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991.
A series of experiments investigated the potential role of microbial mats in nutrition of the early settlement stages of Penaeus semisulcatus. From 3 days post-metamorphosis, the microbial mat supported high growth and survival rates in postlarvae, equivalent to
that supported by a control diet of Artemia nauplii and mussel. Examination of gut contents indicated that benthic postlarvae feed indiscriminately on the microbial
mat. However, when postlarvae were fed separated size-fractions of the microbial mat, only the fraction containing a high
concentration of infauna (mainly nematodes) was able to support the same growth as intact microbial mat. This appears to be
due to the low nitrogen content (0.4–0.9 mmol g−1) of the various size-fractions, compared to that of infauna (4.0 mmol g−1). The stable isotope composition of the dietary size-fractions and postlarval shrimp tissue supports the hypothesis that
the shrimp assimilated C and N primarily from the associated infauna. This may be due to selective feeding that is not apparent
from stomach contents, due to rapid digestion of fauna soft tissues, or to differential assimilation of infaunal prey relative
to other microbial mat components. The results demonstrate that microbial mats may support survival and growth in early-stage
penaeid shrimp postlarvae on intertidal mud flats. 相似文献
992.
Gine Roll Skjærvø Bård G. Stokke Eivin Røskaft 《Behavioral ecology and sociobiology》2009,63(8):1133-1140
The aim of this study was to test the hypothesis that parent–offspring conflict over parental investment might have led to
the rarity of dizygotic twins in humans. We explored the theoretical prediction that twins maximize their inclusive fitness
by the death of a co-twin, while mothers of twins maximize fitness by raising both twins to independence. We used life history
data (1700–1900) from two parishes in Central Norway to compare differences in inclusive fitness (measured as number of children
reared to the age of 16 years, using Hamilton's rule) between twins and mothers of twins. Our results show that twins maximize
their inclusive fitness by the death of a co-twin, while mothers of twins raise more children by rearing both twins to adulthood.
However, because twins growing up as singletons may produce higher or at least equal number of offspring than the sum of the
two twins growing up together, mothers might gain more grandchildren by allowing twins to grow up as singletons. To conclude,
both selfish twins and their mothers might benefit by the death of a co-twin, indicating that there is no parent–offspring
conflict responsible for the rareness of twins in these human populations. Finally, we discuss the results in the light of
“The Insurance Egg Hypothesis” and “The Natural Selection Hypothesis”. 相似文献
993.
Thomas G. Reichenauer Sunil Panamulla Siripala Subasinghe Bernhard Wimmer 《Environmental geochemistry and health》2009,31(5):573-579
The tsunami disaster in the Indian Ocean in December 2004 caused devastation of agricultural soils by salt water over wide
areas. Many rice fields located close to the coast were affected by the flood of seawater. Electric conductivity (EC) of soils
in tsunami-affected rice fields was found to be higher compared to unaffected fields 2 years after the tsunami. Four soil
amendments (gypsum, dolomite, cinnamon ash and rice-husk-charcoal) were tested for their influence on improving the yield
parameters of rice grown in a tsunami-affected and a non-affected area. Yield parameters were compared with an untreated control
of the same cultivar (AT362) and with a salt resistant rice variety (AT354). The salt resistant variety had the highest grain
yield. The two amendments gypsum and rice-husk-charcoal led to an increase in grain yield compared to the untreated control,
whereas dolomite and cinnamon ash had no significant effect on grain yield. 相似文献
994.
Elva J. H. Robinson Thomas O. Richardson Ana B. Sendova-Franks Ofer Feinerman Nigel R. Franks 《Behavioral ecology and sociobiology》2009,63(5):779-636
Ant colonies are factories within fortresses (Oster and Wilson 1978). They run on resources foraged from an outside world fraught with danger. On what basis do individual ants decide to leave the safety of the nest? We investigated the relative roles of social information (returning nestmates), individual experience and physiology (lipid stores/corpulence) in predicting which ants leave the nest and when. We monitored Temnothorax albipennis workers individually using passive radio-frequency identification technology, a novel procedure as applied to ants. This method allowed the matching of individual corpulence measurements to activity patterns of large numbers of individuals over several days. Social information and physiology are both good predictors of when an ant leaves the nest. Positive feedback from social information causes bouts of activity at the colony level. When certain social information is removed from the system by preventing ants returning, physiology best predicts which ants leave the nest and when. Individual experience is strongly related to physiology. A small number of lean individuals are responsible for most external trips. An individual’s nutrient status could be a useful cue in division of labour, especially when public information from other ants is unavailable. 相似文献
995.
Natural muds used as or in cosmetics may expose consumers to toxic metals and elements via absorption through the skin, inhalation
of the dried product, or ingestion (by children). Despite the extensive therapeutic and cosmetic use of the Dead Sea muds,
there apparently has been no assessment of the levels of such toxic elements as Pb, As, or Cd in the mud and mud-based products.
Inductively coupled plasma mass spectrometry analysis of eight toxic elements in samples collected from three black mud deposits
(Lisan Marl, Pleistocene age) on the eastern shore of the Dead Sea in Jordan revealed no special enrichment of toxic elements
in the mud. A similar analysis of 16 different commercial Dead Sea mud cosmetics, including packaged mud, likewise revealed
no toxic elements at elevated levels of concern. From a toxic element standpoint, the Dead Sea black muds and derivative products
appear to be safe for the consumer. Whatever the therapeutic benefits of the mud, our comparison of the elemental fingerprints
of the consumer products with those of the field samples revealed one disturbing aspect: Dead Sea black mud should not be
a significant component of such items as hand creams, body lotions, shampoo, and moisturizer. 相似文献
996.
To understand trace radionuclide (uranium) migration occurring in rocks, a granitic batholith located at the Korea Atomic
Energy Research Institute (KAERI) site was selected and investigated. The rock samples obtained from this site were examined
using mineralogical methods, including scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The changes
in the distribution pattern of uranium (U) and small amounts of trace elements, and the mineralogical textures affected by
weathering, were examined. Based on the element distribution analyses, it was found that Fe2+ released from fresh biotite is oxidized in short geological time, forming amorphous iron oxides, such as ferrihydrite, around
silicate minerals. In that case, the amorphous ferrihydrite does not show distinct adsorption for U. However, as it gradually
crystallizes to goethite or hematite, the most U-rich phases were found to be associated with the secondary iron oxides having
granular forms. This evidence suggests that the geological subsurface environment is favorable for the crystallized iron oxides
to keep their structures more stable for a long time as compared with the amorphous phases. There is a possibility that the
long residence of U which is in contact with the stable crystalline phases of iron may finally lead to the partial sequestration
of U in their structure. Consequently, it seems that Fe-oxide crystallization can be a dominating mechanism for U uptake and
controls long-term U transport in granites with low U contents. 相似文献
997.
Ocean acidification (OA) and the biological consequences of altered seawater chemistry have emerged as a significant environmental
threat to healthy marine ecosystems. Because a more acidic ocean interferes with fixation of calcium carbonate to form shells
or calcified skeletons, future ocean chemistry may significantly alter the physiology of calcifying marine organisms. These
alterations may manifest themselves directly in the calcification process, or have synergistic effects with other environmental
factors such as elevated temperatures. New tools permit us to explore subtle changes in gene expression patterns in response
to environmental conditions. We raised sea urchins (Strongylocentrotus franciscanus) under conditions simulating future atmospheric CO2 levels of 540 and 970 ppm. When larvae raised under elevated CO2 conditions were subjected to 1-h acute temperature stress, their ability to mount a physiological response (as measured by
expression of the molecular chaperone hsp70) was reduced relative to those raised under ambient CO2 conditions. These results represent the first use of gene expression assays to study the effects of OA on sea urchin development.
They highlight the importance of looking at multiple environmental factors simultaneously as this approach may reveal previously
unsuspected biological impacts of atmospheric changes. 相似文献
998.
Young green turtles (Chelonia mydas) spend their early lives as oceanic omnivores with a prevalence of animal prey. Once they settle into neritic habitats (recruitment),
they are thought to shift rapidly to an herbivorous diet, as revealed by studies in the Greater Caribbean. However, the precise
timing of the ontogenic dietary shift and the actual relevance of animal prey in the diet of neritic green turtles are poorly
known elsewhere. Stable isotopes of carbon, sulfur and nitrogen in the carapace scutes of 19 green turtles from Mauritania
(NW Africa), ranging from 26 to 102 cm in curved carapace length (CCLmin), were analyzed to test the hypothesis of a rapid
dietary shift after recruitment. Although the length of residence time in neritic habitats increased with turtle length, as
revealed by a significant correlation between turtle length and the δ13C and the δ34S of the scutes, comparison of the δ15N of the innermost and outermost layers of carapace scutes demonstrated that consumption of macrophytes did not always start
immediately after recruitment, and turtles often resumed an animal-based diet after starting to graze on seagrasses. As a
consequence, seagrass consumption did not increase gradually with turtle size and animal prey largely contributed to the diet
of turtles within the range 29–59 cm CCLmin (76–99% of assimilated nutrients). Seagrass consumption by turtles larger than
59 cm CCLmin was higher, but they still relied largely on animal prey (53–76% of assimilated nutrients). Thus, throughout
most of their neritic juvenile life, green turtles from NW Africa would be better classified as omnivores rather than herbivores.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
999.
Arsenite [As(III)]-oxidizing bacteria play important roles in reducing arsenic [As] toxicity and mobility in As-contaminated
areas. As-resistant bacteria were isolated from the soils of two abandoned mines in the Republic of Korea. The isolated bacteria
showed relatively high resistances to As(III) up to 26 mM. The PCR-based 16S rRNA analysis revealed that the isolated As-resistant
bacteria were close relatives to Serratia marcescensa, Pseudomonas putida, Pantoea agglomerans, and Alcaligenes sp. Among the five As-resistant bacterial isolates, Alcaligenes sp. strain RS-19 showed the highest As(III)-oxidizing activity in batch tests, completely oxidizing 1 mM of As(III) to As(V)
within 40 h during heterotrophic growth. This study suggests that the indigenous bacteria have evolved to retain the ability
to resist toxic As in the As-contaminated environments and moreover to convert the species to a less toxic form [e.g., from
As(III) to As(V)] and also contribute the biogeochemical cycling of As by being involved in speciation of As. 相似文献
1000.
We investigated the constraints on sulfide uptake by bacterial ectosymbionts on the marine peritrich ciliate Zoothamnium niveum by a combination of experimental and numerical methods. Protists with symbionts were collected on large blocks of mangrove-peat.
The blocks were placed in a flow cell with flow adjusted to in situ velocity. The water motion around the colonies was then
characterized by particle tracking velocimetry. This shows that the feather-shaped colony of Z. niveum generates a unidirectional flow of seawater through the colony with no recirculation. The source of the feeding current was
the free-flowing water although the size of the colonies suggests that they live partly submerged in the diffusive boundary
layer. We showed that the filtered volume allows Z. niveum to assimilate sufficient sulfide to sustain the symbiosis at a few micromoles per liter in ambient concentration. Numerical
modeling shows that sulfide oxidizing bacteria on the surfaces of Z. niveum can sustain 100-times higher sulfide uptake than bacteria on flat surfaces, such as microbial mats. The study demonstrates
that the filter feeding zooids of Z. niveum are preadapted to be prime habitats for sulfide oxidizing bacteria due to Z. niveum’s habitat preference and due to the feeding current. Z. niveum is capable of exploiting low concentrations of sulfide in near norm-oxic seawater. This links its otherwise dissimilar habitats
and makes it functionally similar to invertebrates with thiotrophic symbionts in filtering organs.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献