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21.
Miniature collar-type transmitters originally designed by W.W. Cochran, Illinois, were adapted for use on timber wolves(Canis lupus sp.) in east-central Ontario. Wild timber wolveswere captured in steel traps, restrained with a forked stick,fitted with radio-collars and released at point of capture.Receivers were adapted for use in trucks, airplanes, and forwalking in rough bush country. Maximum ranges were 3.2 km withground and 9.6 km with aircraft receivers. A preadult femaletagged in July, 1964, and a lactating adult female tagged inJune, 1965, were tracked intermittently for 5.5 and 2.5 months,respectively. Tracking periods for six other animals of bothsexes, ranging in age from pups to adults, varied from 2 daysto 4 months. The lactating female and her associated pack regularlyreturned to three preferred "resting sites" for various periodsduring July and August. Preferred areas were well drained, semi-open,mixed conifer-hardwood stands in close proximity to swamps orbeaver ponds. The preadult female ranged in an area frequentedby a pack, but frequently remained independent of it. A preadultmale, tagged in the same region, wandered over a slightly largerarea than the female. Tagged animals were active throughoutall periods of the day or night. Activity increased slightlyduring the early evening hours. There was a slight correlationbetween weather conditions and patterns of behavior and activity.Apparently, tagged individuals were quickly accepted by othermembers of the pack. 相似文献
22.
Reciprocal Ammonium Transport Into and Out of Plant Roots: Modifications by Plant Nitrogen Status and Elevated Root Ammonium Concentration 总被引:3,自引:0,他引:3
Wheat and oat were grown for 20 d on a nitrate-containing solution(nitrogen-replete plants) or for the last 6 d of this periodon a nitrate-free solution (nitrogen-depleted plants). Exposureof the nitrogen-depleted plants on day 20 to nitrate-free solutionscontaining 500 mmol m3 ammonium (96 A% 15N) resultedin a cumulative net influx of 15N-ammonium over an 8 h periodthat was appreciably greater than that of the nitrogen-repleteplants. Both the initial rate and the more restricted rate afterthe first hour were enhanced by nitrogen deprivation. In thenitrogen-replete plants, cumulative net efflux of endogenous14N-ammonium was approximately equivalent to net ammonium uptakeduring the first hour, and was essentially complete after 12h. Pretreating nitrogen-depleted plants for 5 h in 500 mmolm3 15N-ammonium (99 A% 15N) resulted in root ammoniumconcentrations of 12.7?1.1 and 16.0?0.4 µmol for wheat and oat, respectively. Subsequent net efflux of 15N-ammoniumto 500 mmol m3 exogenous 14N-ammonium exceeded theseinitial amounts within 2 h. Increasing ambient 14N-ammoniumto 5000 mmol m3 increased net 15N-ammonium efflux suchthat net loss of the maximal original amount in the root tissuewas exceeded within 0.75 h. The data for both species indicatesubstantial reciprocal transfers of ammonium into and out ofroots of ammonium-treated plants and a significant degradationof recently synthesized products of ammonium assimilation concurrentwith ammonium assimilation. Key words: Accumulation, ammonium, efflux, oat, root, uptake, wheat 相似文献
23.
MICHAEL C. DICKMAN CYNTHIA ANNETT † GEORGE W. BARLOW 《Biological journal of the Linnean Society. Linnean Society of London》1990,39(3):239-249
The Midas cichlid ( Cichlasoma citrinellum ) of Nicaragua shows stable polychromatism in that a consistent, small proportion of the fish in nature lose their melanophores and thereby become gold-coloured. Before metamorphosis, all fish look alike. We asked whether the pre-transformed offspring of gold and normal morphs might differ in their morphological and physiological responses to white and to black backgrounds despite looking the same. More chromatophores developed in all juveniles exposed for two weeks to a black than to a white background. When moved from one background to the other, the fish adjusted to white faster than to black. Most importantly, genetically normal fish (N) colour-matched quicker than genetically gold fish (G) irrespective of the direction of change. Adjustment in G was also more variable, indicating poorer control. A parallel pattern was recorded photometrically in melanophores of excised scales: aggregation of pigment was faster than dispersion. And pigment in the melanophores of N aggregated and dispersed swifter than did those of G. Therefore, pre-metamorphosed juvenile G could be more vulnerable to predation than are juvenile N. This reveals a possible source of selection against the offspring of gold morphs before they become gold-coloured. 相似文献
24.
MAHMOUD FADL ALI E. DAVID MORGAN 《Biological reviews of the Cambridge Philosophical Society》1990,65(3):227-247
- 1 Chemical communication plays an important part in the lives of insects, and particularly in lives of those that live in groups or social organizations.
- 2 Chemicals which are used in communication in the general sense are called semiochemicals, and there are a number of subdivisions recognized under this title.
- 3 Pheromones are a category of semiochemicals which are used for communication between individuals of the same species.
- 4 Pheromones are in turn subdivided into primer and releaser pheromones. The former produce a relatively long-lasting physiological change in the receiver, and the latter stimulate the receiver to some immediate behavioural response.
- 5 Far more is known about releaser pheromones at present because they are easier to study.
- 6 Nine categories of releaser pheromone are recognized here, used by both social and non-social insects.
- 7 Sex pheromones are widely used to bring the sexes together for mating, and they have been extensively studied in Lepidoptera.
- 8 Invitation pheromones, encouraging the species to feed or oviposit at an explored site, are not extensively known.
- 9 Aggregation pheromones are designed to bring individuals together into groups which may be temporary in sub-social insects, or permanent in social insects.
- 10 Dispersal or spacing pheromones are used by other species to reduce intraspecific competition for scarce resources.
- 11 Alarm pheromones are a broad and sometimes unclearly defined group which communicate alarm or attack, chiefly in colonial species.
- 12 Trail pheromones, applied to a surface by an individual, to be followed by another, are confined to Hymenoptera, Isoptera and a few Lepidoptera as far as is known.
- 13 Territorial and home range pheromones may be widely distributed, but as yet few of them have been recognized.
- 14 Surface and funeral pheromones are even less well known. Surface pheromones may play a large part in species or colony recognition.
- 15 We can expect the number and complexity of pheromones to be much greater in social insects, a part of the subject which until now has received relatively less attention.
- 16 As our understanding of the subject grows we may expect other categories to be added to this list.
25.
Impact of initial density of cowpea aphid Aphis craccivora Koch (Aphididae) at infestation on the growth and yield of aphid-susceptible cowpea cultivar ICV-1 and aphid-resistant cultivar ICV-12, was investigated. Plants at the seedling, flowering and podding stages of development were infested with five aphid densities consisting of 0, 2, 5, 10 and. 20 aphids per plant and maintained for 22 days. Extended leaf heights of plants and aphid counts were recorded at 7, 12, 17 and 22 days after infestation. Two crop growth parameters (biomass duration and leaf area duration), and two plant yield parameters (number of pods per plant and number of seeds per pod) were recorded. Due to the occurrence of parthenogenesis and changes in population dynamics during infestations, aphid densities were converted into cumulative cowpea aphid-days, to facilitate data analyses and interpretation. ANOVA indicated that there was significant (P=s 0.05) difference in aphid-day accumulations between the two cultivars when infested at the seedling stage. Accumulations on cv. ICV-1 were greater than on cv. ICV-12. However, no such differences between the cultivars were detected when plants were infested at flowering and podding stages. Therefore, the seedling stage was used for comparisons of the impact of cowpea aphid-days on the growth and yield parameters of the two cultivars. At the 95% confidence intervals, ICV-12 plants were consistently taller than ICV-1 plants. Infested ICV-1 seedlings showed stunting and other growth deformities which were not observed on ICV-12 plants. Regression analyses revealed substantial reductions in the growth and yield parameters of ICV-1 relative to ICV-12. Overall, cowpea aphid-days provided a convenient and reliable method for studying the aphid population dynamics and the subsequent impact on plant growth and yield performance. 相似文献
26.
Rao-Blackwellisation of sampling schemes 总被引:15,自引:0,他引:15
27.
M J WILSON D M GLEN S K GEORGE J D PEARCE C W WILTSHIRE 《The Annals of applied biology》1994,125(2):377-390
A field experiment on winter wheat in autumn 1991 investigated the effect of the rhabditid nematode, Phasmarhabditis hermaphrodita, applied to soil at five dose rates (108 - 1010 infective larvae ha-1) immediately after seed sowing, on slug populations and damage to seeds and seedlings. The nematode was compared with methiocarb pellets broadcast at recommended field rate immediately after drilling and no molluscicide treatment. Slug damage to wheat seeds and seedlings was assessed 6 and 13 wk after drilling. Seedling survival increased and slug grazing damage to seedlings declined linearly with increasing log nematode dose. These two measures of slug damage were combined to give an index of undamaged plant equivalents, which also increased linearly with increasing log nematode dose. ANOVA showed that, after 6 wk, there were significantly more undamaged plant equivalents on plots treated with the two highest nematode doses (3 × 109 and 1 × 1010 ha-1) than on untreated plots, but the number of undamaged plant equivalents on methiocarb-treated plots was not significantly greater than that on untreated plots. Slug populations were assessed by refuge trapping and soil sampling. Deroceras reticulatum was the commonest of several species of slugs recorded. During the first 4 wk after sowing, significantly more slugs were found under refuge traps on plots treated with certain doses of P. hermaphrodita than under traps on untreated plots and more showed signs of nematode infection than expected from the prevalence of infection in slugs from soil samples, suggesting that the presence of P. hermaphrodita altered slug behaviour. Application of P. hermaphrodita had no significant impact on numbers or biomass of slugs in soil during a 27 wk period after treatment, except after 5 wk when slug numbers were inversely related to log nematode dose. However, by this time, numbers in soil samples from untreated plots had declined to levels similar to those in plots treated with the highest dose of nematodes. During the first 5 wk after treatment, c. 20% of slugs in soil samples from untreated plots showed symptoms of nematode infection. It is suggested that this represented the background level of infection in the experimental field rather than spread of infection from treated plots. The apparent lack of impact of P. hermaphrodita on slug numbers and biomass in soil suggests that its efficacy in protecting wheat from slug damage was through inhibition of feeding by infected slugs. 相似文献
28.
Identification of predominant environmental factors structuring stream macroinvertebrate communities within a large agricultural catchment 总被引:11,自引:0,他引:11
- 1 Patterns of macroinvertebrate community composition were examined in streams within a 40000-km2 catchment in central Michigan, U.S.A., to identify the major environmental gradients influencing community variation. Agriculture and associated clay and sandy soils predominated in much of the region.
- 2 Eighty macroinvertebrate taxa were collected from stream surveys conducted during May and August 1990. Community composition varied primarily by the proportions of Plecoptera and Ephemeroptera. Benthic communities from the heaviest agricultural zones were most different from those at other sites.
- 3 Chemical composition among the sites varied most in relation to nutrients (NH3, NO3, PO4). Other parameters were relatively similar. Physical characteristics of the sites were scored in six habitat categories: (i) substrate characteristics, (ii) instream cover, (iii) channel morphology, (iv) riparian zone and stream-bank conditions, (v) riffle/run quality, (vi) pool quality. Most physical habitat scores were lowest in the intense agriculture zones.
- 4 The relative importance of physical and chemical variables in explaining variation in macroinvertebrate communities was quantified using canonical correspondence analysis. Substrate characteristics were most important in both surveys. Significant correlations (P<0.05 and P<0.10) were observed between substrate quality and total numbers of Ephemeropteran, Plecopteran, and Trichopteran taxa. These relationships reflected correlations from sites in the clay soil-type region (P<0.01 and P<0.10) which contrasted with non-significant results from the less impacted, sandy soil-type region.
- 5 Effective stream restoration efforts in this region will require the alteration of local land-use activities that influence the physical habitat. Further development of empirical relationships between catchment activities and substrate and channel characteristics within natural geomorphic regions is essential for the evaluation of restoration projects.
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