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501.
Aneil F. Agrawal Nicole Combs Edmund D. Brodie III 《Behavioral ecology and sociobiology》2005,57(6):566-574
The evolution of life history characters, including parental care behaviors, depends on costs and benefits. When offspring can influence parental behaviors, parent-offspring conflict over parental care can occur, but only if these parental behaviors are costly. Mother burrower bugs (Sehirus cinctus) exhibit extended and complex care of offspring. Mothers guard eggs until hatching and then attend and provision offspring for approximately 2 weeks after hatching. Using four experimental treatments, we attempted to identify the costs associated with specific components of these behaviors. Under laboratory conditions, egg guarding increases inter-clutch interval, but provisioning does not appear to be very costly. We discuss additional ecological factors that may be important in mediating provisioning costs under natural conditions. Through analysis of individual maternal performance, we find no evidence for trade-offs between successive clutches. These data suggest that variation in overall condition may obscure variation in allocation strategies.Communicated by F. Trillmich 相似文献
502.
Emlen and Oring (1977) suggested that monogamy in birds is maintained because of the need for strict biparental care. A corollary of their suggestion is that paternal care should decrease under conditions of high food abundance. An alternative is that paternal care would increase if males take advantage of the higher food abundance by trying to reduce the length of the nestling feeding period. We tested these two ideas using yellow warblers (Dendroica petechia) by providing some pairs with supplemental food, thereby reducing the importance of biparental care. However, the extra food did not decrease paternal effort, nor did it increase it (Fig. 2). Early in the nestling period experimental females brooded more but visited their nestlings less than did control females, but later, when brooding times decreased, experimental females fed their nestlings more than did control females (Fig. 3). There were no significant differences in nestling survival (Fig. 5), but nestlings in the control treatment were larger and heavier up to 6 days old (Fig. 6). The main effect of supplemental food was on maternal, not paternal behaviour. Models of biparental care assume interdependence between the parental effort of both parents. In this species, however, males and females provide for their brood independently from each other. 相似文献
503.
Distribution and Risk Assessment of Fluoride in Drinking Water in the West Plain Region of Jilin Province, China 总被引:3,自引:0,他引:3
Bo Z Mei H Yongsheng Z Xueyu L Xuelin Z Jun D 《Environmental geochemistry and health》2003,25(4):421-431
The west plain region of Jilin province of northeast China is one of the typical endemic fluorosis areas caused by drinking water for many years. Investigations of hydrogeological and ecoenvironmental conditions as well as endemic fluorosis were conducted in 1998. Results show that the ground water, especially, the water in the unconfined aquifer is the main source of drinking water for local residents. The fluoride concentration in groundwater in the unconfined aquifers is higher than that in the confined aquifer in the west plain of Jilin province. The fluoride concentration in the unconfined aquifer can be used to classify the plain into fluoride deficient area, optimum area and excess area, which trend from west to east. High fluoride (>1.0 mg L(-1)) in drinking water resulted in dental and skeletal fluorosis in local residents (children and pregnant women). There exists a positive correlation between fluoride concentration in the drinking water and the morbidities of endemic fluorosis disease (r1 = 0.781, r2 = 0.872). Health risks associated with fluoride concentration in drinking water are assessed. It has been determined that fluoride concentration in excess of 1.0 mg L(-1) exposes residents to high health risks based on risk identification. The study area is classified into five health risk classes as shown in Figure 4. The risk indexes of this area more than 1.0 are accounted for 68% of the total west plain region. 相似文献
504.
Sociality in some birds, mammals, and social insects was suggested to have evolved through the lengthening and extension of
parental care behaviors to nondirect descendents. In these systems, group members care for young cooperatively and, thus,
increase the reproductive success of the breeders and fitness of the young. Parental care behaviors, such as regurgitation
feeding and matriphagy (consumption of the mother), occur in several subsocial and social spiders. However, it is not known
whether females in a colony cooperate in caring for the young of other females and whether such cooperative care improves
reproductive success. To answer this question, we created experimental colonies of the social spider Stegodyphus dumicola (Araneae, Eresidae), allowing only one female in a group to produce young, simulating reproductive skew occurring in nests
in nature. In this paper, we show for the first time that females of S. dumicola cooperate in providing regurgitated food for young of other females and are even eaten by those young. Young raised by a
group of females were larger and had greater survival than young raised only by their mother. Thus, fitness benefits from
raising broods cooperatively may have favored the evolution of sociality in spiders. 相似文献
505.
We used a brood-size manipulation to test the effect of rearing environment on structural coloration of feathers grown by
eastern bluebird (Sialia sialis) nestlings. Ultraviolet (UV)-blue structural coloration has been shown to be sexually selected in this species. Our experimental
design took advantage of the growth of UV-blue wing feathers in nestlings that are retained as part of the first nuptial plumage.
We cross-fostered nestlings to create enlarged and reduced broods with the purpose of manipulating parental feeding rates
and measured the effect on nestling growth and plumage coloration. Brood size influenced feeding rates to offspring, but the
effect varied with season. In general, male nestlings reared in reduced broods were fed more often, weighed more, and displayed
brighter structural plumage compared to nestlings reared in enlarged broods. Female nestlings appeared to experience less
adverse affects of brood enlargement, and we did not detect an effect of brood-size manipulation on the plumage coloration
of female nestlings. Measures of plumage coloration in both males and females, however, were correlated to hatching date and
nestling mass during feather development. These data provide empirical evidence that environmental quality can influence the
development of the blue structural coloration of feathers and that males may be more sensitive to environmental fluctuations
than females. 相似文献
506.
Varroa jacobsoni, an ectoparasite of the Asian honeybeeApis cerana, has been introduced world-wide, and is currently decimating colonies of the European honeybeeApis mellifera.Varroa's reproductive cycle is tuned to that of drone cells, those mainly parasitized in the original host. We describe here how a single fertilized female, infesting a brood cell, can produce two to four adult fertilized females within the limited time span of bee development (270 h in worker and 320 h in drone cells), despite the disturbance caused by cocoon spinning and subsequent morphological changes of the bee. From observations on transparent artificial cells we were able to show how the mite combats these problems with specialized behaviors that avoid destruction by the developing bee, prepares a feeding site for the nymphs on the bee pupa, and constructs a fecal accumulation on the cell wall which serves as a rendezvous site for matings between its offspring. The proximity of the fecal accumulation to the feeding site facilitates feeding by the maturing progeny. However, communal use of the feeding site leads to competition between individuals, and protonymphs are most disadvantaged. This competition is somewhat compensated by the timing of oviposition by the mites. Use of a common rendezvous and feeding site by two or moreVarroa mothers in multiinfested cells may have developed from the parental care afforded to them as nymphs. 相似文献
507.
508.
509.
This paper addresses increasing concern about the pollution threat of used oil being illegally dumped and the impact of oil on air pollution and freshwater ecosystems in Asian countries. Used oil is a very serious waste management problem. These results call for management action such as maximising the collection and recovery of used oil. The Thai government recognizes the need to recycle used oil and has been active in encouraging programs to accomplish this goal. Thus unless new approaches and incentives are developed, used oil generation may become an increasing serious problem to our environment. The purpose of this study is to examine the technical and economic feasibility, of recycling used oils. In addition, this paper briefly discusses the problems to be overcome and outlines potential mechanisms for providing the necessary disposal controls in order to maximize the protection to public health and environmental quality from potential hazards posed by used lube oil disposal. 相似文献
510.
用气相色谱.电子捕获检测器(GC-ECD)测定南京市郊蔬菜中的有机氯农药残留.结果表明,12种有机氯农药在所有的供试蔬菜中均有检出,DDT和HCH在各蔬菜中的含量较高,分别占有机氯农药总残留量的49.5%~75.0%和13.9%~28.2%.Wα-HCH/Wγ-HCH和WDDE/WDDT的比值在各蔬菜体内均小于或等于1,说明这些蔬菜生长的环境中可能有新的有机氯污染物的输入.各种蔬菜对有机氯农药总量的富集因子为0.41~0.78.富集能力最大的为胡萝卜,蒜苗和菠菜.HCH类农药在各种蔬菜体内的生物富集因子(0.70~1.10)要高于DDT类(0.28~0.80).胡萝卜对HCH和DDT等有机氯农药的富集能力较强,而莴苣、蒜苗和菠菜对六氯苯、狄氏剂,异狄氏剂和硫丹有较高的生物富集能力.虽然各种蔬菜体内有机氯农药的残留量低于国家最大残留限量,但其检出率仍为100%,仍然对农产品质量安全和人类健康造成潜在的威胁.关键词:有机氯农药;蔬菜;残留量;生物富集;人类健康 相似文献