnaeus (1767) designated as lectotype a specimen figured by Rumphius (1705) in his D'Amboinsche Rariteitkamer, referred to in the Systema Naturae, this presumed lectotypification is not valid because Linnaeus did not explicitly indicate that any particular specimen was considered to be the type of the species. Later lectotype designations of Rumphius' illustrations are invalid because they show three different specimens. It seems that the best approach, given the quality of the material and the lack of clarity as to its type status, would be to apply to the ICZN asking to set aside all previous type fixations and designate a neotype, preferably a DNA sequenced specimen of known provenance.


Assuntos
Nautilus/classificação , Estruturas Animais/anatomia & histologia , Estruturas Animais/crescimento & desenvolvimento , Animais , Tamanho Corporal , Livros/história , História do Século XVII , História do Século XVIII , História do Século XIX , História do Século XX , Museus/história , Nautilus/anatomia & histologia , Nautilus/crescimento & desenvolvimento , Tamanho do Órgão , Zoologia/história
16.
Mol Ecol ; 24(13): 3316-28, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26033519

RESUMO

Understanding the distribution of genetic diversity in exploited species is fundamental to successful conservation. Genetic structure and the degree of gene flow among populations must be assessed to design appropriate strategies to prevent the loss of distinct populations. The cephalopod Nautilus pompilius is fished unsustainably in the Philippines for the ornamental shell trade and has limited legislative protection, despite the species' recent dramatic decline in the region. Here, we use 14 microsatellite markers to evaluate the population structure of N. pompilius around Australia and the Philippines. Despite their relative geographical proximity, Great Barrier Reef individuals are genetically isolated from Osprey Reef and Shark Reef in the Coral Sea (FST  = 0.312, 0.229, respectively). Conversely, despite the larger geographical distances between the Philippines and west Australian reefs, samples display a small degree of genetic structure (FST  = 0.015). Demographic scenarios modelled using approximate Bayesian computation analysis indicate that this limited divergence is not due to contemporary gene flow between the Philippines and west Australia. Instead, present-day genetic similarity can be explained by very limited genetic drift that has occurred due to large average effective population sizes that persisted at both locations following their separation. The lack of connectivity among populations suggests that immigrants from west Australia would not facilitate natural recolonization if Philippine populations were fished to extinction. These data help to rectify the paucity of information on the species' biology currently inhibiting their conservation classification. Understanding population structure can allow us to facilitate sustainable harvesting, thereby preserving the diversity of genetically distinct stocks.


Assuntos
Genética Populacional , Nautilus/genética , Animais , Austrália , Teorema de Bayes , Conservação dos Recursos Naturais , Recifes de Corais , Fluxo Gênico , Deriva Genética , Genótipo , Repetições de Microssatélites , Modelos Genéticos , Dados de Sequência Molecular , Filipinas , Densidade Demográfica
17.
PLoS One ; 10(4): e0125558, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25894584

RESUMO

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.


Assuntos
Fenômenos Ecológicos e Ambientais , Foraminíferos/fisiologia , Nautilus/parasitologia , Exoesqueleto/parasitologia , Animais , Nova Caledônia , Vanuatu
18.
PLoS One ; 9(12): e113372, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25470257

RESUMO

Exploration of a landlocked cenote on Lifou (Loyalty Islands) revealed 37 shells of the cephalopod Nautilus macromphalus Sowerby, 1849, in saltwater on the cenote floor, approximately 40 m below the water surface. The occurrence of these shells is unusual because N. macromphalus is restricted to the open marine waters surrounding the island. All of the shells are mature, and nearly all of them are unbroken, with faded red-brown color stripes. We analyzed seven shells to determine their age. Radiocarbon dating yielded ages of 6380±30 to 7095±30 y BP. The 238U-series radionuclides 210Pb (half-life  = 22.3 y) and 226Ra (half-life  = 1600 y) also were measured. Two of the samples showed radioactive equilibrium between the nuclides, consistent with the old radiocarbon dates, but the other five samples showed excess 210Pb. When corrected for radioactive decay, the 226Ra activities were much greater than those found in living Nautilus. We conclude that exposure to high activities of 222Rn and 226Ra in the salty groundwater of the cenote altered the activities originally incorporated into the shells. Human placement of the shells in the cavity is rejected based on their radiocarbon age and the geometry of the cenote. The most probable explanation is that the animals entered the flooded karstic system through a connection on the seaward side at approximately 7,000 y BP, during an interval of slowly rising sea level. Unable to find an exit and/or due to anoxic bottom waters, the animals were trapped and died inside. The open connection with the sea persisted for ∼700 y, but after ∼6400 y BP, the connection was lost, probably due to a roof collapse. This is a rare example of Nautilus in a karstic coastal basin and provides a minimum age for the appearance of N. macromphalus in the Loyalty Islands.


Assuntos
Nautilus/anatomia & histologia , Nautilus/fisiologia , Exoesqueleto/fisiologia , Animais , Cronologia como Assunto , Humanos , Nova Caledônia , Datação Radiométrica , Rádio (Elemento)/análise , Urânio/análise
19.
PLoS One ; 9(6): e100799, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24956107

RESUMO

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.


Assuntos
Nautilus/crescimento & desenvolvimento , Tecnologia de Sensoriamento Remoto/métodos , Gravação em Vídeo , Água , Samoa Americana , Animais , Austrália , Recifes de Corais , Fiji , Filipinas , Fotografação , Dinâmica Populacional
20.
Zoo Biol ; 33(4): 285-94, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24797217

RESUMO

Irregular shell formation and black lines on the outside of live chambered nautilus shells have been observed in all adult specimens at aquariums and zoos soon after the organisms enter aquaria. Black lines have also been observed in wild animals at sites of broken shell, but continued growth from that point returns to a normal, smooth structure. In contrast, rough irregular deposition of shell continues throughout residence in aquaria. The composition and reasons for deposition of the black material and mitigation of this irregular shell formation is the subject of the current study. A variety of analytical techniques were used, including stable isotope mass spectrometry (SI-MS), inductively coupled plasma mass spectrometry (ICP-MS), micro x-ray fluorescence (µXRF), X-ray diffraction (XRD), and scanning electron microscopy (SEM) based X-ray microanalysis. Results indicate that the black material contains excess amounts of copper, zinc, and bromine which are unrelated to the Nautilus diet. The combination of these elements and proteins plays an important role in shell formation, growth, and strengthening. Further study will be needed to compare the proteomics of the shell under aquaria versus natural wild environments. The question remains as to whether the occurrence of the black lines indicates normal healing followed by growth irregularities that are caused by stress from chemical or environmental conditions. In this paper we begin to address this question by examining elemental and isotopic differences of Nautilus diet and salt water. The atomic composition and light stable isotopic ratios of the Nautilus shell formed in aquaria verses wild conditions are presented.


Assuntos
Exoesqueleto/química , Exoesqueleto/crescimento & desenvolvimento , Animais de Zoológico , Dieta , Nautilus/crescimento & desenvolvimento , Animais , Bromo/análise , Cobre/análise , Espectrometria de Massas/veterinária , Microscopia Eletrônica de Varredura/veterinária , Água do Mar/química , Espectrometria por Raios X/veterinária , Difração de Raios X/veterinária , Zinco/análise
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...