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1.
Little is known about how animals from tropical and subtropical climates adjust their energy expenditure to cope with seasonal
changes of climate and food availability. To provide such information, we studied the thermal physiology, torpor patterns
and energetics of the nocturnal blossom-bat (Syconycteris australis 18 g) from a subtropical habitat in both summer and winter. In both seasons, S. australis frequently entered daily torpor at ambient temperatures between 12 and 25°C when food and water were withheld. Unlike patterns
observed in temperate animals, mean minimum metabolic rates during torpor were lower in summer (0.47 ± 0.07 ml O2 g−1 h−1) than in winter (0.75 ± 0.11 ml O2 g−1 h−1). Body temperatures during torpor were regulated at 19.3 ± 1.0°C in summer and at 23.4 ± 2.0°C in winter. Torpor bout duration
was significantly longer in summer (7.3 ± 0.6 h) than in winter (5.5 ± 0.3 h), but in both seasons, bout duration was not
affected by ambient temperature. Consequently, average daily metabolic rates were also significantly lower in summer than
in winter. Body temperatures and metabolic rates in normothermic bats did not change with season. Our findings on seasonal
changes of torpor in this bat from the subtropics are opposite to those made for many species from cold climates which generally
show deeper and longer torpor in winter and are often entirely homeothermic in summer. More pronounced torpor in subtropical
S. australis in summer may be due to low or unpredictable nectar availability, short nights which limit the time available for foraging,
and long days without access to food. Thus, the reversed seasonal response of this subtropical bat in comparison to temperate
species may be an appropriate response to ecological constraints.
Received: 6 May 1997 / Accepted: 19 October 1997 相似文献
2.
Diving behaviour was investigated in female subantarctic fur seals (Arctocephalus tropicalis) breeding on Amsterdam Island, Indian Ocean. Data were collected using electronic Time Depth Recorders on 19 seals during
their first foraging trip after parturition in December, foraging trips later in summer, and during winter. Subantarctic fur
seals at Amsterdam Island are nocturnal, shallow divers. Ninety-nine percent of recorded dives occurred at night. The diel
dive pattern and changes in dive parameters throughout the night suggest that fur seals follow the nycthemeral migrations
of their main prey. Seasonal changes in diving behaviour amounted to the fur seals performing progressively deeper and longer
dives from their first foraging trip through winter. Dive depth and dive duration increased from the first trip after parturition
(16.6 ± 0.5 m and 62.1 ± 1.6 s respectively, n=1000) to summer (19.0 ± 0.4 m and 65 ± 1 s, respectively, n=2000) through winter (29.0 ± 1.0 m and 91.2 ± 2.2 s, respectively, n=800). In summer, subantarctic fur seals increased the proportion of time spent at the bottom during dives of between 10 and
20 m, apparently searching for prey when descending to these depths, which corresponded to the oceanic mixed layer. In winter,
fur seals behaved similarly when diving between 20 and 50 m, suggesting that the most profitable depths for feeding moved
down during the study period. Most of the dives did not exceed the physiological limits of individuals. Although dive frequency
did not vary (10 dives/h of night), the vertical travel distance and the time spent diving increased throughout the study
period, while the post-dive interval decreased, indicating that subantarctic fur seals showed a greater diving effort in winter,
compared to earlier seasons.
Accepted: 1 August 1999 相似文献
3.
Tsuzuki K Okamoto-Mizuno K Mizuno K Iwaki T 《International journal of biometeorology》2008,52(4):261-270
Airflow is an effective way to increase heat loss—an ongoing process during sleep and wakefulness in daily life. However,
it is unclear whether airflow stimulates cutaneous sensation and disturbs sleep or reduces the heat load and facilitates sleep.
In this study, 17 male subjects wearing short pyjamas slept on a bed with a cotton blanket under two of the following conditions:
(1) air temperature (Ta) 26°C, relative humidity (RH) 50%, and air velocity (V) 0.2 m s−1; (2) Ta 32°C, RH 80%, V 1.7 m s−1; (3) Ta 32°C; RH 80%, V 0.2 m s−1 (hereafter referred to as 26/50, 32/80 with airflow, and 32/80 with still air, respectively). Electroencephalograms, electrooculograms,
and mental electromyograms were obtained for all subjects. Rectal (Tre) and skin (Ts) temperatures were recorded continuously
during the sleep session, and body-mass was measured before and after the sleep session. No significant differences were observed
in the duration of sleep stages between subjects under the 26/50 and 32/80 with airflow conditions; however, the total duration
of wakefulness decreased significantly in subjects under the 32/80 with airflow condition compared to that in subjects under
the 32/80 with still air condition (P < 0.05). Tre, Tsk, Ts, and body-mass loss under the 32/80 with airflow condition were significantly higher compared to those
under the 26/50 condition, and significantly lower than those under the 32/80 with still air condition (P < 0.05). An alleviated heat load due to increased airflow was considered to exist between the 32/80 with still air and the
26/50 conditions. Airflow reduces the duration of wakefulness by decreasing Tre, Tsk, Ts, and body-mass loss in a warm humid
condition. 相似文献
4.
H. Ramløv 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(3):224-235
The microclimate in the habitat of the New Zealand alpine weta Hemideina maori is very variable with winter temperatures down to −6 °C under the rocks where the insects are found. Subfreezing temperatures
may in winter prevail for up to 17 days but diurnal cycles of freezing and thawing are common, as is also the case in summer.
Rates of temperature change can be very high and up to −7.20 °C/h. During winter, humidity was high for extended periods ranging
from 70% to 100% relative humidity (RH). In the summer, humidity ranged from 30% RH during the day to 100% RH at night. The
supercooling point of the haemolymph was approximately −8 °C year round, caused by a heat labile substance. The supercooling
point of the haemolymph of an insect of the same genus, Hemideina femorata not regularly exposed to subfreezing temperatures, was ca. −16.5 °C. Thermal hysteresis was not detected in the haemolymph
of H. maori. Haemolymph osmolality varied from 380 mOsm (summer) to 700 mOsm (winter). Body water content was ca. 75% all year round.
Total concentrations of sodium, potassium and chloride in haemolymph varied from 170 mM (winter) to 250 mM (summer). The total
concentration of free amino acids varied from 58 mM (summer) to 263 mM (winter). This variation was mostly due to proline
which varied from ca. 15 mM (summer) to ca. 100 mM (winter). The freeze-tolerant weta H. maori is exposed to a highly variable and cold environment all year round and several properties of its haemolymph composition
can be attributed to these climatic conditions, e.g. the presence of ice-nucleating agents and an increase in the concentration
of proline during cold hardening in the autumn.
Accepted: 22 February 1999 相似文献
5.
The aim of this study was to assess whether the three-compartment model of mean body temperature (Tb3) calculated from the
esophageal temperature (Tes), temperature in deep tissue of exercising muscle (Tdt), and mean skin temperature (Tsk) has the
potential to provide a better match with the thermoregulatory responses than the two-component model of mean body temperature
(Tb2) calculated from Tes and Tsk. Seven male subjects performed 40 min of a prolonged cycling exercise at 30% maximal oxygen
uptake at 21°C or 31°C (50% relative humidity). Throughout the experiment, Tsk, Tb2, Tb3, and Tdt were significantly (P < 0.01) lower at 21°C than at 31°C temperature conditions, while Tes was similar under both conditions. During exercise,
an increase in cutaneous vascular conductance (skin blood flow / mean arterial pressure) over the chest (%CVCc) was observed
at both 21°C and 31°C, while no increase was observed at the forearm at 21°C. Furthermore, the Tb3 and Tdt threshold for the
onset of the increase in %CVCc was similar, but the Tes and Tb2 threshold differed significantly (P < 0.05) between the conditions tested. These results suggest that active cutaneous vasodilation at the chest is related more
closely to Tb3 or Tdt than that measured by Tes or Tb2 calculated by Tes and Tsk during exercise at both 21°C and 31°C. 相似文献
6.
Contribution of central versus sweat gland mechanisms to the seasonal change of sweating function in young sedentary males and females 总被引:1,自引:0,他引:1
Yumiko Taniguchi Junichi Sugenoya Naoki Nishimura Satoshi Iwase Takaaki Matsumoto Yuuki Shimizu Yoko Inukai Maki Sato 《International journal of biometeorology》2011,55(2):203-212
In summer and winter, young, sedentary male (N = 5) and female (N = 7) subjects were exposed to heat in a climate chamber in which ambient temperature (Ta) was raised continuously from 30
to 42°C at a rate of 0.1°C min−1 at a relative humidity of 40%. Sweat rates (SR) were measured continuously on forearm, chest and forehead together with tympanic
temperature (Tty), mean skin temperature ( [`T] s ) \left( {\overline {\hbox{T}} {\hbox{s}}} \right) and mean body temperature ( [`T] b ) \left( {\overline {\hbox{T}} {\hbox{b}}} \right) . The rate of sweat expulsions (Fsw) was obtained as an indicator of central sudomotor activity. Tty and ( [`T] b ) \left( {\overline {\hbox{T}} {\hbox{b}}} \right) were significantly lower during summer compared with winter in males; SR was not significantly different between summer and
winter in males, but was significantly higher during summer in females; SR during winter was higher in males compared with
females. The regression line relating Fsw to ( [`T] b ) \left( {\overline {\hbox{T}} {\hbox{b}}} \right) shifted significantly from winter to summer in males and females, but the magnitude of the shift was not significantly different
between the two subject groups. The regression line relating SR to Fsw was steepened significantly from winter to summer in
males and females, and the change in the slope was significantly greater in females than in males. Females showed a lower
slope in winter and a similar slope in summer compared to males. It was concluded that sweating function was improved during
summer mediated by central sudomotor and sweat gland mechanisms in males and females, and, although the change of sweat gland
function from winter to summer was greater in females as compared with males, the level of increased sweat gland function
during summer was similar between the two subject groups. 相似文献
7.
K. Nakamura Masatoshi Tanaka Yutaka Motohashi Akira Maeda 《International journal of biometeorology》1997,40(2):103-106
This study was conducted to clarify the seasonal difference in body temperature in summer and winter, and to document the
thermal environment of the elderly living in nursing homes. The subjects were 57 healthy elderly people aged ≥63 years living
in two nursing homes in Japan. One of the homes was characterized by subjects with low levels of activities of daily living
(ADL). Oral temperatures were measured in the morning and afternoon, with simultaneous recording of ambient temperature and
relative humidity. Oral temperatures in summer were higher than in winter, with statistically significant differences (P<0.05) of 0.25 (SD 0.61) °C in the morning and 0.24 (SD 0.50) °C in the afternoon. Differences between oral temperatures in
summer and winter tended to be greater in subjects with low ADL scores, even when their room temperature was well-controlled.
In conclusion, the oral temperatures of the elderly are lower in winter than summer, particularly in physically inactive people.
It appears that those with low levels of ADL are more vulnerable to large changes in ambient temperature.
Received: 28 March 1996 / Accepted: 12 November 1996 相似文献
8.
Yankuo Li Zhigang Jiang Chunwang Li Cyril C. Grueter 《International journal of primatology》2010,31(4):609-626
The distribution of food resources in time and space may affect the diet, ranging pattern, and social organization of primates.
We studied variation in ranging patterns in a group of Sichuan snub-nosed monkeys (Rhinopithecus roxellana) over winter and summer in response to variation in their diet in the Qingmuchuan Nature Reserve, China. There was a clear
diet shift from highly folivorous in winter to highly frugivorous in summer. The home range was 8.09 km2 in summer and 7.43 km2 in winter, calculated via the 95% kernel method. Corresponding to the diet shift, the focal group traveled significantly
longer distances in summer (mean 1020 ± 69 m/d) than in winter (mean 676 ± 53 m/d); the daily range was also significantly
greater in summer (mean 0.27 ± 0.02 km2/d) than in winter (mean 0.21 ± 0.01 km2/d). There was no significant variation in home range size between winter and summer, and the monkeys did not use geographically
distinct ranges in summer and winter. However, overlap in the actual activity area and core range between winter and summer
was only 0.13 km2, representing 4.4% of the summer core area and 5.3% of the winter core area. Differences were apparent between summer and
winter ranging patterns: In summer, the group traveled repeatedly and uninterruptedly across its home range and made 3 circles
of movement along a fixed route in 31 d; in winter, the activity area was composed of 3 disconnected patches, and the focal
group stayed in each patch for an average of 8 successive days without traveling among patches. Winter range use was concentrated
on mixed evergreen and deciduous forest patches where leaves and fruits were available, whereas the summer range pattern correlates
significantly positively with the distribution of giant dogwood (Cornus controversa) fruits. Thus it appears that the diet shift of Sichuan snub-nosed monkeys between winter and summer caused the monkeys to
use their home range in different ways, supporting the hypothesis that food resources determine primate ranging patterns. 相似文献
9.
G. M. G. Zilahi-Balogh J. L. Shipp C. Cloutier J. Brodeur 《Journal of Insect Behavior》2009,22(2):134-147
Searching behaviour of two aphelinid parasitoids, Encarsia formosa Gahan and Eretmocerus eremicus Rose and Zolnerowich, was compared in a controlled environment under simulated summer [high light intensity (83 ± 1 W/m2), and 24 ± 1°C] and winter [low light intensity (11 ± 0.5 W/m2), and 20 ± 1°C] greenhouse conditions on tomato leaflets, with and without a single 3rd instar whitefly host, Trialeurodes vaporariorum (Westwood), within a 4-cm tomato leaflet arena. Residence time of both parasitoid species was longer on infested leaflets
vs. clean leaflets, and longer under winter than summer conditions. When parasitoids encountered a host on infested leaflets,
residence time increased. In all cases, residence time of E. formosa was longer that of E. eremicus. Proportion of time spent searching (i.e. antennating leaf surface while walking or standing still) was longer on clean vs.
infested leaflets for both E. formosa and E. eremicus. Walking speed by E. eremicus on clean leaflets was faster than E. formosa under both summer and winter conditions. Host handling time and proportion of host acceptance did not vary among parasitoids.
These findings suggest that E. eremicus could be more efficient in host finding on tomato leaflets than E. formosa over all seasons, especially in the winter when natural light is limiting and where daylight temperatures are ≥20°C. 相似文献
10.
Alexandre Sasseville Dalila Benhaberou-Brun Charlotte Fontaine Marie-Claude Charon 《Chronobiology international》2013,30(5):913-925
Night shiftworkers often complain of disturbed sleep during the day. This could be partly caused by morning sunlight exposure during the commute home, which tends to maintain the circadian clock on a daytime rhythm. The circadian clock is most sensitive to the blue portion of the visible spectrum, so our aim was to determine if blocking short wavelengths of light below 540 nm could improve daytime sleep quality and nighttime vigilance of night shiftworkers. Eight permanent night shiftworkers (32–56 yrs of age) of Quebec City's Canada Post distribution center were evaluated during summertime, and twenty others (24–55 yrs of age) during fall and winter. Timing, efficacy, and fragmentation of daytime sleep were analyzed over four weeks by a wrist activity monitor, and subjective vigilance was additionally assessed at the end of the night shift in the fall–winter group. The first two weeks served as baseline and the remaining two as experimental weeks when workers had to wear blue-blockers glasses, either just before leaving the workplace at the end of their shift (summer group) or 2 h before the end of the night shift (fall–winter group). They all had to wear the glasses when outside during the day until 16:00 h. When wearing the glasses, workers slept, on average ±SD, 32±29 and 34±60 more min/day, increased their sleep efficacy by 1.95±2.17% and 4.56±6.1%, and lowered their sleep fragmentation by 1.74±1.36% and 4.22±9.16% in the summer and fall–winter group, respectively. Subjective vigilance also generally improved on Fridays in the fall–winter group. Blue-blockers seem to improve daytime sleep of permanent night-shift workers. 相似文献
11.
This study compares the thermal ecology of male bearded dragon lizards (Pogona barbata) from south-east Queensland across two seasons: summer (1994–1995) and autumn (1995). Seasonal patterns of body temperature
(T
b) were explored in terms of changes in the physical properties of the thermal environment and thermoregulatory effort. To
quantify thermoregulatory effort, we compared behavioral and physiological variables recorded for observed lizards with those
estimated for a thermoconforming lizard. The study lizards' field T
bs varied seasonally (summer: grand daily mean (GDM) 34.6 ± 0.6°C, autumn: GDM 27.5 ± 0.3°C) as did maximum and minimum available
operative temperatures (summer: GDM T
max 42.1 ± 1.7°C, T
min 32.2 ± 1.0°C, autumn: GDM T
max 31.7 ± 1.2°C, T
min 26.4 ± 0.5°C). Interestingly, the range of temperatures that lizards selected in a gradient (selected range) did not change
seasonally. However, P. barbata thermoregulated more extensively and more accurately in summer than in autumn; lizards generally displayed behaviors affecting
heat load nonrandomly in summer and randomly in autumn, leading to the GDM of the mean deviations of lizards' field T
bs from their selected ranges being only 2.1 ± 0.5°C in summer, compared to 4.4 ± 0.5°C in autumn. This seasonal difference
was not a consequence of different heat availability in the two seasons, because the seasonally available ranges of operative
temperatures rarely precluded lizards from attaining field T
bs within their selected range, should that have been the goal. Rather, thermal microhabitat distribution and social behavior
appear to have had an important influence on seasonal levels of thermoregulatory effort.
Received: 28 April 1997 / Accepted: 29 December 1997 相似文献
12.
We investigated the seasonal variation of sweating response during exercise. Four adult healthy men repeated a moderate bicycle exercise (60 watts) in a climatic chamber of an ambient temperature of 30 degrees C (relative humidity, 45%) in winter, spring, summer, and fall. In summer, sweat rate immediately increased as soon as the exercise started, whereas in winter in a few minutes. The mean sweat rate during exercise was significantly different between winter and summer. The transient reduction of the Tsk was observed at the beginning of the exercise in winter. The Tsk decreased in proportion to increasing of sweat rate in each season. Significantly negative correlations were found between sweat rate and the rate of change of Tsk during exercise in each season. The slope and intercept of regression line were significantly different between winter and summer. The index of sweating was made available for the relative value, changing rate against annual mean value of total sweat loss (delta SR, %). The relative value rather than the absolute value (i.e., expressed as g.m-2.h-1) corrected well with skin temperature. It is suggested that the present results may reflect adapted changes in the thermoregulatory mechanisms to seasonal acclimatization. Moreover, the fall in skin temperature during exercise may be not due to increased evaporative cooling, but may be the result of vasoconstriction probably caused by non-thermal factors. 相似文献
13.
Supercooling points, lower lethal temperatures, and the effect of short-term exposures to low temperatures were examined
during both winter and summer in the adults of six weevil species from three different habitats on Marion Island. Upper lethal
limits and the effects of short-term exposure to high temperatures were also examined in summer-acclimatized adult individuals
of these species. Bothrometopus elongatus, B. parvulus, B. randi, Ectemnorhinus marioni, and E. similis were freeze tolerant, but had high lower lethal temperatures (−7 to −10°C). Seasonal variation in these parameters was not
pronounced. Physical conditions of the habitat appeared to have little effect on cold hardiness parameters because the Ectemnorhinus species occur in very wet habitats, whereas the Bothrometopus species inhabit drier areas. The adults of these weevil species are similar to other high southern latitude insects in that
they are freeze tolerant, but with high lower lethal temperatures. In contrast, Palirhoeus eatoni, a supra-littoral species, avoided freezing and had a mean supercooling point of −15.5 ± 0.94°C (SE) in winter and −11.8 ± 0.98°C
in summer. Survival of a constant low temperature of −8°C also increased in this species from 6 h in summer to 27 h in winter.
It is suggested that this strategy may be a consequence of the osmoregulatory requirements imposed on this species by its
supra-littoral habitat. Upper lethal temperatures (31–34°C) corresponded closely with maximum microclimate temperatures in
all of the species. This indicates that the pronounced warming, accompanied by the increased insolation that has been recorded
at Marion Island, may reduce survival of these species. These effects may be compounded as a consequence of predation by feral
house mice on the weevils.
Received: 4 February 1997 / Accepted: 3 May 1997 相似文献
14.
Hartley LM Packard MJ Packard GC 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(1):45-50
Hatchlings of the North American painted turtle (Chrysemys picta) typically spend their first winter of life inside the shallow, subterranean nest where they completed embryogenesis the
preceding summer. Neonates at northern localities consequently may be exposed during winter to subzero temperatures and frozen
soil. Hatchlings apparently survive exposure to such conditions by supercooling, but the physiological consequences of this
adaptive strategy have not been examined. We measured lactate in hatchling painted turtles after exposure to each of three
temperatures (0 °C, −4 °C, and −8 °C) for three time periods (5 days, 15 days, and 25 days) to determine the extent to which
overwintering hatchlings might rely on anaerobic metabolism to regenerate ATP. Whole-body lactate increased with increasing
duration of exposure and decreasing temperature, and the highest levels were associated with the group that experienced the
highest mortality. These results indicate that animals may develop a considerable lactic acidosis during a winter in which
temperatures fall below 0 °C for weeks or months and that accumulation of lactate may contribute to mortality of overwintering
animals.
Accepted: 20 October 1999 相似文献
15.
Brittany D. Palm David M. Koester William B. DriggersIII James A. Sulikowski 《Environmental Biology of Fishes》2011,92(4):585-589
Landings of the little skate, Leucoraja erinacea, within the territorial waters of the United States are currently regulated by a federal fishery management plan (FMP). For
a FMP to be effective, thorough knowledge of a species’ reproductive biology is essential. Currently, little information exists
on annual fecundity, egg case viability, gestation length, and neonate total length, for the little skate in the Gulf of Maine.
To study these reproductive parameters, mature skates and egg cases were housed in fiberglass tanks with an open seawater
system that provided natural, seasonal fluctuations in water temperature. Egg case deposition was highest during summer months
with a seasonal peak in June. Of the 324 egg cases laid by seven females (c. 46 eggs per year, per female), 74.1% were viable. Gestation lengths ranged from 22 to 54 weeks throughout the four seasons.
Egg cases laid in the fall had the longest gestation times (44.9 weeks, ± 0.13 weeks) and those laid in the spring had the
shortest gestation times (24.5 weeks, ± 0.21 weeks). Total lengths of neonates from spring oviposition were statistically
the longest (10.74 ± 0.05 cm) when compared to neonates from other seasons; however, egg viability was statistically the lowest
for spring when compared seasonally. 相似文献
16.
Aditya Singh Tommy C. Hines Jeffery A. Hostetler H. Franklin Percival Madan K. Oli 《European Journal of Wildlife Research》2011,57(1):15-26
The manner by which animals use space and select resources can have important management consequences. We studied patterns
of habitat selection by northern bobwhites (Colinus virginianus) on Babcock-Webb Wildlife Management Area, Charlotte County, Florida and evaluated factors influencing the sizes of their
home ranges. A total of 1,245 radio-tagged bobwhites were monitored for 19,467 radio days during 2002–2007. The mean ( ± 1
SE) annual home range size, estimated using the Kernel density method, was 88.43 ( ± 6.16) ha and did not differ between genders.
Winter home ranges of bobwhites (69.27 ± 4.92 ha) were generally larger than summer home ranges (53.90 ± 4.93 ha). Annual
and winter home ranges were smaller for bobwhites whose ranges contained food plots compared to those that did not; however,
the presence of food plots did not influence summer home ranges. We used distance-based methods to investigate habitat selection
by bobwhites at two scales: selection of home ranges within the study site (second-order selection) and selection of habitats
within home ranges (third-order selection). Across both scales, bobwhites generally preferred food plots and dry prairie habitat
and avoided wet prairies and roads. This pattern was generally consistent between genders and across years. Our data indicate
that management practices aimed at increasing and maintaining a matrix of food plots and dry prairie habitat would provide
the most favorable environment for bobwhites. 相似文献
17.
Virginie Rolland Jeffrey A. Hostetler Tommy C. Hines H. Franklin Percival Madan K. Oli 《European Journal of Wildlife Research》2011,57(4):717-727
Reproductive success is a critical component of individual fitness, and also an important determinant of growth rates of populations
characterized by early maturity and high fecundity. We used radiotelemetry data collected during 2003–2008 to estimate reproductive
parameters in a declining northern bobwhite (Colinus virginianus) population in South Florida, and to test hypotheses regarding factors influencing these parameters. The overall clutch size
was 12.10 ± 0.22, but females laid more eggs in their first clutch (12.43 ± 0.24) than in subsequent clutches (10.19 ± 0.53)
within a nesting season. Daily nest survival was higher for first (0.966 ± 0.003) than subsequent nests (0.936 ± 0.011). Hatchability
(proportion of laid eggs that hatched conditional upon nest survival to hatching) was 0.853 ± 0.008, but was higher for nests
incubated by females (0.873 ± 0.009) than those incubated by males (0.798 ± 0.018). The proportion of individuals attempting
a second nest was 0.112 ± 0.024 and 0.281 ± 0.040 when the first nest was successful and failed, respectively. Hatchability
was lower when the nesting habitat was burned the previous winter. We found no evidence that food strip density (a management
practice to provide supplemental food) influenced any of the reproductive parameters. Mean summer temperature affected hatchability,
nest survival, and proportion of nests incubated by males. Overall, the reproductive output in our study population was lower
than that reported for most other bobwhite populations, indicating that low reproductive performance may have contributed
to bobwhite population declines in our study site. These results suggest that current management practices, particularly those
related to habitat and harvest management, need careful evaluation. 相似文献
18.
The seasonal variation in the foraging behaviour of king penguins (Aptenodytes patagonicus) was studied at Heard Island (53°05′S, 73°30′E) during 1992/1993. On seven occasions throughout the breeding cycle, time-depth-light
recorders were deployed on breeding adults to record the dive activities and foraging. Foraging locations changed with season:
in autumn and spring 1992, adults foraged between 48–52°S and 74–78°E, about 370 km NNE of Heard Island close to the Polar
Front. Two penguins tracked in winter travelled 2220 km east of Heard Island (95°E) along the northern ice limit, and 1220 km
south of Heard Island to approximately 65°S, respectively. In spring (October), the penguins again foraged further north than
during winter. The foraging area utilised in October overlapped the area where the penguins foraged in March/April. The penguins'
diving behaviour also varied seasonally: the modal depth of deep dives (>50 m) increased from about 100 m in February to 220 m
in October. Mean dive depths increased from 70 ± 52 m in March 1992 to 160 ± 68 m in August 1992. Penguins dived deep (>50 m)
only during daylight hours (16 h in February, 9 h in July). Mean dive durations ranged from 2.9 ± 1.1 min in March 1992 to
5.1 ± 1.2 min in August 1992. Associated with changes in foraging location and dive behaviour was a change in diet composition:
during summer the penguins ingested mainly myctophid fish (>90%) while in winter the most important diet item was squid.
Accepted: 19 October 1998 相似文献
19.
Jeffrey R. Ziegeweid Cecil A. Jennings Douglas L. Peterson 《Environmental Biology of Fishes》2008,82(3):299-307
Many populations of shortnose sturgeon, Acipenser brevirostrum, in the southeastern United States continue to suffer from poor juvenile recruitment. High summer water temperatures, which
may be exacerbated by anthropogenic activities, are thought to affect recruitment by limiting available summer habitat. However,
information regarding temperature thresholds of shortnose sturgeon is limited. In this study, the thermal maximum method and
a heating rate of 0.1°C min−1 was used to determine critical and lethal thermal maxima for young-of-the-year (YOY) shortnose sturgeon acclimated to temperatures
of 19.5 and 24.1°C. Fish used in the experiment were 0.6 to 35.0 g in weight and 64 to 140 days post hatch (dph) in age. Critical
thermal maxima were 33.7°C (±0.3) and 35.1°C (±0.2) for fish acclimated to 19.5 and 24.1°C, respectively. Critical thermal
maxima significantly increased with an increase in acclimation temperature (p < 0.0001). Lethal thermal maxima were 34.8°C (±0.1) and 36.1°C (±0.1) for fish acclimated to 19.5 and 24.1°C, respectively.
Lethal thermal maxima were significantly affected by acclimation temperature, the log10 (fish weight), and the interaction between log10(fish weight) and acclimation temperature (p < 0.0001). Thermal maxima were used to estimate upper limits of safe temperature, thermal preferences, and optimal growth
temperatures of YOY shortnose sturgeon. Upper limits of safe temperature were similar to previous temperature tolerance information
and indicate that summer temperatures in southeastern rivers may be lethal to YOY shortnose sturgeon if suitable thermal refuge
cannot be found. 相似文献
20.
Microbial community structure in the subtropical north-east Atlantic Ocean was compared between 2 years and variation attributed
to environmental variables. Surface seawater communities were analysed by flow cytometry and fluorescence in situ hybridisation.
Probes specific to Alphaproteobacteria, Cyanobacteria, Gammaproteobacteria and Bacteroidetes identified 67–100% of cells. Due to natural variation in the study region due to the occurrence of major currents and islands,
data could not be pooled but were instead divided between distinct water masses. Community structure did not differ greatly
around the Cape Verde Islands between sampling periods but varied substantially in the open ocean, suggesting different environmental
perturbations favour specific bacterial groups. Wind speed varied significantly between years, with moderate to strong breeze
in winter 2008 and gales in winter 2006 (8.9 ± 0.2 ms−1 and 16.0 ± 0.4 ms−1, respectively). Enhanced wind-driven turbulence was associated with domination by the SAR11 clade of Alphaproteobacteria, which were present at 2.4-fold in the abundance of Prochlorococcus (41.8 ± 1.6% cells, compared to 17.7 ± 7.1%). Conversely, the calmer conditions of 2008 seemed to favour Prochlorococcus (40.0 ± 1.2% cells). Prochlorococcus high-light adapted clade HLI were only numerous during wind-driven turbulence, whereas oligotrophic-adapted clade HLII dominated
under calm conditions. Bacteroidetes were most prominent in turbulent conditions (9.5 ± 1.3% cells as opposed to 4.7 ± 0.3%), as were Synechococcus. In 2008, a considerable dust deposition event occurred in the region, which may have led to the substantial Gammaproteobacteria population (22.5 ± 4.0% cells compared to 4.6 ± 0.6% in 2006). Wind-driven turbulence may have a significant impact on microbial
community structure in the surface ocean. Therefore, community change following dust storm events may be linked to associated
wind in addition to dust-derived nutrients. 相似文献