740 research outputs found
Cell death and degeneration in the symbiotic dinoflagellates of the coral Stylophora pistillata during bleaching
No full textRising sea temperatures are increasing the incidences of mass coral bleaching (the dissociation
of the coral–algal symbiosis) and coral mortality. In this study, the effects of bleaching
(induced by elevated light and temperature) on the condition of symbiotic dinoflagellates (Symbiodinium
sp.) within the tissue of the hard coral Stylophora pistillata (Esper) were assessed using a suite
of techniques. Bleaching of S. pistillata was accompanied by declines in the maximum potential
quantum yield of photosynthesis (Fv/Fm, measured using pulse amplitude modulated [PAM] fluorometry),
an increase in the number of Sytox-green-stained algae (indicating compromised algal membrane
integrity and cell death), an increase in 2’,7’-dichlorodihydrofluroscein diacetate (H2DCFDA)-
stained algae (indicating increased oxidative stress), as well as ultrastructural changes (vacuolisation,
losses of chlorophyll, and an increase in accumulation bodies). Algae expelled from S. pistillata
exhibited a complete disorganisation of cellular contents; expelled cells contained only amorphous
material. In situ samples taken during a natural mass coral bleaching event on the Great Barrier Reef
in February 2002 also revealed a high number of Sytox-labelled algae cells in symbio. Dinoflagellate
degeneration during bleaching seems to be similar to the changes resulting from senescence-phase
cell death in cultured algae. These data support a role for oxidative stress in the mechanism of coral
bleaching and highlight the importance of algal degeneration during the bleaching of a reef coral
<i>Hippopotamus guldbergi</i> n. sp. : révision du statut d'<i>Hippopotamus madagascariensis</i> Guldberg, 1883, après plus d'un siècle de malentendus et de confusions taxonomiques
No full textAprès une brève notice sur son auteur, dont l’œuvre scientifique est actuellement mal connue, nous publions la première traduction intégrale en français de la description originale de l’hippopotame holocène disparu Hippopotamus madagascariensis Guldberg, 1883. Cette dernière est écrite en riksmaal, ancienne langue norvégienne inaccessible à la plupart des paléontologues. Nous en donnons un commentaire mammalogique prouvant que le spécimen décrit par Guldberg appartient en réalité à l’autre espèce malgache de petit hippopotame holocène, Hippopotamus lemerlei Grandidier, 1868. Depuis la publication du texte de Guldberg, une confusion initiale a été propagée dans de nombreux travaux, avec d’importantes conséquences en taxonomie. Ainsi, C. J. F. Major a décrit en 1902 comme H. madagascariensis Guldberg, 1883 un nouveau squelette malgache qui est bien différent de H. lemerlei. Mais H. madagascariensis n’étant qu’un nom de remplacement de H. lemerlei, il n’est donc pas utilisable, de ce fait nous proposons le nouveau nom d’Hippopotamus guldbergi pour désigner l’espèce décrite en 1902 par C. J. F. Major.After a short notice upon its author, whose scientific works are presently rather unknown, we publish the first complete translation in French language of the original description of the extinct Holocene Hippopotamus madagascariensis Guldberg, 1883, which was published in Riksmaal, an ancient Norvegian language incomprehensible for most palaeontologists. We provide a mammalogical comment of that description, showing that the Guldberg’s specimen actually pertains to the other small species of Holocene Malagasy hippo, Hippopotamus lemerlei Grandidier, 1868. Since Guldberg’s publication, that initial confusion was spread in many scientific works and has important taxonomical consequences. Thus, in 1902, C. J. F. Major described under the name H. madagascariensis Guldberg, 1883 a new Malagasy skeleton which is quite different from H. lemerlei. But because H. madagascariensis is no more than a replacement name for H. lemerlei, it is not usable. We then propose the new name Hippopotamus guldbergi to designate the species described in 1902 by C. J. F. Major.</p
Australia’s marine resources in a warm, acid ocean
No full textOne of the distinguishing features of our planet is the presence of an ocean that covers 71 per cent of its surface. This vast ocean nurtured life’s beginnings and continues to support the biosphere and ultimately humanity. Approximately a quarter of the world’s population lives along coastlines where people extract food, building materials, energy, cultural signicance and income (Seto and Shepherd, 2009). Oceans are also important in connecting and transporting people and materials over great distances through coastal and ocean-going shipping. In the current period of rapid global change, oceans play a critical role by absorbing around 30 per cent of the carbon dioxide from anthropogenic sources and over 90 per cent of the heat generated by the associated enhanced greenhouse effect (IPCC, 2007). Without the ocean, climate change would be far more severe than it is today. Australia is a maritime country with sovereign rights over an ocean territory that covers 16 million km - almost twice the size of its land area. This ocean area supports industries which are extremely valuable to Australia and yield economic wealth estimated as 25 billion per annum (AIMS, 2012). Recreational shing (supported by over A126-233 million per annum merely along Queensland’s Gold Coast) and Great Barrier Reef tourism (which generates over $A6 billion per annum) are a few examples of the direct benets that marine resources provide to the Australian economy (Poloczanska et al., 2007). In addition to the direct nancial benets to the Australian economy, our marine ecosystems also provide a wide array of other values, including social and lifestyle benets, and indirect yet critically important services such as coastal protection, shoreline stabilization, greenhouse gas regulation, nutrient recycling and the maintenance of water quality (Poloczanska et al., 2007, Martinez et al., 2007). Marine resources play an important role regionally. Many countries in the Asia and the Indo-Pacic region have large populations that reside along their coasts (Martinez et al., 2007). For instance, over 60 per cent of Indonesia’s population lives along its 95,181 km of coastline (Hoegh-Guldberg et al., 2009), a proportion which increases to around 95 per cent for the island countries of the Indo-Pacic (CIA, 2010). Marine resources, consequently, are central to the well-being and food security of people throughout South-East Asia and the Indo-Pacic region. Risks posed by climate change to the economies, livelihoods and security of the region will impact Australia, given Australia’s economic and development role in the South Pacic region
DNA methylation: an epigenetic pathway to cancer and a promising target for anticancer therapy
No full textA ligation assay for multiplex analysis of CpG methylation using bisulfite-treated DNA
No full textDN
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