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261.
262.
Low temperature limits the rate of biochemical reactions and aerobic scopes of cold water ectotherms. To compensate for this
limiting effect, animals living in cold environments often possess physiological or morphological adaptations to maintain
vital functions. Cross-latitudinal comparison of aerobic capacities is one method to test which factors constrain activity
in thermally distinct environments particularly when congeneric studies are carried out on related species with conservative
ecology and habitat. Burrowing is a major aerobic activity of bivalve molluscs that is described here for the first time for
the tropical mangrove species Laternula truncata and Laternula boschasina and then compared with their Antarctic congener Laternula elliptica. About 80% of L. truncata (16.3–46.1 mm shell length) and 63% of L. boschasina (11.3–27.7 mm shell length) buried within 24 h at 28°C. The burrowing rate index (BRI = [3√wet weight/time to bury]×104) ranged between 1.1 and 20.2 for L. boschasina and 1.1–32.9 for L. truncata. These values are 2–3 orders of magnitude less than other tropical bivalve molluscs and are amongst the lowest recorded for
any bivalve. Comparisons with the Antarctic L. elliptica showed little or no differences in BRI (Q
10 of 1.0–1.2 for specimens of the same size). This is contrary to the general pattern over a wide range of bivalves, where
BRI increases with a Q
10 of between 2.9 and 6.4 between high latitudes and the equator. L. elliptica has 25–30% longer relative foot length than tropical congeners of the same size, which could be a morphological adaptation
compensating for reduced burrowing speeds in a colder environment. Burrowing rates within the genus Laternula could, however, also be maintained by differing habitat, ecological and physiological constraints on burrowing capability. 相似文献
263.
Javier Atalah Saskia A. Otto Marti J. Anderson Mark J. Costello Mark Lenz Martin Wahl 《Marine Biology》2007,153(2):199-211
Natural heterogeneity in ecological parameters, like population abundance, is more widely recognized and investigated than
variability in the processes that control these parameters. Experimental ecologists have focused mainly on the mean intensity
of predictor variables and have largely ignored the potential to manipulate variances in processes, which can be considered
explicitly in experimental designs to explore variation in causal mechanisms. In the present study, the effect of the temporal
variance of disturbance on the diversity of marine assemblages was tested in a field experiment replicated at two sites on
the northeast coast of New Zealand. Fouling communities grown on artificial settlement substrata experienced disturbance regimes
that differed in their inherent levels of temporal variability and timing of disturbance events, while disturbance intensity
was identical across all levels. Additionally, undisturbed assemblages were used as controls. After 150 days of experimental
duration, the assemblages were then compared with regard to their species richness, abundance and structure. The disturbance
effectively reduced the average total cover of the assemblages, but no consistent effect of variability in the disturbance
regime on the assemblages was detected. The results of this study were corroborated by the outcomes from simultaneous replicate
experiments carried out in each of eight different biogeographical regions around the world. 相似文献
264.
K. Martin F. G. Cooch R. F. Rockwell F. Cooke 《Behavioral ecology and sociobiology》1985,17(3):257-263
Summary The roles of male and female lesser snow geese (Anser caerulescens) in offspring care are well documented, but we know little about flexibility in these roles and how essential they are for offspring survival. We asked whether uni-parental care was adequate, which sex was required at various stages of the reproductive cycle, and what the costs and consequences were of variable amounts of parental care. We found that two parents were important in acquiring nest sites and producing clutches. Widows losing mates during the latter part of laying or in early incubation experienced similar rates of success in hatching clutches to paired females, but males losing mates during incubation experienced total nest failure. Partial clutch loss, hatch loss, intraspecific nest parasitism, duration of incubation periods and gosling weights at hatch did not differ for pairs or widows. In 1983 at La Pérouse Bay, Manitoba, Canada, widows and pairs had similar incubation behaviour, but widows were harassed more and spent more time in full alert posture while on their nests. In 1952 and 1953 at Southhampton Island, Northwest Territories, widows were significantly lighter in body weight prior to hatch than paired females. Thus while widows can bring clutches to hatch successfully, the loss of mates may result in additional physiological costs. Although all possibilities have not been tested experimentally, it appears that costs to uni-parental care up to hatch are not significant. Data collected so far on consequences of uni-parental care provided during the post-hatch period are equivocal, as in one year survival of goslings from single parent broods seemed poor and in another it did not appeart to differ from pairs. The minimum amount of parental care required to raise snow goslings from hatch to recruitment has yet to be determined. 相似文献
265.
Eliecer Díaz Christine Güldenzoph Markus Molis Christopher McQuaid Martin Wahl 《Marine Biology》2006,149(6):1301-1311
Variabilities in the responses of several South African red and green macroalgae to direct grazing and the responses of one green alga to cues from grazers were tested. We used two feeding experiments: (1) testing the induced responses of three red and one green algae to direct grazing by mesograzers and (2) a multi-treatment experiment, in which the direct and indirect effects of one macrograzer species on the green alga Codium platylobium were assessed. Consumption rates were assessed in feeding assays with intact algal pieces and with agar pellets containing non-polar extracts of the test algae. Defensive responses were induced for intact pieces of Galaxaura diessingiana, but were not induced in pellets, suggesting either morphological defence or chemical defence using polar compounds other than polyphenols. In contrast, exposure to grazing stimulated consumption of Gracilaria capensis and Hypnea spicifera by another grazing species. In the multi-treatment experiment, waterborne cues from both grazing and non-grazing snails induced defensive algal traits in C. platylobium. We suggest that inducible defences among macroalgae are not restricted to brown algae, but that both the responses of algae to grazers and of grazers to the defences of macroalgae are intrinsically variable and complex. 相似文献
266.
Rainer?HaasEmail author Katrin?Scheibner Martin?Hofrichter 《Environmental Sciences Europe》2003,15(4):224
Degradation of organo-arsenical chemical warfare agents by fungal enzyme manganese peroxidase. The fungal enzyme manganese peroxidase was used to degrade different organo-arsenical chemical warfare agents in cell-free reaction mixtures (in vitro). The decrease in the concentration of arsenical chemical warfare agents was determined by gas chromatography after derivatization with thiols. All organo-arsenical compounds tested were converted by room temperature for more than 90%. Aliphatic arsenical compounds were attacked more rapidly than aromatic derivatives. 相似文献
267.
The inherent stochastic nature of the levels and composition of environmental waste discharges are well known to environmental control agencies, who recognize that realistically environmental quality constraints must be formulated in probabilistic terms. Given the specification of environmental constraints in such terms, it is shown that the set of activity vectors which satisfy the constraint will, in general, be nonconvex. This militates against the determination of an efficient solution. A means of avoiding the potentially high computational and informational costs associated with the determination of an efficient solution in such cases is proposed. 相似文献
268.
269.
We examined how reproductive state affected shifts in behavior of adult female Podarcis sicula toward chemical cues from a natural snake predator (Coronella austriaca). The oviparous P. sicula lizards do not experience a major physical burden during reproduction, but gravid females substantially increase duration of basking. Therefore, gravid lizards are likely to experience a greater risk of mortality because they are exposed to predators for longer periods. Both gravid and non-gravid females shifted patterns of locomotion when confronted with snake chemical cues, but the change was notably larger when females were non-gravid. When non-gravid, lizards responded to predator scent by increasing the number of stand-ups and starts, while such a response was not observed when females were gravid. By contrast, gravid lizards clearly reduced the time spent basking in the presence of predator scent, whereas no change in basking behavior was observed when females were non-gravid. Thus, females exhibit differential behavioral responses to predator scents that is dependent on reproductive state. 相似文献
270.
Eupolymnia nebulosa (Montagu) is a widely distributed terebellid polychaete that builds its tubes on the coastal shelf in areas with mixed soft
and hard bottoms. From a long-term survey in the Bay of Banyuls, France (NW Mediterranean), we found an advancement of the
timing of the spawning period coincident with a delayed breakdown of the thermocline. We postulate that persistent high temperatures
can influence gamete development by stimulating oocyte growth, resulting in earlier spawning. During 1992 and 1993, we used
a between-individuals experimental approach to assess the possible effect of temperature on oocyte growth based on: (1) determination
of the growing fraction of the oocyte population (i.e. oocyte net growth); (2) identification of differences in oocyte growth-rate
among females; (3) comparison of non-significantly different size-distributions of the growing oocyte fraction (net oocyte
size-distributions) at the beginning of the experiments with those at the end. No effect of temperature on oocyte growth was
detectable at the population level, but a positive individual response to prolonged high temperature was evident. Thus, the lack of a significant response by the population to prolonged
high temperature does not imply a lack of individual response. We propose a model of oocyte-growth dynamics based on temperature
that incorporates previous observations of extended oogenesis and oocyte growth during periods of both increasing and decreasing
temperature and on the scattered pattern of oocyte size-distributions at the onset of spawning.
Received: 4 November 1996 / Accepted: 18 January 1997 相似文献