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.
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.
Cephalopod carbonate geochemistry underpins studies ranging from Phanerozoic, global-scale change to outcrop-scale paleoecological reconstructions. Interpreting these data hinges on assumed ...similarity to model organisms, such as Nautilus, and generalization from other molluscan biomineralization processes. Aquarium rearing and capture of wild Nautilus suggest shell carbonate precipitates quickly (35 μm/day) in oxygen isotope equilibrium with seawater. Other components of Nautilus shell chemistry are less well-studied but have potential to serve as proxies for paleobiology and paleoceanography. To calibrate the geochemical response of cephalopod δ15Norg, δ13Corg, δ13Ccarb, δ18Ocarb, and δ44/40Cacarb to modern anthropogenic environmental change, we analyzed modern, historical, and subfossil Nautilus macromphalus from New Caledonia. Samples span initial human habitation, colonialization, and industrial pCO2 increase. This sampling strategy is advantageous because it avoids the shock response that can affect geochemical change in aquarium experiments. Given the range of living depths and more complex ecology of Nautilus, however, some anthropogenic signals, such as ocean acidification, may not have propagated to their living depths. Our data suggest some environmental changes are more easily preserved than others given variability in cephalopod average living depth. Calculation of the percent respired carbon incorporated into the shell using δ13Corg, δ13Ccarb, and Suess-effect corrected δ13CDIC suggests an increase in the last 130 years that may have been caused by increasing carbon dioxide concentration or decreasing oxygen concentration at the depths these individuals inhabited. This pattern is consistent with increasing atmospheric CO2 and/or eutrophication offshore of New Caledonia. We find that δ44/40Ca remains stable across the last 130 years. The subfossil shell from a cenote may exhibit early δ44/40Ca diagenesis. Questions remain about the proportion of dietary vs ambient seawater calcium incorporation into the Nautilus shell. Values of δ15N do not indicate trophic level change in the last 130 years, and the subfossil shell may show diagenetic alteration of δ15N toward lower values. Future work using historical collections of Sepia and Spirula may provide additional calibration of fossil cephalopod geochemistry.
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.
Map of the Indo‐Pacific showing sampling locations of Nautilus for this study and photographs of representative animals from each location. There appears to be interesting phenotypic plasticity displayed between different populations of Nautilus pompilius in traits such as size, shell coloration, and hood morphology. Our data suggest that Nautilus from Fiji, Australia, the Philippines, and American Samoa comprise one broadly distributed species.
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Reconstruction of surgical defects located close to eyelid edges, nostrils, or the mouth is challenging, as tension generated by direct closure or skin flaps in these sensitive ...regions tends to cause distortion. New repair techniques that prevent retraction may significantly improve outcomes.
Retrospective study of the use of 2 novel flap designs-the nautilus flap and the bullfighter crutch flap-to repair surgical defects in the peripalpebral, perivestibular, nasal, and perioral areas. The nautilus flap was used to repair 4 peripalpebral defects and 2 perioral defects, and the bullfighter crutch flap to repair 14 nasal ala defects.
Cosmetic and functional outcomes were very satisfactory in all 20 patients, with no cases of ectropion, nasal vestibule collapse, or labial asymmetry. Necrosis did not occur in any of the cases.
The nautilus and bullfighter crutch flaps appear to be excellent choices for reconstructing surgical defects in periorificial areas.
La reconstrucción de defectos quirúrgicos en regiones anatómicas próximas a bordes palpebrales, fosas nasales o boca es un reto debido su tendencia a ser deformadas por la tensión del cierre directo o los colgajos cutáneos. El empleo de nuevas técnicas reconstructivas que eviten la retracción de estas zonas sensibles puede suponer un avance importante.
Se emplean 2 nuevos diseños, el colgajo nautilus y el colgajo en muleta taurina, para la reconstrucción de defectos quirúrgicos periorificiales, realizando una recolección retrospectiva de los mismos en las zonas periparpebral, perivestibular nasal y peribucal. El colgajo nautilus se empleó en 4 pacientes con defectos periparpebrales y 2 peribucales. El colgajo en muleta taurina se utilizó para la reconstrucción de 14 defectos en ala nasal.
En los 20 pacientes se obtuvieron resultados muy satisfactorios tanto a nivel estético como funcional, sin la aparición de ectropión, colapso del vestíbulo nasal o asimetría de borde labial. No se observó necrosis en ningún caso.
Proponemos el colgajo nautilus y el colgajo en muleta taurina como una excelente opción reconstructiva para defectos quirúrgicos localizados en zonas periorificiales.
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La reconstrucción de defectos quirúrgicos en regiones anatómicas próximas a bordes palpebrales, fosas nasales o boca es un reto debido su tendencia a ser deformadas por la tensión del ...cierre directo o los colgajos cutáneos. El empleo de nuevas técnicas reconstructivas que eviten la retracción de estas zonas sensibles puede suponer un avance importante.
Se emplean 2 nuevos diseños, el colgajo nautilus y el colgajo en muleta taurina, para la reconstrucción de defectos quirúrgicos periorificiales, realizando una recolección retrospectiva de los mismos en las zonas periparpebral, perivestibular nasal y peribucal. El colgajo nautilus se empleó en 4 pacientes con defectos periparpebrales y 2 peribucales. El colgajo en muleta taurina se utilizó para la reconstrucción de 14 defectos en ala nasal.
En los 20 pacientes se obtuvieron resultados muy satisfactorios tanto a nivel estético como funcional, sin la aparición de ectropión, colapso del vestíbulo nasal o asimetría de borde labial. No se observó necrosis en ningún caso.
Proponemos el colgajo nautilus y el colgajo en muleta taurina como una excelente opción reconstructiva para defectos quirúrgicos localizados en zonas periorificiales.
Reconstruction of surgical defects located close to eyelid edges, nostrils, or the mouth is challenging, as tension generated by direct closure or skin flaps in these sensitive regions tends to cause distortion. New repair techniques that prevent retraction may significantly improve outcomes.
Retrospective study of the use of 2 novel flap designs—the nautilus flap and the bullfighter crutch flap—to repair surgical defects in the peripalpebral, perivestibular, nasal, and perioral areas. The nautilus flap was used to repair 4 peripalpebral defects and 2 perioral defects, and the bullfighter crutch flap to repair 14 nasal ala defects.
Cosmetic and functional outcomes were very satisfactory in all 20 patients, with no cases of ectropion, nasal vestibule collapse, or labial asymmetry. Necrosis did not occur in any of the cases.
The nautilus and bullfighter crutch flaps appear to be excellent choices for reconstructing surgical defects in periorificial areas.
Reconstruction of surgical defects located close to eyelid edges, nostrils, or the mouth is challenging, as tension generated by direct closure or skin flaps in these sensitive regions tends to cause ...distortion. New repair techniques that prevent retraction may significantly improve outcomes.
Retrospective study of the use of 2 novel flap designs-the nautilus flap and the bullfighter crutch flap-to repair surgical defects in the peripalpebral, perivestibular, nasal, and perioral areas. The nautilus flap was used to repair 4 peripalpebral defects and 2 perioral defects, and the bullfighter crutch flap to repair 14 nasal ala defects.
Cosmetic and functional outcomes were very satisfactory in all 20 patients, with no cases of ectropion, nasal vestibule collapse, or labial asymmetry. Necrosis did not occur in any of the cases.
The nautilus and bullfighter crutch flaps appear to be excellent choices for reconstructing surgical defects in periorificial areas.
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).
The nautilus, commonly known as a “living fossil,” is endangered and may be at risk of extinction. The lack of genomic information hinders a thorough understanding of its biology and evolution, which ...can shed light on the conservation of this endangered species. Here, we report the first high‐quality chromosome‐level genome assembly of Nautilus pompilius. The assembled genome size comprised 785.15 Mb. Comparative genomic analyses indicated that transposable elements (TEs) and large‐scale genome reorganizations may have driven lineage‐specific evolution in the cephalopods. Remarkably, evolving conserved genes and recent TE insertion activities were identified in N. pompilius, and we speculate that these findings reflect the strong adaptability and long‐term survival of the nautilus. We also identified gene families that are potentially responsible for specific adaptation and evolution events. Our study provides unprecedented insights into the specialized biology and evolution of N. pompilius, and the results serve as an important resource for future conservation genomics of the nautilus and closely related species.
see also the Perspective by Gustavo Sanchez, Oleg Simakov and Daniel S. Rokhsar.
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