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171.
172.
Moult in relation to some aspects of reproduction and growth in swarms of Antarctic krill,Euphausia superba 总被引:3,自引:0,他引:3
In a 14-d period 38 swarms of Antarctic krill,Euphausia superba Dana, were sampled in an area 55.5 x 55.5 km to the southwest of Elephant Island, at the north of the South Shetland Islands. Moult stage, maturity stage, and size of ca. 100 krill from each swarm were measured. Each of the characteristics varied greatly between swarms. Moulting krill were found in most swarms, but in one swarm all of the krill were just about to moult. Ways in which moulting may act as a possible sorting mechanism are discussed. Data for all the analysed krill (ca. 3000 specimens) were used to investigate the interdependence of moult rate, sexual maturation and growth. While all immature krill moulted at approximately the saine rate in the study, there were significant differences in the moulting rates of mature male and female krill. Gravid female krill continued to moult, although less frequently than mature males. As a consequence males had to attach spermatophores to females after each moult. It is likely that variation in moult rate of females and males was related to the energy expenditure required for ovary development in females and spermatophore production and searching behaviour in males. Spawning and moulting were only partly coupled in gravid females. Spawning appeared to take place predominantly during Moult Stage D2. There was no evidence of intermoult growth by intersegmental dilation. 相似文献
173.
H. P. Sanderson Morris Katz 《Journal of the Air & Waste Management Association (1995)》2013,63(10):476-482
Many food, fiber, forage, and forest crops and a number of animals are adversely affected by a variety of air pollutants. The more important and generally occurring of these pollutants are ethylene, fluorides, ozone, peroxyacyl nitrates (PAN), and sulfur oxides. Their effects upon animals and plants can best be judged by criteria which describe the reaction of biologic materials to pollutant concentration and exposure time. Four criteria are recognized: (1) interference with enzyme systems; (2) change in cellular chemical constituents and physical structure; (3) retardation of growth and reduction in production from altered metabolism; and (4) acute immediate tissue degeneration. Information on tissue degenerative effects due to these pollutants is the most common; there are some reports on growth and productivity reduction; but little data are available on cellular alterations and interference with enzymes. Determination and measurement of the latter two criteria are essential to the ultimate definition and prediction of the significance of the effects of pollutants on growth and productivity of agriculture. Dosage data are available which indicate the degenerative effects of some specific pollutants on certain tissues of hosts. Political-social judgments can be made because of the knowledge of the effects of these specific pollutants; this knowledge thus permits the establishment of standards which define air quality necessary for the protection of agriculture. The importance of combined pollutant effects mitigates against the ready setting of standards on an airshed or significant regional basis. The setting of standards for a single polluiant effects upon crops and animals effectively serves as a precedent and indicates the necessity of establishing air quality values for pollutant mixtures emitted into and produced within the air resource at different geographic locations as the polluted air moves throughout the typically multigovernment jurisdictions of the airsheds. 相似文献
174.
175.
The Ethics and Politics of Animal Welfare
in New Zealand: Broiler Chicken Production as a Case Study
Michael C. Morris 《Journal of Agricultural and Environmental Ethics》2009,22(1):15-30
The cause of poor welfare in broilers is multifactorial, but genotype is a major contributor. Modern broilers have been bred
for rapid growth, and this leads to increases in lameness and ascites as the legs and hearts of the heavier birds find it
difficult to cope with the extra demands placed on them. Visible lameness indicative of pain is more common in New Zealand
than in Europe. The government, however, insists that New Zealand welfare standards are higher than Europe. The government
also appears to have a strong antipathy to those demanding better welfare for broilers. Reasons for this antipathy and disparities
between government statements and research results are discussed. Government publications reveal that animal welfare is seen
as a question of image for market access and that there is little concern with animal welfare as an ethical imperative for
its own sake. The Animal Welfare Act in theory makes it an offence to ill treat an animal, but in practice allows exemptions
for industrial agriculture. The interests of animals may be better protected by an independent animal welfare advisory service. 相似文献
176.
177.
178.
179.
Morris Deutsch Fred Ruggles 《Journal of the American Water Resources Association》1974,10(5):1023-1039
ABSTRACT. Flooding along the Mississippi River and some of its tributaries was detected by the multispectral scanner (MSS) on the Earth Resources Technology Satellite (ERTS-1) on at least three orbits during the spring of 1973. The ERTS data provided the first opportunity for mapping the regional extent of flooding at the time of the imagery. Special optical data processing techniques were used to produce a variety of multispectral color composites enhancing flood-plain details. One of these, a 2-color composite of near infrared bands 6 and 7, was enlarged and registered to 1:250,000-scale topographic maps and used as the basis for preparation of flood image maps. Two specially filtered 3-color composites of MSS bands 5, 6, and 7 and 4, 5, and 7 were prepared to aid in the interpretation of the data. The extent of the flooding was vividly depicted on a single image by 2-color temporal composites produced on the additive-color viewer using band 7 flood data superimposed on pre-flood band 7 images. On May 24, when the floodwaters at St. Louis receded to bankfull stage, imagery was again obtained by ERTS. Analysis of temporal data composites of the pre-flood and post-flood band 7 images indicate that changes in surface reflectance characteristics caused by the flooding can be delineated, thus making it possible to map the overall area flooded without the necessity of a real-time system to track and image the peak flood waves. Regional planning and disaster relief agencies such as the Corps of Engineers, Office of Emergency Preparedness, Soil Conservation Service, interstate river basin commissions and state agencies, as well as private lending and insurance institutions, have indicated strong potential applications for ERTS image-maps of flood-prone areas. 相似文献
180.
High-speed films of swimmingAcanthocyclops robustus were used to test a crustacean swimming-model based on numerical analysis of thrust production. Predicted body velocities and jump distances were usually within 75% of those observed. Most of the thrust which propels.A. robustus is produced by movements of the 2nd, 3rd, and 4th thoracic swimming legs, with only small contributions from the first thoracic swimming legs. A model analyzed without the first antennae suggested that the antennae do not produce significant thrust. The leg and antennal movements could be described with trigonometric equations (cosine curves), but were best described by polynomial fits of position vs time data from the films. Patterns of swimming velocity varied among four episodes that were modeled, and followed differences in swimming-leg motions. Model results for the small (cephalothorax length = 0.6 mm) cyclopoidA. robustus and those which have been reported for the large calanoid copepodPleuromamma xiphias and other swimmers indicate that mechanical efficiency (30%) does not scale with body size, whereas jump distance (one body length), proportion of thrust generated by hydrodynamic added mass (70%), and net cost of transport,C
p
(40 to 109 cal g–1 km–1) do.Please address all correspondence and requests for reprints to G. Gust at the University of South Florida, St. Petersburg 相似文献