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1.
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   

2.
Diel rhythms in serum glucose, lactate, cholesterol, triglycerides and thyroid hormones were studied in red porgy, Pagrus pagrus, held under different photoperiod regimes (constant darkness – DD, 8L:16D,12L:12D), at a constant temperature (17.1–18.7 °C) and fed with commercial pellets, by means of a self-feeder. A clear diurnal rhythm in feeding activity, regardless of the photoperiod regime was demonstrated. All serum components showed significant diel rhythms, although they were not necessarily consistent or circadian in periodicity. As well as this, differences in the average values among the varying treatments were observed. Fish held under the 12L:12D protocol displayed significantly higher average T4, T3 and lactate levels during the day rather than at night. Maximum glucose values occurred 8–12 h after dawn and maximum lactate concentrations at 06:00 or 14:00 h. Diel variations in cholesterol were evident only in the DD group with peak values inversely correlated with the rhythm of food intake. Triglycerides displayed a similar pattern of changes. Significant diel fluctuations in T4 serum levels were observed only in fish exposed to the 12L:12D protocol, with peak values at dawn. A clear diurnal peak (10:00 h) in T3 concentrations was observed in fish subjected to the 12L:12D regime, while fish exposed to the 8L:16D protocol showed two peaks: one in the photophase (10:00 h) and another in the scotophase (02:00 h). The light–dark alternation and the general activity rhythm of fish seem to be the main synchronizers of the diel rhythms observed in this study.  相似文献   

3.
Fasting and refeeding have considerable effects on thyroid hormone metabolism. In tilapia (Oreochromis niloticus), fasting results in lower plasma T3 and T4 concentrations when compared to the ad libitum fed animals. This is accompanied by a decrease in hepatic type II (D2) and in brain and gill type III (D3) activity. No changes in kidney type I (D1) activity are observed. Refeeding results in a rapid restoration of plasma T4 values but not of plasma T3. Plasma T3 remains low for two days of refeeding before increasing to normal levels. Liver D2 and gill D3 also do not increase until two days after refeeding. Brain D3, on the other hand, rises immediately upon refeeding. These results suggest that the change in hepatic D2 activity is one of the main factors responsible for the changes in plasma T3 observed during starvation and refeeding in tilapia. This finding supports the hypothesis that, in contrast to mammals and birds, liver D2 is the primary source of plasma T3 in fish. Although the deiodinases important for the gross regulation of plasma T3 during fasting/refeeding differ (mammals: D1 and D3, birds: D3, fish: D2), they all occur in the liver, suggesting that the organ itself may play a crucial role. In addition, the changes in brain and gill D3 suggest that these enzymes constitute a fine tuning mechanism for regulation of T3 availability at the cellular or plasma levels, respectively.  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 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   

6.
The study examined the combined effects of time of feeding (post-dawn, midday-pre-dusk) and ration level (1.5%, 2.0%, 2.5%) on the diurnal rhythms of plasma growth hormone (GH), L-thyroxine (T4), triiodo-L-thyronine (T3), cortisol and glucose concentrations in rainbow trout (Oncorhynchus mykiss) maintained under constant ambient water temperature and natural photoperiod.Plasma GH and glucose concentrations exhibited marked diurnal rhythms, with significant postprandial peaks that were phase-shifted with time of feeding. The ration level did not appear to alter these feeding time-entrained rhythms, but the amplitude of the changes (peaks) were more pronounced in trout fed the higher ration levels. Plasma cortisol concentrations showed distinct diurnal rhythms, with peaks during the photophase and the scotophase in all the treatment groups. The time of feeding did not appear to influence these rhythms, and there was no evidence of a postprandial increase in any group.Plasma GH, cortisol and glucose concentrations were significantly higher in groups fed the 2.5% ration compared with animals fed either 1.5 or 2.0% rations.The diurnal rhythms of plasma T4 concentrations were not affected by the time of feeding or ration level; the peak values generally occurred during the photophase in all the treatment groups. Plasma T3 concentrations did not show any significant diurnal patterns, nor were they influenced by ration levels or time of feeding.To whom correspondence should be addressed  相似文献   

7.
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   

8.
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   

9.
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   

10.
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   

11.
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   

12.
Serum thyroid hormone concentrations were measured during the seven stages of metamorphosis (1–7) of the southern hemisphere lamprey, Geotria australis. The respective mean concentrations ± SEM of serum thyroxine (T4) and triiodothyronine (T3) fell from 31.73 ± 4.09 and 5.06 ± 0.70 nM in large ammocoetes sampled in February, at the time when metamorphosis was initiated, to 4.54 ± 0.36 and 1.03 ± 0.12 nM at stage 5. Although there was a small, but significant, recovery of serum T4 concentrations during stages 6 and 7, no such corresponding statistically significant rise occurred in serum T3 concentrations. Serum thyroid hormone concentrations in ammocoetes sampled during the period when metamorphosis was taking place, exhibited a marked seasonal increase between February and May–June (late autumn/early winter); serum T3 and T4 concentrations peaked in May–June and were, respectively, > 2 fold and > 8 fold higher than those recorded for samples in late February (mid summer). By mid-July the serum T4 and T3 levels had declined from the peak values. Ammocoetes taken from streams at 16°C in June and acclimated to aquaria water at 25°C or 6°C had significantly lower serum T3 and T4 concentrations at the higher temperature, and also a lower serum T4, but not T3 concentration, at the lower temperature. Treatment of separate groups of ammocoetes with either propylthiouracil or T3 for 70 days significantly depressed and raised respectively, the serum thyroid hormone and hepatic T3 concentrations and caused significant changes in the body weight, but did not induce the onset of metamorphosis.  相似文献   

13.
Studies were conducted to explore the effect of cohort sampling and stocking density on the interactions between plasma growth hormone (GH), thyroid hormone and cortisol concentrations in rainbow trout. Depending on the experimental design, plasma GH concentrations were either suppressed, or elevated by sequential removal of cohorts from the holding aquarium. Since plasma cortisol concentrations consistently increased during cohort sampling, regardless of experimental design, it would appear that the apparent correlation (direct or inverse) is the result of concomitant changes, i.e. not necessarily a cause-effect relationship. Plasma GH concentrations of rainbow trout were not correlated with eviscerated body weight.Trout stocked at 150 kg m–3 exhibited a significantly lower mean growth rate, hepatosomatic index, hepatic lipid reserve, plasma triiodo-l-thyronine (T3) concentration andin vitro hepatic T3 production than trout stocked at 60 kg m–3. These observations are consistent with the former group being food deprived or ration restricted. Stocking density appeared to have no effect on plasma GH or cortisol concentrations, or on the pituitary-interrenal axis response to stressor challenge, or the thyroid tissue response to exogenous TSH challenge.  相似文献   

14.
The present study was performed to assess to what degree supplemented dietary iodine (I) was retained in selected tissues, including the fillet of adult Atlantic salmon (Salmo salar) reared in sea water. Atlantic salmon weighing approximately 1.5 kg were randomly assigned to three net pens per treatment and fed moist pellets (based on minced saithe and herring) supplemented with 0, 40 or 80 mg iodine (as KI) kg?1 on dry weight basis for 150 days. The iodine concentrations in the experimental feeds were analysed to be 10, 54 and 86 mg kg?1 dry weight, respectively. Growth, mortality and blood haemoglobin concentration (Hb) were recorded. Iodine concentrations were measured in muscle, liver and kidney after 90 and 150 days of feeding by inductively coupled plasma‐mass spectrometry. In addition, plasma thyroxine (T4) and triiodo‐thyronine (T3) were determined. The weight gain during the period was approximately 1 kg for all treatments. There were no mortalities, and blood Hb levels were within normal ranges. The iodine concentration in muscle, liver and kidney were all affected by the dietary iodine level, despite wide intratreatment variation. After 150 days, fillets of fish fed 10, 54 and 86 mg I kg?1 showed mean concentrations of 0.4, 0.5 and 0.9 mg I kg?1 wet weight, respectively, whereas the iodine concentration in the liver and the kidney increased approximately three times in the dietary groups. Similarly, plasma T4 and T3 showed great variation within the treatments. No significant correlations were found between individual tissue iodine concentration and thyroid hormone concentration in any of the groups at any sampling time. This preliminary feeding experiment showed that fillet iodine in adult Atlantic salmon can be increased up to 1.4 mg I kg?1 wet weight by dietary iodine 80 times the minimum requirement for salmonids, without impacting health, performance or plasma thyroid hormone status.  相似文献   

15.
The self-feeding pattern of yellowtail, Seriola quinqueradiata, maintained in floating net cages was examined throughout a year, and the influence of seasonal changes of the photoperiod and water temperature on the feeding pattern was investigated. Two groups of 50 yellowtail (initial mean body weight about 50 and 80 g, respectively) were kept in two experimental net cages (2×3×4 m deep), with a self-feeding device installed on each. It was possible to maintain yellowtail in net cages using a self-feeder throughout almost a year. The number of daily food demands was greatly affected by the seasonal changes in water temperature. Yellowtail showed high self-feeding activity, above 18 °C; depressing water temperatures did not influence the activity when the water temperature was over 18 °C. However, the activity decreased when the water temperature fell below 18 °C. The feeding pattern in a 24-h period was greatly affected by the temporal changes in light intensity. Annual observations revealed that yellowtail showed generally crepuscular plus nocturnal feeding behavior and had two peaks of feeding activity a day. These peaks appeared at dawn and dusk; moreover, a clear association between the most active time of self-feeding and the period of the greatest change in light intensity was observed. The results suggest that a change in light intensity might stimulate the appetite of yellowtail or that there is a light level at which yellowtail prefer to eat.  相似文献   

16.
In the present investigation, significant annual/seasonal variations were noticed in plasma and pituitary gonadotropin (GTH) which were correlated with gonado-somatic index, plasma estradiol-17β, and nuclear E2 receptor (NE2R) in the pituitary, hypothalamus and telencephalon. The NE2R concentrations and dissociation constant (k d) values showed significant seasonal variations with high values in the late preparatory phase and low values in the postspawning phase. The NE2R levels were the highest in the pituitary, followed by the hypothalamus and telencephalon in all the seasons. In the prespawning phase, ovariectomy (OVX) elicited a strong negative feedback on GTH secretion with a bimodal pattern of release and elevated the NE2R levels and k d values, without producing any significant change in the resting phase suggesting that E2 appears to exert differential feedbacks on GTH secretion.  相似文献   

17.
《Fisheries Research》1987,5(1):91-97
The diel patterns in catch rate and, by inference, activity of eight deep-water crustacean species have been assessed by repeated trawling at a location with a depth of 430 m on the continental slope of northwest Australia. The patterns of catch rate identified show that, despite the depth, one highly valued commercial species, Metanephrops australiensis, had peaks of catchability near dusk and dawn. In general, male M. australiensis of all sizes displayed similar diel patterns in catch rate, while the females were more variable. Four species, including Metanephrops andamanicus, showed no detectable diel changes in catch rate. Two caridean shrimps and a penaeid prawn were caught in greater numbers during daylight hours, which suggests a substantial nocturnal vertical migration.  相似文献   

18.
A 7‐week study was conducted to investigate the effect of different fasting and re‐feeding regimes on compensatory growth and some physiological parameters of juvenile Siberian sturgeon (Acipenser baerii). Fish (46.5 ± 0.5 g) were fed on a diet (containing 450 g/kg crude protein and 20 MJ/kg digestible energy) according to four feeding regimes in triplicate including: control group (C, fed everyday), W1 (2 weeks of feeding followed by 1 week of fasting and 4 weeks of re‐feeding), W2 (1 week of feeding followed by 2 weeks of fasting and 4 weeks of re‐feeding) and W3 (3 weeks of fasting followed by 4 weeks of re‐feeding). The fasted groups including W1 (119.6 ± 2.1 g), W2 (118.0 ± 1.7 g) and W3 (108.5 ± 4.8) significantly lost their weights during fasting phase and did not attain the final weight of the C (137.3 ± 1.7 g) after re‐feeding phase. The re‐feeding phase increased the specific growth rate in the fasted groups compared to the C (p < .05). After the fasting phase, concentrations of T3, T4, glucose, total protein and triglyceride in plasma of fasted groups were decreased, but levels of total cholesterol, aspartate aminotransferase, alkaline phosphatase and lactate dehydrogenase increased compared to the C. After re‐feeding phase, except for glucose level, all mentioned metabolites were restored in the plasma of W1 group, but total protein level and aspartate aminotransferase concentrations in plasma were not restored in W2 and W3 groups. Overall, our finding demonstrated 4 weeks of re‐feeding was too short to induce full compensatory growth in A. baerii juveniles.  相似文献   

19.
A cDNA encoding the subunit of thyrotropin (TSH) was isolated from a goldfish (Carassius auratus) pituitary gland cDNA library. By comparing the sequence with other teleost TSHs, a signal peptide of 19 amino acids and a mature hormone of 131 amino acids were predicted for goldfish TSH subunits. The resulting putative mature hormone of 131 amino acids had well-conserved cysteine positions and a putative N-linked glycosylation site; homology was 51–67% with TSHs from other teleosts, 38–43% with tetrapod TSHs, but only 27 and 29% with goldfish GTH-I and -II, respectively. We also examined the effects of thyroid hormones (TH) and thiourea (TU, an inhibitor of TH production) treatments on TSH and GTH subunit gene expressions in the goldfish pituitary gland. After thyroxine (T4) treatment, circulating T4 concentration increased and TSH mRNA level decreased. Supressing the amount of circulating T4 and triiodothyronine (T3) by TU treatment increased the TSH mRNA level. Moreover, T4 replacement therapy (simultaneous treatment of both TU and T4) caused a high level of circulating T4 and a low level of circulating T3, and a decrease in the TSH mRNA level. Thus, changing levels of circulating TH exert a negative feedback on the level of TSH subunit mRNA in goldfish in vivo. On the other hand, GTH subunit mRNA levels were not affected by changes in the levels of circulating TH.  相似文献   

20.
The diel changes in plasma AVT, IT and Mel in rainbow trout (Oncorhynchus mykiss) were studied to assess potential relationships. Blood was sampled at 05:00, 11:00, 16:00, 22:30 and 05:00 in freshwater-adapted fish and at 22:30 in brackish water-adapted fish maintained under natural photoperiod. A few of the FW-acclimated fish were assigned to one of two experimental groups and adapted to DD or LL lighting regimes. Blood samples were taken at 11:00 and 22:30. Hormones were extracted from plasma by solid phase extraction and determined by high-performance liquid chromatography. Marked diel variations in AVT and Mel were detected in fish maintained under natural photoperiod. Plasma AVT (fmol ml–1) increased during the light to reach the maximal level at the end of that phase (261.7±23.1). Thereafter, AVT concentration decreased and became minimal at 05:00 (68.9±11.5) 3 h before the sunrise. Plasma Mel (pmol ml–1) increased between 16:00 and 22:30 when a peak value was reached (1204.0±55.5). Thereafter, Mel levels decreased and were minimal after the onset of the light phase (242.8±37.0). IT levels displayed no significant diel changes. Linear regression analysis indicated the negative correlation between plasma Mel and AVT for five collecting times of the daily 24 h cycle in freshwater fish and at 22:30 in brackish water fish. A similar correlation occurred at 11:00 in the DD group and at 22:30 in the LL group. To elucidate the character of the Mel-AVT relationships further studies are required.  相似文献   

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