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991.
To standardize conditions during the final maturation and ovulation of ovarian follicles from Japanese eel, we have developed
a culture system for the production of fertilizable eggs from post-vitellogenic ovarian follicles in vitro. Post-vitellogenic
ovarian follicles were incubated in culture medium supplemented with 17α,20β-dihydroxy-4-pregnen-3-one (DHP) with or without
bovine serum albumin (BSA) to assess the effects of protein concentration. Eggs that ovulated during incubation were fertilized,
and the remaining follicles were incubated in prostaglandin F2α (PGF2α) for a further 3 or 6 h before fertilization. Male eels were injected repeatedly with human chorionic gonadotropin. The quality
of eggs obtained under the different culture conditions was evaluated after artificial fertilization in terms of hatching
success. Hatching rates tended to decrease with increasing concentrations of BSA in the incubation medium in a dose-dependent
manner. The addition of PGF2α drastically increased the number of eggs that ovulated, but the rate of hatching was greatly decreased compared with eggs
obtained earlier by DHP incubation alone. The larvae obtained from artificially fertilized eggs produced in vitro survived
for 14 days without feeding. We conclude that in vitro culture systems thus have a great potential for the acquisition of
good quality eggs under tightly controlled artificial conditions, culminating in the production of eel larvae. 相似文献
992.
Quantifying landscape pattern and ecosystem service value changes in four rapidly urbanizing hill stations of Southeast Asia 总被引:1,自引:0,他引:1
Context
Hill stations are known for their favorable cool climate and natural environments which generate valuable ecosystem services that benefit the local population, tourists and visitors. However, rapid urbanization threatens the sustainability of these highly valued fragile landscapes.Objectives
We aim to characterize and quantify the changes in the landscape patterns and ecosystem service values (ESVs) of Baguio (Philippines), Bogor (Indonesia), Dalat (Vietnam), and Pyin Oo Lwin (Myanmar), and discuss their implications to landscape sustainability.Methods
We used remote sensing imagery to map land-use/cover (2001 and 2014), and spatial metrics and gradient analysis to characterize the changes in landscape pattern. We employed a benefit transfer method to estimate the changes in ESV and human-to-ESV ratio. A land-change model was used to simulate different scenarios of future built-up expansions (2014–2030).Results
The landscapes of Dalat and Pyin Oo Lwin are becoming more fragmented, while those of Baguio and Bogor are getting more aggregated. Dalat had the highest decrease (absolute change) in ESV and H-ESV ratio, while Bogor had the highest percentage decrease (2001–2014).Conclusions
Rapid urbanization has been a major factor in the landscape transformation of Baguio, Bogor, Dalat and Pyin Oo Lwin. If the current built-up expansion rate will speed up, the decline in future ESV and H-ESV ratio (2014–2030) will be higher than if the rate will continue or slow down. Unless the concept of landscape sustainability is taken seriously in landscape and urban planning, the respective ‘values’ of these precious hill stations will become less and less.993.
Although the role of habitat fragmentation in species declines is well recognised, the effect of habitat quality on species
distributions is often studied using presence–absence models that ignore metapopulation dynamics. We compared three approaches
to model the presence–absence of North Island robins in 400 sites among 74 fragments of native forest in a 15,000-ha agricultural
landscape in New Zealand. The first approach only considered local habitat characteristics, the second approach only considered
metapopulation factors (patch size and isolation), and the third approach combined these two types of factors. The distribution
of North Island robins was best predicted by patch isolation, as their probability of occurrence was negatively correlated
with isolation from neighbouring patches and from the closest major forests, which probably acted as a source of immigrants.
The inclusion of habitat factors gave only a slight increase in predictive power and indicated that robins were more likely
to occur in areas with tall canopy, tall understory and low density of young trees. We modelled the effect of isolation using
an index of functional patch connectivity based on dispersal behaviour of radio-tracked juveniles, and this functional index
greatly improved the models in comparison to classical indices relying on Euclidean distances. This study highlights the need
to incorporate functional indices of isolation in presence–absence models in fragmented landscapes, as species occurrence
can otherwise be a misleading predictor of habitat quality and lead to wrong interpretations and management recommendations. 相似文献
994.
A total of 24 candidate plus trees (CPTs) of Pongamia pinnata (L.) Pierre. were selected to elucidate their variation and diversity based on thirteen quantitative traits (4 pod traits,
6 seed traits of parent trees and 3 progeny traits) at Forest Research Centre, Institute of Forest Productivity — Mandar,
Ranchi district during 2005–2007. The results show that, CPT-19 had maximum for seven traits viz, pod length (65.6 mm), 100-pod
weight (542.4 g), seed 2D (two dimension) area (351.2 mm2), seed length (27.9 mm), seed breadth (17.4 mm), 100-seed weight (217.9 g) and plant height (164.3 cm). The traits, 100-pod
weight and 100-seed weight had a high heritability (98.4%, 96.9%) accompanied with high genetic advance (46.0%, 34.9%). There
is a positive significant correlation between 100-pod weight and 100-seed weight traits at both genotypic and phenotypic levels
with plant height, collar diameter and volume index at 30 MAS (months after sowing). Volume index expressed a moderate heritability
(47.4%) accompanied with high genetic advance (48.4%), indicating that the character is governed by additive gene effects.
In divergence study, 24 accessions were grouped into 6 clusters on the basis of non-hierarchical euclidian cluster analysis.
The genotypes in cluster IV (CPT-5, CPT-6, CPT-7, CPT-12, CPT-16, CPT-18, CPT-22) and cluster III (CPT-4, CPT-8, CPT-9, CPT-20,
CPT-21) were most heterogeneous and can be best used within group hybridization. The wide diversity exists between the cluster
V and II, followed by cluster II and I and crosses between CPTs of these clusters may result in substantial segregates. It
is revealed that the existence of substantial variation and diversity can be utilized for genetic resource conservation and
further tree improvement programmers of the species. 相似文献
995.
There is a fundamental divergence of opinion between the EU and the US over how food products derived from genetically modified organisms should be labeled. This has less to do with safety, as moves towards the international harmonization of safety standards continue apace, and rather more to do with the consumers' right to know about the origins of the food they are consuming. This paper uses a framework drawn from the global public goods (GPG) literature of economics and the work by international relations theorists on formal international organizations (FIO) to explain why there is presently no global consensus on the manner (voluntary or mandatory) in which GM food products should be labeled. 相似文献
996.
Tradable biodiversity credit systems provide flexible means to resolve conflicts between development and conservation land-use
options for habitats occupied by threatened or endangered species. We describe an approach to incorporate the influence of
habitat fragmentation into the conservation value of tradable credits. Habitat fragmentation decreases gene flow, increases
rates of genetic drift and inbreeding, and increases probabilities of patch extinction. Importantly, tradable credit systems
will change the level of fragmentation over time for small and/or declining populations. We apply landscape equivalency analysis
(LEA), a generalizable, landscape-scale accounting system that assigns conservation value to habitat patches based on patch
contributions to abundance and genetic variance at landscape scales. By evaluating habitat trades using two models that vary
the relationship between dispersal behaviors and landscape patterns, we show that LEA provides a novel method for limiting
access to habitat at the landscape-scale, recognizing that the appropriate amount of migration needed to supplement patch
recruitment and to offset drift and inbreeding will vary as landscape pattern changes over time. We also found that decisions
based on probabilities of persistence alone would ignore changes in migration, genetic drift, and patch extinction that result
from habitat trades. The general principle of LEA is that habitat patches traded should make at least equivalent contributions
to rates of recruitment and migration estimated at a landscape scale. Traditional approaches for assessing the “take” and
“jeopardy” standards under the Endangered Species Act based on changes in abundance and probability of persistence may be
inadequate to prevent trades that increase fragmentation. 相似文献
997.
Orang Estegamet 《Russian Agricultural Sciences》2010,36(2):125-126
Three-breed hybrids Cuban zebu x (Azerbaijan zebu x Aberdeen Angus) surpassed the Azerbaijan zebu and two-breed Azerbaijan
zebu with Brown Latvian, Black Pied, and Aberdeen Angus breeds in weight, length, width, area, and thickness of hides. Minimum
indices were obtained or purebred animals. 相似文献
998.
A species of the genus Gonoclostera Butler, 1877, G.fangi sp.nov., from Yunnan, China is described in the present paper. Generic diagnosis and list of world species, as well as the photos of adults and genitalia of the new species are also provided. 相似文献
999.
1000.