Spiny lobster development: mechanisms inducing metamorphosis to the puerulus: a review

This review outlines current knowledge of mechanisms effecting metamorphosis in decapod crustaceans and insects. The comparative approach demonstrates some of the complexities that need resolving to find an answer to the question raised frequently by ecologists: “What triggers metamorphosis in spiny lobsters?” It is evident that crustacean moulting and metamorphosis are genetically controlled through endocrine systems that mediate gene expression. The molecular mechanisms underlying these developmental processes have been studied intensively in insects, particularly in the fruitfly, Drosophila melanogaster (Diptera), and some lepidopteran species. Comparatively, there is minimal information available for a few decapod crustacean species, but none for spiny lobsters (Palinuridae). Nothing was known of hormone signalling transduction pathways, via nuclear receptors (NRs) and gene activation during larval moults in palinurids—until a recent, ground-breaking study of early phyllosomal development of Panulirus ornatus by Wilson et al. (Rock Lobster Enhancement and Aquaculture Subprogram. FRDC Project 2000/263, Australian Govt, Fisheries Research and Development Corporation and Australian Institute of Marine Science, Nov 2005). Their study not only identified homologues of five hormone NRs of D. melanogaster, but also patterns of gene regulation showing strong similarities to those of gene expression found in insect larval development. Their results indicated that control of moulting and metamorphosis in palinurids closely parallels that in insects, suggesting that insects can serve as model systems for elucidating molecular mechanisms in larval decapods. In insects and crustaceans, the steroid hormone, ecdysone, (20E) initiates moulting. In insects, juvenile hormone (JH) mediates the type of larval moult that occurs, either anamorphic or metamorphic. The latter results when the level of JH in the haemolymph drops in the final larval instar. High levels of JH inhibit the metamorphic moult during insect larval development. The interaction of 20E and JH is not fully understood, and the operative molecular mechanisms are still being elucidated. No nuclear receptor for JH has been identified, and alternative JH signalling pathways await identification. In decapod crustaceans, methyl farnesoate (MF), a precursor of JH, replaces the latter in other functions mediated by JH in insects; but there is little evidence indicating that MF plays a similar ‘antimetamorphic’ role in decapod larval moults

The Evolution of Oxygen and Magnesium in the Bulge and Disk of the Milky Way

We show that the Galactic bulge and disk share a similar, strong, decline in [O/Mg] ratio with [Mg/H]. The similarity of the [O/Mg] trend in these two, markedly different, populations suggests a metallicity-dependent modulation of the stellar yields from massive stars, by mass loss from winds, and related to the Wolf-Rayet phenomenon, as proposed by McWilliam & Rich (2004). We have modified existing models for the chemical evolution of the Galactic bulge and the solar neighborhood with the inclusion of metallicity-dependent oxygen yields from theoretical predictions for massive stars that include mass loss by stellar winds. Our results significantly improve the agreement between predicted and observed [O/Mg] ratios in the bulge and disk above solar metallicity; however, a small zero-point normalization problem remains to be resolved. The zero-point shift indicates that either the semi-empirical yields of Francois et al. (2004) need adjustment, or that the bulge IMF is not quite as flat as found by Ballero et al. (2007); the former explanation is preferred. Our result removes a previous inconsistency between the interpretation of [O/Fe] and [Mg/Fe] ratios in the bulge, and confirms the conclusion that the bulge formed more rapidly than the disk, based on the over-abundances of elements produced by massive stars. We also provide an explanation for the long-standing difference between [Mg/Fe] and [O/Fe] trends among disk stars more metal-rich than the sun.Comment: 22 pages including 5 figures. Submitted to the Astronomical Journa

Spiny lobster development: do the final-stage phyllosoma larvae of Jasus edwardsii swim towards the coast?

Several papers from New Zealand have all suggested that late-stages, or at least the final stage phyllosomas of Jasus edwardsii can swim horizontally from offshore to inshore towards the coast. This was largely based on the observation that the late-stage phyllosomas were distributed inshore of the mid-stage phyllosomas off the east coast of New Zealand. A review of these data, plus additional information on the diurnal vertical migration behaviour of the phyllosoma larvae of J. edwardsii not available at the time of publication of the earlier papers,suggests an alternative explanation. These new data clearly show different diurnal vertical migration behaviour of the mid and the late-stage phyllosoma. It is suggested that even small differences in the vertical movements of the phyllosoma larvae can result in dramatic changes in their horizontal distribution because these movements take them into different current layers and this, not horizontal swimming, is probably responsible for the different locations of the mid and late-stage phyllosomas of J. edwardsii off the east coast of New Zealand

Coordinates and 2MASS and OGLE identifications for all stars in Arp's 1965 finding chart for Baade's Window

Aims: We seek to provide 2MASS and OGLE identifications and coordinates for all stars in the finding chart published by Arp\,(1965). This chart covers the low extinction area around NGC 6522, also known as Baade's window, at coordinates (l,b)=(1.02,-3.92). Methods: A cross correlation, using numerical techniques, was performed between a scan of the original finding chart from Arp (1965) and 2MASS and OGLE-II images and stellar coordinates. Results: We provide coordinates for all stars in Arp's finding chart and 2MASS and OGLE identifications wherever possible. Two identifications in quadrant II do not appear in the original finding chart.Comment: 30 pages, accepted by A&A as a Research Not

Abundance Ratios in the Galactic Bulge and Super Metal-Rich Type II Nucle osynthesis

We present abundance results from our Keck/HIRES observations of giants in the Galactic Bulge. We confirm that the metallicity distribution of giants in the low-reddening bulge field Baade's Window can be well-fit by a closed-box enrichment model. We also confirm previous observations that find enhanced [Mg/Fe], [Si/Fe] and [Ca/Fe] for all bulge giants, including those at super-solar metallicities. However, we find that the [O/Fe] ratios of metal-rich bulge dwarfs decrease with increasing metallicity, contrary to what is expected if the enhancements of the other $\alpha$-elements is due to Type II supernovae enrichment. We suggest that the decrease in oxygen production may be due to mass loss in the pre-supernova evolution of metal-rich progenitors.Comment: Conference proceeding to Nuclei in the Cosmos VIII, Vancouver, BC, July, 2004. Based on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundatio

Using paired-end sequences to optimise parameters for alignment of sequence reads against related genomes

<p>Abstract</p> <p>Background</p> <p>The advent of cheap high through-put sequencing methods has facilitated low coverage skims of a large number of organisms. To maximise the utility of the sequences, assembly into contigs and then ordering of those contigs is required. Whilst sequences can be assembled into contigs <it>de novo</it>, using assembled genomes of closely related organisms as a framework can considerably aid the process. However, the preferred search programs and parameters that will optimise the sensitivity and specificity of the alignments between the sequence reads and the framework genome(s) are not necessarily obvious. Here we demonstrate a process that uses paired-end sequence reads to choose an optimal program and alignment parameters.</p> <p>Results</p> <p>Unlike two single fragment reads, in paired-end sequence reads, such as BAC-end sequences, the two sequences in the pair have a known positional relationship in the original genome. This provides an additional level of confidence over match scores and e-values in the accuracy of the positional assignment of the reads in the comparative genome. Three commonly used sequence alignment programs: MegaBLAST, Blastz and PatternHunter were used to align a set of ovine BAC-end sequences against the equine genome assembly. A range of different search parameters, with a particular focus on contiguous and discontiguous seeds, were used for each program. The number of reads with a hit and the number of read pairs with hits for the two end sequences in the tail-to-tail paired-end configuration were plotted relative to the theoretical maximum expected curve. Of the programs tested, MegaBLAST with short contiguous seed lengths (word size 8-11) performed best in this particular task. In addition the data also provides estimates of the false positive and false negative rates, which can be used to determine the appropriate values of additional parameters, such as score cut-off, to balance sensitivity and specificity. To determine whether the approach also worked for the alignment of shorter reads, the first 240 bases of each BAC end sequence were also aligned to the equine genome. Again, contiguous MegaBLAST performed the best in optimising the sensitivity and specificity with which sheep BAC end reads map to the equine and bovine genomes.</p> <p>Conclusions</p> <p>Paired-end reads, such as BAC-end sequences, provide an efficient mechanism to optimise sequence alignment parameters, for example for comparative genome assemblies, by providing an objective standard to evaluate performance.</p

Teaching smarter: how mining ICT data can inform and improve learning and teaching practice

The trend to greater adoption of online learning in higher education institutions means an increased opportunity for instructors and administrators to monitor student activity and interaction with the course content and peers. This paper demonstrates how the analysis of data captured from various IT systems could be used to inform decision making process for university management and administration. It does so by providing details of a large research project designed to identify the range of applications for LMS derived data for informing strategic decision makers and teaching staff. The visualisation of online student engagement/effort is shown to afford instructors with early opportunities for providing additional student learning assistance and intervention – when and where it is required. The capacity to establish early indicators of ‘at-risk’ students provides timely opportunities for instructors to re-direct or add resources to facilitate progression towards optimal patterns of learning behaviour. The project findings provide new insights into student learning that complement the existing array of evaluative methodologies, including formal evaluations of teaching. Thus the project provides a platform for further investigation into new suites of diagnostic tools that can, in turn, provide new opportunities to inform continuous, sustained improvement of pedagogical practice

Something borrowed, something blue:the nature of blue metal-poor stars inferred from their colours and chemical abundances

Blue metal-poor (BMP) stars are main sequence stars that appear bluer and more luminous than normal turnoff stars. They were originally singled out by using B−V and U−B colour cuts.Early studies found that a larger fraction of field BMP stars were binaries compared to normal halo stars. Thus, BMP stars are ideal field blue straggler candidates for investigating internal stellar evolution processes and binary interaction. In particular, the presence or depletion in lithium in their spectra is a powerful indicator of their origin. They are either old, halo blue stragglers experiencing internal mixing processes or mass transfer (Li-depletion), or intermediate-age, single stars of possibly extragalactic origin (2.2 dex halo plateau Li). However, we note that internal mixing processes can lead to an increased level of Li. Hence, this study combines photometry and spectroscopy to unveil the origin of various BMP stars. We first show how to separate binaries from young blue stars using photometry, metallicity and lithium. Using a sample of 80 BMP stars (T > 6300 K), we find that 97% of the BMP binaries have V−Ks0 < 1.08 ± 0.03, while BMP stars that are not binaries lie above this cut in two thirds of the cases. This cut can help classify stars that lack radial velocities from follow-up observations. We then trace the origin of two BMP stars from the photometric sample by conducting a full chemical analysis using new high-resolution and high signal-to-noise spectra. Based on their radial velocities, Li, α and s- and r-process abundances we show that BPS CS22874-042 is a single star (A(Li) = 2.38 ± 0.10 dex) while with A(Li)= 2.23 ± 0.07 dex CD-48 2445 is a binary, contrary to earlier findings. Our analysis emphasises that field blue stragglers can be segregated from single metal-poor stars, using (V−Ks) colours with a fraction of single stars polluting the binary sample, but not vice versa. These two groups can only be properly separated by using information from stellar spectra, illustrating the need for accurate and precise stellar parameters and high-resolution, high-S/N spectra in order to fully understand and classify this intriguing class of stars. Our high-resolution spectrum analysis confirms the findings from the colour cuts and shows that CS 22874−042 is single, while CD −48 2445 is most likely a binary. Moreover, the stellar abundances show that both stars formed in situ; CS 22874−042 carries traces of massive star enrichment and CD −48 2445 shows indications of AGB mass transfer mixed with gases ejected possibly from neutron star mergers

Metal-poor stars towards the Galactic bulge:a population potpourri

We present a comprehensive chemical abundance analysis of five red giants and two horizontal branch (HB) stars towards the southern edge of the Galactic bulge, at (l, b) ~ (0°,−11°). Based on high-resolution spectroscopy obtained with the Magellan/MIKE spectrograph, we derived up to 23 chemical element abundances and identify a mixed bag of stars, representing various populations in the central regions of the Galaxy. Although cosmological simulations predict that the inner Galaxy was host to the first stars in the Universe, we see no chemical evidence of the ensuing massive supernova explosions: all of our targets exhibit halo-like, solar [Sc/Fe] ratios, which is in contrast to the low values predicted from Population III nucleosynthesis. One of the targets is a CEMP-s star at [Fe/H] = −2.52 dex, and another target is a moderately metal-poor ([Fe/H] = −1.53 dex) CH star with strong enrichment in s-process elements (e.g., [Ba/Fe] = 1.35). These individuals provide the first contenders of these classes of stars towards the bulge. Four of the carbon-normal stars exhibit abundance patterns reminiscent of halo star across a metallicity range spanning −2.0 to −2.6 dex, i.e., enhanced α-elements and solar Fe-peak and neutron-capture elements, and the remaining one is a regular metal-rich bulge giant. The position, distance, and radial velocity of one of the metal-poor HB stars coincides with simulations of the old trailing arm of the disrupted Sagittarius dwarf galaxy. While their highly uncertain proper motions prohibit a clear kinematic separation, the stars’ chemical abundances and distances suggest that these metal-poor candidates, albeit located towards the bulge, are not of the bulge, but rather inner halo stars on orbits that make them pass through the central regions. Thus, we caution similar claims of detections of metal-poor stars as true habitants of the bulge