| mollusk shell formation: mapping the distribution of organic matrix components underlying a single aragonitic tablet in nacre. | control over mineral formation in mollusk shells is exerted by the macromolecules of the organic matrix. using histochemical methods, we mapped the carboxylates and sulfates of proteins and polysaccharides on the surfaces of decalcified interlamellar matrices from the nacreous shell layer of the cephalopod nautilus pompilius, expanding upon an earlier study by crenshaw and ristedt [crenshaw, m.a., ristedt, h., 1976. the histochemical localization of reactive groups in septal nacre from nautilus ... | 2006 | 16413789 |
| macromolecular structure of the organic framework of nacre in haliotis rufescens: implications for growth and mechanical behavior. | we have performed a macromolecular structural analysis of the interlamellar and intertabular parts of the organic framework of the nacreous part of the shell of haliotis rufescens, including the identification of structural chitin. using histochemical optical microscopy we have mapped the locations of carboxylates and sulfates of proteins and chitin on the surfaces and within the core of the interlamellar layers and the intertabular matrix that together form the external organic matrix of compos ... | 2008 | 18538582 |
| comparative bioaccumulation of trace elements between nautilus pompilius and nautilus macromphalus (cephalopoda: nautiloidea) from vanuatu and new caledonia. | the concentrations of 16 trace elements were investigated and compared for the first time in the digestive and excreting tissues of two nautilus species (cephalopoda: nautiloidea) from two geologically contrasted areas: (1) n. macromphalus from new caledonia, a region characterized by its richness in nickel ores and its lack of tectonic activities and (2) n. pompilius from the vanuatu archipelago showing high volcanic and tectonic activities. in both nautilus species, results clearly highlighted ... | 2009 | 18556066 |
| evolution of the arginine kinase gene family. | arginine kinase (ak), catalyzing the reversible transfer of phosphate from mgatp to arginine yielding phosphoarginine and mgadp, is widely distributed throughout the invertebrates and is also present in certain protozoa. typically, these proteins are found as monomers targeted to the cytoplasm, but true dimeric and contiguous dimeric aks as well as mitochondrial ak activities have been observed. in the present study, we have obtained the sequences of the genes for aks from two distantly related ... | 2006 | 20483252 |
| nautilus pompilius life history and demographics at the osprey reef seamount, coral sea, australia. | nautiloids are the subject of speculation as to their threatened status arising from the impacts of targeted fishing for the ornamental shell market. life history knowledge is essential to understand the susceptibility of this group to overfishing and to the instigation of management frameworks. this study provides a comprehensive insight into the life of nautilus in the wild. at osprey reef from 1998-2008, trapping for nautilus was conducted on 354 occasions, with 2460 individuals of one specie ... | 2011 | 21347356 |
| nautilus at risk--estimating population size and demography of nautilus pompilius. | the low fecundity, late maturity, long gestation and long life span of nautilus suggest that this species is vulnerable to over-exploitation. demand from the ornamental shell trade has contributed to their rapid decline in localized populations. more data from wild populations are needed to design management plans which ensure nautilus persistence. we used a variety of techniques including capture-mark-recapture, baited remote underwater video systems, ultrasonic telemetry and remotely operated ... | 2011 | 21347360 |
| vertical distribution and migration patterns of nautilus pompilius. | vertical depth migrations into shallower waters at night by the chambered cephalopod nautilus were first hypothesized early in the early 20(th) 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 ... | 2011 | 21364981 |
| evolution of molluscan hemocyanin structures. | hemocyanin transports oxygen in the hemolymph of many molluscs and arthropods and is therefore a central physiological factor in these animals. molluscan hemocyanin molecules are oligomers composed of many protein subunits that in turn encompass subsets of distinct functional units. the structure and evolution of molluscan hemocyanin have been studied for decades, but it required the recent progress in dna sequencing, x-ray crystallography and 3d electron microscopy to produce a detailed view of ... | 2013 | 23454609 |
| comparative cephalopod shell strength and the role of septum morphology on stress distribution. | the evolution of complexly folded septa in ammonoids has long been a controversial topic. explanations of the function of these folded septa can be divided into physiological and mechanical hypotheses with the mechanical functions tending to find widespread support. the complexity of the cephalopod shell has made it difficult to directly test the mechanical properties of these structures without oversimplification of the septal morphology or extraction of a small sub-domain. however, the power o ... | 2016 | 27672501 |
| immunohistochemical localization of cardio-active neuropeptides in the heart of a living fossil, nautilus pompilius l. (cephalopoda, tetrabranchiata). | neuropeptides play an important role in modulating the effects of neurotransmitters such as acetylcholine and noradrenaline in the heart and the vascular system of vertebrates and invertebrates. various neuropeptides, including substance p (sp), vasoactive intestinal polypeptide (vip) and fmrfamide, have been localized in the brain in cephalopods and the neurosecretory system of the vena cava. previous studies involving cephalopods have mainly focussed on the modern, coleoid cephalopods, whereas ... | 2004 | 15323346 |