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991.
Yoshinori SHINTANI Yuka MASUZAWA Yuzuru HIROSE Ryôhei MIYAHARA Fumiya WATANABE Jun‐ya TAJIMA 《Entomological Science》2010,13(3):273-279
The bug Andrallus spinidens (F.) (Heteroptera: Pentatomidae) is a polyphagous predator of insect larvae, which is distributed in tropical and warm temperate zones worldwide. Seasonal occurrence and diapause induction of this bug were studied in a population in Miyazaki, southern Kyushu, Japan. The field research showed that A. spinidens produces three or four generations a year and is most abundant from mid‐summer to autumn. Reproductive activity of field‐collected adults decreased from late summer to autumn, indicating that this bug enters adult diapause in autumn. Only adults were found in early spring and these were reproductive. Laboratory experiments showed that, irrespective of photoperiod, adult diapause is induced at lower temperatures (≤22.5°C), whereas it is avoided at higher temperatures (≥25°C). Ambient temperature falls across the critical range from late summer to autumn. Thus, the bug clearly overwinters in adult diapause induced by low temperatures and this diapause is terminated during the course of winter. 相似文献
992.
Aims: Vibrio cholerae is an important bacterial pathogen that causes global cholera epidemic. Although they are commonly found in coastal waters around the world, most environmental isolates do not contain cholera toxin genes. This study investigates vibriophages in southern California coastal waters and their ability to transfer cholera toxin genes. Methods and Results: Lytic phages infecting V. cholerae were isolated from Newport Bay, California, between May and November, while none was found in winter. Some of the phage isolates can infect multiple environmental V. cholerae strains and El Tor strains. All phages contained double‐stranded DNA. Transduction experiments using kanamycin‐resistant gene marked CTXΦ demonstrated that some environmental vibriophages can transfer CTXΦ genes from O1 El Tor strain to environmental non‐O1/O139 V. cholerae via generalized transduction. Conclusions: Vibriophages are important components of the natural aquatic ecosystem. They play an important role in influencing the dynamics and evolution of V. cholerae in the environment. Significance and Impact of the Study: This study demonstrates the significance of vibriophages in the coastal environment and transduction as one of the mechanisms of pathogenicity evolution among environmental V. cholerae. 相似文献
993.
Baseline information on the parasites of frequently caught species of the characids namely Hydrocynus vittatus , Alestes baremoze , Brycinus macrolepidotus and Brycinus leuciscus was investigated in Anambra River from August 2004 to July 2005. The parasites recovered were the Myxosporid, Myxobolus sp (Protozoa), Polyopistocotylids, Diplozoon ghanense and Neodipolzoon polycotyleus (Monogeneans), the Caryophyllid Caryophylleus sp (Cestoda) and Rhabdochona sp (Nematoda). The prevalence of Caryophylleus sp in B. macrolepidotus (14.2%) and A. baremoze (8.1%) as well as Rhabdochon sp and Myxobolus sp in H . vittatus (9.6% and 7.8% respectively) was relatively high (>7.0%); while the other parasite species Myxobolus sp in B. leuciscus (2%), D. ghanense in B. macrolepidotus (1.9%) and N. polycotyleus in A. baremoze (1.9%) had a much lower prevalence (2.7%). Distribution of parasites was clearly seasonal. Dissolved oxygen (8.0–14.0) mg l−1 and pH (5.5–7.0) influenced the occurrence of the parasites whereas temperature (20.1–27.5 DC) showed no much effect. 相似文献
994.
The seasonal dynamics of Bythonomus lemani (Lumbriculidae) were studied for the first time and the knowledge of Bothrioneurum vejdovskyanum (Tubificidae) was extended based on four quantitative samples of oligochaetes taken monthly in the Rokytná River (Czech Republic)
during a two-year study (April 1999–April 2001). The influence of water temperature, velocity, depth, discharge, pH, conductivity,
dissolved oxygen amount and biochemical oxygen demand (BOD) on their life cycles was evaluated. Habitat preferences of the
juvenile and adult stages were recorded. Time series analysis was used to determine the worm densities, seasonality and trends.
For Byth. lemani one distinct reproduction cycle per year was found and this was regulated by temperature, while Both. vejdovskyanum showed a one-year cycle not significantly dependent on measured environmental variables. The overall trend was an increase
in density for Byth. lemani and a decrease in density for Both. vejdovskyanum. Byth. lemani showed a significant negative correlation between the trend of its density and BOD concentration. 相似文献
995.
The present study reports the seasonal and physiological variations of copper, zinc, magnesium, iron sodium chlorine, potassium,
calcium, phosphorus, urea, alkaline phosphatase (ALP), creatinine (CR), aspartate aminotransfrase (AST), alanine aminotransferase
(ALT), cholesterol, albumin, globulin, lactate dehydrogenase (LDH), and total protein concentrations in cattle. Two groups
of mated (n=14) and nonmated (n=10), healthy cows were selected for the study. Serum samples were collected at each of four periods: (1) early pregnancy
(May), (2) midpregnancy (August), (3) late pregnancy (October), and (4) lactation (February). Physiological variations result
in changes of cholesterol, calcium, LDH, and total protein concentrations. Phosphorus varies only with seasonal but not physiological
changes, whereas ALP, copper, magnesium, and potassium concentrations change with physiological and seasonal conditions. The
copper concentration is increased through the pregnancy. Neither the seasonal nor the physiologic variations affect zinc,
iron, sodium, chlorine, calcium, urea, creatinine, albumin, and globulin values in both groups in all periods. Thus, these
values can be used as reference for both mater and nonmated bovines. The measured total protein might not reflect its true
value because of dehydration during the hot season. These observations suggest that seasonal and physiologic variations have
to be taken into consideration for the correct interpretation of serum chemistry and elements status in cattle. Nutritional
supplements are required for cattle during certain periods to avoid a decline of their performance, which would then represent
consequent economic loses. 相似文献
996.
Influence of seasonal variation on bioassessment of streams using macroinvertebrates 总被引:6,自引:6,他引:0
The EU Water Framework Directive requires assessment of the ecological quality of running waters using macroinvertebrates.
One of the problems of obtaining representative samples of organisms from streams is the choice of sampling date, as the scores
obtained from macroinvertebrate indices vary naturally between seasons, confounding the detection of anthropogenic environmental
change. We investigated this problem in a 4th order calcareous stream in the western Carpathian Mountains of central Europe,
the Stupavsky potok brook. We divided our 100 m study site into two stretches and took two replicate samples every other month
alternately from each stretch for a period of 1 year, sampling in the months of February, April, June, August, October and
December. Multivariate analysis of the macroinvertebrate communities (PCA) clearly separated the samples into three groups:
(1) April samples (2) June and August samples (3) October, December and February samples. Metric scores were classified into
two groups those that were stable with respect to sampling month, and those that varied. Of the metrics whose values increase
with amount of allochthonous organic material (ALPHA_MESO, hyporhithral, littoral, PASF, GSI new, DSI, CSI), the highest scores
occurred in February, April, October and December, while for metrics whose values decrease with content of organic material
(DSII, DIS, GFI D05, PORI, RETI, hypocrenal, metarhithral, RP, AKA, LITHAL, SHRED, HAI) the highest values occurred in February,
April, June and December. We conclude that sampling twice a year, in early spring and late autumn, is appropriate for this
type of metarhithral mountain stream. Sampling in summer is less reliable due to strong seasonal influences on many of the
metrics examined while sampling in winter is inappropriate for logistical reasons.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users. 相似文献
997.
Field experiments were conducted in Sicily (south Italy) to assess chlorophyll (Chl) fluorescence parameters in response of
potato crop to nitrogen dose, to variation in genotype and in plant age, and to detect relationships between Chl content,
fluorescence parameter Fv/Fm, and tuber yield. The experiment included five nitrogen doses (0, 10, 20, 30, and 40 g m−2) and four genotypes (Spunta, Sieglinde, Daytona, and Igea). Chl fluorescence parameters (initial fluorescence, F0, maximum fluorescence, Fm, variable fluorescence, Fv, Fv/Fm, Tmax (the time required to reach Fm), and Chl content were measured weekly between the appearance of the fifth and sixth leaves and the onset of plant senescence.
A positive linear relationship was established between nitrogen supply and Chl content, F0, and Tmax. Nitrogen supply up to 10 g m−2 also had a positive effect on Fm and Fv, but above this rate it reduced Fv/Fm. Spunta had the highest Chl content, Fm, Fv, and Fv/Fm, but the lowest F0, whereas Sieglinde had the lowest Chl content, Fv, Fv/Fm, and Tmax and the highest F0. The cvs. Igea and Daytona exhibited intermediate Chl fluorescence parameters. Chl content and Tmax decreased with increasing plant age, whereas F0, Fm, and Fv increased until complete canopy development and thereafter declined until crop maturity. Tuber and plant dry matter yield
were significantly correlated with Chl content, F0, and Tmax. Thus Chl fluorescence and content detect differences in the response of potato to N supply, can discriminate between genotypes,
predict plant age, and yield performance under field conditions. 相似文献
998.
Sockman KW Sharp PJ Schwabl H 《Biological reviews of the Cambridge Philosophical Society》2006,81(4):629-666
How much effort to expend in any one bout of reproduction is among the most important decisions made by an individual that breeds more than once. According to life-history theory, reproduction is costly, and individuals that invest too much in a given reproductive bout pay with reduced reproductive output in the future. Likewise, investing too little does not maximize reproductive potential. Because reproductive effort relative to output can vary with predictable and unpredictable challenges and opportunities, no single level of reproductive effort maximizes fitness. This leads to the prediction that individuals possessing behavioural mechanisms to buffer challenges and take advantage of opportunities would incur fitness benefits. Here, we review evidence in birds, primarily of altricial species, for the presence of at least two such mechanisms and evidence for and against the seasonal coordination of these mechanisms through seasonal changes in plasma concentrations of the pituitary hormone prolactin. First, the seasonal decline in clutch size of most bird species may partially offset a predictable seasonal decline in the reproductive value of offspring. Second, establishing a developmental sibling-hierarchy among offspring may hedge against unpredictable changes in resource availability and offspring viability or quality, and minimize energy expenditure in raising a brood. The hierarchy may be a product, in part, of the timing of incubation onset relative to clutch completion and the rate of yolk androgen deposition during the laying cycle. Because clutch size should influence the effects of both these traits on the developmental hierarchy, we predicted and describe evidence in some species that females adjust the timing of incubation onset and rate of yolk androgen deposition to match clutch size. Studies on domesticated precocial species reveal an inhibitory effect of the pituitary hormone prolactin on egg laying, suggesting a possible hormonal basis for the regulation of clutch size. Studies on the American kestrel (Falco sparverius) and other species suggest that the seasonal increase in plasma concentrations of prolactin may regulate both a seasonal advance in the timing of incubation onset and a seasonal increase in the rate of yolk androgen deposition. These observations, together with strong conceptual arguments published previously, raise the possibility that a single hormone, prolactin, functions as the basis of a common mechanism for the seasonal adjustment of reproductive effort. However, a role for prolactin in regulating clutch size in any species is not firmly established, and evidence from some species indicates that clutch size may not be coupled to the timing of incubation onset and rate of yolk androgen deposition. A dissociation between the regulation of clutch size and the regulation of incubation onset and yolk androgen deposition may enable an independent response to the predictable and unpredictable challenges and opportunities faced during reproduction. 相似文献
999.
Xishuangbanna is located at the northern edge of the distribution of tropical forests in Southeast Asia, and it has a very high frequency of radiation fog, especially during the dry season (November-April). In this study, rainwater, throughfall, intercepted fog water (fog drip) by forest canopy, and stream water were collected in January 2002 and December 2003 for stable isotopic analysis at a tropical seasonal rain forest site in Xishuangbanna, Southwest China. The objective of the study is to estimate the evaporation rate from the forest floor. The stable hydrogen (δD) and oxygen isotope composition (δ18O) of rainwater, throughfall, fog drip, and stream water was determined using an isotope ratio mass spectrometer. Stream water during the non-storm runoff period was considered to reflect the effect of evaporation from the forest floor. The evaporation rates from the forest floor were estimated using isotope composition values in stream water and the total throughfall was estimated using the Rayleigh distillation equation under equilibrium conditions. The results indicated that the annual weighted means of δD and δ18O in fog drip were consistently more enriched than those of rainwater and stream water, and the fog drip was thought to contain water that had evaporated and recycled. The weighted means of δD and δ18O in stream water during the non-storm runoff period were 5.69% and 0.39% more enriched than those of the total throughfall (rain throughfall + fog drip) in 2002, while in 2003 these were 5.05% and 0.28%, respectively. Evapotranspiration in the humid year 2002 and the dry year 2003, computed from the water balance, was 1186 mm and 987 mm, respectively, which was quite low when compared with the values reported in some humid tropical forests. Consequently, the evaporation rate from the forest floor was 5.1% of the evapotranspiration in 2002, and 3.1% in 2003. The lower evaporation rate was thought to be mainly a result of the influence of the high frequency of heavy radiation fog on the rain forest during the night in the dry season (November-April). 相似文献
1000.
M. S. Selina G. V. Konovalova T. V. Morozova T. Yu. Orlova 《Russian Journal of Marine Biology》2006,32(6):321-332
At present 8 species of Alexandrium genus have been found in seas and adjacent waters of Russia: A. acatenella, A. catenella, A. insuetum, A. margalefii, A. ostenfeldii, A. pseudogonyaulax, A. tamarense, and A. tamutum. The distribution and population density of Alexandrium species varied within the surveyed area of the Pacific: in the Sea of Japan and Sea of Okhotsk, 7 species were recorded; 3 species were recorded along the Pacific coast of Kamchatka; and 2 species were found in the Bering Sea. A. tamarense was the most widespread and abundant species over the area. A. insuetum was recorded only in the Sea of Japan, and A. catenella, in the Sea of Okhotsk (Terpeniya Bay). The highest concentration of Alexandrium spp. (2–7 million cells/l) was recorded along the Pacific coast of Kamchatka and in the Bering Sea; in the Sea of Okhotsk, a rather high concentration (51000 cells/l) was registered in Aniva Bay; in the Sea of Japan, the highest concentration was recorded in Peter the Great Bay (6000 cells/l). The distribution of cysts (spores) in surface sediments of the Pacific coast of Russia as a whole reflected the pattern of distribution of vegetative cells of Alexandrium. Cysts of Alexandrium cf. tamarense prevailed all over the area, with the maximum concentration along the Pacific coast of Kamchatka. Beyond that type of cysts, insignificant numbers of cysts of Alexandrium cf. minutum were recorded in Peter the Great Bay and Aniva Bay. Analysis of seasonal dynamics revealed that cells of Alexandrium spp. occurred in Peter the Great Bay from June up to September, and along the Pacific coast of Kamchatka from April to October. In the first region, the maximum density was recorded in August; it was provided by A. pseudogonyaulax (59% of the total density of Alexandrium), A. tamarense (35%), and A. insuetum (6%). In the second region, it was recorded in July, thanks only to development of A. tamarense. 相似文献