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1.
Low numbers and unreliable wild catch of the native flat oyster, Ostrea angasi , spat has resulted in the NSW flat oyster industry being reliant on hatchery-produced spat. The need to produce culchless spat in the hatchery stimulated investigation of several catecholamines to induce metamorphosis in O. angasi larvae. Larvae were treated with one of four neuroactive catecholamines (epinephrine, epinephrine bitartrate, l -Dopa and GABA) at one of four concentrations (10−3, 10−4, 10−5 or 10−6  m ) for one of three treatment durations (0.5, 1–2 h) to determine morphogenic action for culchless spat production. Epinephrine bitartrate at 10−3 and 10−4  m and epinephrine at 10−3, 10−4 and 10−5  m , for a treatment duration of 1–2 h, produced significantly greater numbers of spat and culchless spat, compared with any other treatment combination. The other catecholamines tested did not induce a significant increase in the total number of spat or culchless spat, over untreated controls. Separate trials found that long-term treatment (24 h) with epinephrine bitartrate and epinephrine at morphogenic concentrations inhibited metamorphosis. Consecutive daily use of epinephrine bitartrate increased the numbers of spat and culchless spat produced, but did not affect larval or short-term post-larval survival. Treatment with 10−3  m epinephrine bitartrate or 10−4  m epinephrine for 1 h is recommended for routine commercial production of culchless flat oyster spat.  相似文献   

2.
Gustatory response of marbled rockfish Sebastiscus marmoratus was recorded from the facial nerve supplying the anterior palate. In amino acids, the lowest threshold was for L -proline at 10−6–10−5 M; in ATP-related substances, the value for inosine was approximately 10−5 M and in organic acids, the value for L -lactic acid was approximately 10−6 M. An almost complete self-adaptation was observed for stimulants after 5 s application. While a weak solution of L -lactic acid as adapting stimulus depressed the response to it completely, it did not appreciably affect the response to 10-times or more concentrated L -lactic acid solution. In contrast to a weak solution, a moderate solution caused a severe depression of the response to stronger solutions, resulting in a shift of the dose–response curve towards a high concentration range. Time for recovery from adaptation differed depending on chemicals and stimulus duration: for 10−4 M L -lactic acid, it took about 2.3 and 4.5 s for 1/2 recovery of response magnitude under unadapted condition from the adaptation after 1 s- and 5 s-stimulation, respectively. L -Lactic acid and L -alanine strongly depressed the response to each other, yielding a rightward shift of the dose–response curve. A similar profound cross-adaptation was also observed between inosine and 5'-inosinic acid. The possible role of gustation is discussed.  相似文献   

3.
ABSTRACT:   An apparatus to measure the locomotor activity of aquatic benthic organisms at variable low light levels was developed and the diurnal behavioral pattern of the abalone Haliotis discus discus was measured at various low light intensities. During the experiment, abalone were exposed to 12 h light–dark cycles of complete darkness, 0 µmol/m2/s throughout the 12 h dark cycle and, during periods I (days 1–8) and III (days 19–26), the 12 h light cycles were set at 10 µmol/m2/s. During period II (days 10–17), abalone were exposed to a light level during the 12 h light cycles of 1 × 10−5, 1 × 10−6, 1 × 10−7 or 1 × 10−8 µmol/m2/s and the changes in locomotor activity assessed. At daytime levels of 1 × 10−5 µmol/m2/s, typical behavioral patterns were observed of high locomotory activity during the night-time cycle. However, at lower light intensities, the distinction between day and night activity patterns became less clear and, at intensities lower than 1 × 10−7 µmol/m2/s, the difference between activity during the light and dark cycles became negligible. Based on this, we conclude that the threshold of light level perception in relation to locomotor activity is approximately 1 × 10−7 µmol/m2/s. The significance of these results in relation to the entrainment of behavior in abalone is discussed.  相似文献   

4.
Abstract:   The cephalopod receptor of particle motion was identified. In a previous study, it was suggested that statocysts served this function, but there was no direct supporting evidence, and epidermal hair cells had not been conclusively ruled out. Experiments on Octopus ocellatus were conducted using respiratory activity as an indicator of sound perception. Intact animals clearly responded to 141-Hz particle motion at particle accelerations below 1.3 × 10−3 m/s2, and the mean perception threshold at this frequency was approximately 6.0 × 10−4 m/s2. Specimens in which the statoliths had been surgically removed did not show any response for accelerations up to 3.9 × 10−3 m/s2 at 141 Hz, which was approximately 16 dB greater than the mean perception threshold at this frequency. Specimens that had undergone a control operation in which the statoliths remained intact showed positive responses at 2.8 × 10−3 m/s2 for the same frequency stimulus. This indicates that the statocyst, which is morphologically similar to the inner ear system in fish, is responsible for the observed responses to particle motion in O. ocellatus . This is the first direct evidence that cephalopods detect kinetic sound components using statocysts.  相似文献   

5.
Effect of nonylphenol (NP) products from different companies on in vitro vitellogenin (VTG) synthesis was compared using tilapia ( Oreochromis mossambicus ) hepatocytes cultures. Addition of NP at a concentration of 10−3 M to the medium caused death of hepatocytes (NP-A and NP-B) and delay of monolayer formation (NP-C). No cell death was observed at a concentration of 10−4 M (NP-A, -B and -C) but cell adhesion was slower than control. These results suggest that high concentration of NP is toxic against tilapia hepatocytes. When effects of estradiol-17β (E2, 10−7 M) and NP (10−4 M) on in vitro VTG synthesis were examined, addition of E2 and NP-A and NP-B to the media resulted in elevation of VTG. NP-C did not induce VTG in the medium. Co-treatment of NP-B and tamoxifen, a non-steroidal anti-estrogen, reduced VTG synthesis. These results suggest that NP has estrogenic potential in primary cultures of tilapia hepatocytes and acts through binding to the estrogen receptor, and that there is a difference in the induction level of VTG among different NP products.  相似文献   

6.
The ingestion rate (ng liposome larva–1 h–1) of extruded [1–14C] palmitic acid-labelled liposomes containing physiological saline (PHS) or cod fish extract (CFE), was tested in 5-day-old gilthead seabream Sparus aurata and white grouper Epinephelus aeneus larvae. A follow-up study compared the assimilation of radioactive free fatty acid (FFA) label of these two liposome treatments into six phospholipid and neutral lipid fractions as well as the nonlipid fraction in 5-day-old seabream. In seabream larvae, there was a 50-fold ( P  < 0.05) increase in the net consumption rate when fed CFE liposomes (2305.8 ng liposome larva–1 h–1) compared with liposomes containing physiological saline (42.7 ng liposome larva–1 h–1). A similarly significant ( P  < 0.05) but less marked pattern was also observed in the grouper larvae where the CFE treatment larvae ingested 238.5 ng liposome larva–1 h–1 compared with 54.3 ng liposome larva–1 h–1 in larvae fed the PHS liposomes. In seabream larvae ingesting CFE and PHS liposomes, radioactivity was found in all larval fractions analysed. However, marked treatment differences ( P  > 0.05) in assimilation were found only in the triacylglycerol fraction (3.4 and 0.6 dpm larva–1 h–1, respectively) and nonlipid fraction (11.2 and 15 dpm larva–1 h–1, respectively).  相似文献   

7.
Rainbow trout, Oncorhynchus mykiss (Walbaum), were exposed continuously to infectious pancreatic necrosis virus (IPNV) at 0, 101, 103 or 105 plaque forming units (pfu) L−1 of water to estimate the effects of chronic IPNV exposure on early life stages. Fish density averaged 35 fish L−1 (low density) or 140 fish L−1 (high density), and the tank flow rate was 250 mL−1 min. Virus exposure began at 6 days before hatch and continued until fish were 44 days old. Cumulative per cent mortality, analysis of survival and hazard functions, and discrete-time event analysis were used to explore the patterns of survival and mortality. In eggs and fish exposed to IPNV, mortality significantly greater than in the 0 pfu L−1 exposure did not occur until IPNV concentration was 105 pfu L−1 at low fish density and 103 pfu IPNV L−1 at high fish density. These results suggest that in the natural aquatic environment, where rainbow trout densities are likely to be considerably lower than in this study, mortality resulting from infection with IPNV will very likely not occur when ambient concentrations of virus are ≤103 pfu IPNV L−1. In aquaculture rearing units, trout density is likely to be as high or higher than the densities used in this study. Therefore, continuous inputs of virus at concentrations greater than 101 pfu L−1 may result in IPN epidemics in aquaculture facilities.  相似文献   

8.
ABSTRACT:   Anadromous Coilia ectenes was sampled from the Yangtze estuary at Chongming and two of the primary upstream spawning grounds at Jingjiang and Anqing in April, May, June and August 2006. Gonad development was analyzed for females. In April, fish were collected in the estuary and at Jingjiang, but not at Anqing. No female was mature (gonad at stages IV or V) at either location. In May, 45% of the females were mature in the estuary, 9% at Jingjiang and 5% at Anqing. In June, 86% were mature in the estuary, 83% at Jingjiang and 7% at Anqing. In August, C. ectenes was absent at Jingjiang. No female was mature in the estuary, and all females were mature at Anqing. Absolute fecundity ( AF ) increased significantly with standard length ( SL ) by a power function AF  = 2.27 × 10−6 ×  SL 2.67 ( r 2 = 0.57, n  = 48, P  < 0.05). Mature females in the estuary were smaller than those at Jingjiang and Anqing. Conservation of spawners in the upstream spawning grounds is important because they have a size-related fecundity advantage over the smaller spawners in the estuary.  相似文献   

9.
ABSTRACT:   The migratory history of anadromous white-spotted charr Salvelinus leucomaenis collected from Japanese coastal waters, was examined in terms of strontium (Sr) and calcium (Ca) uptake in the otolith, by means of wavelength dispersive X-ray spectrometry using an electron microprobe. Otolith Sr concentration or Sr : Ca ratios of anadromous S. leucomaenis , fluctuated strongly along the life history transect in accordance with the migration (habitat) pattern from sea to fresh water. The anadrmous S. leucomaenis showed phase L (low Sr : Ca ratio) from the core to the point 1000–2500 µm distant, averaging 1.3 × 10−3 to 2.7 × 10−3 and thereafter, the ratios increased sharply, being higher than 5.0 × 10−3 to 10.0 × 10−3. These findings indicated that otolith Sr : Ca ratios reflected individual life histories, enabling a sea habitat to be identified from a freshwater habitat in this species.  相似文献   

10.
We used nested-polymerase chain reaction (PCR) to detect Roundup Ready soybean in aquatic feeds and feeding tilapias. A template concentration of 10−10 g μL−1 DNA solution could be detected with a dilute degree of 0.01%. Most (90.6%) of the aquatic feeds containing soybean byproduct included exogenous DNA segments. We also compared genetically modified (GM) soybean with non-GM soybean diets in feeding tilapias ( Oreochromis niloticus , GIFT strain) and examined the residual fragments (254 bp) of GM soybeans. Tilapias receiving GM soybean diets had DNA fragments in different tissues and organs, indicating that exogenous GM genes were absorbed systemically and not completely degraded by the tilapia's alimentary canal.  相似文献   

11.
ABSTRACT:   The habitat use and migration of ayu Plecoglossus altivelis was compared to that of ice goby Leucopsarion petersi using otolith microchemistry analysis. Both species were collected along the Sanriku Coast. Otolith Sr : Ca ratios of ayu fluctuated strongly along the life history transect in accordance with the migration (habitat) pattern from fresh water to sea water. The Sr : Ca ratios of the center region averaged 3.2 × 10−3; thereafter, the ratios increased sharply, averaging 9.2 × 10−3, and were maintained at the higher levels until the outermost regions. By contrast, the Sr : Ca ratios of ice goby showed consistently high values along the life history transect of the otolith, ranging 9.0 × 10−3 in the center to 9.2 × 10−3 in regions outside the center, with further increases around the otolith edge. These findings indicate that ayu shows a typical amphidromous migratory pattern, while ice goby does not show the anadromous migratory pattern previously reported. The use of a freshwater environment during the early developmental stage in ice goby along the Sanriku Coast was less prominent than that of ayu in the same region.  相似文献   

12.
The use of near infrared reflectance spectroscopy (NIRS) was investigated as an alternative method for predicting moisture (M), oil, crude protein (CP), ash, salt as NaCl, total volatile nitrogen (TVN) and buffer capacity in fishmeal. The NIRS calibration models were developed using the modified partial least squares (MPLS) regression technique. One thousand and ten ( n =1010) fishmeal samples were used to predict chemical composition for quality control in the fishmeal industry. Equations were selected based on the lowest cross validation errors (SECV). The coefficient of determination in calibration ( R 2) and SECV were 0.93 and 3.9 g kg–1 dry matter (DM); 0.85 and 5.7 g kg–1 DM; 0.92 and 3.7 g kg–1 DM; 0.91 and 4.7 g kg–1 DM; 0.88 and 6.7 g kg–1 DM; 0.94 and 1.8 g kg–1 DM; for M, CP, oil, ash, TVN and NaCl, respectively. It was concluded that NIRS can be used as a method to monitor the quality of fishmeal under industrial conditions.  相似文献   

13.
AKINORI  DAN  MASANORI  HIRAOKA  MASAO  OHNO  ALAN T.  CRITCHLEY 《Fisheries Science》2002,68(6):1182-1188
ABSTRACT: Although most members of the genus Enteromorpha are important edible green algae, some species are also potentially economically valuable crops. Samples of E. prolifera were obtained from the Yoshino River estuary, Tokushima, Japan and cultured in laboratory conditions at 10°C, a salinity of 20 psu, under white light with 12 h light : 12 h dark cycle and at a photon fluence rate (PFR) of 40 μmol/m2 per s for 30 days. In the present study, the effect of salinity and PFR on the induction of reproductive cells and rhizoid formation were investigated. Synchronous formation of swarmers by thalli was induced in excised disks of 1.2 mm diameter after 2–5 days incubation. The optimum salinity for maturation of reproductive cells was between 5.0 and 52.0 psu, and between 13.2 and 45.3 psu for swarmer release, although the lower limit for swarmer release was 5.0 psu. Maturation of reproductive cells and swarmer release required a PFR higher than 16 μmol/m2 per s. The minimum PFR for swarmer release was 8 μmol/m2 per s. Many rhizoids were formed between 1.6 and 52.0 psu and photon fluence rates between 8 and 320 μmol/m2 per s. Rhizoids were formed in a polarized manner.  相似文献   

14.
Quantitative real time PCR, recently developed in molecular biology, is applied in this paper to quantify the white spot syndrome virus (WSSV) in infected shrimp tissue. The WSSV content in moribund shrimp of all species tested ( Penaeus stylirostris, P. monodon, P. vannamei ) ranged from 2.0 × 104 to 9.0 × 1010 WSSV copies μg–1 of total DNA ( n =26). In whole moribund post-larvae, 4.3 × 109 WSSV copies μg–1 of DNA were detected which is equivalent to 5.7 × 1010 WSSV copies g–1 of post-larvae. The comparison of WSSV content between different tissues showed that muscle and hepatopancreas tissues contained 10 times less virus than gills, pleopods and haemolymph. With inocula of known virus content, bioassays by immersion challenge showed that a minimum of five logs of WSSV copies was necessary to establish disease in the challenged shrimp. In contrast, five logs of WSSV copies injected into shrimp muscle produced a LT-50 of 52 h. This real time polymerase chain reaction (PCR) technique is sensitive (four copies), specific (negative with DNA from shrimp baculoviruses and parvoviruses), dynamic (seven logs) and easy to perform (96 tests in <4 h).  相似文献   

15.
ABSTRACT:   Phytoplankton used in fish hatcheries is mass-cultured in the open air and usually contains large numbers of bacteria. In commercial fish production, the phytoplankton cultures are usually added into the larval rearing tanks; however, the numbers and types of bacteria introduced into the rearing tanks simultaneously are unknown. In this study, the bacterial community structures in Nannochloropsis sp. cultures were analyzed by using fluorescence in situ hybridization (FISH). A direct viable count (DVC)-FISH analysis was also performed as DVC is useful for the detection of actively growing cells. Total numbers of bacteria in Nannochloropsis sp. cultures ranged from 7.72 × 105−2.39 × 106 cells/mL. High proportions of the total bacteria (31.6–53.6%) in the Nannochloropsis sp. cultures showed growth potential. DVC-FISH analysis revealed that α-proteobacteria and the Cytophaga – Flavobacterium cluster were abundant in the bacterial community of actively growing cells. Thus, the high growth potentials of the distinct bacterial communities in Nannochloropsis sp. culture must influence the bacterial communities in larval rearing tanks.  相似文献   

16.
Live adult brine shrimp, Artemia franciscana (Latreille), were enriched with erythromycin to determine if Artemia could accumulate therapeutic levels for subsequent feeding to young fish. Three trials were conducted to determine the erythromycin incorporation and survival rates of enriched Artemia when fed either liposomes containing erythromycin or various erythromycin suspensions. Erythromycin concentration in Artemia fed a liposome suspension was low (∼ 5 μg mL−1) relative to Artemia fed the direct suspension (> 100 μg mL−1) over the same time period. When enriched with suspensions up to 1 g erythromycin L−1 sea water for 14 h, Artemia survival was not significantly affected ( P > 0.05) relative to controls. Using a suspension of 1 g L−1, tissue erythromycin concentrations of 109 ± 16 μg erythromycin mL−1  Artemia homogenate (mean ± SEM) were achieved after 12 h. Concentrations above 170 μg mL−1 were obtained using suspensions of 2–5 g L−1, but Artemia survival significantly ( P < 0.05) decreased.  相似文献   

17.
The use of wrasse as cleaner fish in farming of Atlantic salmon, Salmo salar L., is now widespread in Scotland, Ireland and Norway, but little is known about the susceptibility of these fish to the common pathogens of cage-cultured salmon. The susceptibility of goldsinny wrasse, Ctenolabrus rupestris L., to infectious pancreatic necrosis virus (IPNV) was investigated. Captive-bred C. rupestris were infected with IPNV-Sp (Shetland strain) using a bath challenge method. Two infection doses were used, low (4.1 × 105 pfu mL−−1) and high (2.4 × 106 pfu mL−−1), with two replicates for each experiment. Bathing times were 1 h for the low dose and 5 h for the high dose. A maximum prevalence of infection (30%) was seen 2 weeks post-infection in replicate 1 of the low dose experiment and was accompanied by low tissue titres. The tissue titres dropped to an undetectable level by 4 weeks post-infection. In the high dose experiment, a high prevalence of infection was seen along with moderate titres in tissues as well as a marked pathological response. Both prevalence and intensity declined rapidly and the fish recovered. In the high dose experiment, faecal titres followed the same pattern as those in the tissues. The implications for the use of wrasse in the farming of Atlantic salmon are discussed.  相似文献   

18.
Postlarvae of Litopenaeus vannamei were acclimated and stocked in lake-based cages at the following stocking densities: 10, 20, 30 and 40 shrimp m−2. Another set of shrimp was stocked in concrete tanks as reference samples at 30 shrimp m−2. Significant differences were observed among stocking densities throughout the 95-day culture. The final weight at harvest decreased with increasing stocking density: mean weights of 23.3, 15.8, 13.0, 10.9 and 14.6 g for the 10, 20, 30, 40 shrimp m−2 and reference tanks were observed respectively. There were no significant differences in survival throughout the culture period, ranging between 69% and 77%. Daily growth rates (range: 0.11–0.24 g day−1) and specific growth rates (range: 3.54–4.34%) also differed significantly among stocking densities, both increasing with decreasing stocking density. The feed conversion ratio in the cages did not differ among the stocking densities, ranging from 1.53 to 1.65. The relationship between stocking density and mean individual weight at harvest followed the equation y =81.06 x −0.54 ( R 2=0.938) and that of stocking density and production (in g m−2) is y =58.01 x −0.46 ( R 2=0.834).  相似文献   

19.
We examined seasonal, annual variation and horizontal distribution of zooplankton in the Sea of Japan from 1966 to 1990. Zooplankton was most abundant in the spring. The spring maximum appeared in February–March and in April–May in the southern and eastern parts of the study areas, respectively. In the summer and autumn, a secondary peak was most conspicuous in the eastern part. The difference between the estimated biomass at night and day was large in the spring and small in summer and autumn. The biomass in the offshore southern area peaked about every 3 years between 1966 and 1983, and increased abruptly in 1990. The density in the area north of 39°N or 40°N was high. Total biomass estimated in the upper 150 m layer in the Sea of Japan (106 km2) was 9.5 × 106 t in the daytime and 16.6 × 106 t at night.  相似文献   

20.
This study investigated infection dynamics of infectious salmon anaemia virus (ISAV) by conducting two experiments to examine minimum infective dose and viral shedding of ISAV. In terms of minimum infective dose, the high variability between replicate tanks and the relatively slow spread of infection through the population at 1 × 101 TCID50 mL−1 indicated this dose is approaching the minimum infective dose for ISAV in seawater salmon populations. A novel qPCR assay incorporating an influenza virus control standard with each seawater sample was developed that enabled the quantity of ISAV shed from infected populations to be estimated in values equivalent to viral titres. Viral shedding was first detected at 7 days post-challenge (5.8 × 10−2 TCID50 mL−1 kg−1) and rose to levels above the minimum infective dose (4.2 × 101 TCID50 mL−1 kg−1) on day 11 post-challenge, 2 days before mortalities in ISAV inoculated fish started. These results clearly demonstrate that a large viral shedding event occurs before death. Viral titres peaked at 7.0 × 101 TCID50 mL−1 kg−1 15 days post-infection. These data provide important information relevant to the management of ISA.  相似文献   

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