Caldeirão, Steno bredanensis: registo de uma nova espécie para os Açores, com algumas notas sobre o seu comportamento

O caldeirão, Steno bredanensis, foi observado por duas vezes nos Açores. A primeira vez em 14-8-95 num grupo de 50-60 indivíduos de idades variadas. Movimentaram-se na proa do navio e pareceram alimentar-se durante parte do encontro. Um golfinho foi visto empurrar um peixe-balão insuflado pela superfície. A segunda ocorrência foi em 20-8-95 e seria provavelmente o mesmo grupo de 50-60 animais. Este grupo foi observado debaixo de água alimentando-se de trombeteiro, Macrorhamphosus scolopax, juntamente com cagarros, Calonectris diomedea borealis. São relatadas outras observações no comportamento desta espécie.ABSTRACT: Rough-toothed dolphin, Steno bredanensis were observed twice in the Azores. The first time on 14-8-95 a group of 50-60 individuals of mixed ages was seen. They bow rode and appeared to be feeding during part of the encounter. One dolphin was seen pushing an inflated puffer fish along the surface. The second occurrence was on 20-8-95 and was probably the same group of 50-60 animals. This group was observed underwater feeding on snipe fish, Macrorhamphosus scolopax, along with Cory's shearwaters, Calonectris diomedea borealis. A few other behavioural observations are made

Structural colour from a helicoidal cellulose architecture in the secondary cell wall: Optical properties, cell wall composition, structure and morphology of components, and their assembly and interactions.

Structural colours are produced by constructive interference of light scattered from periodically arranged interfaces within nanostructured materials. A common strategy of plants to achieve structural coloration consists of assembling cellulose microfibrils into helicoidal structures. Examples of these architectures can be found in phylogenetically distant species and in different tissues of plants, such as in the endocarp of the fruit of $\textit{Margaritaria nobilis}$, an eudicot, and in the fronds of $\textit{Microsorum thailandicum}$, a fern. In this thesis, I studied the optical response and anatomical features of the adaxial and abaxial epidermal layers of cells of $\textit{M. thailandicum}$. The optical variation between fronds, between cells, and within cells, both for the adaxial and abaxial surface, were quantified by polarised optical microscopy and microspectroscopy. The adaxial reflection is mainly in the blue range (400-550 nm), with a narrow distribution of reflection peak maxima and peak widths, while the abaxial reflection spans almost the entire visible range (400-650 nm), and spectra are broader and show more varied features. The anatomical structure responsible for this optical behaviour was confirmed by electron microscopy. Numerical modelling based on the microscopy data indicates that there is much more complexity in the helicoidal architecture than just simple local defects. The significant difference between the adaxial and abaxial epidermal cell walls hints at fundamental differences in their biosynthesis. For the endocarp of the fruit of $\textit{M. nobilis}$, I correlated the optical response to the ultrastructure of the secondary cell wall, and the morphology and chemical structure of its main components, cellulose and xylan. The composition of the endocarp was characterised as 9 \% extractives, 36 \% cellulose, 23 \% xylan, and 30 \% lignin. The cellulose microfibrils were isolated in a long series of chemical purifications, and found to be extremely short - around 500 nm - and highly crystalline, as determined via nuclear magnetic resonance spectroscopy and X-ray diffraction. Xylan was found to be the most abundant hemicellulose and its primary structure was characterised via enzyme digestions, gel electrophoresis and mass spectrometry. It has acetyl groups on every other xylose unit, no arabinose and around 4 \% of glucuronic acid decoration. By combining the information on the xylan with the morphological characteristics of the cellulose microfibrils, I speculate about their assembly into the helicoidal architecture during the cell wall biosynthesis, based on findings from coarsed-grain modelling, and on their interactions in the final tissue, based on small angle X-ray scattering studies

Expression of ZebrafishragGenes during Early Development Identifies the Thymus

AbstractRecent experiments have demonstrated that zebrafish is a vertebrate in which it is possible to carry out large-scale mutagenic screens to identify genes involved in specific developmental pathways. To follow development of the immune system in zebrafish, we have analyzed the expression of the recombination activating genes,rag1andrag2,which we have previously isolated and characterized. These genes catalyze the rearrangement of immunoglobulin genes in immature B lymphocytes and of T cell receptor genes in immature T lymphocytes and are therefore appropriate markers to follow the development of organs containing these cells. By whole-mountin situhybridization, we detected expression of bothraggenes in a paired organ in the head, beginning on the fourth day after fertilization. Histological examination of this organ indicated that it corresponds to the thymus, as described for other fish, an organ that has not previously been identified in zebrafish. By histological analysis, the thymus primordium appears at 54 hr but does not enlarge significantly until 30 hr later. The thymus continues to enlarge and reaches its mature histological organization at 1 month. The pronephros, the major hematopoietic organ in the adult fish, begins to develop hematopoietic tissue about 2 weeks after fertilization. By 1 month, mature lymphocytes are distinguishable in the tissue surrounding renal tubules. Lymphocytes appear in the kidney too late for screening by whole-mountin situhybridization; however, the pattern ofrag1expression in the thymus forms the basis of an assay for mutations affecting development of the thymus or its constituent lymphocytes

Photonics in Nature: From Order to Disorder

The most vibrant and striking colours in living organisms are often caused by a combination of pigments and nano-scale transparent architectures, which interact with light to produce so-called structural colours. These colours are the result of light interfering with the nanoscale structures that are present in the materials. Such colour-producing structures are not perfect, and irregularities in the arrangements (disorder) are present in many organisms. However, disorder in natural structures is not detrimental but functional, as it allows a broader range of optical effects. This chapter reviews and attempts to classify structurally coloured organisms, highlighting the influence that disorder has on their visual appearance. It also showcases how photonic systems, such as the blue Morpho butterfly and the white Cyphochilus beetle, are capable of obtaining optical properties (long-distance visibility and whiteness, respectively) where disorder seems to be highly optimized, indicating that disorder is important for obtaining complex visual effects in natural systems. The chapter first introduces the mathematical concepts required for analysing disordered systems, such as the Fourier transform and the structure factor. Then, ordered and disordered natural photonic systems are reviewed. This is followed by examples of completely disordered structures responsible of white appearances. Finally, we review the possibilities of hierarchical organisation and pixelated surfaces to widen the range of optical appearances

Zebrafish immunoglobulin IgD: Unusual exon usage and quantitative expression profiles with IgM and IgZ/T heavy chain isotypes

The zebrafish is an emerging model for comparative immunology and biomedical research. In contrast to the five heavy chain isotype system of mice and human (IgD, IgM, IgA, IgG, IgE), zebrafish harbor gene segments for IgD, IgM, and novel heavy chain isotype called IgZ/T which appears restricted to bony fishes. The purpose of this study was to design and validate a suite of quantitative real time RT-PCR protocols to measure IgH expression in a vertebrate model which has considerable promise for modeling both pathogenic infection and chronic conditions leading to immune dysfunction. Specific primers were designed and following verification of their specificty, relative expression levels of IgD, IgM, and IgZ/T were measured in triplicate for zebrafish raised under standard laboratory conditions. During embryonic stages, low levels of each heavy chain isotype (IgH) were detected with each increasing steadily between 2 and 17 weeks post fertilization. Overall IgM > IgZ > IgD throughout zebrafish development with the copy number of IgM being several fold higher than that of IgD or IgZ/T. IgD exon usage was also characterized, as its extremely long size and presence of a stop codon in the second IgD exon in zebrafish, raised questions as to how this antibody might be expressed. Zebrafish IgD was found to be a chimeric immunoglobulin, with the third IgD exon spliced to the first IgM constant exon thereby circumventing the first and second IgD exons. Collectively, the qRT-PCR results represent the first comparative profile of IgD, IgM, IgZ/T expression over the lifespan of any fish species and the primers and assay parameters reported should prove useful in enabling researchers to rapidly quantify changes in IgH expression in zebrafish models of disease where altered IgH expression is manifested.National Institutes of Health (U.S.

Controlling the self-assembly behavior of aqueous chitin nanocrystal suspensions

As with many other bio-sourced colloids, chitin nanocrystals (ChNCs) can form liquid crystalline phases with chiral nematic ordering. In this work, we demonstrate that it is possible to finely tune the liquid crystalline behavior of aqueous ChNC suspensions. Such control was made possible by carefully studying how the hydrolysis conditions and suspension treatments affect the colloidal and self-assembly properties of ChNCs. Specifically, we systematically investigate the effects of duration and acidity of chitin hydrolysis required to extract ChNCs, as well as the effects of the tip sonication energy input, degree of acetylation, pH and ionic strength. Finally, we show that by controlled water evaporation, it is possible to retain and control the helicoidal ordering in dry films, leading to hierarchical architecture analogous to that found in nature, e.g. in crab shells. We believe that this work serves as a comprehensive insight into ChNC preparation and handling which is required to unlock the full potential of this material in both a scientific and industrial context.This work was supported by the European Research Council [ERC-2014-STG H2020 639088], the BBSRC David Phillips Fellowship [BB/K014617/1], the EPSRC [EP/N509620/1], and Lord Lewis Research Studentship in Chemistry