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1.
Variations in growth and survival of hatchery-reared post-metamorphicjuveniles of great scallop Pecten maximus prompted anexamination of settlement and postlarval development. The effects ofseawater flow and temperature on great scallop metamorphosis andpostlarvae were studied over a 4–5 week period. In allexperiments, and regardless of environmental conditions, great scallopmetamorphosed after a 2–3 week period with values of 35 to70%. Subsequently, spat numbers increased slightly. Spatmortality generally occurred from the third week onward and reachedlevels as high as 30% by the fifth week under standardconditions. At 20 °C, however, 60% mortality levels wererecorded. Differences in spat growth rate, ranging from 37 to 45 mday–1, were noticed at different seawater flow ratesbut no clear tendency could be discerned. Temperature affected spatgrowth with an increase in size from 24 m day–1 at15 °C to 35 m day–1 at 18 °C. Conversely,growth was suppressed at 20 °C (14 m day–1).For optimal metamorphosis and postlarval development in great scallop, aseawater flow of 4.3 L h–1 per sieve and a temperatureof 15 °C are recommended. 相似文献
2.
The endemic, anadromous cyprinidChalcalburnus tarichi is the only fish species known to occur in alkaline Lake Van (Eastern Anatolia, Turkey). EightC. tarichi were maintained individually in Lake Van water (17 – 19°C; pH 9.8; 153 mEq·I–1 total alkalinity; 22 total salinity) and tank water samples analyzed for 24 h in 2 to 4 h intervals. At zero time, < 1µM ammonia was present and urea was undetectable in the tank water; at 24 h, total ammonia and urea made up 114±32 and 35±25µM, respectively. Over the experimental period, ammonia-N and urea-N excretion averaged 1041±494 and 607±169moles·kg–1 fish·h–1, respectively. The extent of urea excretion was highly variable between specimens. Uric acid excretion was not detectable.Urea was present at high concentrations in all tissues and plasma (25 – 35moles·g–1·ml–1) of freshly caughtC. tarichi; total ammonia content of the tissues was by a factor of 1.9 (liver) to 3.0 (brain) lower. High arginase activity (2.4±0.2 U·min–1·g–1) was detected in the liver ofC. tarichi but ornithine carbamoylphosphate transferase, a key enzyme of the ornithine-urea-cycle, was absent. Ureagenesis is likely through degradation of arginine and/or uricolysis. High glutamine synthetase activity (11±0.6 U·min–1·g–1) and low ammonia content in brain suggest that, like other teleosts,C. tarichi has an efficient ammonia detoxification in the brain, but in no other tissue.Nitrogenous waste excretion at alkaline pH is discussed. The ability ofC. tarichi to excrete high levels of ammonia at extremely alkaline pH is unique among teleosts studied so far. The mechanism of ammonia excretion under Lake Van conditions remains to be elucidated. 相似文献
3.
Protein synthesis was assessed in rainbow trout (Oncorhynchus mykiss) hearts perfused with medium containing 3H phenylalanine. Isolated hearts from fish acclimated to 5° and 15°C were used as the model system, and were perfused at variable test temperatures and pH. Protein synthesis expressed as nmol PHE mg protein–1 h–1 was two fold higher in hearts from fish acclimated to 15°C and tested at 15°C and extracellular pH 7.6 than in hearts from fish acclimated to 5°C and tested at 5°C and extracellular pH 8.0. The prime determinant of the decreased rate of protein synthesis was thermal history. Fish acclimated to 5°C had lower levels of RNA mg protein–1 than fish held at 15°C. There was a direct linear relationship between the rate of protein synthesis in nmol PHE mg protein–1 h–1 and RNA content. RNA activity (nmol PHE g RNA–1 h–1 remained constant regardless of thermal history or perfusion condition. Elevated pH resulted in only a marginal decrease in protein synthesis. Test temperature had no effect on in vitro rates of protein synthesis. 相似文献
4.
Soft water acclimated (Ca2+ 0.02 mM; Na+ 0.03 mM; K+ 0.01 mM; pH 7.0), cannulated brown trout (Salmo trutta) were exposed to various pH and aluminium (Al) regimes (pH 7.0, pH 5.0, pH 5.0 plus Al: 50, 25, and 12.5 g l–1) for up to 5 days in order to determine (i) the sublethal concentration of Al at pH 5.0 for this species (ii) their ionoregulatory and respiratory status. No mortality or physiological disturbances were evident at pH 7.0 or pH 5.0. All trout died within 48 h at pH 5.0 in the presence of Al at 50 g l–1 and 67% died over the 5 day period at pH 5.0 in the presence of Al at 25 g l–1. Fish at these lethal Al concentrations showed significant decreases in arterial blood oxygen content (CaO2) but no changes in plasma osmolarity or the concentrations of plasma Na+, K+ and Cl–. Physiological disturbance was more marked at the 50 g l–1 Al concentration. The surviving fish at 25 g l–1 showed few signs of physiological recovery while continually exposed to this regime. No fish died during the exposure to water of pH 5.0 containing 12.5 g l–1 Al, but physiological disturbance was still apparent. These sublethally-stressed trout showed a transient decline in the plasma concentrations of Na+ and Cl–1. Although CaO2 decreased, recovery was evident. The data suggest that in the brown trout, environmental Al concentration is as important as pH and calcium concentration in determining the physiological status of the fish. 相似文献
5.
A recombinant carp growth hormone (rcGH) was used to develop for a GH radioreceptor binding assay in the goldfish (Carassius auratus). Specific binding of125I-rcGH to goldfish liver membranes was a pH, time, temperature, and membrane protein dependent process. Scatchard and LIGAND analysis indicated a single class of high affinity and low capacity binding site, with an association constant (Ka) of 1.9×1010 M–1 and a maximum binding capacity (Bmax) of 9 fmol mg–1 protein. Liver tissue displayed the highest125I-rcGH binding of all the tissues examined. Displacement of125I-rcGH with various unlabeled teleost and mammalian GHs and prolactins revealed that the goldfish hepatic binding site was highly specific for teleost GH. Intraperitoneal administration of 0.1, 1.0, and 10 g rcGH g–1 body weight to hypophysectomized goldfish resulted in a 27, 52, and 68% decrease in total binding sites, respectively. Injection of a high dose of rat prolactin (rPRL) (5 g rPRL g–1 body weight) also resulted in a 32% decrease in total binding sites. These results suggest that endogenous GH may have a role in the regulation of its own receptors in the goldfish. 相似文献
6.
The rate of oxygen consumption of minced whole body was determined volumetrically, as an indication of metabolic rate in vitro (M
in vitro
), at 20°C in porgy Pagrus major ranging from 0.0002 g (just after hatch) to 2.9 g (67 days old) in body mass. A triphasic relationship was found between M
in vitro
of individual fish (l.min–1) and wet body mass W (g). During the prolarval stage accompanied with the transitional period to the postlarval stage (0.00020–0.00023 g, 0–6 days old), the mass-specific metabolic rate in vitro (M
in vitro
/W in l.g–1.min–1) increased with age (D in days) as expressed by an equation M
in vitro
/W = 3.88 + 0.74/D. During the postlarval stage (0.00031–0.003 g, 8–22 days old), M
in vitro
/W remained almost constant, independent of body mass following an equation M
in vitro
/W = 5.24 W–0.085. During the juvenile and adolescent stages (0.0047–2.9 g, 30–67 days old), M
in vitro
/W decreased with increasing body mass following an equation M
in vitro
/W = 1.66 W–0.235. These results correspond with the triphasic relationship between metabolism in vivo and body mass observed in intact porgy of 0.0002–270 g (Oikawa et al. 1991). It is concluded, therefore, that the dependence of mass-specific metabolic rate on body size exists in vitro as well as in vivo, during the early stages in the porgy. Based on these results, factors controlling the metabolism-size relationship are discussed. 相似文献
7.
Four groups of 1+ year-old Atlantic salmon, Salmo salar, pre-smolts were reared under various temperature regimes: constant 10 °C from November onwards; ambient temperature until either 15 December or 1 February, then 10 °C; or ambient temperature throughout (control; 2–3 °C November–March). From 20 May onwards, temperature in all groups was ambient, increasing from 10 °C to 17 °C in late July. Rearing temperature had no significant effect on either the timing of completion of smolting, or the duration of the smolt-window. Mean gill Na+-K+ ATPase activity was not significantly affected by temperature regime; it increased in all groups from < 2.0 mol Pi mg protein–1 h–1 (units) in January to 5–7 units in mid-April, then back to < 2.0 units in July. Survival in 96 h, 37) salinity (S) tolerance tests was similar in all groups, increasing from < 10% in early March, to > 90% from mid-April to mid-June, then decreasing to < 20% by early July. Increased winter temperature significantly increased growth and condition factor compared with the control, but during April–May all four groups exhibited similar temporary decreases in condition factor in association with the completion of smolting. 相似文献
8.
Embryonic development and larval hatching of the monogenean Diplectanum aequans, gill parasite of sea bass Dicentrarchus labrax, was studied in relation to different prophylactic treatments. Groups of eggs of D. aequans were submitted to different in vitro treatments: formalin (300 and 100 L L–1 per 1 hour), Neguvon® (trichlorphon 0.2 mg L–1 per 48 hours) and dehydration for 4 and 8 hours. Percentages of hatched larvae, aborted larvae and undeveloped embryos were estimated in comparison with the control group. Results showed that 300 L L–1 formalin and dehydration treatments were able to reduce larval hatching significantly, while Neguvon® and 100 L L–1 formalin treatments had no effect. 相似文献
9.
Antarctic fish of the family Channichthyidae (Icefishes) lack the respiratory pigments haemoglobin and myoglobin. The morphometrics and ultrastructure of the ventricular myocardium of a benthic icefish,Chaenocephalus aceratus has been compared with that of a red-blooded Notothenioid fish,Notothenia neglecta, of similar habit.The mass of ventricular muscle as a percentage of bodyweight is 3 times greater in adultC. aceratus (0.32%) thanN. neglecta (0.11%). Myoglobin concentration in the ventricle ofN. neglecta, 20 nmoles/g, is comparable to that of temperate teleosts with similar activity patterns. The volume and surface densities of mitochondria are 41.5% and 0.32 m–1 for Icefish and 25% and 0.15 m–1 forN. neglecta, Cytochrome oxidase activities are similar in the two tissues whilst the volume density of myofibrils is higher forN. neglecta (47%) thanC. aceratus (29.9%).The proliferation of mitochondria in the myocardium of Icefish will reduce the diffusion path-length for oxygen between ventricular lumen and the outer mitochondrial membrane and may compensate for the absence of myoglobin. 相似文献
10.
The pattern of changes of activity of the urea cycle enzymes and the rate of urea-N excretion were studied in the perfused liver of an Indian air-breathing ureogenic walking catfish, Clarias batrachus. The liver was perfused with different concentrations of NH4Cl for a period of 60 min to determine the role of ammonia for stimulation of hepatic ureogenesis and the threshold level of ammonia loading needed to cause such stimulation. Both the urea-N excretion and the ammonia uptake by the perfused liver were found to be a saturable process. Ammonia accumulated significantly in the liver infused with 1.25 moles g liver –1 min–1 of NH4Cl, followed by a maximum accumulation of about 28.5 moles g wet wt–1 with the infusion of 5.08 moles g liver–1 min–1. The Vmax of the urea-N excretion (0.47 mol g liver–1 min–1) was obtained with the addition of 5.08 moles g liver–1 min–1 of NH4Cl. Both the tissue and the specific activity of the urea cycle enzymes, except ornithine transcarbamylase and arginase, were stimulated significantly with the infusion of either 1.25 or 5.08 moles g liver–1 min–1 of NH4Cl. Maximum stimulation of tissue activity of carbamoyl phosphate synthetase (about 120%) was seen with the infusion of 5.08 mol g liver–1 min–1, and for argininosuccinate synthetase (about 135%), and argininosuccinate lyase (about 50%) with the infusion of 10.81 mol g liver–1 min–1 of NH4Cl. Higher accumulation of ammonia of about 10–15 mol g wet wt–1 from the physiological level in the perfused liver while infusing with NH4Cl was suggested to be one of the major causes of stimulation of ureogenesis. The presence of such physiological adaptive strategy is probably necessary in this unique group of air-breathing walking catfish to survive under hyper-ammonia stress in their normal habitat or while living outside water or while burrowing inside mud. 相似文献
11.
In two separate experiments, haddock (Melanogrammus aeglefinus) larvae were raised under different photoperiods (24L : 0D or 15L : 9D), or different combinations of tank colour (black or white) and light intensity (1.1 mol s–1 m–2 or 18 mol s–1 m–2). Growth (0.8% day–1 in standard length; 2.9% day–1 in body area) and survival (2%) were not significantly different between photoperiod treatments after 35 days. Larval survival was greater in white versus black tanks after 41 days (2% versus l%, respectively). Growth of larvae was impaired in black tanks at low (1.1 mol s–1 m–2) light intensity (0.8% day–1 in standard length and 2.2% day–1 in body area versus 1.1% day 21 in standard length and 3.1% day–1 in body area, for all other treatments). Transmission and reflection of light was low in black tanks at low incident light, and there was very little upwelling light. The resultant poor prey to background contrast probably resulted in larvae being unable to consume sufficient food to sustain a level of growth comparable to that in other treatments. 相似文献
12.
The ingestion of an inert feed as a sole food source was investigated in larval silver sea bream (Sparus sarba) fed an alginate-based microparticulate diet. Using the auto-fluorescent properties of pigments associated with the alginate base, ingestion and gut content were investigated over a 6 h experimental period in fed and unfed larvae. By extracting and measuring chlorophyll a (Chl a) and phaeopigment content of feeding larval fish and relating this to standardized Chl a and phaeopigment content of the diet, relative to diet weight, it was determined that individual fed 7-day old larvae had a maximum gut content of 1.05±0.09 g diet while 14-day old fed fish had a maximum gut content of 3.17±0.90 g diet. On average, the gut content of 14-day old fish was 2.89 times greater than the gut content of 7-day old fish. The dry weight of larval sea bream increased from 43±4.2 g at day 7 to 134.3±20.4 g at day 14 indicating that growth of fish fed this inert feed was substantial. Gut pigment dynamics suggested that Chl a was degraded to phaeopigments by 7-day but not 14-day old larvae and the individual gut dietary content varied considerably in 14-day old fish. The maximum Chl a and phaeopigment content in larval sea bream was 0.4 ng ind–1 and 0.55 ng ind–1 for 7-day old fish and 1.54 ng ind–1 and 2.81 ng ind–1 for 14-day old fish respectively. The present method may potentially allow simple and direct assessment of larval fish feed ingestion in both an experimental and commercial setting. 相似文献
13.
PKC activity was detected in spleen extracts from the turbot, Scophthalmus maximus, a teleost flatfish that is farmed commercially in several countries, in assays with the substrate EGF- R651–658 as phosphate acceptor. The activity was purified about 700-fold by a three-step chromatographic procedure (DEAE-cellulose, phenyl-Sepharose and threonine-Sepharose). Maximal activity was obtained in the presence of the typical PKC cofactors Ca2+ (0.1 mM) PtdS (20 g ml–1) and either DAG (2 g ml–1) or PMA (2 g ml–1). Activity was dose-dependently inhibited by H7 and by the PKC-specific inhibitors PKC19–36 and N-myristoylated PKC19–31. The rate of phosphorylation was highest with the PKC-specific substrate MARCKS161–175. In immunoblotting, MC5 (a mouse monoclonal antibody raised against bovine PKC) recognized bands of 80 and 100 kDa. Immunoblotting with antibodies raised against mouse PKC isozymes (, , , , , , and ) indicated the presence of all these isozymes in turbot spleen. 相似文献
14.
Studies of the enzyme fructose-1,6-bisphosphatase (FBPase) of rainbow trout (Oncorhynchus mykiss) have been undertaken in order to illuminate aspects of skeletal muscle gluconeogenesis in these animals. Maximal activities in crude homogenates of several organs suggest that the liver possesses the greatest FBPase activity on a unit g–1 tissue basis but that the white muscle, owing to its bulk, contributes substantially to whole body FBPase activity. Studies of fructose-6-phosphate-1-kinase (PFK) and FBPase in crude homogenates of several organs suggests an important role for intracellular pH in regulating the relative carbon flux through the FBPase/PFK locus in vivo. Furthermore, a three-step purification scheme is described for trout white muscle FBPase by which a stable and homogeneous (by SDS PAGE) enzyme preparation (isoelectric point = 7.2; molecular weight = 37.6 kd) was obtained. Kinetic studies of the purified enzyme were undertaken at 20°C under conditions reflective of "rest" and "exercise/recovery" intramuscular pH in vivo. Affinity for substrate (F-1,6-P2) was increased (Km = 6.88 versus 2.44 mol 1-–1 as was enzyme activity when pH was lowered from 7.0 to 6.5. Various inhibitor metabolites are identified including F-2,6-P2 (mixed-type inhibitor, Ki = 0.201 mol 1–1, pH 7.0) and AMP (non-competitive inhibitor, Ki = 0.438 mol 1–1, pH 7.0). Inhibition by F-2,6-P2 was strongly alleviated by a reduction in pH from 7.0 to 6.5 (I50 increased from 0.14 to 0.32 mol 1–1). AMP on the other hand was a more potent inhibitor at pH 6.5 but this inhibition was totally reversed under conditions of citrate, NH4
+ and AMP typical of muscle during recovery from exercise in vivo. In purified white muscle enzyme preparations, FBPase demonstrated maximal activity at pH 6.5 whereas the optimal pH of PFK was 7.0 or greater. Indeed, it appears from these in vitro data that regulation by metabolite levels as well as pH are required for net FBPase flux in vivo. It is concluded, therefore that trout white muscle FBPase demonstrates the potential to play an important enzymatic role in the control of intramuscular gluconeogenesis in these animals. The results are discussed in relation to present knowledge regarding the metabolic responses of trout white muscle to, and its subsequent recovery from, exhaustive exercise. 相似文献
15.
Effects of the native GnRHs and various agonists have been evaluated on the spawning of an Indian catfish, Heteropneustes fossilis. This study tested salmon (s) GnRH agonists and mammalian (m) GnRH agonists where a D-amino acid residue was substituted alone at position 6 or the C-terminal was modified with ethylamide. GnRH agonists with a combination of these structural modifications were also evaluated separately for their effect on the spawning of the catfish. Native sGnRH, [Pro9 NEt]-sGnRH agonist and chicken (c) GnRH-II exhibited similar activity and induced spawning within 14–18 h at a dose of 100 g kg–1 body weight (BW). [D-Lys6]-sGnRH agonist and [D-Lys6 Pro9 NEt]-sGnRH agonist, induced spawning at a dose of 100 g kg–1 BW and 1 g kg–1 BW, respectively. The most notable observation in this study was the ineffectiveness of [D-Ala6]-mGnRH agonist and [Des Gly10 D-Ala6 Pro9 NEt]-mGnRH agonist. The results obtained suggest that substitution at position 6 alone, and in conjunction with an ethylamide-based modification at the C-terminal in the native sGnRH structure, increases the potency of the tested agonists to induce spawning in the catfish. This study also discusses the potential use and incorporation of cGnRH-II for the development of more generic spawning induction therapies. 相似文献
16.
Asian catfish, Clarias batrachus, were fed semi-purified basaldiets containing 0, 0.1, 0.5, 1, 3 and 5 mg biotin kg–1diet for 60 days. Fish fed the control diet (no biotin) showed(P < 0.05) higher mortality, lower weight gain, specificgrowth rate (SGR), feed efficiency ratio (FER) and protein efficiencyratio (PER) than in fish fed diets supplemented with biotin. The highestweight gain, SGR, FER and PER were noticed in fish fed 1 mg biotinkg–1, followed by 0.5, 5, 3 and 0.1 mg biotinkg–1, except for PER (followed by 0.5, 5, 0.1 and 3 mgbiotin kg–1). Quadratic analysis showed that the optimumdietary biotin requirements for maximal weight gain, PER and PER were2.49, 2.54 and 2.52 mg kg–1, respectively. Liver biotinconcentrations were influenced by levels of biotin in the diet.Concentration of liver biotin increased as level of dietarysupplementation increased and no biotin was detected in the liver of thecontrol fish. Liver pyruvate carboxylase and acetyl CoA carboxylaseactivities were higher in fish fed biotin-supplemented diets than incontrols. Biotin concentrations, pyruvate carboxylase and acetyl CoAcarboxylase activities in liver associated with normal growth rangedfrom 10.59 to 10.66 g g–1, 147.97 to 148.18 units mgprotein–1 and 12.76 to 12.78 units mg protein–1, respectively. Biotin deficiency symptoms such as anorexia, darkskin colour and convulsions were observed in fish fed the control diet.The optimum dietary biotin requirement for maximal growth of C.batrachus is about 2.49 mg kg–1 diet. 相似文献
17.
Jacques Rinchard Godfrey Mbahinzireki Konrad Dabrowski Kyeong-Jun Lee Mary-Ann Garcia-Abiado Joseph Ottobre 《Aquaculture International》2002,10(1):11-28
Five experimental diets containing increasing proportions of cottonseedmeal (CSM) protein (0, 25, 50, 75 and 100%; diets 1 to 5, respectively) toreplace fish meal (FM) protein were formulated for intensive culture of tilapiaOreochromis sp. Each diet was fed to three replicategroupsof fish (mean weight ± SE = 11.3 ± 3.9 g) in30L aquaria connected as a closed recirculating-water system andmaintained at 27 ± 1 °C. Fish were fed three times adayby hand at a rate of 3% of body weight during four weeks, after which thefeeding rate was gradually decreased to reach 1.5% at 16 weeks. Thesubstitutionof 75 and 100% of FM proteins by CSM proteins resulted in significantly lowerbody weights in both sexes. In both sexes, gonadosomatic indexes and plasmaconcentrations of sex steroids (testosterone, 11-ketotestoterone,estradiol-17 and 17,20-dihydroxy-4-pregnen-3-one) were notsignificantly different among dietary treatments. The concentration ofgossypol,an antifertility agent contained in CSM, was measured in reproductive tissues.The total gossypol concentration in the testis was consistently lower than thatmeasured in the ovaries of the same group. Moreover, in both sexes, theconcentration of the (+)isomer of gossypol was always higher than that of(–)isomer. The total gossypol concentrations in testes increasedsignificantly with the increase of CSM in the diet. The highest levels of the(+)isomer (7.64 ± 0.62 g g–1)were found in the testes of fish fed diet 4, whereas the (–)isomerreached its highest values in the testes of fish fed diet 5. The highest levelsof both enantiomers of gossypol were found in the ovaries of fish fed diet 4(14.2 ± 2.7 and 5.6 ± 1.5 g g–1for (+) and (–)isomers, respectively). In both sexes, thehistological analysis of the gonads did not reveal differences among the fishfed different levels of CSM. Although CSM at any levels did not affect thereproductive parameters examined in this study, it cannot be used to substitutemore than 50% of FM since at higher levels growth of tilapia was compromised. 相似文献
18.
Starry flounder (Platichthys stellatus) were cannulated and a bolus of 9 Ci14C-creatine in saline was injected into the caudal vein. The fish were sacrificed at intervals ranging from 1h to 36d after label injection. Creatine pool size (PCr+Cr) and creatinine (Crn) content in blood, muscle, gills and liver were analyzed and specific activities (SA) determined.Mean concentrations of PCr+Cr/Crn in PCA-extracts of muscle, gills, liver and blood of experimental fish (at rest) were 38.1/2.40, 4.1/0.25, 5.6/0.45 and 0.3/n.d. mol.g–1 respectively.Within 10 min, plasma SA had decreased by approximately 90%. In white muscle, the rate of14C–Cr appearance as well as label disappearance was slow compared to gills and liver. In fish examined 36d postinjection, mean SA in muscle had decreased to 23% of maximum SA which occurred 24h after injection.14C–Cr was incorporated into the liver tissue at a very high rate, SA being two orders of magnitude higher in liver than in white muscle. Over the first 6d, retention of label was observed in liver; after 36d only 3% of the original label was detected.Creatine pool size (PCr+Cr) in white muscle decreased with food deprivation. In flounder sacrificed after 36d, PCr+Cr was only 52% that of fed control fish, suggesting that creatine or precursors for its biosynthesis are supplied with the diet. 相似文献
19.
20.
L. R. Harris M. H. Cake D. J. Macey I. C. Potter 《Fish physiology and biochemistry》1990,8(6):451-457
The concentration of total non-haem iron and its ferritin iron component, and the activity of the enzyme superoxide dismutase
(SOD), were measured in the livers of ammocoetes, metamorphosing animals (stages 1–7) and recently metamorphosed downstream
migrants of the lamprey Geotria australis. Total non-haem iron in the liver rose significantly from 0.15–0.55 μg.mg wet weight−1 in ammocoetes and metamorphosing stages 1–3 to 2.2–2.9 μg.mg−1 in stages 5–7 and to 8.8 μg.mg−1 in downstream migrants. The comparable values for ferritin iron were 0.06–0.26, 1.4–2.0, and 5.3 μg.mg−1. Superoxide dismutase activity fell sharply from 0.39 μg.mg−1 in large ammocoetes to between 0.07 μg.mg−1 in stage 1 and 0.15 μg.mg−1 in stage 6, before rising significantly to 0.26 μg.mg−1 in stage 7 and 0.35 μg.mg−1 in downstream migrants. The sharp fall in SOD activity at the beginning of metamorphosis is assumed to be related to the
marked decline in plasma iron which occurs at the onset of this non-trophic phase in the life cycle. It is proposed that the
subsequent increase in SOD activity in the liver of G. australis with increasing iron represents a mechanism aimed at reducing the potentially toxic effects of iron accumulation. This view
is consistent with the significant and positive correlation found between both total non-haem and ferritin iron and SOD activity
in the liver of non-trophic animals. 相似文献