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991.
Generalized additive models were used to synthesize the data from 52 publications on the gonad growth and spawning seasonality
of Paracentrotus lividus and identify spatial and temporal patterns in the reproductive processes. According to our results, Atlantic populations
spawn in spring and develop large gonads (6.4 ± 0.2% of fresh body weight (mean ± SE)), which increase in size toward higher
latitudes. While in the Mediterranean, the gonads are smaller (3.1 ± 0.1%), possibly as the result of successive spawnings
which impede nutrients accumulating in the gonads. Differences were also observed between habitats: gonad production was higher
in seagrass meadows in the Mediterranean and in subtidal rocky substrates in the Atlantic. Food availability might cause these
variations as well as the negative correlation observed between depth and the gonad index for rocky substrates. Sex and body
size do not seem to influence greatly gonad growth. 相似文献
992.
Assessing Cd,Pb, Zn human bioaccessibility in smelter-contaminated agricultural topsoils (northern France) 总被引:5,自引:0,他引:5
Pelfrêne A Waterlot C Mazzuca M Nisse C Bidar G Douay F 《Environmental geochemistry and health》2011,33(5):477-493
The extractability of Cd, Pb, and Zn was investigated in contaminated agricultural topsoils located in an area highly affected
by the past atmospheric emissions of two smelters in northern France in order to assess their mobility and human bioaccessibility.
The determination of Cd, Pb, and Zn bioaccessibility (Unified Barge Method, in vitro test) was made to evaluate the absolute
trace element (TE) bioavailability. The results highlighted differences in bioaccessibility between Cd, Pb, and Zn (Cd > Pb > Zn).
The mean values of the bioaccessible fractions of Cd, Pb, and Zn during the gastric phase were 82, 55, and 33%, respectively,
of the pseudototal concentrations, whereas during the gastrointestinal phase, the bioaccessible fractions of metals decreased
to 45, 20, and 10%, respectively. Stepwise multiple regression analysis showed that human bioaccessibility was affected by
various physicochemical parameters (i.e., sand, carbonates, organic matter, assimilated P, free Al oxides, and pseudototal
Fe contents). Sequential extractions were performed as an indication of the TE availability in these soils. Cadmium occurred
in the more available fractions, Pb was mostly present as bound by oxides, and a significant contribution to the pseudototal
Zn concentration was defined as the unavailable residual form related to the crystalline structures of minerals. The concepts
of bioavailability and bioaccessibility are important for quantifying the risks associated with exposure to environmental
pollutants and providing more realistic information for human health. 相似文献
993.
Intransitive communities, those in which species' abilities cannot be ranked in a hierarchy, have been the focus of theoretical and empirical research, as intransitivity could help explain the maintenance of biodiversity. Here we show that models for intransitive competition embedding slightly different interaction rules can produce opposite patterns. In particular, we find that interactions in which an individual can be outcompeted by its neighbors, but cannot outcompete its neighbors, produce negative frequency dependence that, in turn, promotes coexistence. Whenever the interaction rule is modified toward symmetry (the individual and the neighbors can outcompete each other) the negative frequency dependence vanishes, producing different coexistence levels. Macroscopically, we find that asymmetric interactions yield highest biodiversity if species compete globally, while symmetric interactions favor highest biodiversity if competition takes place locally. 相似文献
994.
Marie Czamanski Adi Nugraha Philippe Pondaven Marine Lasbleiz Annick Masson Nicolas Caroff Robert Bellail Paul Tréguer 《Marine Biology》2011,158(12):2847-2862
The elemental carbon (C), nitrogen (N) and phosphorus (P) compositions of the whole-body and gut content of wild marine fish
inhabiting the Bay of Biscay (Northeast Atlantic) were studied. Furthermore, the literature was examined for studies of aquacultured
fish, reporting the elemental composition of the whole-body fish, that of their food, and nutrient assimilation and gross
growth efficiencies (GGE). In both wild-caught and aquacultured fish, significant differences in C, N and P elemental composition
were found between species, with P being the most variable component. Differences among species in terms of C, N and P content
could be explained by varying proportions of storage compounds in whole-body fish, and varying degrees of ossification. Aquacultured
fish feces were found to be P-rich, because of a lower P assimilation efficiency, compared to C or N assimilation efficiencies.
Examination of aquacultured fish literature also revealed that C, N and P GGE and nutrient resupply ratios agreed with basic
principles of homeostatic regulation of whole-body fish elemental composition. Extrapolation of the results to broader marine
systems indicated that fish may be important for conveying nutrients toward the ocean interior. 相似文献
995.
In this paper, we argue that understanding marine ecosystem functioning requires a thorough appreciation of the role of intraguild
predation to system dynamics. The theoretical predictions of intraguild predation models might explain some of the community
features observed in marine ecosystems such as low diversity in upwelling and productive systems and species alternation in
response to moderate external forcing. Finally, we argue that an ecosystem approach to fisheries requires that the size–structure
of fish populations should be taken into account and that it is extremely important to account for the predators of early
stages (eggs and larvae) to gain a thorough understanding of the key interactions between species. 相似文献
996.
The assessment of relevant spatial scales at which ecological processes occur is of special importance for a thorough understanding
of ecosystem functioning. In coastal ecosystems, the variability of trophic interactions has been studied at different spatial
scales, but never at scales from centimetres to metres. In the present study, we investigated the link between habitat structure
and small-scale variability of food web functioning on intertidal boulder field ecosystems. Two microhabitats, boulder-top
and boulder-bottom, were considered, and the trophic ecology of invertebrate consumers was studied using stable isotope tracers.
We found for two of the main suspension feeders of northern Atlantic rocky shores (the sponges Halichondria panicea and Hymeniacidon sanguinea) consistent 15N enrichment for individuals sampled under boulders, suggesting that these consumers relied on different trophic resource
according to the microhabitat inhabited, at a centimetre scale. The high δ15N signatures found underneath boulders suggested higher use of highly decomposed organic matter in this microhabitat. The
isotopic difference between the two microhabitats decreased in higher trophic level consumers, which likely foraged at a spatial
scale including both microhabitats. Finally, our results reveal that in highly heterogeneous habitats such as boulder fields,
trophic interactions are likely to vary strongly in space, which should be considered in future researches. The link between
habitat physical structure and food web variability might also contribute to the high biological diversity characterizing
heterogeneous ecosystems. 相似文献
997.
Orb web spiders of the genus Argiope are permanently located at the hub of the orb web and are thus vulnerable to changing environmental conditions. Severe damage
to the web by non-prey animals can have a significant impact on survival, through the cost of producing expensive silk and
the loss of foraging opportunities. Thus, selection should favor web protection mechanisms, and the conspicuous web decorations,
typical of Argiope spiders, may play a role. Decorated webs suffer less damage than undecorated webs, consistent with the view that they advertise
the presence of the web to non-prey animals that may damage the web. However, whether spiders respond to web damage by increasing
investment in web decorations has not been investigated. We subjected adult St. Andrew's Cross spider (Argiope keyserlingi) females to three levels of web damage and recorded their subsequent web-decorating behavior. Mild damage, similar to that
caused by impacting prey, did not affect either web building or decorating behavior. However, spiders subjected to substantial
web damage both reduced the size of subsequent webs and increased investment in web decoration size. These data are consistent
with an advertising role of web decorations. 相似文献
998.
Cynthia A. Ursino María C. De Mársico Mariela Sued Andrés Farall Juan C. Reboreda 《Behavioral ecology and sociobiology》2011,65(12):2279-2286
Obligate avian brood parasites lay their eggs in nests of other species (hosts), which raise parasitic young. Parasitic nestlings
are likely to influence host’s parental behaviours as they typically beg for food more vigorously than young host for a given
hunger level. However, few studies have tested this idea, with conflicting results. These prior studies were largely limited
to biparental hosts, but little is known about the effect of brood parasitism on parental behaviours in hosts that breed cooperatively.
We followed a multimodel approach to examine the effect of brood parasitism on nest provisioning and helper recruitment in
the baywing (Agelaioides badius), a cooperative breeder parasitised by screaming (Molothrus rufoaxillaris) and shiny (Molothrus bonariensis) cowbirds. Multimodel inference results indicated that feeding visits increased with nestling age, cooperative group size
and number of cowbird nestlings in the brood. Brood size had little influence on feeding visits, which further suggests that
baywings adjusted their provisioning effort in response to cowbird parasitism. In addition, nests parasitised artificially
with shiny cowbird eggs or hatchlings recruited more helpers than unmanipulated nests having only host or screaming cowbird
young. Our results provide novel evidence that brood parasitism and cooperative breeding interact in determining the levels
of nest provisioning. 相似文献
999.
Maria Clara P. Amorim José Miguel Simões Vitor C. Almada Paulo J. Fonseca 《Behavioral ecology and sociobiology》2011,65(4):707-716
Signal attributes should show different degrees of variability depending on the information to be conveyed. Species identity
is usually associated with stereotyped features of a signal, whereas other types of information such as individual quality
and motivation are associated with signal plasticity. Lusitanian toadfish males form aggregations during the breeding season
and emit a tonal advertisement call (the boatwhistle) to attract mates to their nests. We test the hypothesis that the boatwhistle
can convey information both on individual identity and motivation by checking how signal parameters vary with time. We study
how the physical (tide level) and social (calling alone or in a chorus) environments and male calling rate affect this advertisement
signal and how all these external and internal factors (environment, social and male motivation) blend to modulate the Lusitanian
toadfish’s advertisement call. Boatwhistles of each male were very stereotyped in short periods of time (minutes), but intra-male
signal variability greatly increased in a longer time scale (days). Nevertheless, significant differences among males could
still be found even in a long time scale. Pulse period was the acoustic feature that most contributed to discriminate among
males. Tide level and male calling rate modulated boatwhistle characteristics, and there was a differential effect of tide
on call attributes depending on male calling rate. Social acoustic environment only affected calling rate. These results suggest
that inter-individual differences in call characteristics and call plasticity may mediate both male–male assessment and mate
choice. 相似文献
1000.
Claire Suchet Laurent Dormont Bertrand Schatz Martin Giurfa Valérie Simon Christine Raynaud Jérôme Chave 《Behavioral ecology and sociobiology》2011,65(5):1015-1027
Two wild subspecies of snapdragon, Antirrhinum majus, subspecies pseudomajus and striatum, differ in floral color and can be visually discriminated by insect visitors. The extent to which olfactory cues derived
from floral scents contribute to discrimination between snapdragon subspecies is however unknown. We tested whether these
two subspecies differ in floral scent and whether these olfactory differences are used by bumblebees (Bombus terrestris) to discriminate between them. We grew individuals of both subspecies, collected from a total of seven wild populations,
under controlled conditions. We quantified the volatile organic compounds (VOCs) emitted by the flowers using gas-chromatography/mass-spectrometry/flame-ionization-detection.
We studied antennal detection of VOCs by bumblebees, by means of electroantennogram study (EAG). We also performed behavioral
experiments in a Y-maze to determine the innate response of bumblebees to the main floral VOCs emitted by our snapdragon subspecies.
The floral scent of Antirrhinum majus pseudomajus contained three volatile benzenoids absent in the floral scent of Antirrhinum majus striatum. One of them, acetophenone, contributed over 69% of the absolute emissions of A. majus pseudomajus. These benzenoids elicited a significantly higher EAG response compared with other VOCs. In the Y-maze, bumblebees were significantly
less attracted by acetophenone, suggesting an aversive effect of this VOC. Our findings indicate that bumblebees are able
to discriminate between the two Antirrhinum majus subspecies. Differences in flower scent between these subspecies and olfactory bumblebee preferences are discussed in the
light of biochemical constraints on VOCs synthesis and of the role of flower scent in the evolutionary ecology of A. majus. 相似文献