首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
The yeast Saccharomyces cerevisiae is one of the commonest probiotics incorporated in aquafeeds. An 84-day feeding trial was conducted to evaluate the effects of varying dietary inclusions of S. cerevisiae, 0% (control), 3% (YF3), 5% (YF5), and 7% (YF7), on growth, stress tolerance, and disease resistance in juvenile (body mass ~?21 g) Nile tilapia (Oreochromis niloticus). Fish were randomly distributed in groups of 20 into 12 1-m3 hapas and fed isoenergetic (~?17 kJ g?1 gross energy) and isonitrogenous (~?300 g kg?1 crude protein) diets at 3% of their bulk weight daily. Specific growth rates were significantly higher for the yeast-fed fish (0.77–0.78% day?1) than for the control fish (0.60% day?1) and resulted in significantly higher mean final weights for the yeast-treated groups. Protein and lipid retention efficiencies were also significantly higher in the yeast-fed fish than in the control group. In subsequent stress challenge trials, the yeast-fed fish had greater tolerance to acute heat as well as hypoxia exposure than the control fish. Survival rates of the yeast-treated groups following sudden exposure to elevated water temperature (40 °C) ranged from 82.5 to 100% compared to 15% for the control. Mean survival rates following a 24-h hypoxia exposure were also generally significantly higher for the yeast-fed fish. The probiotic groups recorded a relative percent survival (RPS) of 75% after a 14-day Aeromonas hydrophila infection challenge. The results of this study indicate that S. cerevisiae as an additive in Nile tilapia diets has beneficial impacts on growth, stress tolerance, and disease resistance.  相似文献   

2.
Flounder metamorphosis: its regulation by various hormones   总被引：1，自引：0，他引：1  
Metamorphosis in the flounder has often been compared with the transition of tadpoles into frogs. The dorsal fin rays of the Japanese flounder (Paralichthys olivaceus) elongate during prometamorphosis when thyroid hormone levels are low, and are resorbed during metamorphic climax when thyroid hormone levels are high. Using an in vitro system for the culture of the flounder fin rays, we have examined how various hormones affect the resorption process. Both thyroxine (T4) and triiodothyronine (T3) directly stimulated fin ray shortening, T3 being more potent than T4. Other hormones, such as prolactin, cortisol and sex steroids, did not directly affect the resorption process but modified the tissue's response to thyroid hormones. Similar observations were obtained from in vivo studies. We also monitored the changes in the whole body concentrations of various hormones during early development and metamorphosis, and related these with the thyroid hormone profiles in order to get a better picture of their interactions. The gaps in the present status of research on the role of thyroid hormones during metamorphosis in the Japanese flounder are also discussed.  相似文献   

3.
Fan  Wenqiao  Huang  Mengjun  Xu  Jingming  Zhang  Meixia  Jiang  Yusong  Cai  Mingcheng  Sun  Hanchang  Li  Xiaoying 《Aquaculture International》2021,29(3):925-939
  相似文献   

4.
Water salinity affects survival, growth and metamorphosis of anuran tadpoles. Hoplobatrachus rugulosus is considered not only as a freshwater amphibian but is also found in brackish wetlands. However, whether salinity change interferes with hatching, survival, body mass and development of H. rugulosus tadpoles is unknown. We found that salinity levels of <4‰ did not affect of survival or hatching of H. rugulosus eggs. At an early larval stage, tadpoles could tolerate up to 9‰ salinity for 96 h; however, body water content decreased when salinity was >5‰. After a 3‐week experiment, body weights of tadpoles exposed to 2‰ and 4‰ salinities were higher but that of the 6‰ group was lower compared with the 0‰ group. More than 90% of tadpoles exposed to 2‰ and 4‰ salinity showed complete metamorphosis. Salinity levels <4‰ promoted survival of tadpoles better than 0‰, whereas none of tadpoles in the 6‰ group became juvenile frogs in 50 days. Time taken to reach metamorphosis was shorter for 2‰ and 4‰ (47.22 ± 0.28 and 47.26 ± 0.33 days, respectively) than for 0‰ (49.31 ± 0.35 days). Juvenile frogs in the 2‰ group had greater body weight than the control. It could be concluded that salinity of <4‰ increased survival and body weight of H. rugulosus tadpoles, and shortened the time taken to reach metamorphosis.  相似文献   

5.
The effects of a range of different sublethal salinities were assessed on physiological processes and growth performance in the freshwater ‘tra’ catfish (Pangasianodon hypophthalmus) juveniles over an 8-week experiment. Fish were distributed randomly among 6 salinity treatments [2, 6, 10, 14 and 18 g/L of salinity and a control (0 g/L)] with a subsequent 13-day period of acclimation. Low salinity conditions from 2 to 10 g/L provided optimal conditions with high survival and good growth performance, while 0 g/L and salinities >14 g/L gave poorer survival rates (p < 0.05). Salinity levels from freshwater to 10 g/L did not have any negative effects on fish weight gain, daily weight gain, or specific growth rate. Food conversion ratio, however, was lowest in the control treatment (p < 0.05) and highest at the maximum salinities tested (18 g/L treatment). Cortisol levels were elevated in the 14 and 18 g/L treatments after 6 h and reached a peak after 24-h exposure, and this also led to increases in plasma glucose concentration. After 14 days, surviving fish in all treatments appeared to have acclimated to their respective conditions with cortisol levels remaining under 5 ng/mL with glucose concentrations stable. Tra catfish do not appear to be efficient osmoregulators when salinity levels exceed 10 g/L, and at raised salinity levels, growth performance is compromised. In general, results of this study confirm that providing culture environments in the Mekong River Basin do not exceed 10 g/L salinity and that cultured tra catfish can continue to perform well.  相似文献   

6.
Total dissolved gas (TDG) supersaturation generated in the river may result in gas bubble disease to Chinese sucker (Myxocyprinus asiaticus Bleeker) and cause their mortality. To assess the effects of TDG supersaturation on Chinese suckers in laboratory, juvenile fish were exposed to different levels of TDG supersaturated water. All of the fish died when the TDG saturation reached and exceeded 125%, but none died at TDG of 120% saturation in 96 h. To evaluate the effects of intermittent exposure of TDG supersaturation, Chinese suckers were exposed to TDG of 130% for a specific duration and then provided a recovery period at 100% saturation. The results showed that some remission is possible for intermittent exposure. Because of the characteristics of natural rivers, experiments exploring the TDG supersaturation detection and avoidance abilities of Chinese suckers were conducted and demonstrated the fish can avoid TDG supersaturation in both the horizontal and vertical directions when higher TDG levels were available. The results indicate the tolerance threshold of juvenile Chinese suckers is a TDG level of 120% saturation.  相似文献   

7.
Water salinity has effects on growth and metamorphosis of anuran species, including Hoplobatrachus rugulosus. Previously, we reported that cultured H. rugulosus tadpoles at low salinities (2–4‰) were of bigger size and grew faster than those in fresh water (FW). However, at a higher salinity level of 6‰, their sizes were reduced and the metamorphosis was delayed. It was therefore hypothesized that high salinity‐induced osmotic stress affected secretion of prolactin (PRL), which acts as osmoregulatory hormone and a regulator of metamorphosis in amphibians. In this study, transferring tadpoles into 4‰ and 6‰ brackish water increased the PRL levels by ~1.2‐ and ~twofold, respectively, as compared to FW group. These osmotic challenges also increased the total body fluid osmolality and levels of Na+, Cl? and Ca2+. The contents of triiodothyronine (T3) were significantly reduced in 4‰ and 6‰ groups, but not 2‰ group. Three sizes (49, 29 and 23 kDa) of H. rugulosus PRL receptors (PRLRs) were detected, and their protein expression was found in the skin, gill, tail fin, brain, intestine, heart, liver and kidney. The expression of PRLR‐49k protein was significantly higher in both skin and gills in 2–4‰ groups, whereas that of PRLR‐29k and PRLR‐23k were higher in gills and lower in skin of the 6‰ group than FW group. In conclusion, salinity challenge, particularly 4‰ and 6‰, increased the levels of PRL, while decreasing the T3 levels, which could explain why salinity markedly modulated growth, metamorphosis and survival of tadpoles.  相似文献   

8.
Aloes are now considered a very interesting source of bioactive compounds among which phytosterols should play a major role. The present study is an attempt to investigate the hypocholesterolemic activity of Aloe vera associated with its impact on the reproductive status of juvenile goldfish. Therefore, the short- and long-term effects of feeding supplementary diet containing aloe components (20 mg aloe/g diet; 2 %) on plasma lipids, plasma vitellogenin, and hepatic estrogen receptor α/β1 mRNA levels in goldfish were examined. Results of GC–MS for phytosterols show high abundance of β-sitosterol in freeze-dried powder of Aloe vera whole leaves. Moreover, a 2 % aloe powder dietary supplement was not found estrogenic in juvenile goldfish after either 7- or 30-day treatment, but was consistent in plasma hypocholesterolemic effects following long-term exposure. The present data further support that plasma cholesterol modulation induced by phytosterols may not be related to estrogen-like activity.  相似文献   

9.
Gas bubble disease and improper inflation of swim bladders in larval striped bass Morone saxatilis have been recently related in laboratory studies to very low levels of gas supersaturation. In other species, kills resulting from gas supersaturation have been reported in natural waters as large as Galveston Bay. We monitored warmwater ponds during spring to determine the extent of naturally occurring gas supersaturation and compared these levels with levels of gas saturation in ponds equipped with airlift pumps. Total gas pressure averaged 110% in the morning at the surface of non-aerated ponds and in the afternoon in ponds with airlift pumps. At other times of the day total gas pressure averaged 106–107% at the surface and bottom, morning and afternoon, in both aerated and non-aerated ponds. No evidence of gas bubble disease was found in 15-day-old striped bass fry cultured for 42 days in either aerated or non-aerated ponds.  相似文献   

10.
An investigation was conducted under laboratory conditions to analyse the mechanisms of prey capture by tadpoles, Bufo regularis Reuss, and to determine the minimum size at which the predation pressure by tadpoles on the larvae of African catfish, Heterobranchus longifilis Val., becomes insignificant. It was observed that the tadpoles fed on the larvae by suction without any specific capture strategies regardless of their sizes. The predation pressure was very high (100% mortality) during yolk-sac absorption and reduced gradually as the larvae increased in size. Based on these results, it was suggested to transfer the fry into nursing ponds only when they have reached a size greater than 10 mm TL (5–7 days) so as to avoid their predation during the primary nursing phase.  相似文献   

11.
This study evaluated the effects of short-term exposure to sublethal levels of nitrite on oxidative stress parameters and histology of juvenile Brazilian flounder Paralichthys orbignyanus. An assessment of fish recovery was also performed. Fish were exposed to 0.08 (control), 5.72, 10.43, and 15.27 NO2-N mg L?1 for 10 days followed by the same recovery time. Gill, liver, and muscle samples were collected after 1, 5, and 10 days of exposure and after recovery for the measurement of antioxidant capacity against peroxyl radicals (ACAP), glutathione-S-transferase (GST) activity, content of non-protein (NPSH) and protein thiols (PSH), and lipid peroxidation levels by thiobarbituric acid-reactive substances (TBARS) content. Nitrite exposure induced alterations which compromised the overall antioxidant system (reduced ACAP and GST activity) and enhanced oxidative damage in lipids and proteins. Increases in GST activity and NPSH and PSH contents were also demonstrated. The recovery period allowed for resumption of basal levels for all (treatment 5.72 NO2-N mg L?1) or some of the evaluated parameters (other treatments). In conclusion, exposure to nitrite concentrations from 5.72 to 15.27 NO2-N mg L?1 induced oxidative stress and antioxidant responses in juvenile Brazilian flounder. The 10-day recovery period was sufficient for a complete resumption of basal physiological condition of fish exposed to concentrations of up to 5.72 NO2-N mg L?1.  相似文献   

12.
A comparison was made of growth performance in bullfrog Rana catesbeiana tadpoles and biogenic capacity in culture tanks with gravel, sand and hard bottoms. Stage 25 (Gosner) tadpoles from a single cohort were stocked in 1‐m2 fibreglass tanks at 50 m?2. Two treatments and a control were employed, with three replicates each: T1=tadpoles reared in tanks with 0.02 m deep layer of sterilized silica gravel (2360 μm particle size); T2=tadpoles reared in tanks with 0.02 m deep layer of sterilized beach sand (250 μm particle size); and C=a control treatment with tadpoles reared in tanks with no soft substrate (conventional method). Tadpoles were fed on a 40% protein, powdered specific bullfrog feed at 13% body weight day?1. Results for survival, timing to metamorphosis, specific growth rate and weight gain exhibited no statistical differences between treatments (P>0.05). However, tadpoles in T1 had an apparent overall better performance based on numerical indicators. Biotic colonization was also statistically similar (P>0.05) between treatments, showing an overall poor biogenic capacity for the tested substrates. Only three taxa, at low abundances, were recorded for phytoplankton and phytobenthos: cyanophiceae, chlorophyceae, and bacillariophyceae. Zooplankton was represented by two microinvertebrate groups, rotifera and protozoa. The statistical similarities between treatments may reflect that bullfrog tadpoles do not exploit naturally occurring aquatic biota when sufficient suspended artificial feed particles are present.  相似文献   

13.
A 60-day experiment was carried out to study the effect of sub-lethal concentration of cypermethrin (1/10th of LC50) exposure on haematological and biochemical parameters of the Indian major carp, Catla catla fingerlings. Under exposure, the total erythrocyte count, total leucocyte count, haemoglobin content and haematocrit were decreased. All the studied serum parameters viz. total serum protein, albumin, globulin contents and albumin–globulin ratio were significantly decreased in cypermethrin-exposed fishes. A marked increase was recorded in alanine aminotransferase and aspartate aminotransferase activities in liver, whereas lactate dehydrogenase activity of muscle and acetylcholine esterase activity in brain were inhibited in cypermethrin-exposed fish. The membrane transport enzymes (total adenosine triphosphatase, sodium–potassium adenosine triphosphatase and magnesium adenosine triphosphatase) activities were decreased significantly in the gills of C. catla exposed to sub-lethal concentration of cypermethrin. The present study indicates that sub-lethal exposure of C. catla fingerlings to cypermethrin alters the haematological and biochemical parameters.  相似文献   

14.
  • 1. Lineage‐specific communication systems may offer innovative ways of targeting control measures at invasive species.
  • 2. Recent work has identified such a scenario in invasive cane toads (Bufo marinus) in Australia: toad tadpoles flee from chemical cues derived from crushed conspecifics, and this ‘alarm pheromone’ reduces tadpole survival rates and reduces body size at metamorphosis.
  • 3. Before this method can be applied in the field, however, the signal's specificity needs to be tested against a wide range of Australian frog taxa, especially tropical species sympatric with cane toads. A signal that affected native frogs as well as toads clearly would be of little use for toad control.
  • 4. Laboratory studies on cane toads and nine native frog taxa from the wet–dry tropics of the Northern Territory (Cyclorana australis, C. longipes, Limnodynastes convexiusculus, Litoria caerulea, L. dahlii, L. nasuta, L. rothii, L. rubella, Opisthodon ornatus) show that toad tadpoles rarely react to chemical cues from crushed frog tadpoles, and that frog tadpoles rarely react to chemical cues from crushed toad tadpoles. Crushed toad tadpoles occasionally elicited low‐level attraction (to a potential food source) by frog tadpoles.
  • 5. Overall, frog tadpoles were less responsive to chemical cues (either from crushed conspecifics or crushed toads) than were toad tadpoles. The low level of cross‐lineage reactivity is encouraging for the feasibility of using cane toad alarm pheromones to control this invasive species in Australia; the risk of collateral damage to sympatric native frogs appears to be minimal. Copyright © 2009 John Wiley & Sons, Ltd.
  相似文献   

15.
There were not any past studies about metallothionein isoforms (smtB and mt2) having anti-oxidative functions on zebrafish after Cd2+ exposure. On the other hand, the anti-oxidative enzymatic factors such as superoxide dismutase (sod), glutathione peroxidase (gpx1a), and catalase (cat) are used as references to investigate whether the smtB and mt2 have anti-oxidative responses on the gills and brain of zebrafish after 1–6 h of 0 and 1.78 μM Cd2+ exposure. The anti-oxidative system such as sod, cat, and gpx1a mRNA expressions demonstrated a cascade response upon Cd2+-induced oxidative stress in the present study. Interestingly, the smtB mRNA expression levels increased by 3.2- to 6.1-fold, and mt2 raised by 4.1- to 11.3-fold in gills at 1 and 3 h after exposure to Cd2+, respectively. On the other hand, the smtB mRNA levels increased by 10.6- to 58.6-fold, but mt2 mRNA levels increased by 2.3- to 11.1-fold in brain at 1 and 3 h after exposure to Cd2+, respectively. In addition, both tissues showed increased apoptosis levels at 3 h, and recovery after 6 h of Cd2+ exposure. From the results, we suggest that both mt2 and smtB play a role in anti-oxidation responses within 6 h after exposure to Cd2+. In conclusion, the smtB mRNA levels have a higher response than mt2 in the brain, but both mRNA expressions appear to have a similar pattern in the gill. We suggest that smtB plays an important role to defend oxidative stress in the brain of adult zebrafish upon acute Cd2+ exposure.  相似文献   

16.
Metals can influence the gonadal steroidogenesis and endocrine systems of fish, thereby affecting their reproduction. The effects of aluminum and manganese in acidic water were investigated on steroidogenesis in sexually mature male Astyanax altiparanae. Whether mature male fish recover from the effects of metals in metal-free water was also assessed. The fish were exposed to 0.5 mg L?1 of isolated or combined aluminum and manganese in acidic pH (5.5) to keep the metals bioavailable. The fish underwent 96 h of acute exposure, and samples were taken 24 and 96 h after the beginning of the experiment. The fish were then maintained in metal-free water for 96 h. Plasma levels of testosterone, 11-ketotestosterone, 17β-estradiol, and cortisol were measured. Acidic water increased the plasma concentration of testosterone and 11-ketotestosterone. Aluminum increased the testosterone levels after 96 h of exposure. Manganese increased the 17β-estradiol levels after 24 h of exposure and maintained at high levels until the end of the experiment. With the exception of acidic pH, which increased cortisol levels after 24 h of exposure, no changes were observed in this corticosteroid during the acute experiment. Aluminum and manganese together also altered steroid levels but without a standard variation. The fish recovered from the effects of most exposure conditions after 96 h in metal-free water. A. altiparanae could use reproductive tactics to trigger changes in testicular steroidogenesis by accelerating spermatogenesis and spermiogenesis, which may interfere with their reproductive dynamics.  相似文献   

17.
A 60-day feeding trial was conducted to study the effect of dietary microbial levan on growth performance and metabolic responses of Cyprinus carpio fry exposed to sublethal dose (1/10th LC50) of fipronil [(±)-5-amino-1-(2,6-dichloro-α,α,α-trifluoro-p-tolyl)-4-trifluoromethylsulfinylpyrazole-3-carbonitrile]. Two hundred and twenty five fry were randomly distributed in five treatments in triplicates. Four purified diets were prepared with graded levels of microbial levan. Five different treatment groups were levan control L0P0 (basal feed + 0 % levan without exposure to pesticide); pesticide control L0P1 (basal feed + 0 % levan with exposure to pesticide); L0.25P1 (basal feed + 0.25 % levan with exposure to pesticide); L0.50P1 (basal feed + 0.50 % levan with exposure to pesticide); and L0.75P1 (basal feed + 0.75 % levan with exposure to pesticide). Weight gain% and specific growth rate were significantly higher (p < 0.05) in levan fed groups compared to their non-levan fed counterpart. Highest (p < 0.05) content of ascorbic acid in muscle, liver and brain tissues was observed with higher level of dietary levan. Glucose-6-phosphate dehydrogenase activity decreased with the increasing level of dietary levan in the liver and muscle. Aspartate aminotransferase activity exhibited a second order polynomial relationship with the dietary levan, both in liver (Y = ?1.001x 2 + 5.366x + 5.812, r 2 = 0.887) and muscle (Y = ?0.566x 2 + 2.833x + 6.506, r 2 = 0.858) while alanine aminotransferase activity showed third order polynomial relationship both in liver (Y = 1.195x 3 ? 12.30x 2 + 35.23x + 9.874, r 2 = 0.879) and muscle (Y = 0.527x 3 ? 8.429x 2 + 31.80x + 8.718, r 2 = 0.990). Highest (p < 0.05) superoxide dismutase activity in gill was observed in the group fed with 0.75 % levan supplemented diet. Overall results indicated that dietary microbial levan at 0.75 % in C. carpio fry ameliorated the negative effects of fipronil and augmented the growth.  相似文献   

18.
An experiment was carried out to investigate the effects of rearing density on growth, metamorphosis and behavioural patterns of feeding in bullfrog, Rana catesbeiana Shaw, tadpoles. Stage 25 (Gosner) tadpoles from a single cohort were stocked at 0.5, 1.0, 2.0, 4.0 and 8.0 L–1 in 6-L plastic containers. A combination of phytoplankton and supplementary feed was used. There was an inverse relationship between rearing density and growth and metamorphosis above two organisms L–1. Tadpoles reared at 0.5 and 1.0 L–1 reached the metamorphic climax in 135 and 120 days, respectively, whereas more than 80% of all tadpoles reared at 4 and 8 L–1 did not metamorphose at all. Intraspecific competition appeared to be consistent among the cultured organisms regardless of the rearing density. Smaller tadpoles were displaced to sites distant from feeding points during supplementary feed addition, while no displacement was observed during phytoplankton addition. It is concluded that bullfrog tadpoles grow well at up to two organisms L–1 and that intraspecific competition is present within cultured tadpoles regardless of stocking density and may result from intrinsic genetic variability.  相似文献   

19.
An experiment was conducted to compare growth and timing to metamorphosis of bullfrog Rana catesbeiana (Shaw) tadpoles feeding on phytoplankton and on supplementary feed. Three interconnected, round, 4 m diameter concrete tanks were used in the experiment. Tanks 1 and 2 were stocked with juvenile tilapia, Oreochromis niloticus (L.) to stimulate phytoplankton through faecal fertilization. A third tank remained without fish. Stage 25-Gosner bullfrog tadpoles were placed in 0.042 m3 cages at 1 I?1. Experimental treatments consisted of: (1) tadpoles feeding solely on phytoplankton (P); (2) P + 13% body weight day?1 (bw day1) supplementary feeding (SF); (3) P + 9.75% bw day?1 SF; (4) P + 6.5% bw day?1 SF; (5) P + 3.25% bw day?1 SF; and (6) tadpoles feeding solely on supplementary feed at 13% bw day?1. Final weight was lowest in those organisms feeding exclusively on supplementary feed, followed by those feeding on phytoplankton. Treatments 2 and 3 showed the highest weight (3.65 and 3.64 g, respectively). After 70 days, 50% of the tadpoles in treatment 4 (6.5% bw day?1) reached metamorphic climax, followed by treatment 5 (33%). Only 8% of tadpoles feeding exclusively on live food reached metamorphosis. It is concluded that in the presence of abundant phytoplankton, it is possible to reduce up to 50% of the standard supplementary feeding rate and still have normal growth and metamorphosis. Tilapia represents a good alternative for biofertilization.  相似文献   

20.
  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号