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1.
Recent evidence suggests that many Australian agamids show temperature‐dependent sex determination (TSD) with variation in sex determining mechanisms among closely related taxa. However, as shown in other vertebrates, sex ratios can also be influenced by genetic or phenotypic differences among females in their propensity to produce sons or daughters, and these influences might confound any thermal effects of incubation per se. To address these issues, we investigated the determinants of sex ratios in the mallee dragon Ctenophorus fordi, together with a detailed analysis of karyotypes. There was no detectable variation in sex ratios arising from variation among females, clutches or incubation temperatures, which might indicate genetic sex determination for this species. However, there was no evidence of cytologically distinct sex chromosomes using standard banding techniques. The sex ratio pattern in C. fordi strongly contrasts with the results for the congener Ctenophorus pictus, where sex ratios show variation among females. Thus, Australian agamids offer promising opportunities to address fundamental issues in sex ratio biology.  相似文献   

2.
Many egg-laying reptiles possess temperature-dependent sex determination (TSD) in which outcome of gonadogenesis is determined by incubation temperature during a temperature-sensitive period of development. Prior studies on Malayemys macrocephala showed that incubation temperatures influence gonadal development and suggested that M. macrocephala exhibits TSD. However, information on the temperature-sensitivity period in this species was unknown until the current study. Turtle eggs were collected from rice fields in central Thailand from December 2016 to February 2017. In the laboratory, eggs were incubated at male-biased temperature (26 °C) and shifted to female-biased temperature (32 °C), or vice versa. Single shift experiments were performed systematically during embryonic stages 13–21. After hatching, sex of individual turtles was determined by histological analysis. We found that the sex determination of M. macrocephala is affected by temperature up to stage 16 of embryonic development.  相似文献   

3.
An experimental investigation revealed that cocoon production by E. foetida (Oligochaeta) increased linearly with increase in temperature in the range 10 to 25 °C. Diurnally fluctuating temperature did not have a marked influence on total cocoon production at the temperature levels of 10, 15 and 25 °C. A highly significant difference in cocoon production occurred between a constant temperature of 20 °C and a mean temperature of 20 °C (which fluctuated diurnally between 12 and 28 °C). Maximum cocoon production was obtained at 25 °C with each worm producing a cocoon every second day. The investigation also showed that temperature does influence the number of hatchlings per cocoon. At a temperature of 25 °C fewer worms hatched per cocoon than at 20 °C.  相似文献   

4.
Objective: To determine if a correlation exists among auricular, rectal and pulmonary artery (PA) temperatures in hypothermic dogs. Design: Prospective study. Setting: Angiography suite at a college of veterinary medicine. Animals: Sexually intact female research hounds (13.9–25.4 kg; n=8). Measurements and main results: Dogs were anesthetized for instrumentation with a percutaneously placed, thermistor‐tipped, PA catheter. Anesthesia was maintained until the core body temperature decreased to 36.6°C (97.8°F). Anesthesia was discontinued, and auricular and rectal temperatures were obtained every 15 minutes until the PA temperature reached 38.3°C (100.9°F). A strong correlation was noted among the 3 methods of temperature measurement (P<0.001; R≥0.846). No statistical difference was detected among measurement methods at baseline, the minimum temperature attained, nor the median temperature attained. However, at the maximum temperature attained, auricular measurements (37.7±0.4°C or 99.8±0.7°F) were lower than either the rectal (38.3±0.3°C or 100.9±0.5°F) or PA (38.3±0.3°C or 100.9±0.5°F) temperature measurements (P=0.001). Conclusion: There is a strong correlation among rectal, auricular and PA temperatures. Auricular temperature may be used to monitor core body temperature during postoperative rewarming; however, it might be slightly lower than core temperature as normothermia is reached.  相似文献   

5.
The effect of temperature on the rate of gut evacuation in Barbus aeneus was investigated in two ways. In the first, juvenile fish, kept under conditions of constant temperature, were fed marked food items and the time elapsing until these appeared in the faeces was noted. In the second, fish of a range of sizes were caught in the P.K. le Roux dam and immediately placed in cages in the dam to prevent their access to food. Groups of fish were sacrificed at intervals and the contents of standardized gut sections weighed. The field experiment was carried out in summer and in winter. The laboratory experiment yielded the relationship: P = 6270 × t-2,11 where P is the passage time in hours and T is the temperature in °C. This gives passage times of the order of 8 h at 25°C and 39 h at 11,5°C. The field experiment indicated that there was an exponential relationship between degree of fullness and rate of evacuation, and that complete evacuation required about 24 h in summer, but more than 5 days in winter.  相似文献   

6.
Abstract

The effect of temperature and salinity on the elimination of enrofloxacin (EF) in Manila clams Ruditapes philippinarum was investigated. The clams, cultured under different temperatures and salinities (16°C and 30‰, 22°C and 30‰, or 22°C and 20‰), were exposed to EF at 5 μg/mL of water in a medicated bath. After a 24-h exposure, the concentration of EF in various tissues was measured by high-performance liquid chromatography and the elimination rate of EF in those tissues was investigated by regression analysis. After the treatment, the initial concentrations of EF among tissues were (in decreasing order) plasma > gill > visceral mass > foot > adductor muscle. In all tissues the elimination half-life (t 1/2) of EF in the clams cultured at 22°C and 20‰ and 16°C and 30‰ were markedly longer than in those cultured at 22°C and 30‰, and the t 1/2 at 16°C and 30‰ was slightly longer than that at 22°C and 20‰. Slight differences were also observed in t 1/2 values among various tissues. These data indicate that both temperature and salinity had significant effects on the elimination of EF in the Manila clams and that lower temperature or salinity could result in slower elimination.

Received January 21, 2011; accepted December 2, 2011.  相似文献   

7.
Terrain can influence vegetation composition, diversity, and biogeochemical cycling in grassland ecosystems. Solar radiation, soil temperature, and moisture distribution are dependent on terrain, which, in turn, can affect plant community structure, rate of litter mass decomposition, and carbon, nitrogen, and phosphorus release. A litter decomposition experiment was conducted over 12 mo at a site representing typical steppe grasslands to better understand the effects of terrain on biogeochemical cycling. The study site had both northeast (shaded) and southwest (sunny) facing aspects with each aspect having three slopes: 15°, 30°, 45°. Litterbags were used for collection of plant community litter from each location. The results indicated that slope and aspect both have significant effects on decomposition rate of litter mass and release rate of C, N, and P. The most rapid decomposition rate of litter mass was on 45° sunny slopes (k value 1.82 × 10‒3 d−1). The most rapid release of C was on 30° shaded slopes with release rate of 4.54 g C yr‒1. The release rate of N decreased with increasing slope steepness but was more rapid on shaded compared with sunny slopes. The most rapid release of P (10.51 mg P yr‒1) occurred on 45° shaded slopes. The total effects of solar radiation and soil temperature on litter mass decomposition were larger, with 0.91 and 0.93, respectively. Soil temperature, litter functional diversity, and initial C/N had positive effects on the litter C release. The release of litter N was mainly promoted by soil temperature. Soil moisture appeared to promote the release of litter P. Overall, terrain influenced litter mass decomposition and C, N, and P release by its effect on the distribution of solar radiation, soil temperature and moisture, and through modification of functional diversity, initial C/N ratios, and water content of litter in typical steppe.  相似文献   

8.
C.R. Brown 《African Zoology》2013,48(4):166-172
Oxygen consumption of individual long-fingered bats, Miniopterus schreibersii, was measured at air temperatures (Tr) between 2 and 42°C and that of clusters of four and six bats between 5 and 30°C. BMR of individuals was estimated to be 2.29 ml O2 g 1 h-1 between 34 and about 38°C. M. schreibersii showed two different responses to Ta, either maintaining body temperature (Tb) by increasing metabolic rate, or allowing Tb to fall close to ambient temperature and conserving energy (torpor). Euthermic clusters of four and six bats had lower rates of mass-specific oxygen consumption and lower thermal conductances than individuals at equivalent temperatures and torpid clusters maintained a greater temperature differential between Tb and Ta. Lowest rates of metabolism were measured for euthermic bats at air temperatures higher than those available to them in their natural roost in summer, so typical roost temperatures result in metabolic rates that are about 2 4–3.1 times estimated BMR. Roost temperatures of M. schreibersii in South Africa are substantially higher in winter than are generally accepted as being suitable for hibernation but these do not substantially affect torpid metabolic rates, which are low and independent of ambient temperature below 22°C. Clearly at least some species of insectivorous bats are capable of hibernating at temperatures generally considered to be too warm for this activity.  相似文献   

9.
Identifying the mechanism for sex determination in amphibians is challenging. Very little is known about sex determination mechanisms of Rana dybowskii, a species of importance to evolutionary and conservation biology. We screened for sex-linked molecular markers in R. dybowskii in China using target region amplification polymorphism with 2 fixed primers against the sequences of Dmrt1. We found 2 male-linked molecular markers in R. dybowskii, which were 222 bp and 261 bp long. The detection rates of 222 bp marker in males form Xinglong, Huadian, and Dandong were 93.79%, 69.64%, and 13.64%, respectively, while the rate in females from Huadian was 27.50%. Besides, the detection rates of 261 bp marker in the above 3 regions were only observed in males at the rate of 93.79%, 87.50%, and 32.73%, respectively. The inheritance patterns of sex-linked molecular markers showed that the 2 sex-linked molecular markers were heterozygous. Compared to the XY-male parent, progeny from XX-pseudo-male parent possessed lower sex reversal ratio at the same rearing temperature, and the proportion of female froglets from an XX-pseudo-male parent was more than 95% at low rearing temperature (15°C). Our findings suggest that R. dybowskii displays male heterogamety, and the 2 sex-linked molecular markers may have a guiding significance for the protection and utilization of R. dybowskii.  相似文献   

10.
Abstract

Water temperature, a pivotal factor influencing interactions between teleosts and pathogens, was examined to determine its effects on the kinetics of xenoma formation and dissolution subsequent to experimental exposure of rainbow trout Oncorhynchus mykiss to the microsporidian gill pathogen Loma salmonae. The permissive water temperature range in which xenomas developed was between 9° and 20°C. Parasite development was arrested at temperatures outside this range, as indicated by the absence of visible xenomas among exposed fish. In addition, when these trout were subsequently moved to temperatures within the permissive range, xenomas failed to develop. Water temperature, within the permissive range, had no significant effect on either the number of xenomas that formed or the proportion of fish that developed xenomas following gastric intubation with a standard dose of spores. The relationship between water temperature and xenoma onset-time was best described (R 2 = 88.3%) by polynomial regression analysis: onset = 320 ? 33.4T + 0.9547T 2, where T is temperature (°C). Xenoma onset rate was also described through a modified degree-days model, yielding a predictive equation appropriate for use under conditions of fluctuating temperature. The thermal units, expressed as days × (°C above 7°C) necessary for xenoma onset were 298.6 on average. Xenoma dissolution rates, from the time of onset, also appeared to have a trend; more rapid dissolution occurred as temperatures increased. However, this trend correlated minimally with regression models.  相似文献   

11.
Global climate change is altering patterns of temperature variation, with unpredictable consequences for species and ecosystems. The Metabolic Theory of Ecology (MTE) provides a powerful framework for predicting climate change impacts on ectotherm metabolic performance. MTE postulates that physiological and ecological processes are limited by organism metabolic rates, which scale predictably with body mass and temperature. The purpose of this study was to determine if different metabolic proxies generate different empirical estimates of key MTE model parameters for the aquatic frog Xenopus laevis when allowed to exhibit normal diving behavior. We used a novel methodological approach in combining a flow-through respirometry setup with the open-source Arduino platform to measure mass and temperature effects on 4 different proxies for whole-body metabolism (total O2 consumption, cutaneous O2 consumption, pulmonary O2 consumption, and ventilation frequency), following thermal acclimation to one of 3 temperatures (8°C, 17°C, or 26°C). Different metabolic proxies generated different mass-scaling exponents (b) and activation energy (EA) estimates, highlighting the importance of metabolic proxy selection when parameterizing MTE-derived models. Animals acclimated to 17°C had higher O2 consumption across all temperatures, but thermal acclimation did not influence estimates of key MTE parameters EA and b. Cutaneous respiration generated lower MTE parameters than pulmonary respiration, consistent with temperature and mass constraints on dissolved oxygen availability, SA:V ratios, and diffusion distances across skin. Our results show that the choice of metabolic proxy can have a big impact on empirical estimates for key MTE model parameters.  相似文献   

12.
Objective To examine whether sub-optimal temperature induced stress and immunosuppression in farmed saltwater crocodile (Crocodylus porosus) hatchlings. Design A clinico-pathological study. Animals A total of 140 hatchlings were used. Procedure Body weight and length, plasma corticosterone and immunoglobulin concentrations and total and differential white blood cell counts were measured in 140 hatchlings from five clutches divided between five water temperature treatment groups. Initially all groups were housed at 32°C for 10 weeks, then two groups (L, LC) were changed to low temperature (28°C) and two groups (H, HC) to high temperature (36°C), while one group (C) remained at 32°C. The LC and HC groups were maintained at these temperatures for 10 days, after which the water temperature of both groups was returned to 32°C. Blood samples were collected twice (at 6 and 9 weeks of age) before the initial temperature change, and at 10 days and 4 weeks after the initial temperature change (at 11.5 and 14 weeks of age). Results Except for an increase in plasma corticosterone in the HC group and a decrease in the L group when the temperature change was first introduced, changes in plasma corticosterone were not significant. There were no significant changes in immunoglobulin concentrations. There were, however, significant decreases in the total white cell and lymphocyte counts in the LC group after the temperature was decreased to 28°C, and an increase in these counts after water temperature was returned to 32°C. Clutch of origin had significant effects on body weight and length gains, and there were negative relationships between body weight and corticosterone concentrations and between body weight and immunoglobulin concentrations. Conclusions As haematological changes indicative of stress were not associated with significant changes in serum corticosterone, immunosuppression in young crocodiles may be independent of the hypothalamic-pituitary-adrenal cortical axis.  相似文献   

13.
In order to conserve and culture the cichlid fish Archocentrus nigrofasciatus, more information about its reproductive biology and its larval behavior and morphogenesis is necessary. Currently, temperatures ranging from 21 to 27 °C are used in ornamental aquaculture hatcheries. Lower temperatures are preferred to reduce the costs of water heating, and 23 °C is usually the selected temperature. However, there is limited information on culturing protocols for ornamental species and most of the information generated on this topic remains scarce. Thus, the present study examines the morphological development of Archocentrus nigrofasciatus during the yolk‐sac period up to the age of 100 h post‐hatching in relation to 2 temperature regimes used in ornamental aquaculture: a temperature of 27 °C (thermal optimum) and a decreased temperature of 23 °C (thermal tolerance). The results of this study suggest that the 27 °C temperature generates intense morphological changes in yolk‐sac development in a shorter period. This has advantages as it reduces the time of yolk‐sac larval development, and, thus, minimizes the transition phase to exogenous feeding and maximizes the efficiency at which yolk is converted into body tissues. The present paper provides necessary information to produce freshwater ornamental fish with better practices so as to increase larval survival and capitalize on time for growth.  相似文献   

14.
Abstract

A study was performed to investigate the effect of environmental temperature (18°C or 28°C) and increasing levels of pea fibre in the diet on digestive tract, visceral organ size, digestibility and energy metabolism in rats. Thirty-six male Wistar rats, initial liveweight (LW) 77-79 g, were allocated to six groups and housed at either 18°C (three groups) or 28°C (three groups). Three wheat starch, fish meal and pea fibre-based diets were prepared to contain 100, 200 and 300 g pea fibre kg?1 (68, 110 and 157 g dietary fibre kg?1 DM) and 160 g protein (N × 6.25) kg?1. One group of rats at each temperature was fed one of the diets for four balance periods. Gas-exchange measurements were made and urine and faeces were quantitatively collected. Food to gain ratio was higher (P <.05) at 18°C than at 28°C and increased (P <.05) as the level of fibre was increased. The weight of the visceral organs from rats housed at 18°C was higher (P<.05) than at 28°C. The empty weight of the small intestine, caecum and colon increased (P <.05) as the level of pea fibre was increased. The digestibility of DM, protein and dietary fibre (DF) was lower (P <.05) at 18°C than at 28°C. As the level of pea fibre was increased, the digestibilities of nutrients and energy decreased (P <.05). However, the digestibility of DF increased (P <.05) as the level of pea fibre was increased. The partial digested energy value for pea fibre was 11.9 kJ g?1. The metabolizable energy (ME) intake and heat production at 18°C (1128 and 974 kJ (W0.75 day)?1 respectively) were higher (P<.05) than at 28°C (831 and 674 kJ (W0.75 day)?1 respectively). As the level of pea fibre was increased, ME intake (W0.75 day)?1 and heat production (W0.75 day)?1 decreased (P <.05). Heat production as a percentage of ME was higher (P <.05) at 18°C than at 28°C: 86.6% and 81.2%, respectively. Heat production as a percentage of ME was higher (P <.05) for rats fed the 100 g pea fibre kg?1 diet than the 200 or 300 g pea fibre kg?1 diet. In conclusion, environmental temperature as well as DF influenced digestive tract and visceral organ size, digestion and protein and energy metabolism.  相似文献   

15.
To investigate the effects of inoculants and environmental temperature on fermentation quality and bacterial diversity of alfalfa silage, first‐cut alfalfa was ensiled with or without two screened lactic acid bacteria (LAB) strains, Lactobacillus plantarum, LP, and Lactobacillus casei, LC. Each treatment was divided into three parts and stored at 20°C, 30°C, 40°C, respectively. After 60 days ensiling, fermentation characteristics were measured and bacterial diversity was investigated by 16S ribosomal RNA gene sequencing using Illumina MiSeq platform. LP and LC decreased pH, coliform bacteria counts and increased lactic acid content at 20°C, and the two strains decreased pH, ammonia‐N concentration, coliform bacteria counts at 30°C. When the environmental temperature was 40°C, silage treated with LC showed lower LAB and coliform bacteria counts and higher lactic acid content than the untreated and LP treated silages. Butyric acid mainly appeared in silages stored at 40°C. The relative abundance of Lactobacillus in alfalfa silages stored at 20°C and 30°C was highest and increased after LP and LC were added. Garciella was another dominant genus in silages stored at 40°C. In conclusion, LP and LC improved fermentation quality of alfalfa silage by increasing Lactobacillus proportions at 20°C and 30°C; ensiling alfalfa at 40°C was difficult because of Garciella.  相似文献   

16.
The pharmacokinetics and tissue residues of moroxydine hydrochloride were studied in gibel carp at water temperature of 15 and 25 °C. Samples (blood, skin, muscle, liver, and kidney) were collected over 10 days after the treatment and analyzed by high‐performance liquid chromatography with an ultraviolet detector. The results indicated that the influence of water temperature on the metabolism of the drug was significant. The plasma concentration–time data of moroxydine hydrochloride conformed to single‐compartment open model at the two water temperatures. There were higher absorption rate (t1/2ka) and longer elimination half‐lives (t1/2ke) at 15 °C (4.29 and 15.87 h, respectively) compared with those at 25 °C (3.02 and 4.22 h, respectively). The maximum plasma concentration (Cmax) and the time‐point of maximum plasma concentration (Tp) were 2.98 μg/mL and 10.35 h at 15 °C and 3.12 μg/mL and 4.03 h at 25 °C, respectively. The distribution volume (Vd/F) of moroxydine hydrochloride was estimated to be 4.55 L/kg at 15 °C and 2.89 L/kg at 25 °C. The total body clearance (CLb) of moroxydine hydrochloride was determined to be 0.25 and 0.49 L/(h·kg) at 15 °C and 25 °C, respectively; the areas under the concentration–time curve were 75.89 μg·h/mL at 15 °C and 42.33 μg·h/mL at 25 °C. The depletion of moroxydine hydrochloride in gibel carp was slower with a longer half‐life period, especially at lower water temperature that was tested.  相似文献   

17.
Abstract

The effect of water temperature on the progress of experimentally induced Cytophaga psychrophila infection was investigated in juveniles of coho salmon Oncorhynchus kisutch, chinook salmon O. tshawytscha, and rainbow trout O. mykiss (formerly Salmo gairdneri). A virulent strain of C. psychrophila was administered to fish by subcutaneous injection. Infected fish were held in tanks containing pathogen-free well water at temperatures ranging from 3 to 23°C. Mean times from infection to death of the fish were shortest at 12–15°C, which were the temperatures associated with the shortest time for doubling the population of this bacterium in vitro. Juvenile steelhead (anadromous rainbow trout) injected with viable C. psychrophila cells and held in 22°C water did not become diseased.  相似文献   

18.
To determine the effect of bacteria on the development of the ripening flavor of cured meat, pork loins were cured with pickles containing 8 or 16% sodium chloride at 0 and 8°C. The bacterial flora, total free amino acid content and total free fatty acid content in the cured loins, sensory properties of cooked pork loins and the relationships between the proteolytic and lipolytic activities of isolates and curing conditions were investigated. Desirable bacteria, including salt‐tolerant bacteria and lactic acid bacteria, were predominant under the condition of 8% sodium chloride in the pickles and a curing temperature of 8°C. The total free amino acid content and total free fatty acid content at a curing temperature of 8°C were higher than those at 0°C. Cooked pork loins cured in pickles containing 8% sodium chloride at a temperature of 8°C for more than 7 days were preferred in terms of color, flavor and taste. Before the curing procedure, gram‐negative bacteria (Vibrio, Acinetobacter, Pseudomonas and Enterobacteriaceae) were predominant in the pork loins. During the curing period, the numbers of viable gram‐positive bacteria (Micrococcus, Staphylococcus and Pediococcus) increased and the numbers of viable gram‐negative bacteria decreased. Strains of Micrococcus and Staphylococcus with proteolytic and/or lipolytic activities in cured meat also increased during the curing period and were more predominant in the pork loins cured in pickles containing 8% sodium chloride and at a curing temperature of 8°C than in pork loins cured in pickles containing 16% sodium chloride and at a curing temperature of 0°C. The actions of these bacteria were thought to be important factors affecting the flavor of the cured pork. Micrococcus and Staphylococcus with proteolytic activity might contribute to the development of the ripening flavor of ham. The results of the present study together with the results of further investigations on the relationships of the enzyme activities of Micrococcus and Staphylococcus in cured meat with a preferable flavor would be useful for establishing a novel effective method for using bacteria to produce ham of a high quality.  相似文献   

19.
The specific oxygen consumption rate (VO 2 IMb) of Labeo capensis, the freshwater mudsucker, was determined for small and large fish at winter (8°C) and summer (23°C) temperatures. VO JMb was also determined during hypoxic conditions of the experimental water. It was found that VO JMb does not differ substantially compared with other active fish. The VO 4Mb for a fish with a body mass of 250 g is 0,053 ml 0 2 per gram wet body mass per hour for fish acclimated at 8°C and 0,127 ml 0 2 per gram per hour for fish acclimated at 23°C. The calculated mass exponent, b, is 0,71 at 23°C and 0,68 at 8°C. Hypoxic conditions are relatively well tolerated especially by 23°C- adapted fish.  相似文献   

20.
The coat of seven ‘Landseer’ Newfoundland dogs was irradiated using an infra-red source for 25 min. In each dog, at a site of each colour (black and white), skin and coat temperatures were monitored, and coat air humidity measured with a specially designed instrument. Almost no differences were noted at sites with differing coat colour. Skin temperature rose from 35 °C to a plateau at 39 °C, whilst coat temperature rose from 30 °C to 41 °C. Relative humidity of coat air initially rose, then fell significantly (P < 0.001). The absolute humidity initially almost doubled (P < 0.001), but then fell, although remaining significantly higher than that of ambient air. It was concluded that an initial burst of sweating was followed by lower but continuing secretion. This was not, however, of great importance in cooling. In a separate study the skin temperature of black coated dogs exposed to bright sunshine was explored. The mean temperature was almost identical to that of the plateau skin temperature noted in Newfoundland dogs.  相似文献   

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