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1.
Knowing the trophic level of marine organisms is essential to understanding their ecological role in the ecosystem and for quantifying the ecosystem effects of fishing to establish effective management of fishing resources. In comparison to other systems, information about the trophic level of marine organisms in the Persian Gulf and Oman Sea is very scarce. Here, the main aim was to estimate trophic level in these areas using all available diet information from different marine species using TrophLab software. The trophic level of 32 fish species was estimated with the available diet data. The trophic level ranged from 2.28 to 4.50. High trophic levels were found for Chorocentrus nudus (TL = 4.7), Saurida tumbil (TL = 4.6), Rhizoprionodon acutus (TL = 4.5), Torpedo sinuspersici (TL=4.5), Gymnura poecilura (TL = 4.5), Sphyraena putnamae (TL = 4.5) and Euthynnus affinis (TL = 4.5). In contrast, lower trophic levels were estimated for Tenualosa ilisha (TL = 2.28) and Sardinella sindensis (TL = 2.92). As expected, a positive correlation was found between the trophic level and body size, indicating changes in the diet due to variations in predatory capacities. The results of this study may be useful in the formulation of trophic indicators and modelling of the ecosystems. 相似文献
2.
The occurrence of changes in the trophic level (TL) of sharks with growth has not been quantified until now. Here length-related
changes on Squatina guggenheim Marini trophic level were determined, and shifts in type, size and trophic level of its prey were analysed. Sampling took
place during five bottom trawl surveys conducted in the Argentine–Uruguayan Common Fishing Zone during spring (December/1995,
October/1997) and fall (March/1997, March–April/1998, May–June/1998), using an Engel bottom-trawl net to capture the sharks.
Three length groups were defined based on diet composition and using a cluster analysis (group I, 23–60 cm; group II, 61–80 cm;
group III, 81–91 cm L
T). An ANOSIM procedure detected significant differences (P < 0.05) in the diet spectrum between the three length groups. The smallest sharks (group I) ingested fish prey ranging from
5 to 21 cm L
T, medium sharks (group II) fed on fish prey between 11 and 35 cm L
T, and largest sharks (group III) preyed on fish between 13 and 40 cm L
T. Diet structure of length groups were discriminated by almost the same prey taxa that characterized them. The increase of
S. guggenheim body length promoted a decrease in the relative importance of small pelagic fishes. Contrarily, prey as medium benthopelagic
fishes, medium pelagic squid and medium benthopelagic fishes showed an inverse tendency, indicating a broad diet spectrum
of adults. Predator-length and prey-length relationship indicated a trend where 44.8% of S. guggenheim diet was integrated by prey <20% of their own body length and 32.8% of their diet was composed by prey >30% of their own
length. The increase of mean prey weight was associated with the increase of predator weight and length. Smallest sharks (group
I) were identified as secondary consumers (TL < 4) whereas medium sharks (group II) and largest sharks (group III) were placed
as tertiary consumers (TL > 4). The study revealed an increase in S. guggenheim TL with shark growth as a consequence of changes on type, size and TL of prey ingested. 相似文献
3.
The frequency of individuals with empty stomachs (FES) can vary greatly among northern pike populations. However, the FES
has only seldom been analyzed in this species and its meaning is still not fully understood. It has been suggested that a
high FES may reflect a strongly piscivorous behaviour while low FES could reflect a higher utilization of invertebrates. We
compared the stomach contents and the trophic position of northern pike in 16 populations of individuals feeding mainly on
fish or benthic invertebrates. We tested the hypothesis that northern pike with empty stomachs or with fish in their stomachs
have a higher trophic position than individuals feeding on invertebrates. Carbon (δ13C) and nitrogen (δ15N) stable isotope signatures were used to estimate the trophic position of individuals. We found no significant difference
in the trophic position among piscivores, invertebrate feeders, and northern pike with empty stomachs. The average trophic
position of northern pike was high (mean ± SD = 4.3 ± 0.4, n = 66) and was correlated with total length. These results indicate that, although invertebrates could be an important part
of the diet of northern pike in Canadian Shield lakes, fish are still the dominant prey. Hence, feeding on invertebrates in
our study lakes would reflect an opportunistic rather than a specialized feeding strategy. 相似文献
4.
Matthew T. Craig 《Ichthyological Research》2007,54(1):81-84
A preliminary analysis of 175 specimens of the white-streaked grouper, Epinephelus ongus (Serranidae), was undertaken to determine life history characteristics of the species. Sagittal otoliths, stomachs, and a
subsample of gonads were removed to determine age at length, diet, and reproductive strategy. The von Bertalanffy growth equation
was used to describe growth in this species and yielded the growth parameters L∞ = 438.3, K = 0.04334, and t0 = −8.752. Fish ranged in age from 1 to 20 years. Diet was consistent with other serranid species and included crabs, shrimps,
octopi, and fishes. Based on a very limited number of specimens (n = 12), the larger size and older age of males compared to females suggests that E. ongus may be a protogynous hermaphrodite. 相似文献
5.
William E. Magnusson M. Carmozina de Araújo Renato Cintra Albertina P. Lima Luiz A. Martinelli Tânia M. Sanaiotti Heraldo L. Vasconcelos Reynaldo L. Victoria 《Oecologia》1999,119(1):91-96
We studied the energy flow from C3 and C4 plants to higher trophic levels in a central Amazonian savanna by comparing the carbon stable-isotope ratios of potential
food plants to the isotope ratios of species of different consumer groups. All C4 plants encountered in our study area were grasses and all C3 plants were bushes, shrubs or vines. Differences in δ13C ratios among bushes (xˉ = −30.8, SD = 1.2), vines (xˉ = −30.7, SD = 0.46) and trees (xˉ = −29.7, SD = 1.5) were small. However the mean δ13C ratio of dicotyledonous plants (xˉ = −30.4, SD = 1.3) was much more negative than that of the most common grasses (xˉ = −13.4, SD = 0.27). The insect primary consumers had δ13C ratios which ranged from a mean of −29.5 (SD = 0.47) for the grasshopper Tropidacris collaris to a mean of −14.7 (SD = 0.56) for a termite (Nasutitermes sp.), a range similar to that of the vegetation. However, the common insectivorous and omnivorous vertebrates had intermediate
values for δ13C, indicating that carbon from different autotrophic sources mixes rapidly as it moves up the food chain. Despite this mixing,
the frogs and lizards generally had higher values of δ13C (xˉ = −21.7, SD = 1.6; xˉ = −21.9, SD = 1.8, respectively) than the birds (xˉ = −24.8, SD = 1.8) and the only species of mammal resident in the savanna (xˉ = −25.4), indicating that they are generally more dependent on, or more able to utilise, food chains based on C4 grasses.
Received: 7 May 1998 / Accepted: 30 November 1998 相似文献
6.
A feeding trial was performed in the laboratory with the catfish species Pterygoplichthys disjunctivus to determine stable carbon (13C) and nitrogen (15 N) turnover rates and discrimination factors in non-lethally sampled tissues (red blood cells, plasma solutes, and fin).
A second feeding trial was conducted to determine what P. disjunctivus could assimilate from low-quality wood-detritus—refractory polysaccharides (e.g., cellulose), or soluble wood-degradation products inherent in wood-detritus. This was performed
by feeding the fish an artificial wood-detritus diet with fibrous (δ13C = −26.36‰; δ15
N = 2.13‰) and soluble portions (δ13C = −11.82‰; δ15
N = 3.39‰) that had different isotopic signatures and monitoring the dynamics of isotopic incorporation in the different tissues
over time. Plasma solutes turned over more quickly than red blood cells for 13C and 15 N. However, in contrast to previous studies of juvenile fishes, C and N incorporation was primarily driven by catabolic tissue
turnover as opposed to growth rate. Tissue-diet discrimination factors for 15 N varied from 4.08 to 5.17‰, whereas they were <2‰ for 13C (and less than 0.3‰ for plasma and red blood cells). The results of trial two suggested that P. disjunctivus could not assimilate refractory polysaccharides. Moreover, the δ13C and δ15 N signatures of wild-caught P. disjunctivus from Florida confirmed their detrital trophic standing in Floridian aquatic ecosystems. 相似文献
7.
Hirofumi Inoue Satoko Akiyama Mari Maeda-Yamamoto Atsushi Nesumi Takuji Tanaka Akira Murakami 《Cell stress & chaperones》2011,16(6):653-662
Previously, we reported that oral feeding of 1% green tea polyphenols (GTPs) aggravated the dextran sulfate sodium (DSS)-induced
colitis in mice. In the present study, we assessed the toxicity of 1% GTPs in several organs from normal and DSS-exposed mice.
Sixty-two male ICR mice were initially divided into four groups. Non-treated group (group 1, n = 15) was given standard diet and water, GTPs (group 2, n = 15) received 1% GTPs in diet and water, DSS (group 3, n = 15) received diet and 5% DSS in water, and GTPs + DSS group (group 4, n = 17) received 1% GTPs in diet and 5% DSS in water. We found that group 4 significantly increased (P < 0.05) kidney weight, the levels of serum creatinine and thiobarbituric acid-reactive substances in both kidney and liver,
as compared with those in group 3. The mRNA expression levels of antioxidant enzymes and heat-shock proteins (HSPs) in group
4 were lower than those of group 3. For instance, heme oxygenase-1 (HO-1), HSP27, and 90 mRNA in the kidney of group 4 were
dramatically down-regulated as compared with those of group 3. Furthermore, 1% GTPs diet decreased the expression of HO-1,
NAD(P)H:quinone oxidoreductase 1 (NQO1) and HSP90 in kidney and liver of non-treated mice. Taken together, our results indicate
that high-dose GTPs diet disrupts kidney functions through the reduction of antioxidant enzymes and heat-shock protein expressions
in not only colitis but also non-treated ICR mice. 相似文献
8.
Local genetic differentiation in Proteopsis argentea (Asteraceae), a perennial herb endemic in Brazil 总被引:1,自引:1,他引:0
F. F. Jesus V. N. Solferini J. Semir P. I. Prado 《Plant Systematics and Evolution》2001,226(1-2):59-68
Proteopsis argentea (Asteraceae, Vernonieae) is a perennial herb endemic to the “campos rupestres” of the Espinha?o Range in Minas Gerais, Brazil,
with fragmented populational distribution. Eleven populations were sampled, throughout the entire distribution of the species,
and assayed for isozyme variation. Low intra-population genetic diversity was found (P = 19.2; A = 1.30; He = 0.058) whereas
species level diversity was higher (P = 55.5, A = 2.0, He = 0.093). The most geographically isolated population showed exclusive
alleles at two loci, whereas two populations less than 2 km apart from each other showed inverted frequencies for two alleles.
Mean genetic identity was high (I = 0.974), but the large Fst (0.30) indicates that the species could lose an important part
of its genetic variation with the extinction of a single population. Our findings indicate that geographic isolation alone
cannot explain population differentiation: localized pollinator behaviour and selection, for example, may be contributing
to the patterns observed.
Received February 18, 2000 Accepted November 1, 2000 相似文献
9.
The present study was carried out to determine the effects of different sources of selenium (Se; sodium selenite [Na2SeO3] or selenomethionine [Se-Met]) supplementation on egg production, egg quality, levels of malondialdehyde (MDA), and Se in
serum and egg yolk in heat-stressed Japanese quail (Coturnix coturnix japonica). The birds (n = 360; 55 days old) were randomly assigned to 12 treatment groups consisting of six replicates of five birds each in a 2 × 2 × 3
factorial arrangement of treatments (temperatures, selenium sources, selenium levels). Birds were kept in wire cages in a
temperature-controlled room at either 22 (thermoneutral) or 34°C (heat stress) for 8 h/day (09:00–17:00; till the end of study)
and fed a basal (control) diet or the basal diet supplemented with either 0.15 or 0.30 mg of Na2SeO3 or selenomethionine/kg of diet. Heat exposure decreased live weight, feed intake, feed efficiency, egg production, and egg
quality when basal diet was fed (P < 0.0001). A linear increase in feed intake (P = 0.001) and body weight (P = 0.001), egg production (P = 0.001), and improvement in feed efficiency (P = 0.001) and egg quality (P = 0.001) were found in Se-supplemented quail reared under heat stress conditions. Serum, egg white, and egg yolk Se (P ≤ 0.001) concentrations increased linearly, whereas serum, liver, and egg yolk MDA concentrations decreased linearly (P = 0.001) as dietary Na2SeO3 or Se-Met supplementation increased. An interaction between dietary Se sources, temperature, and levels of supplementation
(P ≤ 0.05) for these parameters was detected. Supplementation with Se improved egg production, egg quality, and antioxidant
status of birds, and the effects of Se-Met were relatively greater than Na2SeO3 in heat-stressed quail. Results of the present study suggest that supplementation with Se-Met can be considered to be more
protective than Na2SeO3 by reducing the negative effects of oxidative stress induced by heat stress in quail. 相似文献
10.
Assessment of anadromous salmon resources in the diet of the Alexander Archipelago wolf using stable isotope analysis 总被引:8,自引:0,他引:8
The Alexander Archipelago wolf (Canis lupus ligoni) is unique to southeast Alaska, occurring on islands south of Frederick Sound and along the mainland between Dixon Entrance
and Yakutat Bay. Sitka black-tailed deer (Odocoileus hemionus sitkensis) are an important prey species for wolves across the southern part of the region. Spawning salmon (Onchorynchus sp.) are seasonally available but their presence in wolf diets has not previously been quantified. We examined the range
of bone collagen δ13C and δ15N values for wolves throughout southeast (n = 163) and interior (n = 50) Alaska and used a dual-isotope mixing model to determine the relative contribution of salmon-derived marine protein
in the diet. Southeast Alaska wolves consumed significantly more salmon (mean ± SE: 18.3 ± 1.2%) than did wolves from interior
Alaska (9.1 ± 0.6%, P<0.001). Wolves on the southeast Alaska mainland appeared to have higher marine isotopic signatures than island wolves, although
this difference was not significant. Variation among individual wolf diets was higher for southeast than for interior Alaska
wolves, and variation was highest in coastal mainland wolf diets (P<0.001). Marine resources may augment the diet of southeast Alaska wolves during seasonal or annual fluctuations in the availability
of deer, particularly in those areas on the mainland where densities of terrestrial ungulates are relatively low.
Received: 1 July 1998 / Accepted: 23 February 1999 相似文献
11.
Influence of different periods of exposure to hot environment on rumen function and diet digestibility in sheep 总被引:2,自引:0,他引:2
U. Bernabucci N. Lacetera P. P. Danieli P. Bani A. Nardone B. Ronchi 《International journal of biometeorology》2009,53(5):387-395
Effects of different periods of exposure to hot environments on rumen function, diet digestibility and digesta passage rate
were studied in four adult not-pregnant Sardinian ewes housed in a climatic chamber. The ewes were kept in individual metabolic
cages. The trial lasted 83 days; 17 days were spent under thermal comfort conditions (TC) [temperature-humidity index (THI) = 65.0 ± 2.0],
followed by 49 days under elevated THI (ETHI: THI = 82.0 ± 2.5) and 17 days under thermal comfort (TC; THI = 65.0 ± 1.0).
Five digestibility and passage rate trials were carried out during the 83 days. Trials 1 and 5 were carried out under TC;
trials 2, 3 and 4 were carried out under ETHI. Values of rectal temperatures (39.7 ± 0.3°C) and respiratory rate (118.4 ± 31.8
breaths/min) indicated that sheep under ETHI were heat-stressed. Heat stress caused an increase (P < 0.01) in water intake, and reductions (P < 0.05) in dry matter intake, rumen pH, rumen cellulolytic and amylolytic bacteria count, rumen osmolarity, organic matter,
dry matter, neutral detergent fibre, acid detergent fibre and non-structural carbohydrates digestibility coefficients, and
a reduction of digesta passage rates. Under ETHI, diet digestibility and passage rate of digesta were reduced in a time-dependent
fashion. Variation of diet digestibility under ETHI was not related to passage rate of digesta and feed intake. Reduction
of cellulolytic and amylolytic bacteria and the adaptive response to hot environment seem to be related to alteration of digestibility
observed in ewes chronically exposed to hot environment. 相似文献
12.
Galactosemic cataracts are characterized by electrolyte disturbances resulting in osmotic imbalance and loss of transparency.
We have studied the defensive role of quercetin, a bioflavonoid, against the alterations of calcium (Ca2+), sodium (Na+), and potassium (K+) concentrations in galactose-induced cataract in a rodent model. The experimental study was conducted on weanling male Wistar
rats with an average body weight of 34 ± 0.9 g. Different groups received normal stock AIN 93 diet (group A, n = 8), AIN 93 diet with 30% galactose (group B, n = 8), and AIN 93 diet with 30% galactose + quercetin at 400 mg/100 g diet (group C, n = 8). Aldose reductase activity and protein content and concentrations of Ca2+, Na+, and K+ were determined in normal and cataractous lenses. Treatment with quercetin resulted in a significant decrease in Na+ and Ca2+ and aldose reductase levels and an increase in K+ and protein levels in galactosemic cataractous lenses. These results imply that inclusion of quercetin contributes to lens
transparency through the maintenance of characteristic osmotic ion equilibrium and protein levels of the lens. 相似文献
13.
Since fishery management regulations have shifted much of the groundfish trawl effort in the northeastern Pacific from the
continental shelf to the slope, fishery impacts on unassessed demersal slope rockfish species like the aurora rockfish (Sebastes aurora) may have increased. Understanding the life history of these species is a critical first step in developing management strategies
to protect them from overharvest. In this study we employ cross-dating methods to validate the annual periodicity of growth
increments and investigate the age, growth and maturity of aurora rockfish, a species for which life history information is
quite limited. Specimens were collected on an opportunistic basis from Oregon commercial landings and from research cruises,
over the years 2003–2006. Age was estimated for 438 individuals using otoliths processed via the break-and-burn method. The
maximum estimated age was 118 years for females (n = 324) and 81 years for males (n = 114). The von Bertalanffy growth function showed that males grow faster and reach a smaller maximum size than females (males:
L
inf = 34, K = 0.09, t
0 = −1.9; females: L
inf = 37, K = 0.06, t
0 = −5.5), though both sexes demonstrate relatively slow growth. Visual assessment of ovaries showed that the aurora rockfish
is a synchronous spawner with parturition occurring in May and June off Oregon. Female age and length at 50% maturity were
calculated at 12.6 years and 26 cm, respectively (n = 307). Maturity and age data provided evidence for a protracted adolescence in this species. 相似文献
14.
The chromosomes of 31 species of Passiflora, distributed throughout the subgenera Astrophea, Calopathanthus, Distephana, Dysosmia, Passiflora, Plectostemma and Tacsonia were analysed. Three different karyotypes were observed: 2n = 12, 24, 36; 2n = 18, 72 and 2n = 20. The karyotype of these
species was almost always constituted of metacentric and submetacentric chromosomes with variable karyotype symmetry. In the
group with x = 6, represented by the subgenus Plectostemma, six diploid species with 2n = 12, one tetraploid with 2n = 24 (P. suberosa) and an intraspecific polyploid with 2n = 12, 36 (P. misera) were analysed. P. pentagona (subgenus Astrophea) may also be included in this karyological group since it presents 2n = 24 and may be of polyploid origin, with x = 6. The
interphase nuclei in this group were areticulate, except those of P. morifolia and P. pentagona with semi-reticulate characteristics. Two small terminal heterochromatic blocks, positive for chromomycin A3, were identified in the largest chromosome pair of P. capsularis and P. rubra, species very closely related, while P. tricuspis displayed four chromosomes with proximal blocks. In the group with x = 9, represented mainly by subgenus Passiflora, 20 species with 2n = 18 and one with 2n = 72 were studied. They presented chromosomes larger than those species with x = 6
and interphase nuclei of semi-reticulate type, except for P. mixta with areticulate nuclei. Four terminal CMA+ blocks were observed in P. edulis, six blocks in P. caerulea and P. racemosa, while five blocks were observed in the single P. amethystina plant analysed. P. foetida (subgenus Dysosmia), the only species with 2n = 20, exhibited six chromosomes with CMA+ blocks and interphase nuclei of the areticulate type. The meiotic analysis of representatives of the three groups (P. foetida, P. suberosa, P. cincinnata and P. racemosa) always presented regular pairing and regular chromosome segregation, except in P. jilekii where a tetravalent was observed. The analysis of the chromosome variation within the genus and the family suggests that
the base number of Passiflora may be x1 = 6 or x1 = 12, whereas x2 = 9 is only an important secondary base number.
Received April 11, 2000 Accepted October 5, 2000 相似文献
15.
Lucilene Lima dos Santos Marcelo Alves Ramos Suzene Izídio da Silva Margareth Ferreira de Sales Ulysses Paulino de Albuquerque 《Economic botany》2009,63(4):363-374
Caatinga Ethnobotany: Anthropogenic Landscape Modification and Useful Species in Brazil’s Semi-Arid Northeast This study explores the contribution of anthropogenic landscapes in providing useful botanical resources to a Caatinga community
in Pernambuco, Brazil. Ethnobotanical data were collected through semi-structured interviews using the checklist-interview
method and by means of a “field herbarium” of the most abundant species in the anthropogenic zones. We recorded 119 species
distributed in 36 families, of which 79 were found to be useful. Forage was the most prominent use category, containing 84%
of the citations, followed by medicinals (36.70%), foods (10.12%), and wood (8.86%). Herbaceous species predominated (63.29%),
followed by shrubs (3.79%), sub-shrubs (21.51%), trees (8.86%), and creepers (2.53%). Trees exhibited a greater number of
uses than other life-forms (p < 0.05). Significant differences in richness were found, with the highest richness of species
(χ2 = 60.28, p < 0.05), genera (χ2 = 49.03, p < 0.05), and families (χ2 = 20.16, p < 0.05) appearing in the rainy season.
We concluded that fodder use was the most important category in our anthropogenic research areas, accounting for a higher
number of species, genera, and families. The next most important categories were medicinal, timber, and food plants, respectively. 相似文献
16.
A 42-day experiment was conducted to compare the effects of various levels of sodium selenite (SS) and Se-enriched yeast (SY)
on chicken productivity, carcass traits, and breast Se concentration. Six hundred 1-day-old Cobb 500 broiler chicks were placed
on 1 of 6 experimental treatments. The treatments consisted of feeding a diet without Se supplementation (basal diet) or basal
diet with 0.6 mg/kg supplemented Se supplied by SS, SY, or a mix of the two (0.45 SS + 0.15 SY; 0.3 SS + 0.3 SY; 0.15 SS + 0.45
SY). Chicks in all Se-supplemented treatments had significantly higher final body weight and eviscerated weight than those
on the basal diet (P < 0,05) and no significant differences were observed among selenium source (P < 0.05). Also, chicks in all Se-supplemented treatments had significantly higher Se contents in breast tissue than the control
group (P < 0.05). Replacing SS by SY in the broiler diets resulted in increased concentrations of Se in the breast (P < 0.01). Strong correlations were found between breast Se concentrations and the level of SY supplementation of the broiler
diet (r = 0.992). The results from this experiment indicate that SY is a superior source of selenium for the production of selenized
meat, and can be used, without any detrimental effect on chicken performance, for adding nutritional value to broiler meat
and thus safely improving human selenium intake. 相似文献
17.
Hair samples of 15 adult male Atlantic walruses (Odobenus rosmarus rosmarus) collected from anaesthetized individuals at Svalbard, Norway, were analysed for cadmium and total mercury. The mean level
of cadmium was 0.860 ± 0.321 μg/g dry weight (median = 0.811, range = 0.349–1.51 μg/g dry weight) and the mean level of mercury
was 0.235 ± 0.100 μg/g dry weight (median = 0.251, range = 0.121–0.424 μg/g dry weight). Levels of cadmium and mercury in
hair of walruses from other areas are not known. Both cadmium and mercury levels in hair of walruses from Svalbard are relatively
low compared to the levels found in the hair of other marine mammal species. It has been documented from a number of marine
species, including marine mammals such as ringed seals and polar bears, that both cadmium and mercury levels at Svalbard are
lower than in other areas. It is uncertain as to what degree levels in hair reflect levels in internal organs in walruses.
In rare and highly endangered species or populations tissue samples can be difficult to collect. In walruses, it is possible
to collect hair from anaesthetized individuals or at the haul-out sites during moult, to monitor heavy metal levels of the
population.
Accepted: 6 December 1998 相似文献
18.
Borgwardt N Culik BM 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(2):100-106
Open-flow oxygen and carbon dioxide respirometry was used in Neumünster Zoo (Germany) to examine the energy requirements
of six Asian small-clawed otters (Amblonyx cinerea) at rest and swimming voluntarily under water. Our aim was to compare their energy requirements with those of other warm-blooded
species to elucidate scale effects and to test whether the least aquatic of the three otter species differs markedly from
these and its larger relatives. While at rest on land (16 °C, n = 26), otters (n = 6, mean body mass 3.1 ± 0.4 kg) had a respiratory quotient of 0.77 and a resting metabolic rate of 5.0 ± 0.8 Wkg−1(SD). This increased to 9.1 ± 0.8 Wkg−1 during rest in water (11–15 °C, n = 4) and to 17.6 ± 1.4 Wkg−1 during foraging and feeding activities in a channel (12 °C, n = 5). While swimming under water (n = 620 measurements) in an 11-m long channel, otters preferred a speed range between 0.7 ms−1 and 1.2 ms−1. Transport costs were minimal at 1 ms−1 and amounted to 1.47 ± 0.24 JN−1 m−1 (n = 213). Metabolic rates of small-clawed otters in air were similar to those of larger otter species, and about double those
of terrestrial mammals of comparable size. In water, metabolic rates during rest and swimming were larger than those extrapolated
from larger otter species and submerged swimming homeotherms. This is attributed to high thermoregulatory costs, and high
body drag at low Reynolds numbers.
Accepted: 21 December 1998 相似文献
19.
James Nelson Jeffrey Chanton Felicia Coleman Christopher Koenig 《Environmental Biology of Fishes》2011,90(3):243-252
To determine the feasibility of using stable isotopes to track diet shifts in wild gag, Mycteroperca microlepis, populations over seasonal timescales, we conducted a repeated measures diet-shift experiment on four adult gag held in the
laboratory. Fish were initially fed a diet of Atlantic mackerel, Scomber scombrus, (mean δ13C = −21.3‰ ± 0.2, n = 20) for a period of 56 days and then shifted to a diet of pinfish, Lagodon rhomboids, (mean δ13C = −16.6‰ ± 0.6, n = 20) for the 256 day experiment. We developed a non-lethal surgical procedure to obtain biopsies of the muscle, liver, and
gonad tissue monthly from the same four fish. We then determined the δ13C value of each tissue by isotope ratio mass spectrometry. For the gonad tissue we used the relationship between C/N and lipid
content to correct for the influence of lipids on δ13C value. We observed a significant shift in the δ13C values of all of the tissues sampled in the study. Carbon turnover rates varied among the three tissues, but the shift in
diet from mackerel to pinfish was clearly traceable through analysis of δ13C values. The turnover rates for muscle tissue were 0.005‰ day−1, and for gonad tissue was 0.009‰ day−1. Although it is generally thought that tissue turnover rates in ectotherms are driven primarily by growth, we found that
metabolic rate can be a major factor driving tissue turnover in adult gag. 相似文献