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731.
732.
The growth of insoluble, membrane-limited spherical granules has been studied in the barnacleElminius modestus Darwin, collected on 26 March 1983 from the shore of the Huon River, Tasmania. X-ray microprobe analysis of these granules using a non-aqueous fixation method established their elemental composition (in order of abundance) to be phosphorus, zinc, potassium, sulphur and chlorine. Formation of granules is initiated on exposure to high zinc levels in the ambient seawater. Granules were first detected in barnacles transplanted from an area of low seawater zinc levels to one with high levels after 12 d exposure. Over a period of 5 mo, granules increased both in numbers and diameter and were concentrated in specialized cells around the gut, the stratum perintestinale. Barnacles positioned at mid-tide level in high ambient zinc levels, developed greater numbers of larger granules than those positioned below low-tide level. Rate of uptake of zinc was higher in the former group during the first month, after which similar rates were observed in the two groups. Barnacles transplanted from an area of high to one of low seawater zinc concentration, lost zinc slowly (0.3% body load per day over an 11 wk period). There was no evidence to suggest that zinc granules are excreted intact across the gut. We conclude that zinc granules represent a detoxification mechanism for surplus zinc. 相似文献
733.
Age-specific social dominance affects habitat use by breeding American redstarts (Setophaga ruticilla): a removal experiment 总被引:2,自引:0,他引:2
Summary By removing older males from their breeding territories, we tested the hypothesis that age-related dominance behavior influenced the pattern of habitat selection by breeding American redstarts Setophaga ruticilla (Aves: Parulinae). Fifteen older male redstarts removed in five experimental replicates during three breeding seasons were replaced by ten yearling and five older males; no redstart males of either age colonized the control sites during the same time periods, although two yearlings disappeared. Significantly more yearling males (67%, n=9) colonized the vacated areas than were present in the redstart population at large (26.8%, n=209). We reject the alternative hypothesis that yearling male redstarts occupy different habitats from older males because of age-related (innate) habitat preferences. Redstarts that colonized the territories made vacant by our removals (i.e., floaters) were a behaviorally heterogeneous group of animals. The presence of both yearling and older male floaters indicates that suitable habitat is limiting for this species and that intraspecific competitive interactions are important in habitat distribution, and potentially in population regulation. 相似文献
734.
Resin is an important building material in the nests of honeybees, but little is known about how it is handled within the nest and how its collection is controlled. We studied the functional organization of resin work to better understand how a colony adaptively controls its intake of resin. Two hypotheses have been proposed for how resin collectors stay informed of the need for additional resin: (1) the unloading difficulty hypothesis (resin need is sensed indirectly by the unloading delay) and (2) the caulking activity hypothesis (resin need is sensed directly while engaged in using resin). A falsifiable prediction of the latter hypothesis, but not of the former, is that resin collectors not only gather resin outside the hive but also regularly handle resin inside the hive (taking it from other bees and using it to caulk crevices). Consistent with this prediction are our findings that in the resin sector of a colony’s economy, unlike in the pollen, nectar, and water sectors, there is no strict division of labor between the collectors and the users of a material. Over the course of a day, bees seen collecting resin were also commonly seen using resin. Moreover, we found that the unloading locations of resin collectors are unlike those of water and nectar collectors, being deep inside the hive (at the sites of resin use) rather than at the hive entrance. This arrangement facilitates the engagement in resin use by resin collectors. We conclude that the caulking activity hypothesis is well-supported, but that the unloading difficulty hypothesis also remains viable, for we found that resin collectors experience variable delays in getting rid of their loads, from less than 15 min to more than an hour, consistent with this hypothesis. The stage is now set for experimental tests of these two hypotheses. Both may be correct, which if true will imply that social insect workers, despite their small brains, can acquire and integrate information from multiple sources to improve their knowledge of conditions within the colony. 相似文献
735.
Honey bee foragers as sensory units of their colonies 总被引:5,自引:0,他引:5
Thomas D. Seeley 《Behavioral ecology and sociobiology》1994,34(1):51-62
Forager honey bees function not only as gatherers of food for their colonies, but also as sensory units shaped by natural selection to gather information regarding the location and profitability of forage sites. They transmit this information to colony members by means of waggle dances. To investigate the way bees transduce the stimulus of nectar-source profitability into the response of number of waggle runs, I performed experiments in which bees were stimulated with a sucrose solution feeder of known profitability and their dance responses were videorecorded. The results suggest that several attributes of this transduction process are adaptations to enhance a bee's effectiveness in reporting on a forage site. (1) Bees register the profitability of a nectar source not by sensing the energy gain per foraging trip or the rate of energy gain per trip, but evidently by sensing the energetic efficiency of their foraging. Perhaps this criterion of nectar-source profitability has been favored by natural selection because the foraging gains of honey bees are typically limited by energy expenditure rather than time availability. (2) There is a linear relationship between the stimulus of energetic efficiency of foraging and the response of number of waggle runs per dance. Such a simple stimulus-response function appears adequate because the range of suprathreshold stimuli (max/min ratio of about 10) is far smaller than the range of responses (max/min ratio of about 100). Although all bees show a linear stimulus-response function, there are large differences among individuals in both the response threshold and the slope of the stimulus-response function. This variation gives the colony a broader dynamic range in responding to food sources than if all bees had identical thresholds of dance response. (3) There is little or no adaptation in the dance response to a strong stimulus (tonic response). Thus each dancing bee reports on the current level of profitability of her forage site rather than the changes in its profitability. This seems appropriate since presumably it is the current profitability of a forage site, not the change in its profitability, which determines a site's attractiveness to other bees. (4) The level of forage-site quality that is the threshold for dancing is tuned by the bees in relation to forage availability. Bees operate with a lower dance threshold when forage is sparse than when it is abundant. Thus a colony utilizes input about a wide range of forage sites when food is scarce, but filters out input about low-reward sites when food is plentiful. (5) A dancing bee does not present her information in one spot within the hive but instead distributes it over much of the dance floor. Consequently, the dances for different forage sites are mixed together on the dance floor. This helps each bee following the dances to take a random sample of the dance information, which is appropriate for the foraging strategy of a honey bee colony since it is evidently designed to allocate foragers among forage sites in proportion to their profitability. 相似文献
736.
Three general methods to calculate soil contaminant cleanup levels are assessed: the truncated lognormal approach, Monte Carlo analysis, and the house-by-house approach. When these methods are used together with a lead risk assessment model, they yield estimated soil lead cleanup levels that may be required in an attempt to achieve specified target blood lead levels for a community. The truncated lognormal approach is exemplified by the Society for Environmental Geochemistry and Health (SEGH) model, Monte Carlo analysis is exemplified by the US EPA's LEAD Model, and the house-by-house approach is used with a structural equation model to calculate site-specific soil lead cleanup levels. The various cleanup methods can each be used with any type of lead risk assessment model. Although all examples given here are for lead, the cleanup methods can, in principle, be used as well with risk assessment models for other chemical contaminants to derive contaminant-specific soil cleanup levels. 相似文献
737.
Jacques M. Pasteels Claudine Theuring Donald M. Windsor Thomas Hartmann 《Chemoecology》2003,13(1):55-62
Summary. Sequestration and processing of pyrrolizidine alkaloids
(PAs) by leaf beetles of the genus Platyphora were investigated. Tracer
experiments with labeled alkaloids were performed with P. eucosma
feeding on Koanophyllon panamense (Asteraceae, tribe Eupatorieae). P.
eucosma catalyzes the same reactions previously demonstrated for P.
boucardi specialized to Prestonia portobellensis (Apocynaceae): (i)
epimerization of rinderine to intermedine; (ii) esterification of
retronecine yielding insect-specific PAs; (iii) efficient transport of
the PAs as free bases into the defensive secretions. P. bella feeding on
Tournefortia cuspidata (Boraginaceae) shows the same sequestration
behavior and ability to synthesize the specific retronecine esters. P.
ligata, a species phylogenetically closely related to the PA adapted
species and clustering in the same clade, but feeding on a host plant
devoid of PAs, feeds easily on PA treated host-plant leaves, but does
not sequester or metabolize PAs. P. kollari a species clustering outside
the PA clade refused to feed on its food-plant leaves painted with PAs.
The results are discussed in relation to host-plant selection of the PA
adapted species and the role of PAs in chemical defense.
Received 20 September 2002; accepted 18 November 2002. 相似文献
738.
Thomas D. Seeley 《Behavioral ecology and sociobiology》1989,24(3):181-199
Summary A honey bee colony operates as a tightly integrated unit of behavioral action. One manifestation of this in the context of foraging is a colony's ability to adjust its selectivity among nectar sources in relation to its nutritional status. When a colony's food situation is good, it exploits only highly profitable patches of flowers, but when its situation is poor, a colony's foragers will exploit both highly profitable and less profitable flower patches. The nectar foragers in a colony acquire information about their colony's nutritional status by noting the difficulty of finding food storer bees to receive their nectar, rather than by evaluating directly the variables determining their colony's food situation: rate of nectar intake and amount of empty storage comb. (The food storer bees in a colony are the bees that collect nectar from returning foragers and store it in the honey combs. They are the age group (generally 12–18 day old bees) that is older than the nurse bees but younger than the foragers. Food storers make up approximately 20% of a colony members.) The mathematical theory for the behavior of queues indicates that the waiting time experienced by nectar foragers before unloading to food storers (queue length) is a reliable and sensitive indicator of a colony's nutritional status. Queue length is automatically determined by the ratio of two rates which are directly related to a colony's nutritional condition: the rate of arrival of loaded nectar foragers at the hive (arrival rate) and the rate of arrival of empty food storers at the nectar delivery area (service rate). These two rates are a function of the colony's nectar intake rate and its empty comb area, respectively. Although waiting time conveys crucial information about the colony's nutritional status, it has not been molded by natural selection to serve this purpose. Unlike signals, which are evolved specifically to convey information, this cue conveys information as an automatic by-product. Such cues may prove more important than signals in colony integration. 相似文献
739.
Thomas D. Seeley 《Behavioral ecology and sociobiology》1986,19(5):343-354
Summary To understand how a colony of honeybees keeps its forager force focussed on rich sources of food, and analysis was made of how the individual foragers within a colony decide to abandon or continue working (and perhaps even recruit to) patches of flowers. A nectar forager grades her behavior toward a patch in response to both the nectar intake rate of her colony and the quality of her patch. This results in the threshold in patch quality for acceptance of a patch being higher when the colonial intake rate of nectar is high than when it is low. Thus colonies can adjust their patch selectivity so that they focus on rich sources when forage is abundant, but spread their workers among a wider range of sources when forage is scarce. Foragers assess their colony's rate of nectar intake while in the nest, unloading nectar to receiver bees. The ease of unloading varies inversely with the colonial intake rate of nectar. Foragers assess patch quality while in the field, collecting nectar. By grading their behavior steeply in relation to such patch variables as distance from the nest and nectar sweetness, foragers give their colony high sensitivity to differences in profitability among patches. When a patch's quality declines, its foragers reduce their rate of visits to the patch. This diminishes the flow of nectar from the poor patch which in turn stimulates recruitment to rich patches. Thus a colony can swiftly redistribute its forager force following changes in the spatial distribution of rich food sources. The fundamental currency of nectar patch quality is not net rate of energy intake, (Gain-Cost)/Time, but may be net energy efficiency, (Gain-Cost)/Cost. 相似文献
740.
We studied the extent to which worker honey bees acquire information from waggle dances throughout their careers as foragers. Small groups of foragers were monitored from time of orientation flights to time of death and all in-hive behaviors relating to foraging were recorded. In the context of a novice forager finding her first food source, 60% of the bees relied, at least in part, on acquiring information from waggle dances (being recruited) rather than searching independently (scouting). In the context of an experienced forager whose foraging has been interrupted, 37% of the time the bees resumed foraging by following waggle dances (being reactivated) rather than examining the food source on their own (inspecting). And in the context of an experienced forager engaged in foraging, 17% of the time the bees initiated a foraging trip by following a waggle dance. Such dance following was observed much more often after an unsuccessful than after a successful foraging trip. Successful foragers often followed dances just briefly, perhaps to confirm that the kind of flowers they had been visiting were still yielding forage. Overall, waggle dance following for food discovery accounted for 12–25% of all interactions with dancers (9% by novice foragers and 3–16% by experienced foragers) whereas dance following for reactivation and confirmation accounted for the other 75–88% (26% for reactivation and 49–62% for confirmation). We conclude that foragers make extensive use of the waggle dance not only to start work at new, unfamiliar food sources but also to resume work at old, familiar food sources. 相似文献