Nucleotide sequence and mRNA expression analysis of <Emphasis Type="Italic">β</Emphasis>-actin gene in the orange-spotted grouper <Emphasis Type="Italic">Epinephelus coioides</Emphasis>

The full-length cDNA, encoding the orange-spotted grouper β-actin and spanning 1920 bp including a poly (A) tail, was cloned from its brain cDNA library. The open reading frame encodes a protein of 375 amino acids. Sequence analysis indicated that it contained the typical structural features of cytoplasmic actins, and showed higher homology with other vertebrate β-actin than any other members of the actin family. The partial genomic sequence indicated that the organization of the β-actin gene in the orange-spotted grouper might also be conserved. Northern blot analysis indicated that it was expressed at high levels in the brain, spleen, adipose tissue, ovary, and liver, but at low levels in the gill filament and heart, and at a very low level in the kidney. The expression of β-actin gene in the skeletal muscle was barely detectable. These results indicated that the expression of the orange-spotted grouper β-actin gene showed significant variation in different tissues. Therefore, caution should be taken when using β-actin gene as an internal control in the normalization of gene expression among tissues. Whereas, semi-quantitative RT-PCR analysis indicated that treatment with 17α–methyltestosterone (MT) had little effect on the mRNA expression of β-actin gene in the in vitro incubated hypothalamus, pituitary, and ovary fragments of the orange-spotted grouper, suggesting β-actin can be used as an internal control for RT-PCR analysis of MT effects on gene expression in these tissues.     

Effect of nitrite exposure on oxygen-carrying capacity and gene expression of <Emphasis Type="Italic">NF-κB</Emphasis>/<Emphasis Type="Italic">HIF-1α</Emphasis> pathway in gill of bighead carp (<Emphasis Type="Italic">Aristichthys nobilis</Emphasis>)

Nitrite (NO₂^?) contamination of water can severely impact the health of aquatic life and is a major concern for commercial aquaculture. In order to study the effect of nitrite on Aristichthys nobilis, we investigated the oxygen-carrying capacity, NF-κB/HIF-1α pathway, and the gill tissue structure under nitrite stress. In the current study, bighead carp (initial weight 180.05?±?0.092 g) were exposed to nitrite (48.634 mg/L) for 96 h and then for 96 h recovery test. After nitrite exposure for 6 h, hypoxia-inducible factor-1α (HIF-1α) and nuclear factor-κB (NF-κB) mRNA expression increased significantly in the gill of bighead carp (P?<?0.05). After nitrite exposure for 12 h, hemoglobin (Hb) and methemoglobin reductase (MHBR) content in blood decreased significantly (P?<?0.05); TLR4 mRNA expression increased significantly (P?<?0.05). After nitrite exposure for 24 h, methemoglobin (MetHb) content increased significantly (P?<?0.05). After recovery test, all the indicators except TLR4 mRNA expression level recovered to initial level. In conclusion, nitrite exposure can affect hemoglobin dynamics, as oxidization of nitrite by hemoglobin results in the reduction of Hb to MetHb leading to hypoxia and nitrite exposure can also result into gill tissue damage. In the face of nitrite exposure, NF-κB and HIF-1α mRNA expression level increased immediately to protect the body from oxidative damage and eased hypoxic condition caused by nitrite. It was also observed that nitrite damage is recoverable in Aristichthys nobilis, but it may be need more than 96 h.     

Protective effect of squilla chitosan–silver nanoparticles for <Emphasis Type="Italic">Dicentrarchus labrax</Emphasis> larvae infected with <Emphasis Type="Italic">Vibrio anguillarum</Emphasis>

Antimicrobial nanoparticle therapy was proposed as an alternative strategy to reduce the use of antibiotics in larval-rearing systems. Antibacterial potential of the prepared squilla chitosan–silver nanoparticles and its protective effect on Dicentrarchus labrax (sea bass) larvae in the early stages were studied against Vibrio angularium. Different concentrations of squilla chitosan (Csq) and squilla chitosan–silver nanoparticles (Csq–AgNps) (1, 2, 5, 10, and 20 %) were, in vitro, tested against V.anguillarum and expressed as a role of Log₁₀ mean. Sea bass larvae were treated using: 10 % Csq and 5 % Csq–AgNps as effective inhibitory concentrations against the pathogen either encapsulated during the feeding regime or added directly to the model system via the water from the onset of 4 weeks. The long-term administration of Csq–AgNps through enriched food for both non-infected and infected systems had survival % of 74.5 ± 1.5 and 72.5 ± 2.5, respectively. Larval clinical observations using Csq–AgNps were studied compared with the two controls. The current study found that 5 % encapsulated Csq–AgNps was enough to suppress infection and considered as an alternative to antibiotics in controlling virulent fish pathogens.     

Distribution patterns of settlement-stage juveniles of <Emphasis Type="Italic">Girella punctata</Emphasis> and <Emphasis Type="Italic">Girella leonina</Emphasis> on the rocky coast of the Kanto–Izu region,Japan

The early life history of girellid fishes in Japanese waters is unclear, and little is known about their species-specific reproductive strategies. We examined seasonal changes of distribution patterns for settlement-stage juveniles of Girella punctata and Girella leonina on the rocky shore in the regions of Kanto and Izu, Japan, to infer the influence of the Kuroshio Current on their reproduction. We collected 813 settlement-stage juveniles mainly in Sagami Bay and genetically identified the species. The juveniles of G. punctata were collected on the rocky shore in Sagami Bay during April to August, with the abundant catch in May and June. Thus, we infer that juvenile G. punctata ubiquitously inhabit the rocky shore in the area in spring and summer. By contrast, juveniles of G. leonina were rarely collected in Sagami Bay, with a total catch of only 66. Notably, no juveniles were collected during the wintertime in Sagami Bay, although an abundant catch of G. leonina had been previously reported for Sagami Nada off Sagami Bay during January to March. This clear-cut difference between the areas likely reflects the difference in proximity to the path of the Kuroshio Current. We expect that the Kuroshio Current strongly influences the reproductive success of G. leonina.     

Reproductive dynamics and nursery habitat preferences of two commercially important Indo-Pacific red snappers <Emphasis Type="Italic">Lutjanus erythropterus</Emphasis> and <Emphasis Type="Italic">L. malabaricus</Emphasis>

Red snappers were examined for reproductive biology and age-0 habitat preferences. Spawning in red snappers occurred throughout the year in northern Australia and eastern Indonesia; at least 10–30% of females and 40–80% of males were in ripe or spawning condition in most months. Northern Australian populations showed a spawning peak from July to December (L. erythropterus) and September to March (L. malabaricus). Eastern Indonesian L. malabaricus had a less defined pattern with two peaks: January–March and October. Size at first maturity was 240 mm for males and 250–300 mm for females. L ₅₀ estimates were similar between species in northern Australia: 270–280 mm (males) and 350–370 mm (females). Maximum batch fecundity was 676,100 oocytes for L. erythropterus and 997,000 oocytes for L. malabaricus. Higher mean abundances of age-0 L. erythropterus were found in silty and coarse sand/rubble estuarine habitats of northern Australia (456 ± 119 fish/km²) compared with sandy coastal habitats (5 ± 3 fish/km²). Most age-0 snapper caught at Sape (eastern Indonesia) were L. malabaricus (91%) with mean abundances of 312 ± 14 fish/km². The similarities in the reproductive characteristics of red snappers suggest that successful management approaches adopted in northern Australia should be considered in eastern Indonesia.     

Talking to the dead: using <Emphasis Type="Italic">Post</Emphasis>-<Emphasis Type="Italic">mortem</Emphasis> data in the assessment of stress in tiger sharks (<Emphasis Type="Italic">Galeocerdo cuvier</Emphasis>) (Péron and Lesueur, 1822)

Sharks are very sensitive to stress and prone to a high mortality rate after capture. Since approximately 50 million of sharks are caught as bycatch every year, and current recommendations to reduce the impact of commercial fishing strongly support immediate release, it is imperative to better understand post-release mortality caused by the stress of capture and handling. Blood samples allow the assessment of stress levels which are valuable tools to reduce mortality in commercial, recreational and scientific fishing, being essential for the improvement in those conservation measures. Biochemical analyses are widely used for sharks as stress indicators, with secondary plasma parameters (lactate, glucose and ions) being the most often employed assays. However, it is virtually impossible to determine baseline plasma parameters in free-ranging sharks, since blood withdrawal involves animal capture and restrain, which are stressful procedures. This study aims at analyzing secondary parameters of five healthy tiger sharks captured with circular hooks and handlines in Fernando de Noronha (Northeastern Brazil) and comparing them with secondary parameters of three dead tiger sharks caught off Recife (also Northeastern Brazil). The results showed that the analysis of some plasma constituents in dead animals may be an efficient tool to assess stress and lethality. However, traditional parameters such as glucose and calcium, need to be used with caution. The results also demonstrated the extreme importance of urea and phosphorus for assessing stress response and mortality in tiger sharks, both parameters frequently neglected and of utmost importance for shark’s homeostasis.     

Segregation of microsatellite loci in second generation hybrid striped bass (<Emphasis Type="Italic">Morone saxatilis</Emphasis> × <Emphasis Type="Italic">Morone chrysops</Emphasis>)

Within the framework of a larger project aimed to assess the potential of second generation hybrid striped bass for German aquaculture the genotypic segregation of five microsatellite loci was analysed in two progeny lots (n = 74 and 76, respectively). There was no consistent correlation between microsatellite genotypes and phenotypic category (white bass, hybrid, or striped bass). None of the individuals expressed neither only white bass nor only striped bass genotypes at all five loci. On the other hand, only hybrid genotypes at all five loci were detected in three individuals of lot 1 and four individuals of lot 2. Single loci tests for conformity of microsatellite genotypic segregation with Mendelian rules revealed significant deviations (P < 0.05) in four cases for lot 1 and in three cases for lot 2. If pooled over all five loci, both lots displayed highly significant deviations (P < 0.01) with an excess of hybrid genotypes and a deficiency of white bass genotypes. It is concluded that stabilizing selection performed on hybrid genotypes might be a suitable approach for practical aquaculture in Europe if the goal is to become independent of first generation hybrid fry supply and/or if establishing domesticated brood stocks of both parental species is impossible. However, more detailed studies on the characteristics and performance of multiple hybrid generations are needed.     

Dietary ascorbic acid influences the intestinal morphology and hematology of hybrid sorubim catfish (<Emphasis Type="Italic">Pseudoplatystoma reticulatum</Emphasis> × <Emphasis Type="Italic">P. corruscans</Emphasis>)

This study evaluated the effect of graded levels of dietary ascorbic acid (AA) (12.47, 20.27, 115.44, 475.50, 737.72, and 850.70 mg kg^?1) on growth, hematology, intestinal morphometry, and phagocyte activity of hybrid sorubim Pseudoplatystoma reticulatum × Pseudoplatystoma corruscans. Fish (n = 420, 14.57 ± 2.71 g, 15.11 ± 0.90 cm) were distributed in 30 polyethylene tanks (80 l) (5 replicates per treatment with 14 fish per tank) and fed for 45 days. Dietary treatment did not have a significant effect on growth metrics (P > 0.05). Fish fed 737.72 mg AA kg^?1 had a higher villi height (289.80 ± 19.96 μm) (P < 0.05) than fish fed 850.70 mg AA kg^?1 (245.4 ± 18.25 μm). Hemoglobin in fish fed 850.70 mg AA kg^?1 (5.34 ± 0.96 g dl^?1) was higher (P < 0.05) than fish fed 12.47 mg AA kg^?1 (3.42 ± 0.55 g dl^?1) and 20.27 mg AA kg^?1 (3.06 ± 1.26 g dl^?1). The erythrocyte number of hybrid sorubim fed 115.40 mg AA kg^?1 (1.73 ± 0.27 × 10⁶ μl^?1) and 475.50 mg AA kg^?1 (1.70 ± 0.28 × 10⁶ μl^?1) were higher (P < 0.05) than in those fed diets containing 20.27 mg AA kg^?1 (1.11 ± 0.34 × 10⁶ μl^?1). There was no significant effect (P > 0.05) of dietary AA on leukocyte and thrombocyte and on phagocyte activity and phagocyte index. Inclusion of AA in feed seems to increase the integrity of the intestinal mucosa and stimulate erythropoiesis in hybrid sorubim catfish.     

Age,growth and mortality estimates for populations of red snappers <Emphasis Type="Italic">Lutjanus erythropterus</Emphasis> and <Emphasis Type="Italic">L. malabaricus</Emphasis> from northern Australia and eastern Indonesia

Lutjanus erythropterus and L. malabaricus were examined for life-history differences among northern Australian and eastern Indonesian populations. Formation of opaque growth increments in otoliths began during April to September for northern Australian fishes and September to April for eastern Indonesian fishes. Maximum observed ages were greater than previously reported: 42 and 48 years for L. erythropterus and L. malabaricus, respectively. Eastern Indonesian red snappers grew faster than northern Australian fish. Growth was similar for northern Australian L. erythropterus populations. However, Kupang and Sape populations of L. erythropterus in eastern Indonesian showed different growth from the Arafura North population, which was similar to northern Australian fish. There were growth differences among northern Australian populations of L. malabaricus. Arafura South and Timor populations were similar, but differed from Groote and Weipa populations. There were no significant differences in growth among populations of L. malabaricus in eastern Indonesia. Total mortality estimates were similar between northern Australian and eastern Indonesian fish: 0.09 and 0.16 year⁻¹ for L. erythropterus and 0.11 and 0.14 year⁻¹ for L. malabaricus, respectively. Life-history characteristics of these red snappers are typical of other tropical snappers: slow-growing and long-lived with low mortality. However, population growth differences suggest that their management should be based on biological information from distinct stocks.     

Optimum time for weaning South African <Emphasis Type="Italic">Scylla serrata</Emphasis> (Forskål) larvae from rotifers to <Emphasis Type="Italic">Artemia</Emphasis>

To determine the optimum time at which to wean Scylla serrata larvae from rotifers onto Artemia two experiments were conducted, approximately 1 month apart, using larvae from two different female crabs. In the first experiment, the larvae in three treatment groups, with nine replicates each, were fed rotifers for the first 8 days after hatching. Artemia were introduced on days after hatch (DAH) 0 – during the first zoeal instar (treatment R + A); on DAH 4 – during the second zoeal instar (treatment R4A); on DAH 8 – during the third zoeal instar (treatment R8A). In a control (ROT) larvae were fed with rotifers exclusively for 18 days until the completion of metamorphosis to megalopa. In the second experiment, the same four feeding schedules as in experiment 1 were used with an additional group of larvae (treatment AC) that were fed only on Artemia throughout the rearing period. Similar results were recorded in the two experiments. Larvae in treatments R + A and R4A performed significantly better than those in treatments R8A, ROT and AC. This was particularly evident when examining the proportion of zoeae which successfully completed metamorphosis to megalopa. Poor performance of larvae in treatments AC and ROT implied that rotifers are needed as a first food, but that rotifers alone do not fill the nutritional requirements of S. serrata larvae. Poor performance of larvae in treatment R8A suggested that the diet should be supplemented with Artemia before the end of the zoea 3 stage.     

Dietary lipid concentrations influence growth,liver oxidative stress,and serum metabolites of juvenile hybrid snakehead (<Emphasis Type="Italic">Channa argus</Emphasis> × <Emphasis Type="Italic">Channa maculata</Emphasis>)

The study was conducted to evaluate the effect of dietary lipid levels on growth, liver oxidative stress, and serum metabolites of juvenile hybrid snakehead (Channa argus × Channa maculata). Five isonitrogenous (crude protein 420 g kg^?1) practical diets containing 58, 87, 115, 144, and 173 g kg^?1 crude lipid (named L58, L87, L115, L144, and L173, respectively) were fed to triplicate groups of 30 fish (mean initial weight 24 g) for 8 weeks. The results showed that the final body weight (58.68–78.81 g), specific growth rate (1.41–1.75 % day^?1), and protein efficiency ratio (1.66–2.64) increased significantly with the increasing dietary lipid levels. Liver lipid contents (71.65–101.80 g kg^?1) and crude lipid (52.10–83.63 g kg^?1) of whole body increased with increasing dietary lipid levels and reached the highest values in fish of L173. Fish of L173 showed lower alkaline phosphatase (23.81 King Unit gprot^?1) and catalase activities (4.44 U mgprot^?1) but higher malondialdehyde content (0.69 nmol mgprot^?1) in liver than the other groups. Higher alanine transaminase activity (8.20 U L^?1), aspartate transaminase activity (63.65 U L^?1), and triglyceride (0.29 mmol L^?1) in serum were observed in fish of L173 compared to the other treatments. Fish of L144 showed higher superoxide dismutase activity and glutathione peroxidase activities in liver than that of fish fed diet L58. Fish fed diet L58 showed lower total cholesterol (3.61 mmol L^?1), high-density lipoprotein cholesterol (1.39 mmol L^?1), and low-density lipoprotein cholesterol (0.46 mmol L^?1) in serum. These results suggested that juvenile snakehead (Channa argus × Channa maculata) achieved good growth performance with dietary lipid level 173 g kg^?1. Diet with 143 g kg^?1 lipid was more conductive to liver health. The appropriate dietary lipid supplementation needs to be determined in further studies.     

The impact of net-isolated polyculture of tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis>) on plankton community in saline–alkaline pond of shrimp (<Emphasis Type="Italic">Penaeus vannamei</Emphasis>)

We used 12 land-based experimental enclosures (6 m × 5 m) in a saline–alkaline pond of shrimp (Penaeus vannamei) to determine the impact of net-isolated polyculture of tilapia (Oreochromis niloticus) on plankton communities for 40 days. Tilapias were stocked in net cages suspended in enclosures, in polyculture ponds including tilapia and shrimp. Four tilapia biomass were tested: 0, 39, 115 and 227 g m⁻². Shrimp stocking biomass were 0.7 g m⁻² in all treatments. There were three replicates in each treatment. Our results showed that the presence of tilapia significantly reduced phytoplankton biomass directly through predation and indirectly through top-down effect. The stocking of tilapia reduced zooplankton biomass, particularly rotifer biomass. However, copepod biomass was not been significantly affected. So, net-isolated polyculture of tilapia can thus have a strong impact on phytoplankton allowing the co-existence of large numbers of copepods with planktivorous fish and improving the water quality of shrimp ponds.     

Genetic and morphological evidence of hybridization between <Emphasis Type="Italic">Nematalosa japonica</Emphasis> and <Emphasis Type="Italic">N. come</Emphasis> (Clupeiformes: Clupeidae) off Okinawa Island,Ryukyu Archipelago,Japan

Two morphologically similar species of gizzard shad, Nematalosa japonica Regan and N. come (Richardson), sympatrically distributed off Okinawa Island, Japan, were examined using an allozyme locus (SOD*) and two nuclear polymerase chain reaction (PCR)-based DNA markers (ITS-1 and CaM), which provided diagnostic identification of each species. In addition, a multiplex PCR-based mitochondrial DNA (mtDNA) marker (16S) was used to characterize the distribution of mtDNA haplotypes among specimens. The species composition of sympatric and allopatric population samples from Tungkang, southern Taiwan, to Okinawa and the Shikoku Islands, Japan, were also examined. Gizzard shad with hybrid genotypes were detected in three populations from Okinawa Island, with hybrid frequency ranging from 1 to 67%. A backcross level of 2% was detected in the dominant hybrid frequencies of one population sample only. Morphological examination of hybrids showed intermediate forms, with hybrid indices of three meristic characters falling between those of the parental species (range 39–53; mean 45). Although principal component analysis showed differences between N. japonica and N. come based on the first principal component scores, hybrids were difficult to identify. Accordingly, satisfactory identification of species and hybrids could be achieved only using genetic tools. We also discuss the cause of hybridization and its relationship with recently conducted reclamation on Okinawa Island.     

Effects of replacing fish meal with rubber seed meal on growth,nutrient utilization,and cholesterol metabolism of tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis> × <Emphasis Type="Italic">O. aureus</Emphasis>)

A feeding trial was conducted to evaluate the effects of replacing fish meal with rubber seed meal (RSM) on growth, nutrient utilization, and cholesterol metabolism of tilapia (Oreochromis niloticus × Oreochromis aureus). Five experimental diets were formulated with 0, 150, 300, 450, and 600 g kg^?1 RSM replacing graded levels of fish meal, respectively. Each diet was randomly assigned to triplicate groups of 25 fish (initial average weight 65.3 g) per aquarium in a rearing system maintained at 29 ± 1 °C for 8 weeks. Dietary 150 g kg^?1 RSM inclusion did not affect the weight gain and daily growth coefficient, whereas these were depressed by a further inclusion. Additionally, feed efficiency ratio and protein efficiency ratio were not affected by dietary RSM inclusion regardless of inclusion level. However, the inclusion of 450 and 600 g kg^?1 RSM decreased the mid-intestinal trypsin, lipase, and amylase activities; the hepatic acyl-CoA/cholesterol acyl transferase; low-density lipoprotein receptor; and 3-hydroxy-3-methyl-glutaryl-CoA reductase activities. Similarly, dietary 600 g kg^?1 RSM inclusion inhibited the plasma catalase and hepatic glutathione peroxidase activities. These results indicated that 150 g kg^?1 RSM can be included in tilapia diets, whereas higher inclusion of RSM inhibited the growth rate, digestive enzyme activity, antioxidant capacity, and cholesterol metabolism.     

Effect of starvation on activities and mRNA expression of lipoprotein lipase and hormone-sensitive lipase in tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis> × <Emphasis Type="Italic">O. areus</Emphasis>)

A 4-week study was conducted to determine the effect of starvation on activities and mRNA expression of lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL) in hybrid tilapia (Oreochromis niloticus × O. areus). The tissue samples were sampled once a week. Results showed that body weight (BW) and hepatosomatic index (HSI) were decreased significantly (P < 0.05) during starvation. The percentages of crude fat and crude protein in the whole body and the fat content in muscle decreased significantly (P < 0.05), while the rate of moisture and crude ash increased significantly (P < 0.05). The response of LPL, HSL activities and mRNA expression in tissues was tissue dependent. The activities of LPL and HSL in muscle at day 7 were elevated by 2.5 times (P < 0.05) and 11.8 times (P < 0.05) of the value at day 0, respectively, and both then decreased to pre-starvation levels at day 14 and finally stabilized at a certain level afterward. LPL and HSL mRNA abundance in muscle remained relatively stable between 0 and 14 day; then, a significant increase was seen after 14 days. In the liver, LPL activity maintained a significantly increasing trend during starvation, while HSL activity rose dramatically at day 7 of starvation by 2.35 times (P < 0.05) and finally stabilized at a certain level. The mRNA abundance of liver LPL increased significantly during the whole process of starvation (P < 0.05), whereas the mRNA abundance of liver HSL decreased significantly at day 7 of starvation, elevating significantly afterward (P < 0.05).     

Comparative analysis of mitochondrial control region in polyploid hybrids of red crucian carp (<Emphasis Type="Italic">Carassius auratus</Emphasis>) × blunt snout bream (<Emphasis Type="Italic">Megalobrama amblycephala</Emphasis>)

The entire sequences of the mitochondrial (mt)DNA control region (CR) and portions of its flanking genes in the red crucian carp (RC) and blunt snout bream (BSB) as well as their polyploid hybrids (3nRB, 4nRB and 5nRB) were determined and subjected to a comparative analysis. The mtDNA-CRs of these five fish species ranged from 923 to 937 bp in length, they had the same flanking gene arrangement as other vertebrates and the pattern of nucleotide substitution bias was also similar to that in other vertebrates. Our data are consistent with the viewpoint of three domains [extended terminal associated sequence (ETAS domain), central conserved sequence block domain and conserved sequence block (CSB) domain] within the mtDNA-CR of mammals. On the basis our comparative analysis of the mtDNA-CRs of these five fish species, we were able to identify the consensus sequences of functional conserved units, including the ETAS, CSB-F, CSB-D, CSB-E, CSB1, CSB2 and CSB3 and putative promoter. The percentage of variable nucleotide positions (41.98%) in the central domain was lower than those in the ETAS and conserved domain (71.70 and 47.12%, respectively), suggesting that the central domain was the most conserved part of the mtDNA-CR. These results provide useful and important information for the further study of mtDNA-CR structure in fish. The sequence similarities of mtDNA-CR among the 3nRB, 4nRB, 5nRB hybrids and their respective female parents were higher than those among the 3nRB, 4nRB, 5nRB hybrids and their respective male parents, providing the direct evidence of stringent maternal inheritance of mtDNA-CR in the 3nRB, 4nRB and 5nRB hybrids.     

Effects of dietary supplementation with green tea waste on growth,digestive enzyme and lipid metabolism of juvenile hybrid tilapia, <Emphasis Type="Italic">Oreochromis niloticus</Emphasis> × <Emphasis Type="Italic">O. aureus</Emphasis>

An 8-week feeding trial was conducted to evaluate the effects of dietary supplementation with green tea waste (GTW) on growth, digestive enzyme and lipid metabolism of juvenile hybrid tilapia, Oreochromis niloticus × O. aureus. The fish (initial mean body weight, 12.63 ± 0.75 g) were fed five experimental diets that included 0 (control), 0.8, 1.6, 3.2 or 6.4 % of GTW in triplicate aquaria, twice daily. Growth performance, plasma metabolites content and liver and intestine digestive enzyme activities were determined. Fish accepted well all experimental diets during the trial, and no mortality was observed. The weight gain increased (P < 0.05) with the increase in GTW inclusion level up to 1.6 %, after which it decreased, but no significant differences between the control and high level (3.2 or 6.4 % of GTW) groups were observed. Moreover, fish fed on diets containing 0.8 and 1.6 % GTW had lower feed conversion ratio (FCR, 1.75 and 1.73, respectively) and had better protein deposition (higher protein efficiency ratio, PER, 1.73 and 1.71, respectively), compared to other treatments. No differences among groups were observed in whole body and dorsal muscle composition with the exception of lipid content which was lower in fish fed 6.4 % GTW diets, compared to other treatments. Lipase activities in liver or intestine were higher in fish fed GTW-supplemented diets with the exception of intestine lipase activities, which was unaffected, compared to the control. Similarly, liver lipoprotein lipase activities were also increased in fish fed diets supplemented a medium dose of GTW (1.6 or 3.2 %), compared to other treatments. However, intestine amylase activities were decreased in fish fed diets containing a high dose of GTW (3.2 and 6.4 %); while the liver amylase activities were unaffected by the GTW supplementation. Blood chemistry parameters were affected by GTW inclusion, except the values of triglycerides, which was unaffected. The values of total cholesterol, HDL cholesterol and LDL cholesterol increased with increasing GTW inclusion level up to 3.2 %, after which the values decreased. These results indicate that diets supplemented with appropriate concentration of GTW (from 0.8 to 1.6 %) may potentially serve as an effective functional food and additive for tilapia to improve growth performance, digestion efficacy and fat metabolism.     

Experimental infection of <Emphasis Type="Italic">Betanodavirus</Emphasis> in freshwater fish <Emphasis Type="Italic">Gambusia affinis</Emphasis> (Baird and Girard, 1853)—a potential infection model for viral encephalopathy and retinopathy

Betanodaviruses are the causative agents of the disease known as viral nervous necrosis (VNN) or viral encephalopathy and retinopathy (VER) in a variety of marine and freshwater fish species. The aim of this study was to demonstrate experimental infection of an isolate of betanodavirus (RGNNV genotype) in freshwater fish, Gambusia affinis, for elucidation of transmission mechanism and potential use as a laboratory model. Morbidity and mortality rate was significantly higher by injection route of infection as compared to immersion by bath and resembled the natural infection of juvenile marine fish. The fish in disease affected group showed severe neurological disorders accompanied by extensive vacuolar degeneration and mild to moderate neuronal necrosis of the brain in comparison to control. Amplification of ~?427 bp product in the variable region of the coat protein gene of betanodavirus was achieved by RT-PCR with 100% sequence homology to RGNNV genotype.