共查询到20条相似文献,搜索用时 31 毫秒
1.
Yu-Nan WU Lin Lin Yu-Chao XIAO Li-Meng Zhou Meng-Si WU Hui-Ying Zhang Jin-Song LIU 《动物学研究》2014,35(1):33-41
Chinese bulbuls(Pycnonotus sinensis) are small passerine birds that inhabit areas of central, southern and eastern China. Previous observations suggest that free–living individuals of this species may change their food intake in response to seasonal changes in ambient temperature. In the present study, we randomly assigned Chinese bulbuls to either a 30 °C or 10 °C group, and measured their body mass(BM), body temperature, gross energy intake(GEI), digestible energy intake(DEI), and the length and mass of their digestive tracts over 28 days of acclimation at these temperatures. As predicted, birds in the 30 °C group had lower body mass, GEI and DEI relative to those in the 10 °C group. The length and mass of the digestive tract was also lower in the 30 °C group and trends in these parameters were positively correlated with BM, GEI and DEI. These results suggest that Chinese bulbuls reduced their absolute energy demands at relatively high temperatures by decreasing their body mass, GEI and DEI, and digestive tract size. 相似文献
2.
Summary Metabolic rates by means of oxygen consumption (VO2) at various ambient temperatures (T
a) and food consumption as well as water intake and thermoregulation were compared between individuals of the Cape porcupine Hystrix africaeaustralis acclimated to T
a=32°C with a photoperiod of 16L:8D summer-acclimated and T
a=10°C; 8L:16D winter-acclimated. The lower critical temperature as well as overall minimal thermal conductance were lower for the winter-acclimated porcupines when compared to summer-acclimated ones, while VO2 at the thermoneutral-zone was significantly (P<0.001) higher in the winter-acclimated porcupines. Dry matter intake, apparent digestible dry matter intake, gross digestible energy intake, as well as water intake, were significantly higher in the winter-acclimated porcupines. Yet, while dry matter intake increased 4 times in the winter-acclimated porcupines, apparent digestible dry matter increased only at a rate of 2.9 times. This difference is better reflected in terms of digestibility efficiency which in the winter-acclimated porcupines is only at a rate of 67.5% while in the summer-acclimated porcupines it is at a rate of 90%. From the results of this study, it is possible to assume that heat production in the winter-acclimated porcupines is partly increased by food intake. Increased heat production on the one hand, and a decrease in overall minimal thermal conductance on the other, seem to be important mechanisms in winter acclimatization of the Cape porcupine. 相似文献
3.
We studied the thermophilic response to feeding of a typical desert adapted anuran from the Monte Desert. Our aim was to evaluate thermal changes in the selected body temperature of adult frogs of Pleurodema nebulosum, and measure the intestinal passage time, and food digestion. Our results show that after feeding, they selected higher micro-environmental temperatures ~ + 2 °C than frogs that remained starved. Pleurodema nebulosum would present a postprandial thermophilic response. The time of retention of food in the digestive tract was thermo-dependent, being lower in those individuals who were incubated at high temperatures (25 °C) compared to those subjected to lower temperatures (20 °C). Although we did not detect effects of temperature on digestive efficiency, the mass of faecal material indicates an increase at temperatures closer to the selected ones, suggesting that the defecation rate is influenced by temperature. Laiuoperinae frogs are characterized by explosive breeding behavior and fast growing rate. The digestive efficiency is essential for acquiring energy necessary for growth, reproduction and refuge-seeking, among others. In this framework, the differential selection of temperatures between moments of fasting and feeding allows the frogs to maintain a high digestive efficiency, maximizing the absorption of nutrients. 相似文献
4.
Summary The water balance of three different sized coexisting species of heteromyid rodents (Dipodomys merriami ca. 39 g;Perognathus fallax ca. 23 g;Perognathus longimembris ca. 9 g) was assessed while consuming two different diets (either wheat or hulled sunflower) at ambient temperatures of 15–30°C.
The metabolism of wheat as the sole food source was calculated to provide a greater metabolic water production (MWP) than
the consumption of sunflower seed because of their different composition. The state of water balance was assessed by measuring
urine concentrations and body weight maintenance on each diet at each temperature. Both measures showed that (i) all species
were able to maintain a more positive water on the higher MWP seed, (ii) for all species there was an ambient temperature
above which water balance could no longer be maintained, (iii) that this temperature was higher with the higher MWP food source
and (iv) water regulatory efficiency was negatively correlated with body mass.Dipodomys showed a reduced digestive efficiency compared toPerognathus. When presented with both seedsDipodomys showed no preference for either seed irrespective of the state of water balance whilst thePerognathus species showed a tendency for an increased preference for the high MWP food source at the higher ambient temperatures. The
ecological implications of these findings are discussed. 相似文献
5.
Kenneth J. Goldman 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(6):423-429
Stomach temperatures of three white sharks, Carcharodoncarcharias, (one reported previously and two new individuals) were intermittently recorded by acoustic telemetry at the South Farallon
Islands, central California. Temperature profiles of the water column were obtained concurrently. Stomach temperatures were
elevated over ambient water temperatures by as much as 14.3 °C. Stomach temperatures varied within a narrow range while ambient
water temperature fluctuated over a much larger range, showing that this species regulates its body temperature. These data,
in combination with previous work on the physiology and anatomy of white sharks, indicate that the white shark is endothermic.
It appears that the heat retention system in lamnid sharks has allowed them to inhabit cold water and remain active predators
of swift and agile prey.
Accepted: 17 February 1997 相似文献
6.
F. Aujard M. Perret G. Vannier 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(7):540-548
The lesser mouse lemur, a small Malagasy primate, is exposed to strong seasonal variations in ambient temperature and food
availability in its natural habitat. To face these environmental constraints, this nocturnal primate exhibits biological seasonal
rhythms that are photoperiodically driven. To determine the role of daylength on thermoregulatory responses to changes in
ambient temperature, evaporative water loss (EWL), body temperature (T
b) and oxygen consumption, measured as resting metabolic rate (RMR), were measured in response to ambient temperatures ranging
from 5 °C to 35 °C, in eight males exposed to either short (10L:14D) or long (14L:10D) daylengths in controlled captive conditions.
In both photoperiods, EWL, T
b and RMR were significantly modified by ambient temperatures. Exposure to ambient temperatures below 25 °C was associated
with a decrease in T
b and an increase in RMR, whereas EWL remained constant. Heat exposure caused an increase in T
b and heat loss through evaporative pathways. Thermoregulatory responses to changes in ambient temperature significantly differed
according to daylength. Daily variations in T
b and EWL were characterized by high values during the night. During the diurnal rest, lower values were found and a phase
of heterothermia occurred in the early morning followed by a spontaneous rewarming. The amplitude of T
b decrease with or without the occurrence of torpor (T
b < 33 °C) was dependent on both ambient temperature and photoperiod. This would support the hypothesis of advanced thermoregulatory
processes in mouse lemurs in response to selective environmental pressure, the major external cue being photoperiodic variations.
Accepted: 4 August 1998 相似文献
7.
Ambient temperature‐mediated enzymic activities and intestinal microflora in Lymantria dispar larvae
JianYong Zeng ZhongBin Shi JianHong Shi JiaXing Guo GuoCai Zhang Jie Zhang 《Archives of insect biochemistry and physiology》2019,102(2)
To understand how ambient temperature affect the gypsy moth larvae, and provide a theoretical basis for pest control in different environments. Fourth instar gypsy moth larvae were incubating for 3 hr at 15℃, 20℃, 25℃, 30℃, 35℃, and 40℃, respectively. Afterward, digestive and antioxidant enzyme activities, total antioxidant capacity, and intestinal microflora community were analyzed to reveal how the caterpillars respond to ambient temperature stress. Results showed that both digestive and antioxidant enzymes were regulated by the ambient temperature. The optimum incubation temperatures of protease, amylase, trehalase, and lipase in gypsy moth larvae were 30℃, 25℃, and 20℃, respectively. When the incubation temperature was deviated optimum temperatures, digestive enzyme activities would be downregulated depending on the extent of temperature stress. In addition, glutathione S‐transferase, peroxidase, catalase, and polyphenol oxidase would be activated under a sufferable temperature stress, but superoxide dismutase and carboxylesterase (CarE) would be inhibited. In addition, results showed that the top two abundant phyla were Proteobacteria and Firmicutes. The phylum Firmicutes abundance was decreased and phylum Proteobacteria abundance was increased by ambient temperature stress. Moreover, it suggested that gypsy moth caterpillars at different ambient temperature mainly differed from each other by Escherichia‐Shigella and Bifidobacterium in control, Acinetobacter in T15, and Lactobacillus in T40, respectively. 相似文献
8.
Jorge Ayala-Berdon Jorge E. Schondube Kathryn E. Stoner 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(5):553-562
Food intake in nectar-feeding animals is affected by food quality, their energetic demands, and the environmental conditions
they face. These animals increase their food intake in response to a decrease in food quality, a behavior named “intake response”.
However, their capacity to achieve compensatory feeding, in which they maintain a constant flux of energy, could be constrained
by physiological processes. Here we evaluated how both a seasonal change in environmental conditions and physiological constraints
affected the food ingestion in the bat Glossophaga soricina. We measured food intake rate during both the wet/warm and dry/cool seasons at sucrose solutions ranging from 146 to 1,022 mmol L−1. We expected that food intake and metabolic demands would be greater during the dry/cool season. Bats ingested ~20% more
food in the dry/cool than in the wet/warm season. Regardless of season, bats were unable to achieve a constant flux of energy
when facing the different sugar concentrations that we used in our experiments. This suggests that the rate of food intake
is physiologically constrained in G. soricina. Using the digestive capacity of bats we modeled their food intake. The analytic model we used predicts that digestive limitations
to ingest energy should have an important effect on the ecology of this species. 相似文献
9.
J. R. Coelho A. J. Ross 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(1):68-76
In spite of the abundance and broad distribution of social wasps, little information exists concerning thermoregulation by individuals. We measured body temperatures of the yellowjackets Vespula germanica and V. maculifrons and examined their thermoregulatory mechanisms. V. germanica demonstrated thermoregulation via a decreasing gradient between thorax temperature and ambient temperature as ambient temperature increased. V. maculifrons exhibited a constant gradient at lower ambient temperatures but thorax temperature was constant at high ambient temperatures. Head temperature exhibited similar patterns in both species. In spite of low thermal conductances, a simple heat budget model predicts substantial heat loads in warm conditions in the absence of thermoregulation. Both species regurgitated when heated on the head. A smaller volume of regurgitant was produced at lower head temperatures and a larger volume at higher head temperatures. Small regurgitations resulted in stabilization of head temperature, while large ones resulted in 4°C decreases in head temperature. Regurgitation was rare when wasps were heated upon the thorax. Abdomen temperature was 3–4°C above ambient temperature, and approached ambient temperature under the hottest conditions. No evidence was found for shunting of hot hemolymph from thorax to abdomen as a cooling mechanism. The frequency of regurgitation in workers returning to the nest increased with ambient temperature. Regurgitation may be an important thermoregulatory strategy during heat stress, but is probably not the only mechanism used in yellowjackets.Abbreviations
M
b
body mass
-
M
th
thorax mass
-
T
a
ambient temperature
-
T
ab
abdomen temperature
-
T
b
body temperature
-
T
h
head temperature
-
T
th
thorax temperature
-
C
t
thermal conductance 相似文献
10.
Lotz CN Martínez del Rio C Nicolson SW 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2003,173(6):455-462
Endotherms must warm ingested food to body temperature. Food warming costs may be especially high for nectar-feeding birds, which can ingest prodigious volumes. We formulated a mathematical model to predict the cost of warming nectar as a function of nectar temperature and sugar concentration. This model predicts that the cost of warming nectar should: (1) decrease as a power function of nectar concentration, and (2) increase linearly with the difference between body temperature and nectar temperature. We tested our model on rufous hummingbirds (Selasphorus rufus). A typical experiment consisted of feeding birds nectar of a given concentration at 39°C (equivalent to body temperature) and then at 4°C, and vice versa. We used the percentage change in metabolic rate between the two food temperatures to estimate the cost of warming nectar. The model's predictions were accurately met. When birds had to hover rather than perch during feeding bouts, estimated food-warming costs were only slightly lower. The cost of warming nectar to body temperature appears to be an important yet overlooked aspect of the energy budgets of nectar-feeding birds. Hummingbirds feeding on 5% sucrose solutions at 4oC have to increase their metabolic rate by an amount equivalent to that elicited by a 15°C drop in ambient temperature.Abbreviations AE assimilation efficiency - C nectar concentration - H' cost of warming food to body temperature - SDA specific dynamic action - Ta ambient temperature - Tb body temperature - Tn nectar temperatureCommunicated by: G. Heldmaier 相似文献
11.
Karl J. Kaiyala Kayoko Ogimoto Jarrell T. Nelson Michael W. Schwartz Gregory J. Morton 《PloS one》2015,10(3)
Survival of free-living animals depends on the ability to maintain core body temperature in the face of rapid and dramatic changes in their thermal environment. If food intake is not adjusted to meet the changing energy demands associated with changes of ambient temperature, a serious challenge to body energy stores can occur. To more fully understand the coupling of thermoregulation to energy homeostasis in normal animals and to investigate the role of the adipose hormone leptin to this process, comprehensive measures of energy homeostasis and core temperature were obtained in leptin-deficient ob/ob mice and their wild-type (WT) littermate controls when housed under cool (14°C), usual (22°C) or ∼ thermoneutral (30°C) conditions. Our findings extend previous evidence that WT mice robustly defend normothermia in response to either a lowering (14°C) or an increase (30°C) of ambient temperature without changes in body weight or body composition. In contrast, leptin-deficient, ob/ob mice fail to defend normothermia at ambient temperatures lower than thermoneutrality and exhibit marked losses of both body fat and lean mass when exposed to cooler environments (14°C). Our findings further demonstrate a strong inverse relationship between ambient temperature and energy expenditure in WT mice, a relationship that is preserved in ob/ob mice. However, thermal conductance analysis indicates defective heat retention in ob/ob mice, irrespective of temperature. While a negative relationship between ambient temperature and energy intake also exists in WT mice, this relationship is disrupted in ob/ob mice. Thus, to meet the thermoregulatory demands of different ambient temperatures, leptin signaling is required for adaptive changes in both energy intake and thermal conductance. A better understanding of the mechanisms coupling thermoregulation to energy homeostasis may lead to the development of new approaches for the treatment of obesity. 相似文献
12.
Jana Podhorna Cindy Aubernon Marie Borkovcova Julien Boulay Valery Hedouin Damien Charabidze 《Insect Science》2018,25(5):883-893
The thermoregulation behavior of Lucilia sericata larvae (Diptera: Calliphoridae), a necrophagous species that feeds on vertebrate cadavers, was investigated. These larvae require high heat incomes to develop, and can elevate temperatures by forming large aggregates. We hypothesized that L. sericata larvae should continue to feed at temperatures up to 38 °C, which can be reached inside larval masses. Thermal regulation behavior such as movement between a hot food spot and colder areas was also postulated. The hypotheses were tested by tracking for 1 h the activity of single, starved third instar larvae in a Petri dish containing 1 food spot (FS) that was heated to a constant temperature of 25 °C, 34 °C or 38 °C with an ambient temperature of 25 °C. The influence of previous conspecific activity in the food on larval behavior was also tested. The crops of larvae were dissected to monitor food content in the digestive systems. Based on relative crop measurements, larvae fed at all food temperatures, but temperature strongly affected larval behavior and kinematics. The total time spent by larvae in FS and the duration of each stay decreased at high FS temperature. Previous activity of conspecifics in the food slightly increased the time spent by larvae in FS and also decreased the average distance to FS. Therefore, necrophagous L. sericata larvae likely thermoregulate during normal feeding activities by adjusting to local fluctuations in temperature, particularly inside maggot masses. By maintaining a steady internal body temperature, larvae likely reduce their development time. 相似文献
13.
C. R. Brown G. G. Foster 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(7):658-664
Summary The effect of clustering behaviour on metabolism, body temperature, thermal conductance and evaporative water loss was investigated in speckled mousebirds at temperatures between 5 and 36°C. Within the thermal neutral zone (approximately 30–35 °C) basal metabolic rate of clusters of two birds (32.5 J·g-1·h-1) and four birds (28.5 J·g-1·h-1) was significantly lower by about 11% and 22%, respectively, than that of individuals (36.4 J·g-1·h-1). Similarly, below the lower critical temperature, the metabolism of clusters of two and four birds was about 14% and 31% lower, respectively, than for individual birds as a result of significantly lower total thermal conductance in clustered birds. Body temperature ranged from about 36 to 41°C and was positively correlated with ambient temperature in both individuals and clusters, but was less variable in clusters. Total evaporative water loss was similar in individuals and clusters and averaged 5–6% of body weight per day below 30°C in individuals and below 25°C in clusters. Above these temperatures total evaporative water loss increased and mousebirds could dissipate between 80 and 90% of their metabolic heat production at ambient temperatures between 36 and 39°C. Mousebirds not only clustered to sleep between sunset and sunrise but were also observed to cluster during the day, even at high ambient temperature. Whereas clustering at night and during cold, wet weather serves a thermoregulatory function, in that it allows the brrds to maintain body temperature at a reduced metabolic cost, clustering during the day is probably related to maintenance of social bonds within the flock.Abbreviations BMR
basal metabolic rate
- bw
body weight
-
C
totab
total thermal conductance
- EWI
evaporative water loss
-
M
metabolism
- RH
relative humidity
-
T
a
ambient temperature
-
T
b
body temperature
-
T
ch
chamber temperature
-
T
cl
cluster temperature
- TEWL
total evaporative water loss
- LCT
lower critical temperature
- TNZ
thermal neutral zone 相似文献
14.
G. N. Stone 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(4):317-326
Body temperatures during free flight in the field, warm-up rates during pre-flight warm-up, and temperatures during tethered flight are measured for four tropical solitary bee species at three sites of differing altitude in Papua New Guinea. All four species are capable of endothermic preflight warm-up; three species give slopes of thoracic temperature on ambient temperature of significantly less than 1, indicating regulation of thoracic temperature. In the kleptoparasitic Coelioxys spp. (Megachilidae) and Thyreus quadrimaculatus (Anthophoridae), warm-up rates and thoracic temperatures in flight are low by comparison with the two provisioning species Creightonella frontalis (Megachilidae) and Amegilla sapiens (Anthophoridae). In both C. frontalis and A. sapiens thoracic temperatures correlate positively and significantly with both ambient temperature and body mass. In A. sapiens, body mass increases with altitude; this can be interpreted as a response to lower ambient temperatures at higher altitude, an example of Bergmann's rule. In both A. sapiens and C. frontalis populations at higher altitude have higher thoracic temperatures independent of differences of body mass, suggestive of additional morphological or physiological adaptation to lower ambient temperatures. In A. sapiens there is no qualitative difference in body temperatures between males and females after controlling for body mass, while male C. frontalis have significantly lower thoracic temperatures than females of the species. This difference between A. sapiens and C. frontalis is discussed with reference to variation in mating systems found in the Apoidea.Abbreviations C.R.I.
Christensen Research Institute
- P.N.G.
Papua New Guinea
- SFT
stable flight temperature
-
T
a
ambient air temperature
-
T
ab
abdominal temperature
-
T
dif
the temperature difference between thorax and abdomen
-
T
ex
thoracic temperature excess
- VFT
voluntary flight temperature 相似文献
15.
J. A. Godiksen M.-A. Svenning R. N. Sinnatamby J. B. Dempson R. Borgstr?m M. Power 《Polar Biology》2011,34(4):591-596
Mean ambient water temperatures experienced by individual young-of-the-year (YOY) Arctic charr, Salvelinus alpinus (L.), from a Svalbard lake were estimated using measurements of oxygen stable isotopes (δ18O) derived from fish otoliths. Otolith-derived water temperatures differed significantly from temperatures recorded at the
outlet river of the Dieset watercourse but were consistent with temperatures previously recorded in shallow littoral areas
of other Svalbard lakes where YOY charr are commonly found. This indicates that fixed-point monitoring does not necessarily
represent the temperatures and thermal habitats used by individual fish. Otolith-derived water temperatures were also positively
related to fish length-at-capture and otolith size, although much of the variation remained unexplained. Differences among
individuals could be related to variability in food availability and food intake as well as variation in the initial fish
size at hatching. Implications for subsequent investigations into how YOY charr respond and adapt to future climate change
are discussed. 相似文献
16.
Test of a digestion optimization model: effect of variable-reward feeding schedules on digestive performance of a migratory bird 总被引:1,自引:0,他引:1
Birds on migration often alternate between feeding and nonfeeding periods, in part because food resources may be patchily
distributed and in part because birds on migration may adopt a risk-prone foraging strategy characterized by selection of
variable rather than constant food rewards. Optimal digestion models predict that increases in intermeal interval like those
encountered by some migratory birds should result in longer retention time of digesta and higher digestive efficiency if birds
are maximizing their rate of energy intake. We tested these predictions by comparing residence time of digesta and extraction
efficiency of lipid for captive yellow-rumped warblers (Dendroica coronata) feeding adlibitum and when we added intervals of time when the birds received no food. We increased the likelihood that the warblers were maximizing
their rate of energy intake by increasing light levels during spring to induce hyperphagia (treatment birds (16L:8D light:
dark cycle) ate 2.13 ± 0.14 g dry food day−1 (n = 8) while control birds (10L:14D) ate 1.25 ± 0.03 g dry food day−1 (n = 6)). Treatment birds offered food only every other 2–3 h ate 50% more during the 4-h test period than when they were always
feeding adlibitum. Despite these differences in food intake, extraction efficiency of glycerol trioleate remained high and constant (93%),
and mouth-to-anus total mean retention time (TMRT) did not change (overall mean: 54.8 ± 6.0 min). Residence time of lipid
in the stomach increased whereas residence time of lipid in the intestine decreased when birds fed only every other 2–3 h
compared to when birds always fed ad libitum. None of the results were consistent with the predictions of the optimal digestion model unless we assume that birds were
minimizing their feeding time rather than maximizing their rate of energy gain. Furthermore, the ability of yellow-rumped
warblers to maintain high extraction efficiency with no change in TMRT suggests some spare digestive capacity when food intake
increases by as much as 50%.
Received: 14 June 1997 / Accepted: 20 November 1997 相似文献
17.
We investigated whether a climatic change in temperature affected daily food intake in migrating male redheaded buntings. Groups of adult male birds (n = 18) were photoinduced into migratory phenotype under increasing spring daylengths (NDL); as the birds began to exhibit night restlessness, Zugunruhe, these were allocated into groups, either with ambient (NDL, variable daily temperature: maximum – 29–44 °C and minimum – 16–33 °C; for food intake (six birds) and activity recording, six birds) until 2 weeks after they concluded migration or with constant temperature (NDT, 22 ± 1 °C; for food intake (six birds)) conditions. As day length increased March onwards, daily food intake increased (hyperphagia) in NDL and NDT groups. However, hyperphagia was slower in NDT birds as compared to NDL birds, suggesting that altered ambient temperature affects daily food intake in migrating buntings. Another group of 12 birds were held under constant daylengths (12L:12D; EDT and constant temperature 22 ± 1 °C). Although the onset of Zugunruhe was delayed under EDT, the day of onset of Zugunruhe was taken as day 0. Daily food intake and body weight before and during migration of EDT birds were compared with that of NDT and NDL groups. Daily food intake and body weight increased in all migrating birds, but hyperphagia continued post-migration in NDT birds. The study suggests that constantly suboptimal temperature despite increasing daylength, NDT, appeared to affect feeding and body weight of migratory buntings as evident from continued hyperphagia and body weight gain, even after concluding migrating activity. 相似文献
18.
I. Ibarrola E. Navarro J. I. P. Iglesias 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(1):32-40
Feeding and digestive parameters were analysed in cockles Cerastoderma edule fed for 3 days on two foods of different qualities, both foods given in two different concentrations. With low quality food,
gut content was found to increase with ingestion rate. Such increased capacity of the gut to allocate food precludes negative
effects upon throughput time, and so absorption efficiency remained nearly constant at the two food concentrations. With high
quality food, gut content remained at high constant values and consequently enhancement of food ingestion rate with a high
food ration leads to a significant reduction in throughput time, resulting in lower absorption efficiencies. Significantly
higher levels of amylases and cellulases have been found within the digestive gland of cockles fed high quality diets. Coincidentally,
absorption of carbohydrates is increased and absorption of lipids decreased in such diets as compared to low quality diets.
Implications of the positive correlation between digestive enzyme activity and food quality are discussed in relation to the
role that both digestive investments and endogenous faecal losses play in digestive processes. Results obtained in this study
indicate that investments in the form of digestive enzymes are a key factor in the functional response of cockles to short-term
variations in the food regime.
Accepted: 13 September 1997 相似文献
19.
Júlio Csar Bicca-Marques Cludia Calegaro-Marques 《American journal of physical anthropology》1998,106(4):533-546
Behavioral thermoregulation in primates may provide a means for the conservation of heat during periods of low ambient temperature and/or food shortage as well as a way to dissipate heat under hot conditions. This article focuses on behavioral thermoregulation in a sexually dichromatic primate, the black-and-gold howling monkey (Alouatta caraya). Two models have been proposed to explain the evolution of sexual dichromatism in this species: thermoregulation and sexual selection. Five hypotheses associated with thermoregulatory behaviors are tested. These are as follows: (1) energy-conserving postures are used mainly under low ambient temperatures; (2) sunny resting places are selected during periods of low temperature; (3) exposure of the less-insulated ventral region to sunlight decreases with increasing temperature; (4) black-colored adult males use energy-conserving postures, sunny places, and exposure of the ventral region to sunlight less frequently than do blonde-colored adult females; and (5) smaller individuals use energy-conserving postures, sunny places, and exposure of the ventral region to sunlight in significantly greater frequency than do larger individuals. Over a 12-month period, behavioral data were collected on a free-ranging habituated group of 15–17 howlers of all age-sex classes. Ambient temperature was measured each hour. The results indicate that during resting, howlers showed a consistent use of heat-conserving postures, showed a preference for sunny places, and exposed their ventral region to sunlight under low ambient temperatures. A preference for shady places, heat-dissipating postures, and exposure of the back were observed under high ambient temperatures. Despite sex differences in adult color patterns and differences in size between age classes, no significant age or sex differences in thermoregulatory behaviors were detected. Failure to confirm a thermoregulation model implies that sexual selection may be responsible for sexual dichromatism in this species. Am J Phys Anthropol 106:533–546, 1998. © 1998 Wiley-Liss, Inc. 相似文献
20.