共查询到20条相似文献,搜索用时 31 毫秒
1.
Luvizotto-Santos R Lee Jt Branco Zp Bianchini A Nery Le 《Journal of experimental zoology. Part A, Comparative experimental biology》2003,295(2):200-205
Lipids seem to be the major energy store in crustaceans. Moreover, they are extremely important in maintaining structural and physiological integrity of cellular and sub cellular membranes. During salinity adaptation, energy-demanding mechanisms for hemolymph osmotic and ionic regulation are activated. Thus, the main goal of this work was to verify the possible involvement of lipids as an energy source in the osmotic adaptation process. The estuarine crab Chasmagnathus granulata was captured and acclimated to salt water at 20 per thousand salinity and 20 +/- 2 degrees C, for 30 days. After acclimation, crabs were divided into groups of ten and transferred to fresh water (0 per thousand ), salt water at 40 per thousand salinity, or maintained in salt water at 20 per thousand salinity (control group), without feeding. Before and seven days after the salinity change, wet weight and lipid concentration in gills, muscle, hepatopancreas, and hemolymph were determined according to the colorimetric assay of sulphophosphovanilin. Results show that hepatopancreas lipids were not mobilized during osmotic stress regulation. Gill and muscle lipids were significantly lower in crabs subjected to hypo-osmotic stress than those subjected to the hyper-osmotic stress or maintained at the control salinity. Our results point to the occurrence of lipid mobilization and involvement of these compounds in the osmotic acclimation process in C. granulata, but with differences between tissues and the osmotic shock (hypo or hyper) considered. 相似文献
2.
Oliveira GT da Silva RS 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》2000,127(3):375-381
The incorporation of [14C]-alanine or [14C]-lactate into glucose was measured in hepatopancreas fractions from Chasmagnathus granulata crabs adapted to a high protein or a carbohydrate-rich diet and submitted or not (control group) to hyposmotic stress. Gluconeogenic capacity and phosphoenolpyruvate carboxykinase (PEPCK) activity increased during acclimation to a dilute medium in C. granulata hepatopancreas. In intact animals, high hemolymph urea levels occurred for the high-protein regimen and for crabs fed both diets and submitted to hyposmotic stress. It could be that the amino acids released during hyposmotic stress are deaminated in the hepatopancreas, and that the carbon chains are used as substrate for gluconeogenesis. Hepatopancreas gluconeogenesis seems to be one of the pathways implicated in the metabolic adjustment of the amino acid pool during hyposmotic stress in C. granulata. 相似文献
3.
Oliveira GT Eichler P Rossi IC Da Silva RS 《Journal of experimental zoology. Part A, Comparative experimental biology》2004,301(3):240-248
C. granulata is a semiterrestrial crab that lives in the mesolittoral and the supralittoral zones of estuaries and faces hypoxia and anoxia when exposed to atmospheric air. The carbohydrate or protein content of the diets administered to the crabs induced different metabolic adjustments during anoxia and post-anoxia recovery period. During the first hour in anoxia a marked increase in L-lactate concentration in hemolymph was induced, followed by a reduction in its levels accompanied by two peaks in hepatopancreas gluconeogenic capacity. Anoxia exposure did not induce a reduction in the hepatopancreas phosphoenolpyruvate carboxykinase activity in either dietary group. Our results suggest that in anaerobiosis this crab uses the conversion of lactate to glucose in hepatopancreas to maintain the acid-base balance and the glucose supply. In post-anoxia recovery, the fate of L-lactate is the hepatopancreas gluconeogenesis in high protein maintained crabs. On the other hand, in the crabs maintained on carbohydrate-rich diet the L-lactate levels decreased gradually in the hemolymph during the post-anoxia recovery; however, the hepatopancreas gluconeogenesis did not increase. In both dietary groups, an increase in the gluconeogenic capacity of hepatopancreas occurred at 30 h of post-anoxia recovery. 相似文献
4.
Sá MG Valenti WC Zanotto FP 《Comparative biochemistry and physiology. Toxicology & pharmacology : CBP》2008,148(2):112-116
Three species of phylogenetically related semi-terrestrial crabs (Superfamily Grapsoidea--Sesarma rectum, Goniopsis cruentata and Neohelice granulata (formerly: Chasmagnathus granulatus) with different degrees of terrestriality were studied to quantify the accumulation of copper (Cu) in hemolymph, gills, hepatopancreas and antennal gland, and its excretion through the faeces. These crabs were fed for 15 days practical diets containing 0 (A), 0.5 (B), 1.0 (C), and 1.5% (D) of added CuCl2 (corresponding to 0, 0.2, 0.5 and 0.7% of Cu2+, respectively). The amount of food ingested was directly proportional to the degree of terrestriality: S. rectum, the most terrestrial species, ate around 2-3 times more than the other crabs, whereas G. cruentata ate 1.5-2 times more than N. granulata, the least terrestrial. The amount of Cu excreted in the feces was proportional to Cu ingestion, and was 76.8% and 64.2% higher for Sesarma fed diet D compared to G. cruentata and N. granulata, respectively. Sesarma also displayed higher Cu concentration in the haemolymph, gills and antennal glands, but not in the hepatopancreas. A detoxifying mechanism followed by elimination was probably present at this last organ, preventing Cu accumulation. More terrestrial crabs, such as Sesarma, may accumulate more Cu in hemolymph and tissues, showing a correlation between metal accumulation and increased terrestriality. In this aspect, contaminated feed sources with Cu may have more impact in conservation of terrestrial crabs. 相似文献
5.
Martins TL Chittó AL Rossetti CL Brondani CK Kucharski LC Da Silva RS 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2011,158(4):400-405
The present study assesses the effects of osmotic stress on phosphoenolpyruvate carboxykinase (PEPCK), fructose 1,6-bisphosphatase (FBPase) and glucose 6-phosphatase (G6Pase) activities and (14)C-total lipid synthesis from (14)C-glycine in the anterior and posterior gills, jaw muscle, and hepatopancreas of Neohelice granulata. In posterior gills, 24-h exposure to hyperosmotic stress increased PEPCK, FBPase and G6Pase activities. Increase in (14)C-lipid synthesis was associated to the decrease in PEPCK activity after 72-h exposure to hyperosmotic stress. Hypo-osmotic stress decreased PEPCK and G6Pase activities in posterior gills; however, (14)C-lipids increased after 72-h exposure to stress. In anterior gills, decreases in the G6Pase activity after 72-h of hyperosmotic stress and in (14)C-lipogenesis after 144-h were observed, while PEPCK activity increased after 144 h. Exposure to hypo-osmotic stress increased (14)C-lipid synthesis and PEPCK activity in anterior gills. Muscle G6Pase activity increased after 72-h exposure to hypo-osmotic stress; however, no significant change was observed in the lipogenesis. PEPCK decreased in muscle after 144-h exposure to hyperosmotic, coinciding with increased (14)C-lipid synthesis. In the hepatopancreas, a decrease in the (14)C-lipogenesis occurred after 24-h exposure to hyperosmotic stress, accompanied by increase in (14)C-lipid synthesis. Additionally, PEPCK activity returned to control levels. The hepatopancreatic lipogenesis from amino acids was not involved in the metabolic adjustment during hypo-osmotic stress. However, gluconeogenesis is one of the pathways involved in the adjustment of the intracellular concentration of nitrogenated compounds. 相似文献
6.
A. KOHZU T. YOSHIOKA T. ANDO M. TAKAHASHI K. KOBA & E. WADA 《The New phytologist》1999,144(2):323-330
The natural abundance of 13 C and 15 N was measured in basidiocarps of at least 115 species in 88 genera of ectomycorrhizal, wood-decomposing and litter-decomposing fungi from Japan and Malaysia. The natural abundance of 13 C and 15 N was also measured in leaves, litter, soil and wood from three different sites. 15 N and 13 C were enriched in ectomycorrhizal and wood-decomposing fungi, respectively, relative to their substrates. Ectomycorrhizal and wood-decomposing fungi could be distinguished on the basis of their δ13 C and δ15 N signatures. Although there was high variability in the isotopic composition of fungi, the following isotope- enrichment factors (ε, mean±SD) of the fungi relative to substrates were observed:
εectomycorrhizal fungi/litter = 6.1±0.4‰15 N
εectomycorrhizal fungi/wood = 1.4±0.8‰13 C
εwood-decomposing fungi/wood = −0.6±0.7‰15 N
εwood-decomposing fungi/wood = 3.5±0.9‰13 C
The basis of isotope fractionation in C metabolism from wood to wood-decomposing fungus is discussed. 相似文献
ε
ε
ε
ε
The basis of isotope fractionation in C metabolism from wood to wood-decomposing fungus is discussed. 相似文献
7.
Abstract. In the marine environment, the range of values of carbon isotope fractionation between particulate tissue of phytoplankton and inorganic carbon can be more than 20‰ (− 35‰ < δ13 C < − 14‰). This review considers the influence of seawater temperature, lipid content of phytoplanktonic cells, kinetic fractionation, and carbon pathway on δ13 C values observed at sea.
In order to study the contribution of carboxylases (RUBISCO and the β-carboxylases phosphoenolpyruvate carboxylase, phosphoenoplpyruvate carboxykinase and pyruvate carboxylase) to variations of particulate δ13 C values at sea, we present results obtained simultenously on carboxylase activities and δ13 C in various environmental conditions. The lowest δ13 C values are clearly associated with predominance of ribulose-1.5-bisphosphate carboxylase activity, but it was more difficult to explain the high δ13 C values. Different hypotheses are discussed. 相似文献
In order to study the contribution of carboxylases (RUBISCO and the β-carboxylases phosphoenolpyruvate carboxylase, phosphoenoplpyruvate carboxykinase and pyruvate carboxylase) to variations of particulate δ
8.
This study investigated the impact of lipid extraction, CaCO3 removal and of both treatments combined on fish tissue δ13 C, δ15 N and C:N ratio. Furthermore, the suitability of empirical δ13 C lipid normalization and correction models was examined. δ15 N was affected by lipid extraction (increase of up to 1·65‰) and by the combination of both treatments, while acidification alone showed no effect. The observed shift in δ15 N represents a significant bias in trophic level estimates, i.e. lipid-extracted samples are not suitable for δ15 N analysis. C:N and δ13 C were significantly affected by lipid extraction, proportional to initial tissue lipid content. For both variables, rates of change with lipid content (ΔC:N and Δδ13 C) were species specific. All tested lipid normalization and correction models produced biased estimates of fish tissue δ13 C, probably due to a non-representative database and incorrect assumptions and generalizations the models were based on. Improved models need a priori more extensive and detailed studies of the relationships between lipid content, C:N and δ13 C, as well as of the underlying biochemical processes. 相似文献
9.
Vinagre TM Alciati JC Regoli F Bocchetti R Yunes JS Bianchini A Monserrat JM 《Comparative biochemistry and physiology. Toxicology & pharmacology : CBP》2003,135(1):67-75
The objective of this work was to evaluate mechanisms of microcystin toxicity on crustacean species. Adult male crabs of Chasmagnathus granulatus (13.97+/-0.35 g) acclimated to low salinity (2 per thousand ) were injected with saline (control) or Microcystis aeruginosa aqueous extract (39.2 microg/l) at 24 h intervals for 48 h. After the exposure period, the anterior and posterior gills were dissected, measuring Na(+),K(+)-ATPase and glutathione-S-transferase (GST) activity. Total oxyradical scavenging capacity (TOSC) and lipid peroxides (LPO) content were also determined. Na(+),K(+)-ATPase activity in anterior gills was significantly lower in crabs injected with toxin than in control crabs, while no significant difference in the enzyme activity was detected in posterior gills. Both sodium and chloride concentration in the hemolymph were not affected by toxin exposure. Significant changes in GST activity were detected in posterior gills, with higher values being observed in the toxin-injected crabs. Crabs exposed to microcystin also showed a significant increase in the TOSC value against peroxyl radicals, for both anterior and posterior gills. Lipid peroxides level did not change in both gill types after exposure to the toxin. The increased levels of TOSC suggest the occurrence of a crab response against oxidative stress induced by toxin injection, which prevents lipid peroxidation. 相似文献
10.
Christopher H. House Victoria J. Orphan Kendra A. Turk Burt Thomas Annelie Pernthaler Jennifer M. Vrentas Samantha B. Joye 《Environmental microbiology》2009,11(9):2207-2215
To assess and study the heterogeneity of δ13 C values for seep microorganisms of the Eel River Basin, we studied two principally different sample sets: sediments from push cores and artificial surfaces colonized over a 14 month in situ incubation. In a single sediment core, the δ13 C compositions of methane seep-associated microorganisms were measured and the relative activity of several metabolisms was determined using radiotracers. We observed a large range of archaeal δ13 C values (> 50‰) in this microbial community. The δ13 C of ANME-1 rods ranged from −24‰ to −87‰. The δ13 C of ANME-2 sarcina ranged from −18‰ to −75‰. Initial measurements of shell aggregates were as heavy as −19.5‰ with none observed to be lighter than −57‰. Subsequent measurements on shell aggregates trended lighter reaching values as 13 C-depleted as −73‰. The observed isotopic trends found for mixed aggregates were similar to those found for shell aggregates in that the initial measurements were often enriched and the subsequent analyses were more 13 C-depleted (with values as light as −56‰). The isotopic heterogeneity and trends observed within taxonomic groups suggest that ANME-1 and ANME-2 sarcina are capable of both methanogenesis and methanotrophy. In situ microbial growth was investigated by incubating a series of slides and silicon (Si) wafers for 14 months in seep sediment. The experiment showed ubiquitous growth of bacterial filaments (mean δ13 C = −38 ± 3‰), suggesting that this bacterial morphotype was capable of rapid colonization and growth. 相似文献
11.
M. DURANCEAU J. GHASHGHAIE F. BADECK E. DELEENS & G. CORNIC 《Plant, cell & environment》1999,22(5):515-523
The variations in δ 13 C in both leaf carbohydrates (starch and sucrose) and CO2 respired in the dark from the cotyledonary leaves of Phaseolus vulgaris L. were investigated during a progressive drought. As expected, sucrose and starch became heavier (enriched in 13 C) with decreasing stomatal conductance and decreasing p i / p a during the first half (15 d) of the dehydration cycle. Thereafter, when stomata remained closed and leaf net photosynthesis was near zero, the tendency was reversed: the carbohydrates became lighter (depleted in 13 C). This may be explained by increased p i / p a but other possible explanations are also discussed. Interestingly, the variations in δ 13 C of CO2 respired in the dark were correlated with those of sucrose for both well-watered and dehydrated plants. A linear relationship was obtained between δ 13 C of CO2 respired in the dark and sucrose, respired CO2 always being enriched in 13 C compared with sucrose by ≈ 6‰. The whole leaf organic matter was depleted in 13 C compared with leaf carbohydrates by at least 1‰. These results suggest that: (i) a discrimination by ≈ 6‰ occurs during dark respiration processes releasing 13 C-enriched CO2 ; and that (ii) this leads to 13 C depletion in the remaining leaf material. 相似文献
12.
Stable isotopes of carbon and nitrogen as indicators of diet and trophic structure of the fish community in a shallow hypereutrophic lake 总被引:5,自引:1,他引:4
Stable carbon (δ13 C) and nitrogen (δ15 N) isotopes were employed to elucidate energy flows and trophic interactions in Lake Apopka, a hypereutrophic lake in central Florida, U.S.A. Isotope compositions of lake biota ranged from −27·1 to −3·0‰ for δ13 C, and from 3·7 to 13·9‰ for δ15 N. The food web was based primarily on plankton production with diatoms, Microcystis and zooplankton dominating the diet of fish. Carbon isotope evidence showed that pico- and nano-phytoplankton were not a direct carbon source for fish, but were important to zooplankton. δ15 N mass balance estimates indicated that planktivorous fish obtained 48–85% of their diets from zooplankton. The ∼3‰ range of δ15 N in gizzard shad reflected increasing dependence on zooplankton as fish grew whereas the positive relationship between total length and δ15 N of largemouth bass reflected increasing predation on larger planktivorous fish with growth. The broad ranges of δ13 C (−25·9 to −9·5‰) and δ15 N (5·8 to 14·4‰) of blue tilapia were indicators of diet diversity. Two presumed omnivores (brown bullhead and white catfish) and piscivores (black crappie, largemouth bass and Florida gar) were found to depend on planktivorous fish. However, stable isotope data revealed no trophic links between blue tilapia, an abundant fish in the near-shore area, and piscivores. 相似文献
13.
J. E. Ciancio † M. A. Pascual ‡ F. Botto § M. Amaya-Santi S. O'Neal ¶ C. Riva Rossi O. Iribarne § 《Journal of fish biology》2008,72(7):1708-1719
In the present study, profiles of stable isotope composition were characterized for two species with partially migratory populations in rivers along the latitudinal gradient of Patagonia, brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss . The effects of factors ( e.g. ontogeny of fishes, location, species and fasting) that may influence the stable isotope analysis (SIA) were evaluated, as was SIA evaluated as a tool to assign individual fish to their corresponding ecotype. Anadromous fishes exhibited enriched δ15 N (15·2 ± 1·0‰; mean ± s . d .) and δ13 C (−19·2 ± 1·3‰) relative to resident fishes'δ15 N (8·8 ± 1·1‰) and δ13 C (−23·2 ± 2·5‰). For both species, the difference in δ15 N was larger between resident (range 6·8–10·7‰) and anadromous (range 14·3–17·8‰) fishes than that in δ13 C. Values of δ13 C, while not as dramatically contrasting in rainbow trout, provided a powerful anadromy marker for brown trout in the region. Increases were found in both δ15 N and δ13 C during the spawning migration of anadromous rainbow trout, most likely due to fasting. Differences in stable isotopes between location, size and species were found, suggesting different stable isotopes base levels in freshwater environments and different trophic levels and feeding location of anadromous populations. The SIA was demonstrated as a powerful tool for ecotype discrimination in Patagonian Rivers, overriding any effect of sampling location, size or species. 相似文献
14.
Heidi Porras-Peters David Aurioles-Gamboa Victor Hugo Cruz-Escalona † Paul L. Koch ‡ 《Marine Mammal Science》2008,24(3):554-576
Stable isotope and scat analyses were used in concert to determine trophic level and dietary overlap among California sea lions from different rookeries in the Gulf of California. Isotopic analysis of the fur of sea lion pups revealed differences in δ15 N and δ13 C values among rookeries during the breeding season. Mean δ15 N and δ13 C values varied from 20.2‰ to 22.4‰ and from −15.4‰ to −14.0‰, respectively. The pattern of differences among rookeries was similar between years in most cases. Isotopic variations among rookeries were associated with differences in prey consumption. There was a significant correlation between δ15 N value and trophic level, as determined by scat analysis. Joint application of isotopic and scat analyses allowed us to identify how the feeding habits of sea lions vary with location. Our results suggest the presence of spatial structure in available prey as well as the localized use of prey by sea lions across the Gulf of California. 相似文献
15.
Lauer MM de Oliveira CB Yano NL Bianchini A 《Comparative biochemistry and physiology. Toxicology & pharmacology : CBP》2012,156(3-4):140-147
The estuarine crab Neohelice granulata was exposed (96h) to a sublethal copper concentration under two different physiological conditions (hyperosmoregulating crabs: 2ppt salinity, 1mg Cu/L; isosmotic crabs: 30ppt salinity, 5mg Cu/L). After exposure, gills (anterior and posterior) were dissected and activities of enzymes involved in glycolysis (hexokinase, phosphofructokinase, pyruvate kinase, lactate dehydrogenase), Krebs cycle (citrate synthase), and mitochondrial electron transport chain (cytochrome c oxidase) were analyzed. Membrane potential of mitochondria isolated from anterior and posterior gill cells was also evaluated. In anterior gills of crabs acclimated to 2ppt salinity, copper exposure inhibited hexokinase, phosphofructokinase, pyruvate kinase, and citrate synthase activity, increased lactate dehydrogenase activity, and reduced the mitochondrial membrane potential. In posterior gills, copper inhibited hexokinase and pyruvate kinase activity, and increased citrate synthase activity. In anterior gills of crabs acclimated to 30ppt salinity, copper exposure inhibited phosphofructokinase and citrate synthase activity, and increased hexokinase activity. In posterior gills, copper inhibited phosphofructokinase and pyruvate kinase activity, and increased hexokinase and lactate dehydrogenase activity. Copper did not affect cytochrome c oxidase activity in either anterior or posterior gills of crabs acclimated to 2 and 30ppt salinity. These findings indicate that exposure to a sublethal copper concentration affects the activity of enzymes involved in glycolysis and Krebs cycle, especially in anterior (respiratory) gills of hyperosmoregulating crabs. Changes observed indicate a switch from aerobic to anaerobic metabolism, characterizing a situation of functional hypoxia. In this case, reduced mitochondrial membrane potential would suggest a decrease in ATP production. Although gills of isosmotic crabs were also affected by copper exposure, changes observed suggest no impact in the overall tissue ATP production. Also, findings suggest that copper exposure would stimulate the pentose phosphate pathway to support the antioxidant system requirements. Although N. granulata is very tolerant to copper, acute exposure to this metal can disrupt the energy balance by affecting biochemical systems involved in carbohydrate metabolism. 相似文献
16.
Four ecotypes of Phragmites australis from different habitats in northwest China were examined to compare their photosynthetic characteristics. In a swamp ecotype, the Δ 13 C value of leaf materials was −34.0‰, and bundle sheath cells contained a small amount of organelles and round-shaped chloroplasts, as being similar to typical C3 plants. In a dune ecotype, the Δ 13 C value was −20.9‰ and bundle sheath cells contained oval-shaped chloroplasts with poorly-developed grana. In light and heavy salt meadow ecotypes, Δ 13 C values were −30.6‰ and −35.6‰, respectively. The shape of bundle sheath chloroplasts in the light salt meadow ecotype was intermediate between those of the swamp and dune ecotypes. Abundance of bundle sheath organelles in the heavy salt meadow ecotype was intermediate. The swamp ecotype had photosynthetic enzyme activities typical of C3 type plants, whereas the dune ecotype had an increased activity of phosphoenolpyruvate carboxylase (PEPC), a key C4 enzyme, and a decreased ribulose 1,5-bisphosphate carboxylase (Rubisco) activity. The light salt meadow and heavy salt meadow ecotypes had substantial activities of PEPC, which indicates potential for C4 photosynthesis. These data suggest that this species evolved the C3 -like ecotype in swamp environments and the C4 -like C3 -C4 intermediate in dune desert environments, and C3 -like C3 -C4 intermediates in salt environments. 相似文献
17.
Carbon-Isotope Ratios and Photosynthetic Pathways in the Neotropical Family Rapateaceae 总被引:1,自引:0,他引:1
Abstract: The Rapateaceae is a small, mainly Neotropical family of terrestrial or occasionally epiphytic herbs that grow on mesic, nutrient-poor sites. Some recent studies suggest that the Rapateaceae may be closely related to the Bromeliaceae, one of the major families containing CAM plants. To investigate the photosynthetic pathway in Rapateaceae, the plant carbon-isotope ratio (δ13 C) was determined for samples from dried herbarium specimens for 85 of the approximately 100 species in the family. The δ13 C values ranged from - 37.7 to - 19.8 ‰. Most Rapateaceae showed δ13 C values typical of C3 plants. However, six species ( Kunhardtia rhodantha Maguire, Marahuacaea schomburgkii (Maguire) Maguire, Saxofridericia compressa Maguire, Stegolepis grandis Maguire, St. guianensis Klotzsch ex Körn. and St. squarrosa Maguire) showed δ13 C values less negative than - 23 ‰, i.e., at the higher end of the range for C3 plants and at the lower end of the distribution for plants exhibiting CAM. The δ13 C values became significantly less negative with increasing altitude (regression analysis indicating a change from about - 30.7 ‰ at sea level to - 22.5 ‰ at 2500 m). Although other environmental factors and the type of tissue analysed may also influence δ13 C values, these results suggest that some Rapateaceae may be capable of performing CAM. Further studies, including measurements of diel gas exchange patterns and leaf organic-acid fluctuations, would be needed to demonstrate CAM in Rapateaceae unequivocally, but living material of many of these enigmatic plants is difficult to obtain. 相似文献
18.
Salinity-mediated carbonic anhydrase induction in the gills of the euryhaline green crab, Carcinus maenas 总被引:1,自引:0,他引:1
Henry RP Gehnrich S Weihrauch D Towle DW 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2003,136(2):243-258
The euryhaline green crab, Carcinus maenas, is a relatively strong osmotic and ionic regulator, being able to maintain its hemolymph osmolality as much as 300 mOsm higher than that in the medium when the crab is acclimated to low salinity. It makes the transition from osmoconformity to osmoregulation at a critical salinity of 26 ppt, and new acclimated concentrations of hemolymph osmotic and ionic constituents are reached within 12 h after transfer to low salinity. One of the central features of this transition is an 8-fold induction of the enzyme carbonic anhydrase (CA) in the gills. This induction occurs primarily in the cytoplasmic pool of CA in the posterior, ion-transporting gills, although the membrane-associated fraction of CA also shows some induction in response to low salinity. Inhibition of branchial CA activity with acetazolamide (Az) has no effect in crabs acclimated to 32 ppt but causes a depression in hemolymph osmotic and ionic concentrations in crabs acclimated to 10 ppt. The salinity-sensitive nature of the cytoplasmic CA pool and the sensitivity of hemolymph osmotic/ionic regulation to Az confirm the enzyme's role in ion transport and regulation in this species. CA induction is a result of gene activation, as evidenced by an increase in CA mRNA at 24 h after transfer to low salinity and an increase in protein-specific CA activity immediately following at 48 h post-transfer. CA gene expression appears to be under inhibitory control by an as-yet unidentified repressor substance found in the major endocrine complex of the crab, the eyestalk. 相似文献
19.
We evaluated diurnal and seasonal patterns of carbon isotope composition of leaf dark-respired CO2 ( δ 13 Cl ) in the C3 perennial shrub velvet mesquite ( Prosopis velutina ) across flood plain and upland savanna ecosystems in the south-western USA. δ 13 Cl of darkened leaves increased to maximum values late during daytime periods and declined gradually over night-time periods to minimum values at pre-dawn. The magnitude of the diurnal shift in δ 13 Cl was strongly influenced by seasonal and habitat-related differences in soil water availability and leaf surface vapour pressure deficit. δ 13 Cl and the cumulative flux-weighted δ 13 C value of photosynthates were positively correlated, suggesting that progressive 13 C enrichment of the CO2 evolved by darkened leaves during the daytime mainly resulted from short-term changes in photosynthetic 13 C discrimination and associated shifts in the δ 13 C signature of primary respiratory substrates. The 13 C enrichment of dark-respired CO2 relative to photosynthates across habitats and seasons was 4 to 6‰ at the end of the daytime period (1800 h), but progressively declined to 0‰ by pre-dawn (0300 h). The origin of night-time and daytime variations in δ 13 Cl is discussed in terms of the carbon source(s) feeding respiration and the drought-induced changes in carbon metabolism. 相似文献
20.
JÖRN PECKMANN BABA SENOWBARI-DARYAN DANIEL BIRGEL JAMES L. GOEDERT 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2007,40(3):273-280
Crustacean microcoprolites are preserved along with crustacean megafossils in an Eocene limestone within the Humptulips Formation in Grays Harbor County, Washington. The limestone formed at a methane seep, as revealed by early diagenetic carbonate phases resembling those of other seep limestones, δ13 Ccarbonate values as low as −27‰, and lipid biomarkers of prokaryotes involved in anaerobic oxidation of methane with δ13 C values as low as −110‰. Recognizable crustacean megafossils are chiefly isolated chelipeds, akin to those of callianassid shrimp. The microcoprolites are pierced by ten longitudinal canals with crescent-shaped outlines in cross-section, arranged in two symmetrical groups. The symmetry plan and number of canals of the microcoprolites identify the Humptulips ichnospecies as Palaxius habanensis Brönnimann & Norton. The occurrence of decapod fossils along with microcoprolites suggests that callianassid shrimp were the producers of the Palaxius , supporting earlier work that attributed this ichnogenus to callianassids. 相似文献