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901.
Company J 《Die Naturwissenschaften》2011,98(1):67-78
The titanosaur Lirainosaurus astibiae is the only sauropod species known from the Late Cretaceous of the Iberian Peninsula. Lirainosaurus did not reach a gigantic body size and is one of the smallest sauropods discovered to date. Histological analysis of Lirainosaurus bones, focused on diaphyseal transverse sections of appendicular elements, reveals that Lirainosaurus did not exhibit the osseous microstructure typical for large sauropods, but is comparable with that of the coeval titanosaurs
Alamosaurus sanjuanensis, Ampelosaurus atacis, and Magyarosaurus dacus, and also shares histological traits with other small to medium-sized sauropodomorph dinosaurs. Lirainosaurus limb bones exhibit a laminar fibrolamellar bone microstructure interrupted by growth marks, fully obliterated in adulthood
by intense secondary remodeling processes which tend to replace completely the primary cortex. Lirainosaurus attained smaller sizes than typical sauropods reducing the rate of primary periosteal osteogenesis and developing an extensive
secondary remodeling well before the adult size was reached. Histological organization of Lirainosaurus long bones is more mature than observed in basal neosauropods at similar ontogenetic stage, documenting a case of peramorphosis
by pre-displacement. This heterochronic growth would be a reversal of the accelerated pattern of bone deposition typical for
the sauropod lineage. 相似文献
902.
Kimura Y 《Die Naturwissenschaften》2011,98(1):87-95
The earliest species of birch mouse, Sicista primus sp. nov., was recovered from the 17-Ma-old (Early Miocene) Gashunyinadege locality, central Nei Mongol, China. It is ~9 Ma
older than the previous first appearance datum of Sicista in Eurasia. This study indicates that North American Macrognathomys is a synonym of Eurasian Sicista, having 12 shared dental characters. As a result, the biogeography of dipodids indicates that Asian Sicista dispersed to North America as opposed to the hypothesis that Sicista originated from the North American clade. Sicista is one of the few extant rodent genera that originated as early as the Early Miocene. 相似文献
903.
Today and in the Tertiary, the geographical distribution of castorids is limited throughout all of the northern continents.
Fossils of the Castoridae genus Steneofiber are abundant in many localities of Eurasia from the late Oligocene to Pliocene period. Recently, Steneofiber fossils were discovered in two localities of northern Thailand, Mae Moh and Chiang Muan coal mines, in layers of late middle
Miocene age. These discoveries represent the first records of castorids from Southeast Asia and correspond to their southernmost
known range. The focus of this study is to describe this new Thai species of Steneofiber and to define its wear stages from the molar occlusal surfaces by using micro-CT scan analysis. The CT scan technique permits
the analysis of the virtual occlusal surface changes from wear, allowing easier comparison to related species of Steneofiber cheek teeth without destroying the teeth. The new species, Steneofiber siamensis n. sp., can be distinguished from the other species of Steneofiber by several distinct characters, longer mesostriid on p4, presence of premesostria and metastria on P4, which are smaller
than most of the other known species. The occurrence of this new castorid also supports a subtropical to tropical paleoclimate
for these two localities of northern Thailand. 相似文献
904.
Sperm competition is thought to be an important selective pressure shaping sperm form and function. However, few studies have
moved beyond gross examinations of sperm morphology. Sperm length is subject to sexual selection via sperm competition in
the scarab beetle Onthophagus taurus. Here, the structure and ultrastructure of spermatozoa in this species were investigated using light and electron microscopy.
Spermatozoa were found to be filiform, measuring about 1,200 mm in length. The sperm head consists of a three-layered acrosome
and a nuclear region bearing the anterior extension of the centriole adjunct. Acrosome and nuclear regions are bilaterally
symmetric, with their axes of symmetry being orthogonal to each other. Head and flagellar structures are connected by a well-developed
centriole adjunct. The sperm heads are asymmetrically surrounded by accessory material and embedded into the cytoplasm of
the spermatocyst cell. The accessory material is produced inside the spermatids and then transferred to the outside due to
a new membrane formed around the sperm’s organelles. The old spermatid membrane separates the accessory material from the
cyst cell. The flagellum contains a 9+9+2 axoneme, two accessory bodies, and two mitochondrial derivatives of unequal size.
The major mitochondrial derivative is significantly larger than the minor one. The axoneme is arranged in a sinusoidal manner
parallel along the major mitochondrial derivative. The spermatozoa show no progressive motility when released in buffer solution
which is likely to be the result of the flagellar arrangement and the structure of the major mitochondrial derivative. The
cross-sectional area of the minor and the major mitochondrial derivatives show different patterns of genetic variation. The
data provide the first estimates of genetic variation in sperm ultrastructure for any species, and give evidence for the persistence
of genetic variation in ultrastructure required for the rapid and divergent evolution that characterizes spermatozoa generally. 相似文献
905.
906.
Kevin Shirley Eric Marland Jenna Cantrell Gregg Marland 《Mitigation and Adaptation Strategies for Global Change》2011,16(3):325-346
We recognize that carbon-containing products do not decay and release CO2 to the atmosphere instantaneously, but release that carbon over extended periods of time. For an initial production of a
stock of carbon-containing product, we can treat the release as a probability distribution covering the time over which that
release occurs. The probability distribution that models the carbon release predicts the amount of carbon that is released
as a function of time. The use of a probability distribution in accounting for the release of carbon to the atmosphere realizes
a fundamental shift from the idea that all carbon-containing products contribute to a single pool that decays in proportion
to the size of the stock. Viewing the release of carbon as a continuous probabilistic process introduces some theoretical
opportunities not available in the former paradigm by taking advantage of other fields where the use of probability distributions
has been prevalent for many decades. In particular, theories developed in the life insurance industry can guide the development
of pricing and payment structures for dealing with the costs associated with the oxidation and release of carbon. These costs
can arise from a number of proposed policies (cap and trade, carbon tax, social cost of carbon, etc), but in the end they
all result in there being a cost to releasing carbon to the atmosphere. If there is a cost to the emitter for CO2 emissions, payment for that cost will depend on both when the emissions actually occur and how payment is made. Here we outline
some of the pricing and payment structures that are possible which result from analogous theories in the life insurance industry.
This development not only provides useful constructs for valuing sequestered carbon, but highlights additional motivations
for employing a probability distribution approach to unify accounting methodologies for stocks of carbon containing products. 相似文献
907.
Shamama Afreen Nitasha Sharma Rajiv K. Chaturvedi Ranjith Gopalakrishnan N. H. Ravindranath 《Mitigation and Adaptation Strategies for Global Change》2011,16(2):177-197
Due to large scale afforestation programs and forest conservation legislations, India’s total forest area seems to have stabilized
or even increased. In spite of such efforts, forest fragmentation and degradation continues, with forests being subject to
increased pressure due to anthropogenic factors. Such fragmentation and degradation is leading to the forest cover to change
from very dense to moderately dense and open forest and 253 km2 of very dense forest has been converted to moderately dense forest, open forest, scrub and non-forest (during 2005–2007).
Similarly, there has been a degradation of 4,120 km2 of moderately dense forest to open forest, scrub and non-forest resulting in a net loss of 936 km2 of moderately dense forest. Additionally, 4,335 km2 of open forest have degraded to scrub and non-forest. Coupled with pressure due to anthropogenic factors, climate change
is likely to be an added stress on forests. Forest sector programs and policies are major factors that determine the status
of forests and potentially resilience to projected impacts of climate change. An attempt is made to review the forest policies
and programs and their implications for the status of forests and for vulnerability of forests to projected climate change.
The study concludes that forest conservation and development policies and programs need to be oriented to incorporate climate
change impacts, vulnerability and adaptation. 相似文献
908.
Charlotte Anne Nakakaawa Paul O. Vedeld Jens B. Aune 《Mitigation and Adaptation Strategies for Global Change》2011,16(1):25-62
Using a map overlay procedure in a Geographical Information System environment, we quantify and map major land use and land
cover (LULC) change patterns in Uganda period 1990–2005 and determine whether the transitions were random or systematic. The
analysis reveals that the most dominant systematic land use change processes were deforestation (woodland to subsistence farmland—3.32%);
forest degradation (woodland to bushland (4.01%) and grassland (4.08%) and bush/grassland conversion to cropland (5.5%) all
resulting in a net reduction in forests (6.1%). Applying an inductive approach based on logistic regression and trend analyses
of observed changes we analyzed key drivers of LULC change. Significant predictors of forest land use change included protection
status, market access, poverty, slope, soil quality and presence/absence of a stream network. Market access, poverty and population
all decreased the log odds of retaining forests. In addition, poverty also increased the likelihood of degradation. An increase
in slope decreased the likelihood of deforestation. Using the stock change and gain/loss approaches we estimated the change
in forest carbon stocks and emissions from deforestation and forest degradation. Results indicate a negligible increase in
forest carbon stocks (3,260 t C yr-1) in the period 1990–2005 when compared to the emissions due to deforestation and forest
degradation (2.67 million t C yr-1). In light of the dominant forest land use change patterns, the drivers and change in carbon
stocks, we discuss options which could be pursued to implement a future national REDD plus strategy which considers livelihood,
biodiversity and climate change mitigation objectives. 相似文献
909.
Jamille Costa Veiga Cristiano Menezes Felipe Andrés León Contrera 《Die Naturwissenschaften》2017,104(3-4):31
The attraction of sexual partners is a vital necessity among insects, and it involves conflict of interests and complex communication systems among male and female. In this study, we investigated the developing of sexual attractiveness in virgin queens (i.e., gynes) of Melipona flavolineata, an eusocial stingless bee. We followed the development of sexual attractiveness in 64 gynes, belonging to seven age classes (0, 3, 6, 9, 15, 18 days post-emergence), and we also evaluated the effect of different social interactions (such as competition between queens and interactions with workers) on the development of attractiveness in other 60 gynes. We used the number of males that tried to mate with a focal gyne as a representative variable of its sexual attractiveness. During the essays, each gyne was individually presented to 10 sexually mature males, and during 3 min, we counted the number of males that everted their genitalia in response to the presence of a gyne. Here, we show that M. flavolineata gynes are capable to (i) maintain their sexual attractiveness for long periods through adult life, (ii) they need a minimum social interaction to trigger the development of sexual attractiveness, and (iii) that gynes express this trait only within a social context. We conclude that the effective occurrence of matings is conditional on potential social interactions that gynes experienced before taking the nuptial flight, when they are still in the nest. These findings bring insights into the factors determining reproductive success in social insects. 相似文献
910.
Michał Zatoń Krzysztof Broda Martin Qvarnström Grzegorz Niedźwiedzki Per Erik Ahlberg 《Die Naturwissenschaften》2017,104(3-4):26
We describe the first known occurrence of a Devonian coelacanth specimen from the lower Famennian of the Holy Cross Mountains, Poland, with a conodont element preserved in its digestive tract. A small spiral and phosphatic coprolite (fossil excrement) containing numerous conodont elements and other unrecognized remains was also found in the same deposits. The coprolite is tentatively attributed to the coelacanth. Although it is unclear whether the Late Devonian coelacanth from Poland was an active predator or a scavenger, these finds provide the first direct evidence of feeding on conodont animals by early coelacanth fish, and one of the few evidences of feeding on these animals known to date. It also expands our knowledge about the diet and trophic relations between the Paleozoic marine animals in general. 相似文献