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1.
The acute and chronic effects of excess iodide (KI or NaI) were studied on thyroid function of rainbow trout at 11±1°C. No Wolff-Chaikoff effect, characteristic of mammals, was observed and instead plasma L-thyroxine (T4) levels increased 6 hr after a single iodide injection. Plasma 3,5,3′-triiodo-L-thyronine (T3) did not change and by 24 hr plasma T4 returned to normal. This iodide-induced elevation in plasma T4 was probably not due to toxic effects demonstrated at higher NaI or KI doses. A single iodide injection also decreased the plasma iodide distribution space, decreased the fractional rate of plasma iodide loss and completely blocked thyroidal uptake of radioiodide. Injections of iodide over a 22-day period elevated plasma iodide 200X with no mortality and no influence on plasma T4 or T3. It is concluded that: (i) apart from the transient 6h increase in plasma T4, trout thyroid function, as judged by plasma hormone levels, is insensitive to considerable iodide excess, (ii) non-invasive iodide suppression of thyroidal radioiodide recycling may be useful in kinetic studies of125I-labeled thyroid hormones, and (iii) fundamental differences in intrathyroidal iodine metabolism appear to exist between mammals and fish.  相似文献   

2.
Plasma levels of L-thyroxine (T4) and 3,5,3-triiodo-L-thyronine (T3) and the percentage of plasma T4 and T3 present in the free (dialyzable) form (%FT4 and %FT3) were measured in 16 species (11 families) of tropical marine teleosts from an inshore Barbados reef. Mean plasma T4 varied from 0.2 ng/ml to 42 ng/ml; mean plasma T3 varied from < 0.2 ng/ml to 50 ng/ml. The highest T4 and T3 levels were recorded in parrot-fish and the lowest levels in filefish. The %oFT4 and %FT3 varied from 0.05–3.41%. Estimated levels of plasma free T4 and free T3 levels ranged from 0.4–466 pg/ml. The extremely wide inter- and intra-species ranges in levels of free T4 and T3 do not support a previous suggestion, based on temperate freshwater salmonid species, that free T4 and T3 levels in fish may fall within a relatively range narrow comparable to that of homeothermic vertebrates.  相似文献   

3.
The trout thyroid secretes L-thyroxine (T4) which undergoes enzymatic deiodination in liver and other tissues. Based on mammalian studies, T4 outer-ring deiodination (ORD) or T4 inner-ring deiodination (IRD) could generate respectively 3,5,3′-triiodo-L-thyronine (T3) or 3,3′,5′-T3(rT3), while subsequent T3ORD or T3IRD could generate respectively 3,5-diiodo-L-thyronine (T2) or 3,3′-T2, and rT3ORD or rT3IRD could generate respectively 3,3′-T2 or 3′,5′-T2. In practice, T4 in trout undergoes hepatic ORD to produce T3 but negligible IRD to produce rT3, and T3 in turn undergoes negligible ORD but modest IRD to produce 3,3′-T2. T4ORD, which is particularly important in converting T4 to the biologically more potent T3, also occurs in gill, muscle and kidney. At least two isozymes are involved: i) a high-affinity, propylthiouracil (PTU)-sensitive T4ORD which displays ping-pong kinetics, requires thiol as a cofactor, and is present in liver, gill and muscle, and ii) a low-affinity, PTU-insensitive T4ORD with sequential kinetics with a thiol cofactor, and is present in liver and kidney. Receptor-bound T3 is derived primarily from the plasma for kidney, mainly from intracellular sources for gill and about equally from both plasma and intracellular sources for liver. Thus, the high-affinity T4ORD may produce T3 for local intracellular use while the low-affinity 5′-monodeiodinase may produce T3 for systemic use. T4ORD activity responds to nutritional factors and the physiologic state of the fish. Furthermore, T3 administered orally for either 6 weeks or 24h reduces the functional level (Vmax) of hepatic T4ORD, and T3 added to isolated hepatocytes also reduces activity, indicating direct T3 autoregulation of T4ORD to maintain hepatocyte T3 homeostasis. However, T3 administration also induces T4IRD to produce biologically inactive rT3 and induces T3IRD to produce 3,3′-T2. Thus, the trout liver has several iodothyronine deiodinase systems which in a coordinated manner regulate tissue T3 homeostasis in the face of a T3 challenge. It does this by decreasing formation of T3 itself, by diverting T4 substrate to biologically inactive rT3 and by increasing the degradation of T3. These deiodinases differ in many respects from any mammalian counterparts.  相似文献   

4.
Extrathyroidal T4 5′-monodeiodination, demonstrated in several teleost species, generates T3 which binds more effectively than T4 to putative nuclear receptors and is probably the active thyroid hormone. T4 to T3 conversion is sensitive to the physiological state and provides a pivotal regulatory link between the environment and thyroid hormone action. T3 generation is enhanced in anabolic states (positive energy balance or conditions favoring somatic growth; food intake or treatment with androgens or growth hormone) and is suppressed in catabolic states (negative energy balance or conditions not favoring somatic growth; starvation, stress, or high estradiol levels associated with vitellogenesis). In fish, as in mammals, thyroidal status may be finely tuned to energy balance and through T3 production regulate energy-demanding processes, which in fish include somatic growth, development and early gonadal maturation.  相似文献   

5.
The diurnal rhythms of plasma glucose, cortisol, growth hormone (GH) and thyroid hormone (T4, T3) concentrations and hepatic glycogen content were measured in rainbow trout that had been entrained to a specific time of daily feeding (post-dawn, midday, pre-dusk); the purpose of the study was to investigate the significance of feeding time on hormones and metabolite patterns. Plasma GH, cortisol and T4 concentrations all showed evidence of a diurnal rhythm in some treatment groups. There was a significant interaction between the time of feeding and plasma GH and cortisol concentration rhythms; for GH, this appeared to be related to the phase-shifting of the post-prandial increases in plasma GH concentrations, and for cortisol, the rhythms were only evident in fish fed in the post-dawn period [diurnal rhythms were not evident in treatment groups fed in at midday or pre-dusk]. Peak plasma T4 concentrations were evident during the photophase in all three treatment groups; however, the time of feeding had a negligible effect on the timing of those peaks. There were no apparent diurnal rhythms of plasma T3 and glucose concentrations, hepatic glycogen content or hepatosomatic index in any of the three treatment groups. To whom correspondence should be addressed  相似文献   

6.
In the present study, we examined the effects of experimentally-induced increases or decreases in plasma concentrations of thyroid hormones on iodothyronine deiodinases in tilapia, Oreochromis niloticus. To obtain hyperthyroid tilapia, fish were injected with porcine follicle stimulating hormone (pFSH) 36 hours before sampling or fed on demand for 11 days with tilapia pellets containing 12 ppm T3. Tilapias were made hypothyroid by providing them food containing 0.2% methimazole for 11 days. Plasma T4 and T3 and the in vitro deiodinase activity in liver, kidney, brain and gill were measured at the end of the treatment period. Injection with pFSH caused an increase in plasma T4 but had no influence on plasma T3 levels. A small increase in plasma T3 was observed in T3-fed fish. Plasma levels of both T4 and T3 were decreased by methimazole treatment. We observed no changes in kidney type I deiodinase (D1), whereas liver type II deiodinase (D2) was increased during hypothyroidism and decreased during hyperthyroidism. Hypothyroidism resulted in a significant decrease in brain, gill and liver type III deiodinase (D3). An pFSH-induced increase in T4 stimulated brain and gill D3 but not liver D3, whereas the opposite was true in T3-fed fish. We conclude that the regulation of D1 and D3 in tilapia is probably different compared to mammals.  相似文献   

7.
Tissue T3 (3,5,3′-triiodo-L-thyronine) concentrations were measured in rainbow trout, Salmo gairdneri, after digestion by Pronase or collagenase and extraction with ethanolic ammonia (99:1, v/v) followed by 2N NH4OH and chloroform. Recoveries of [125I]T3 administered in vivo or in vitro were high and consistent and there was close parallelism between sample dilutions and the radioimmunoassay curve, but recoveries of unlabeled T3 administered in vitro were low and variable. Alternatively, trout were brought to isotopic equilibrium by [125I]T3 infusion for 96 h, the extracted [125I]T3 determined by gel filtration and the tissue T3 content calculated from the specific activity of plasma [125I]T3. By the latter method, tissue T3 concentrations were: intestine (4.2 ng/g), kidney (2.5), liver (2.8), stomach (1.5), heart (1.0), muscle (0.7), gill (0.6) and skin (0.3). Muscle (67% of body weight) comprised the largest tissue T3 pool (82% of all tissues examined). Seven days exposure of trout to water acidified with H2SO4 (pH 4.8) or acidified water containing aluminum (21.6 mM), decreased tissue T3 content generally and particularly in muscle (14% of controls). In conclusion, skeletal muscle is the largest T3 tissue pool and seems highly responsive to altered physiologic state.  相似文献   

8.
With the aim of comparing the effects of oral T3 and NaCl administration on trout hypoosmoregulatory mechanisms, three groups of rainbow trout (Oncorhynchus mykiss Walbaum) held in freshwater (FW) were fed a basal diet (C), the same diet containing 8.83 ppm of 3,5,3-triiodo-L-thyronine (T3) (T) or 10% (w/w) NaCl (N) respectively for 30 d. They were then transferred to brackish water (BW) for 22 d and fed on diet C. Gill (Na++K+)-ATPase activity and its dependence on ATP, Na+ and pH, number of gill chloride cells (CC), serum T3 level as well as fish growth, condition factor (K) and mortality were evaluated. During the FW phase, as compared to C trout, T trout showed a two fold higher serum T3 level, had unchanged gill (Na++K+)-ATPase activity and increased CC number, whereas N trout showed higher gill (Na++K+)-ATPase activity and CC number. At the end of the experiment the enzyme activity was in the order T>N>C groups and all groups showed similar CC number. Both treatments changed the enzyme activation kinetics by ATP and Na+. A transient increase in K value occurred in N group during the period of salt administration. In BW, T and N groups had higher and lower survival than C group respectively. Other parameters were unaffected by the treatments. This trial suggests that T3 administration promotes the development of hypoosmoregulatory mechanisms of trout but it leaves the (Na++K+)-ATPase activity unaltered till the transfer to a hyperosmotic environment.  相似文献   

9.
任春  文华  黄凤  蒋明  吴凡  刘伟  田娟  杨长庚  吴金平 《水产学报》2015,39(4):539-546
采用维生素B1(VB1)含量为0.08(对照组)、0.57、1.13、2.09、4.11和8.09 mg/kg的6种纯化饲料,分别饲养初始体质量为(64.4±1.5)g的吉富罗非鱼12周,研究VB1对其生长性能、部分血清生化指标、肝脏VB1蓄积量及转酮醇酶基因表达量的影响,以确定其对饲料VB1的需要量.结果显示,随着饲料中VB1含量增加,吉富罗非鱼增重率先呈线性增加后趋于稳定,当饲料中VB1含量为1.13、2.09、4.11、8.09 mg/kg时增重率达最大.吉富罗非鱼肝脏VB1含量随着饲料VB1含量增加不断增大,当增加到2.09 mg/kg后趋于稳定.饲料中缺乏VB1显著提高血清丙酮酸含量(P＜0.05),但对全鱼水分、粗脂肪、粗蛋白、灰分无显著性影响(P＞0.05).饲料中添加VB1显著提高血清高密度脂蛋白胆固醇和肝脏转酮醇酶基因表达量(P＜0.05).饲料中VB1含量大于1.13 mg/kg各组的肝脏转酮醇酶活性显著高于VB1含量小于0.57 mg/kg组(P＜0.05).折线回归分析表明,吉富罗非鱼(64 ～325 g)获得最佳生长时对饲料VB1需要量为1.16 mg/kg;肝脏VB1蓄积量达到最大时,对VB1的需要量为2.06mg/kg.  相似文献   

10.
The circadian patterns of several tissue and plasma metabolites, and several plasma hormone concentrations are described in rainbow trout (Oncorhynchus mykiss) that were held in groups under three different photoperiod regimes, and given free access to a demand-feeder. Regardless of photoperiod regime, all the measured parameters showed significant diel rhythms that appeared to be synchronized by dawn; dawn was represented by the concomitant onset of both light and feeding. The diel increases in hepatic glycogen content, and plasma T4 and cortisol concentrations were in phase with the main period of feeding activity, whereas the peaks in plasma T3 and glucose concentrations that may also be triggered by feeding activity, were delayed by several hours. The peaks in hepatosomatic index, plasma non-esterified fatty acids and plasma growth hormone concentrations were 180° out of phase with the main period of feeding activity, and associated with periods of hypophagia and low activity.  相似文献   

11.
The growth rate of farmed fish is an important factor regarding aquaculture success. An understanding of the cellular events that occur in skeletal muscle when fish undergo periods of fasting and refeeding provides information useful in developing alternative feeding strategies for improving muscle growth in commercially cultivated species. To evaluate the effect of 1–3 weeks of fasting and 10 weeks of refeeding in Nile tilapia juveniles, we analyzed the growth performance and changes in muscle cellularity and the expression of the following growth and muscle related genes: MyoD, myogenin, IGF-1, IGF-1 receptor, MuRF-1, atrogin-1 and myostatin. Reduced body mass was observed in all three groups of fasted fish during their time off feed, and 10 weeks of refeeding resulted in partial compensatory growth of body mass. No differences in the frequency of white muscle fiber diameters were observed between fasted and fed control fish treatments. However, changes in gene expression induced by fasting and refeeding were found. IGF-1 receptor, ubiquitin ligases MuRF1 and atrogin-1 expression increased during the 1–3 weeks of fasting, while IGF-1 levels dropped significantly (P < 0.001) compared to the control treatment. Furthermore, myogenin mRNA level in fish submitted to 3 weeks of fasting was higher in comparison to the control treatment (P < 0.05). Overall, our results showed that 1–3 weeks of fasting can induce muscle atrophy activation in Nile tilapia juveniles, and 10 weeks of refeeding is enough to induce only partial compensatory growth.  相似文献   

12.
Growth performance, carcass composition, liver and blood parameters ofscaled carp (C), Cyprinus carpio, and blue tilapia (T),Oreochromis aureus, reared for eight weeks in twomonoculture (100%C and 100%T) and two polyculture (60%C–40%T and40%C-60%T) conditions were investigated. In polyculture 40%C–60%T bothspecies achieved the highest levels of specific growth rate and the lowestlevels of food conversion ratio and carcass lipid content. In addition, theyexhibited the highest values of plasma pO2 and pH and the lowestvalues of plasma pCO2, cholesterol and albumin, although thedifferences among treatments were not significant in the case of tilapia.Tilapia showed significantly lower plasma Cl– levels than underthe other conditions. Carp in monoculture and tilapia in polyculture60%C–40%T had the lowest levels of specific growth rate and significantlyhigher levels of liver lipids and plasma triglycerides than in the other groups.In addition, carp in monoculture exhibited a significantly higher haematocritthan in polyculture. No significant variations among treatments were observedconcerning plasma cortisol, glucose, osmolality, Na+, K+,HCO3 – andHCO3 –/H2CO3 in either species.The combination of scaled carp and blue tilapia, in which blue tilapia were themain species, proved to be the best for both species. It was suggested thatgrowth and physiological changes under mono- and polyculture rearing, in anintensive system, seem to be as a result of a different state of stress relatedto fish behavior.  相似文献   

13.
Blood and ovarian samples were collected at intervals of 4h prior to spawning time from medaka (Oryzias latipes) that were maturationally synchronized with artificial photoperiod (14h light: 10h dark). Plasma estradiol-17β (E2) levels increased rapidly from 16h before spawning and peaked at 8h before spawning. Follicle-enclosed oocytes (ovarian follicles) at different stages of development were isolated from the ovaries and used to study the in vitro effects of thyroid hormone (triiodothyronine; T3) on pregnant mare serum gonadotropin (GTH)-induced E2 production. GTH at a concentration of 100 IU/ml stimulated E2 production by ovarian follicles collected between 32 and 16h before spawning. At 32h before spawning, T3 (5 ng/ml) administered along with GTH (100 IU/ml) resulted in a 3.5 fold increase in E2 production, compared with GTH administered alone. These results suggest that T3 can act on ovarian follicles directly to modulate GTH-stimulated E2 production in the medaka.  相似文献   

14.
The Antarctic notothenioid, Pagothenia bernacchii, were found to have plasma total and free calcium levels, plasma inorganic phosphate and whole body calcium efflux rates which were similar to those seen in other teleosts. But total bone calcium was lower than reported for other teleosts. A single injection of vitamin D3 (5 ng g–1 fish) increased plasma total and plasma free calcium and these increases were associated with an increase in whole body calcium efflux and bone calcification. Conversely, the same treatment with 1,25-(OH)2-D3 reduced plasma free calcium. This seco-steroid also increased the specific activity of 45Ca in bone at 40h post-injection but did not significantly effect total bone calcium, plasma total calcium or whole body calcium efflux. 25-OH-D3 at the same dose had no effect on any of the parameters tested and none of the seco-steroids tested had any effect on plasma total inorganic phosphate. These data show that both D3 and 1,25-(OH)3-D3 can have calcitropic effects in this marine teleost and that these two forms of vitamin D can exert different effects within the same species.  相似文献   

15.
The presence of outer ring deiodinating (ORD) and inner ring deiodinating (IRD) activities was investigated in different tissues of Oreochromis niloticus (Nile tilapia), Clarias gariepinus (African catfish), Oncorhynchus mykiss (rainbow trout) and halmus maximus (turbot). High-Km rT3 ORD is present in the kidney of most of the fishes studied, except in catfish. In turbot, besides the kidney, rT3 ORD is also present in liver, heart and ovary. Low-Km T4 ORD is found in the liver and low-Km T3 IR the brain of all the fishes studied. In addition, low levels of low-Km T3 IRD were demonstrated in gill and skin of Nile tilapia, liver of rainbow trout and gill and kidney of turbot. For the different teleosts, the biochemical properties of the different rT3-deiodinating enzymes mentioned, T4 ORD in liver and T3 IRD in brain and tilapia gill were compared to those of the deiodinases formerly characterized in Oreochromis aureus (blue tilapia). In general, the different deiodinases demonstrate analogous sensitivities to iodothyronines and inhibitors, although minor differences occur. The various deiodinating enzymes all depend on addition of dithiothreitol and demonstrate maximal activity pH between 6.5 and 7. The optimal incubation temperature of rT3 ORD and T4 ORD in tilapia and catfish is 37 °C, in trout and turbot it varies, depending on the tissue, between 25 ° and 37 °C. For the different T3 IRD activities the optimal temperature is 37 °C in warmwater as well as in coldwater species. The apparent Km values for rT3 ORD lay in the M range, for T4 ORD and T3 IRD they lay in the nM range. Vmax values are usually higher in tilapia as compared to the other teleosts studied. Based on the similarities in susceptibility to inhibition by different iodothyronines and inhibitors and the agreement of the apparent Km values, we conclude that the deiodinating enzymes in teleosts are more similar to mammalian deiodinases than is generally accepted.  相似文献   

16.
Fish in a population of Pagothenia borchgrevinki in McMurdo Sound, Antarctica, are affected by a gill disease (X-cell disease) which causes tissue hyperplasia that results in a decreased gill surface area and an increased water/blood diffusion distance. P. borchgrevinki acquires 95% of its oxygen via the gills, but damage to the gills by X-cell disease did not affect this function. There was no compensatory shift to cutaneous respiration. X-cell disease reduced the ability for oxygen uptake at low ambient PO 2 and the decreased uptake was related to the extent of the disease. O 2 max was greatly reduced in X-cell affected fish and substantially reduced their aerobic potential. This effect may impair the ability of diseased fish to catch prey and avoid predators.  相似文献   

17.
黏膜及其表面的共生菌群是鱼类抵御外界不利环境的第一道屏障。为探索养殖罗非鱼表皮和鳃黏膜共生菌菌群的结构特征是否与其健康状况间存在相关关系,本研究运用高通量测序技术,以无乳链球菌腹腔注射攻毒48 h后存活和濒死尼罗罗非鱼为检测对象,检测攻毒前后罗非鱼表皮和鳃黏膜共生菌群落结构差异。结果显示,健康尼罗罗非鱼表皮和鳃黏膜共生菌均存在优势菌群,主要为特吕珀菌属、硫杆菌属、弓形杆菌属、海单胞菌属和弧菌属。人工感染无乳链球菌后存活尼罗罗非鱼表皮和鳃黏膜共生菌菌群与感染前无显著差异;与存活组相比,濒死尼罗罗非鱼的表皮和鳃黏膜共生菌菌群多样性下降,其中弓形杆菌属、假交替单胞菌属、海单胞菌属、假单胞菌属和弧菌属等含量显著下降,链球菌属含量占总菌群的55.30%±1.24%,表明养殖尼罗罗非鱼表皮和鳃黏膜共生菌群落结构可能与其健康状况相关。  相似文献   

18.
旨在研究异齿裂腹鱼(Schizothorax o’connori)缩胆囊素(cholecystokinin, CCK)基因的摄食功能。本研究克隆得到了异齿裂腹鱼CCK基因的cDNA全长,通过生物信息学分析发现其属于CCK-1亚型。异齿裂腹鱼CCK的cDNA全长为773bp,其中开放阅读框(ORF)为372bp,可以编码123个氨基酸。异齿裂腹鱼CCK由1个信号肽和1个典型的CCK-8肽保守结构域组成,为亲水性蛋白,但没有跨膜结构。运用实时荧光定量PCR(Real-timePCR)检测异齿裂腹鱼CCK基因在组织中的分布情况,以及餐前餐后和禁食复喂对其表达量的影响。结果表明,异齿裂腹鱼CCK在各组织中均有表达,其中在脑中表达量最高,在肠道、心脏、肝、脾、肾、皮肤、鳃、眼和鳔中表达量相对较高,在肌肉中表达量最低。餐后CCK基因的表达量显著升高,禁食使异齿裂腹鱼CCK基因的表达量显著下降,而复喂使CCK基因的表达量显著上升,表明CCK基因既是异齿裂腹鱼的餐后饱感信号因子,又是长期调控摄食因子。本研究为异齿裂腹鱼的人工饲养和品种保护等提供了理论依据。  相似文献   

19.
A major problem in tilapia aquaculture is the frequent reproduction of female fish, leading to increased competition for supplemented food and stunted somatic growth. The feasibility of using photoperiod manipulation to arrest the reproductive performance of tilapia Oreochromis niloticus was therefore examined. Newly hatched O. niloticus were reared in the laboratory under 12L:12D photoperiod at 28 °C. Fish (230–340 g) were maintained under 6L:6D, 12L:12D and 14L:10D photoperiod at 28 °C during the course of this study. Effect of photoperiod manipulation on reproductive parameters of fecundity, gamete quality, offspring viability and overall reproductive success were evaluated. Steroid levels (estradiol-17β, E2; testosterone, T) during the spawning cycles of fish were analyzed on days 1 and 3 postspawning and at 3-day intervals thereafter. A total of 72 female fish from each photoperiod treatment were investigated the changing pattern of E2, T and GSI with fish that have spawned once, twice and three times. Fish exposed to 12L:12D and 14L:10D photoperiod spawned successfully throughout the study. Whereas the spawning of fish exposed to 6L:6D photoperiod was arrested after three to four spawning cycles. The arrestment of spawning in fish exposed to 6L:6D photoperiod was paralleled by a significant decrease in plasma levels of E2 (P<0.05). By contrast, there was no major difference in T levels among the treatments. These findings suggest that photoperiod manipulation can be used to arrest the spawning in tilapia O. niloticus. The utility of this in controlling the problem of overcrowding due to excess offspring in tilapia aquaculture is applicable.  相似文献   

20.
We evaluated growth performance and metabolic responses in Nile tilapia (Oreochromic niloticus) juveniles (30.2 ± 0.9 g) subjected to 1 (F1), 2 (F2), or 3 weeks (F3) of fasting and then refed for 10 weeks (10WR) compared to controls (FC), which were fed for the full 13-week trial. Weight gain and specific growth rate (SGR) during fasting were lower in all treatments compared to the FC. However, during refeeding, feed intake/body mass and SGR increased in F1, F2, and F3, inducing partial compensatory growth. The hepatosomatic index (HSI), visceral fat index (VFI), liver glycogen (LG), and carcass lipid levels dropped in all fasted fish compared to FC (P < 0.05), showing a depletion of stored nutrients such as fat and LG. Along with LG, fat reserves were mobilized during fasting to maintain basal metabolism and survival, but these energy constituents returned to control levels at 10WR, at which time HSI was higher in all refed fish compared to FC. Additionally, the variables VFI, LG, and lipid in carcass increased in all refed fish, equaling those of FC at 10WR. The results showed that, in contrast with other protocols that used smaller tilapia juveniles, the feeding strategies utilized for Nile tilapia juveniles in this study (1 to 3 weeks of fasting and 10WR) were able to induce only partial compensatory growth. It can be concluded that in situations that require complete food restriction in juvenile Nile tilapia (30 g), an acceptable strategy is to limit the period of fasting to 1 week or less to minimize losses and to achieve partial compensatory growth.  相似文献   

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