237 resultados para Penguin
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Breeding individuals enter an emergency life-history stage when their body reserves reach a minimum threshold. Consequently, they redirect current activity toward survival, leading to egg abandonment in birds. Corticosterone (CORT) is known to promote this stage. How and to what extent CORT triggers egg abandonment when breeding is associated with prolonged fasting, however, requires further investigation. We manipulated free-living male Adelie penguins with CORT-pellets before their laying period. We then examined their behavioral response with respect to nest abandonment in parallel with their prolactin levels (regulating parental care), and the subsequent effects of treatment on breeding success in relieved birds. Exogenous CORT triggered nest abandonment in 60% of the treated penguins -14 days after treatment and induced a concomitant decline in prolactin levels. Interestingly, prolactin levels in treated penguins that did not abandon their nest were higher at the point of implantation and also after being relieved by females, when compared with abandoning penguins. Among successful birds, the treatment did not affect the number of chicks, nor the brood mass. Our results show the involvement of CORT in the decision-making process regarding egg abandonment in Adelie penguins when incubation is associated with a natural long fast. However, we suggest that CORT alone is not sufficient to trigger nest abandonment but that 1) prolactin levels need to reach a low threshold value, and 2) a rise in proteolysis (i.e. utilization of protein as main energy substrate) seems also to be required.
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"First Penguin books edition, November, 1946."
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"First published 1945"
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Mode of access: Internet.
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Bibliography: p. 365-378.
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Mode of access: Internet.
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Mode of access: Internet.
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"We have taken IQ tests but, strangely, no Compassion Aptitude Tests (CATs). Yet mind and emotions need to be seen as two different parts of the same spectrum, says holistic thinker Henryk Skolimowski, if the human psyche, having taken an unprecedented battering this century, is to be mended. This cannot be accomplished, however, either through the offices of dusty philosophical treatises or popular psychological fixes, only by our arriving at a new way of looking at the world." "In a Grand Theory of participatory mind that builds on the insights of such thinkers as Teilhard de Chardin and Bergson as well as contemporaries Dobzhansky and Bateson, Skolimowski points to a new order, one brought about by a Western mind returning to, then reintegrating, the spiritual. This quest for fresh perspectives, as we approach the twenty-first century, has now become 'the hallmark of our times'."--BOOK JACKET.
Nitrogen ecophysiology of Heron Island, a subtropical coral cay of the Great Barrier Reef, Australia
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Coral cays form part of the Australian Great Barrier Reef. Coral cays with high densities of seabirds are areas of extreme nitrogen (N) enrichment with deposition rates of up to 1000 kg N ha(-1) y(-1). The ways in which N sources are utilised by coral cay plants, N is distributed within the cay, and whether or not seabird-derived N moves from cay to surrounding marine environments were investigated. We used N metabolite analysis, N-15 labelling and N-15 natural abundance (delta(15)N) techniques. Deposited guano-derived uric acid is hydrolysed to ammonium (NH4+) and gaseous ammonia (NH3). Ammonium undergoes nitrification, and nitrate (NO3-) and NH4+ were the main forms of soluble N in the soil. Plants from seabird rookeries have a high capacity to take up and assimilate NH4+, are able to metabolise uric acid, but have low rates of NO3- uptake and assimilation. We concluded that NH4+ is the principal source of N for plants growing at seabird rookeries, and that the presence of NH4+ in soil and gaseous NH3 in the atmosphere inhibits assimilation of NO3-, although NO3- is taken up and stored. Seabird guano, Pisonia forest soil and vegetation were similarly enriched in N-15 suggesting that the isotopic enrichment of guano (delta(15)N 9.9parts per thousand) carries through the forest ecosystem. Soil and plants from woodland and beach environments had lower delta(15)N (average 6.5parts per thousand) indicating a lower contribution of bird-derived N to the N nutrition of plants at these sites. The aquifer under the cay receives seabird-derived N leached from the cay and has high concentrations of N-15-enriched NO3- (delta(15)N 7.9parts per thousand). Macroalgae from reefs with and without seabirds had similar delta(15)N values of 2.0-3.9parts per thousand suggesting that reef macroalgae do not utilise N-15-enriched seabird-derived N as a main source of N. At a site beyond the Heron Reef Crest, macroalgae had elevated delta(15)N of 5.2parts per thousand, possibly indicating that there are locations where macroalgae access isotopically enriched aquifer-derived N. Nitrogen relations of Heron Island vegetation are compared with other reef islands and a conceptual model is presented.
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Microspectrophotometric examination of the retina of a procellariiform marine bird, the wedge-tailed shearwater Puffinus pacificus, revealed the presence of five different types of vitamin A(1)-based visual pigment in seven different types of photoreceptor. A single class of rod contained a medium-wavelength sensitive visual pigment with a wavelength of maximum absorbance (lambda(max)) at 502 nm. Four different types of single cone contained visual pigments maximally sensitive in either the violet (VS, lambda(max) 406 nm), short (SWS, lambda(max) 450 nm), medium (MWS, lambda(max) 503 nm) or long (LWS, lambda(max) 566 nm) spectral ranges. In the peripheral retina, the SWS, MWS and LWS single cones contained pigmented oil droplets in their inner segments with cut-off wavelengths (lambda(cut)) at 445 (C-type), 506 (Y-type) and 562 nm (R-type), respectively. The VS visual pigment was paired with a transparent (T-type) oil droplet that displayed no significant absorption above at least 370 run. Both the principal and accessory members of the double cone pair contained the same 566 nm lambda(max) visual pigment as the LWS single cones but only the principal member contained an oil droplet, which had a lambda(cut) at 413 nm. The retina had a horizontal band or 'visual streak' of increased photoreceptor density running across the retina approximately 1.5 mm dorsal to the top of the pecten. Cones in the centre of the horizontal streak were smaller and had oil droplets that were either transparent/colourless or much less pigmented than at the periphery. It is proposed that the reduction in cone oil droplet pigmentation in retinal areas associated with high visual acuity is an adaptation to compensate for the reduced photon capture ability of the narrower photoreceptors found there. Measurements of the spectral transmittance of the ocular media reveal that wavelengths down to at least 300 nm would be transmitted to the retina.
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WHEN MEDIA ARE NEW: UNDERSTANDING THE DYNAMICS OF NEW MEDIA ADOPTION AND USE, JOHN CAREY AND MARTIN C. J. ELTON (2010) Ann Arbor, MI: University of Michigan Press (374 pp.), ISBN 978-0-472-05085-7, $47.50 (paperback). YOU ARE NOT A GADGET: A MANIFESTO, JARON LANIER (2011) New York: Vintage (240 pp.), ISBN 978-0307389978, $15 (paperback) EXTRAORDINARY CANADIANS: MARSHALL McLUHAN, DOUGLAS COUPLAND (2010) Toronto, Canada: Penguin Canada (208 pp.), ISBN 9780670069224, $26 (hardback)
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Adult male and female emperor penguins (Aptenodytes forsteri) were fitted with satellite transmitters at Pointe-Géologie (Adélie Land), Dumont d'Urville Sea coast, in November 2005. Nine of 30 data sets were selected for analyses to investigate the penguins' diving behaviour at high resolution (doi:10.1594/PANGAEA.633708, doi:10.1594/PANGAEA.633709, doi:10.1594/PANGAEA.633710, doi:10.1594/PANGAEA.633711). The profiles are in synchrony with foraging trips of the birds during austral spring (doi:10.1594/PANGAEA.472171, doi:10.1594/PANGAEA.472173, doi:10.1594/PANGAEA.472164, doi:10.1594/PANGAEA.472160, doi:10.1594/PANGAEA.472161). Corresponding high resolution winter data (n = 5; archived elsewhere) were provided by A. Ancel, Centre d'Ecologie et Physiologie Energétiques, CNRS, Strasbourg, France. Air-breathing divers tend to increase their overall dive duration with increasing dive depth. In most penguin species, this occurs due to increasing transit (descent and ascent) durations but also because the duration of the bottom phase of the dive increases with increasing depth. We interpreted the efficiency with which emperor penguins can exploit different diving depths by analysing dive depth profile data of nine birds studied during the early and late chick-rearing period in Adélie Land, Antarctica. Another eight datasets of dive depth and duration frequency recordings (doi:10.1594/PANGAEA.472150, doi:10.1594/PANGAEA.472152, doi:10.1594/PANGAEA.472154, doi:10.1594/PANGAEA.472155, doi:10.1594/PANGAEA.472142, doi:10.1594/PANGAEA.472144, doi:10.1594/PANGAEA.472146, doi:10.1594/PANGAEA.472147), which backup the analysed high resolution depth profile data, and dive depth and duration frequency recordings of another bird (doi:10.1594/PANGAEA.472156, doi:10.1594/PANGAEA.472148) did not match the requirement of high resolution for analyses. Eleven additional data sets provide information on the overall foraging distribution of emperor penguins during the period analysed (doi:10.1594/PANGAEA.472157, doi:10.1594/PANGAEA.472158, doi:10.1594/PANGAEA.472162, doi:10.1594/PANGAEA.472163, doi:10.1594/PANGAEA.472166, doi:10.1594/PANGAEA.472167, doi:10.1594/PANGAEA.472168, doi:10.1594/PANGAEA.472170, doi:10.1594/PANGAEA.472172, doi:10.1594/PANGAEA.472174, doi:10.1594/PANGAEA.472175).
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Peer reviewed
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According to life-history theory, individuals optimize their decisions in order to maximize their fitness. This raises a conflict between parents, which need to cooperate to ensure the propagation of their genes but at the same time need to minimize the associated costs. Trading-off between benefits and costs of a reproduction is one of the major forces driving demographic trends and has shaped several different parental care strategies. Using little penguins (Eudyptula minor) as a model, we investigated whether individuals of a pair provide equal parental effort when raising offspring and whether their behavior was consistent over 8 years of contrasting resource availability. Using an automated identification system, we found that 72% of little penguin pairs exhibited unforced (i.e., that did not result from desertion of 1 parent) unequal partnership through the postguard stage. This proportion was lower in favorable years. Although being an equal pair appeared to be a better strategy, it was nonetheless the least often observed. Individuals that contributed less than their partner were not less experienced (measured by age), and gender did not explain differences between partners. Furthermore, birds that contributed little or that contributed a lot tended to be consistent in their level of contribution across years. We suggest that unequal effort during breeding may reflect differences in individual quality, and we encourage future studies on parental care to consider this consistent low and high contributor behavior when investigating differences in pair investment into its offspring. Key words: attendance patterns, individual quality, meal size, parental care, reproductive costs, seabirds.
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As England suffered heavy casualties at the front during World War One, the nation closed ranks against outsiders at home. England sought to reaffirm its racial dominance at the heart of the empire, and the Chinese in London became the principal scapegoat for anti-foreign sentiment. A combination of propaganda and popular culture, from the daily paper to the latest theatre sensation, fanned the flames of national resentment into a raging Sinophobia. Opium smoking, gambling and interracial romance became synonymous with London's Limehouse Chinatown, which was exoticised by Sax Rohmer's evil mastermind Fu Manchu and Thomas Burke's tales of lowlife love. England's Yellow Peril exploded in the midst of a catastrophic war and defined the representation of Chinese abroad in the decades to come.