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To our knowledge, this paper is the first record/report of a juvenile light-coloured Weddell seal (Leptonychotes weddellii) at Cape Shirreff, Livingston Island in January 1998, determining that it was an albino individual. Based on available literature,
three cases of albino seals have been reported exclusively for Harbour seal pups, and no albino has been reported for Antarctic
pagophilic true seals. Therefore, this is the first confirmed case of albinism in Antarctic pagophilic true seals species,
indicating that this phenomenon is indeed of a rare occurrence.
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Daniel TorresEmail: |
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Sub-Antarctic Marion Island has had a permanent research station for 50 years and the islands Wandering Albatrosses have been intensively studied for 20 years. The reactions of breeding birds to approaches by a human on foot were recorded. Three response variables were calculated: intensity of vocal reaction (IVR), intensity of non-vocal reaction (INR) and overall response index (ORI). At 5 m from the nest, twice as many birds stood and/or vocalised as at 15 m. Nearest neighbour distance, age and gender did not explain individual variability of responses. Study colony birds had higher IVR scores than non-study colony birds; birds at colonies closest to the station had the highest ORI scores. A better breeding record was associated with lower IVR and ORI scores, but a causative relationship remains to be demonstrated. A minimum viewing distance of 25 m is recommended for breeding Wandering Albatrosses.
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Marienne S. de VilliersEmail: Fax: +27-21-6503434 |
John CooperEmail: |
Peter G. RyanEmail: |
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Methanogens growing on C-1 substrates synthesize 2-carbon acetyl groups in the form of acetyl-CoA for carbon assimilation
using the multienzyme complex acetyl-CoA decarbonylase/synthase (ACDS) which contains five different subunits encoded within
an operon. In species growing on acetate ACDS also functions to cleave the acetate C-C bond for energy production by methanogenesis.
A number of species of Methanosarcina that are capable of growth on either C-1 compounds or acetate contain two separate ACDS operons, and questions have been
raised about whether or not these operons play separate roles in acetate synthesis and cleavage. Methanosarcina thermophila genomic DNA was analyzed for the presence of two ACDS operons by PCR amplifications with different primer pairs, restriction
enzyme analyses, DNA sequencing and Southern blot analyses. A single ACDS operon was identified and characterized, with no
evidence for more than one. MALDI mass spectrometric analyses were carried out on ACDS preparations from methanol- and acetate-grown
cells. Peptide fragmentation patterns showed that the same ACDS subunits were present regardless of growth conditions. The
evidence indicates that a single form of ACDS is used both for acetate cleavage during growth on acetate and for acetate synthesis
during growth on C-1 substrates.
Electronic Supplementary Material Supplementary material is available for this article at
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David A. Grahame (Corresponding author)Email: |
Edward DeMoll (Corresponding author)Email: |
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The recent contribution by Jarmila Kukalová-Peck on Hennigian phylogenetics and hexapod limb evolution is critically evaluated.
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Michael S. Engel (Corresponding author)Email: |
10.
A key point in the analysis of dynamical models of biological systems is to handle systems of relatively high dimensions.
In the present paper we propose a method to hierarchically organize a certain type of piecewise affine (PWA) differential
systems. This specific class of systems has been extensively studied for the past few years, as it provides a good framework
to model gene regulatory networks. The method, shown on several examples, allows a qualitative analysis of the asymptotic
behavior of a PWA system, decomposing it into several smaller subsystems. This technique, based on the well-known strongly
connected components decomposition, is not new. However, its adaptation to the non-smooth PWA differential equations turns
out to be quite relevant because of the strong discrete structure underlying these equations. Its biological relevance is
shown on a 7-dimensional PWA system modeling the gene network responsible for the carbon starvation response in Escherichia coli.
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Laurent Tournier (Corresponding author)Email: |
Jean-Luc GouzéEmail: |
11.
Kevin J. Emerson Sabrina J. Dake William E. Bradshaw Christina M. Holzapfel 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2009,195(4):385-391
For over 70 years, researchers have debated whether the ability to use day length as a cue for the timing of seasonal events
(photoperiodism) is related to the endogenous circadian clock that regulates the timing of daily events. Models of photoperiodism
include two components: (1) a photoperiodic timer that measures the length of the day, and (2) a photoperiodic counter that
elicits the downstream photoperiodic response after a threshold number of days has been counted. Herein, we show that there
is no geographical pattern of genetic association between the expression of the circadian clock and the photoperiodic timer
or counter. We conclude that the photoperiodic timer and counter have evolved independently of the circadian clock in the
pitcher-plant mosquito Wyeomyia smithii and hence, the evolutionary modification of photoperiodism throughout the range of W. smithii has not been causally mediated by a corresponding evolution of the circadian clock.
相似文献
Kevin J. EmersonEmail: |
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Brad E. Erisman Jorge A. Rosales-Casián Philip A. Hastings 《Environmental Biology of Fishes》2008,82(1):23-33
The sexual pattern and sexual development of the leopard grouper, Mycteroperca rosacea, were investigated from 483 specimens collected from the Gulf of California, Mexico. Histological and population data indicated
a gonochoric sexual pattern. Some juveniles passed through an immature bisexual phase of gonadal development, but no evidence
of post-maturational sex change was found. The immature bisexual phase is believed to be associated only with male development.
The size distribution and size at sexual maturity were similar for both males and females. In accordance with predictions
of the size-advantage model, the gonochoric sexual pattern of M. rosacea is likely influenced by its group-spawning mating system.
相似文献
Brad E. ErismanEmail: |
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Richard J. Robins Roland Molinié Renata A. Kwiecień Piotr Paneth Jacques Lebreton Trixie A. Bartholomeusz Albrecht Roscher Birgit Dräger Anna-Carolin Meier François Mesnard 《Phytochemistry Reviews》2007,6(1):51-63
The reaction of N-demethylation plays an important role in the degradation of some alkaloids in a number of organisms. This review presents
how our understanding of the N-demethylation of nicotine in plants has been improved through studies in cell cultures of Nicotiana plumbaginifolia and N. glutinosa using a variety of isotopic techniques. The overall aim is to understand how metabolism recycles the alkaloid skeleton, both
in terms of the metabolic route(s) exploited and the reaction mechanisms of the enzymes involved. The former has been approached
using high-resolution 2-dimensional NMR and GC-MS methods; the latter by determining kinetic isotope effects and modelling
the potential reaction steps. It appears that the mechanism for nicotine demethylation in plants is similar to but has significant
differences from that described for mammals and Pseudomonas bacteria. These differences are discussed.
相似文献
Richard J. RobinsEmail: |
14.
Parente A Conforto B Di Maro A Chambery A De Luca P Bolognesi A Iriti M Faoro F 《Planta》2008,228(6):963-975
The expression of type 1 ribosome-inactivating proteins (RIPs) in Phytolacca dioica L. leaves was investigated. Fully expanded leaves of young P. dioica plants (up to 3 years old) expressed two novel RIPs, dioicin 1 and dioicin 2. The former was also found in developing leaves
from adult P. dioica within about two and a half weeks after leaf development, and the latter continuously synthesized, with no seasonal or ontogenetic
constraint. Fully expanded leaves from adult P. dioica expressed four RIPs (PD-Ls1–4) exhibiting seasonal variation. RIPs were localized in the extracellular space, in the vacuole
and in the Golgi apparatus of mesophyll cells. Dioicin 1 and dioicin 2 showed rRNA N-β-glycosidase activity and displayed the following properties, respectively: (1) Mr values of 30,047.00 and 29,910.00, (2)
pIs of 8.74 and 9.37, and (3) IC50 values of 19.74 (0.658 nM) and 6.85 ng/mL (0.229 nM). Furthermore, they showed adenine polynucleotide glycosylase activity
and nicked pBR322 dsDNA. The amino acid sequence of dioicin 2 had 266 amino acid residues, and the highest percentage identity
(81.6%) and similarity (84.6%) with PAP-II from Phytolacca americana, while its identity with other RIPs from Phytolaccaceae was around 40%.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
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Augusto ParenteEmail: |
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Nagayasu Nakanishi Volker Hartenstein David K. Jacobs 《Development genes and evolution》2009,219(6):301-317
We examined the development of the nervous system in the rhopalium, a medusa-specific sensory structure, in Aurelia sp.1 (Cnidaria, Scyphozoa) using confocal microscopy. The rhopalial nervous system appears primarily ectodermal and contains
neurons immunoreactive to antibodies against tyrosinated tubulin, taurine, GLWamide, and FMRFamide. The rhopalial nervous
system develops in an ordered manner: the presumptive gravity-sensing organ, consisting of the lithocyst and the touch plate,
differentiates first; the “marginal center,” which controls swimming activity, second; and finally, the ocelli, the presumptive
photoreceptors. At least seven bilaterally arranged neuronal clusters consisting of sensory and ganglion cells and their neuronal
processes became evident in the rhopalium during metamorphosis to the medusa stage. Our analysis provides an anatomical framework
for future gene expression and experimental studies of development and functions of scyphozoan rhopalia.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
David K. Jacobs (Corresponding author)Email: |
16.
Alison M. Strange Geoffrey H. Griffiths Sophie Hine Kim Young Graham J. Holloway 《Journal of Insect Conservation》2007,11(3):241-249
The Small Red Damselfly (Ceriagrion tenellum) (De Villiers) (Odonata: Coenagrionidae: Ceriagrion) is classed as vulnerable (Shirt, British Red Data Book, Nature Conservancy Council, Peterborough, UK, 1987) throughout the
UK, and is included in certain Local Biodiversity Action Plans (LBAPs) in the south. A large proportion of any Biodiversity
Action Plan is concerned with the requirement of conservation and management programmes. In order to guide them, information
about the habitat preferences of the species concerned is vital. Detailed habitat information was collected to include a variety
of physical parameters particularly vegetation, both in-channel and bankside. The species was found to be primarily associated
with in-channel emergent broad-leaved plants, bankside grasses and rushes, and shallow, narrow channels with dark organic
substrate. The consequences of these findings are discussed in relation to the conservation and management of C. tenellum.
相似文献
Alison M. StrangeEmail: |
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We tested the pathogenicity of 18 Metarhizium anisopliae (Metschn.) Sorokin isolates and 22 Beauveria bassiana (Balsamo) Vuillemin isolates against Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae) larvae and adults. The efficacy of the most virulent isolate—M. anisopliae K—was evaluated in containers with a concrete bottom covered with wood shavings, under simulated poultry house conditions.
Application of conidia of this isolate to the shavings or directly to the concrete bottom reduced the yield of larvae in 8–15
time compared with the control. In another test, the mortality of mature larvae placed on previously inoculated shavings or
bottom reached 80–90% within 14 days, compared with 14% in the control. The residual activity of conidia kept at 28°C retained
its initial level during 14 days post-inoculation, but declined after three weeks. Based on our data M. anisopliae has considerable potential for the control of A. diaperinus.
相似文献
Michael SamishEmail: Email: |
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Lucien N’Guessan Kouassi Katsuo Tsuda Chie Goto Shigeyuki Mukawa Yositaka Sakamaki Masayuki Nakamura 《BioControl》2009,54(4):537-548
We compared the infectivity of two nucleopolyhedroviruses (NPVs), MyseNPV G isolated from Mythimna separata (Walker) (Lepidoptera: Noctuidae) and SpltNPV S isolated from Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae). MyseNPV G was more pathogenic against M. separata than against S. litura. Although SpltNPV S was more pathogenic than MyseNPV G against S. litura, it did not infect M. separata. Restriction endonuclease (REN) analysis of viral genomic DNA revealed that the two NPVs have quite different REN profiles.
Based on nucleotide sequences of the coding regions of polyhedrin, lef-8 and lef-9, SpltNPV S was closely related to other SpltNPV isolates, whereas MyseNPV G appeared to belong to the Mamestra NPV group, and was distinct from a Chinese isolate of Leucania (=Mythimna) separata NPV. The potential of MyseNPV G and SpltNPV S to control pest insects is discussed.
相似文献
Katsuo Tsuda (Corresponding author)Email: |
19.
M. Irfan-Ullah Giriraj Amarnath M. S. R. Murthy A. Townsend Peterson 《Biodiversity and Conservation》2007,16(6):1917-1925
Aglaia bourdillonii is a plant narrowly endemic to the southern portion of the Western Ghats (WG), in peninsular India. To understand its ecological
and geographic distribution, we used ecological niche modeling (ENM) based on detailed distributional information recently
gathered, in relation to detailed climatic data sets. The ENMs successfully reconstructed key features of the species’ geographic
distribution, focusing almost entirely on the southern WG. Much of the species’ distributional potential is already under
protection, but our analysis allows identification of key zones for additional protection, all of which are adjacent to existing
protected areas. ENM provides a useful tool for understanding the natural history of such rare and endangered species.
相似文献
M. Irfan-UllahEmail: Email: |
20.
We propose a new retina simulation software, called Virtual Retina, which transforms a video into spike trains. Our goal is twofold: Allow large scale simulations (up to 100,000 neurons) in
reasonable processing times and keep a strong biological plausibility, taking into account implementation constraints. The
underlying model includes a linear model of filtering in the Outer Plexiform Layer, a shunting feedback at the level of bipolar
cells accounting for rapid contrast gain control, and a spike generation process modeling ganglion cells. We prove the pertinence
of our software by reproducing several experimental measurements from single ganglion cells such as cat X and Y cells. This
software will be an evolutionary tool for neuroscientists that need realistic large-scale input spike trains in subsequent
treatments, and for educational purposes.
相似文献
Pierre Kornprobst (Corresponding author)Email: |