Fishmeal levels can be successfully reduced in white shrimp (Litopenaeus vannamei) if supplemented with DL‐Methionine (DL‐Met) or DL‐Methionyl‐DL‐Methionine (Met‐Met)

The main objective of this study was to evaluate the effect of methionine supplementation when reducing fishmeal levels in diets for white shrimp (Litopenaeus vannamei). Tested diets consisted of a positive control with 260 g/kg fishmeal (D1), two negative controls with 100 g/kg fishmeal and no amino acid (AA) supplementation (D2) or supplemented with lysine but not methionine (D3), and four additional diets with 100g/kg fishmeal supplemented with increasing levels of DL‐Met (1.0, 2.0 or 3.0 g/kg) (D4, D5, D6) or Met‐Met (1.0 g/kg) (D7). Each diet was fed to four groups of 30 shrimp for 8 weeks at a daily rate of 70 g/kg body weight. Reduction in fishmeal from 260 g/kg down to 100 g/kg did not significantly affect survival rate, feed conversion ratio (FCR), protein efficiency ratio (PER) or protein retention efficiency (PR%) of white shrimp. However, growth performance (final body weight, FBW; weight gain, WG; specific growth rate, SGR) was reduced when dietary fishmeal level was reduced from 260 g/kg (D1) to 100 g/kg without methionine supplementation (D2). The growth performance (FBW, WG and SGR) of shrimp was significantly increased by supplementation of the 100 g/kg fishmeal diet with increasing levels of DL‐Met (p < .05). Same performance as positive control (D1) was achieved with diets containing 100 g/kg fishmeal and supplemented with 3.0 g/kg DL‐Met or 1.0 g/kg Met‐Met. The highest values of growth performance (FBW, WG and SGR) were found in shrimp fed D6 and D7 diets, which were significantly higher than those of shrimp fed D2 and D3 diets (p < .05) but without statistical differences with shrimp fed D1, D4 and D5 diets (p > .05). The highest values of whole‐body and muscle protein contents were found in shrimp fed D1 diet, which were significantly higher than those of shrimp fed all other diets (p < .05). The highest value of intestinal tract proteolytic enzyme activity was found in shrimp fed Met‐Met‐supplemented diet (D7) and followed by the positive control diet (D1) and 3 g/kg DL‐Met‐supplemented diet (D6) (p < .05). The highest values of apparent digestibility coefficients (ADCs) of dry matter and crude protein were found in Met‐Met‐supplemented diet (D7) and followed by the positive control diet (D1) (p < .05). Shrimp fed the D1 diet showed the highest value of total essential amino acid (EAA) and was significantly higher than shrimp fed D2–D3 (p < .05) but without significant difference with shrimp fed D4–D7 (p > .05). In conclusion, results showed that same performance can be achieved with diets containing 260 or 100 g/kg fishmeal supplemented with 3.0 g/kg DL‐Met or 1.0 g/kg Met‐Met. Moreover, supplementation of limiting methionine in low‐fishmeal diets seems to improve the digestive proteolytic activity, improving digestibility of dry matter and protein, and eventually to promote growth of juvenile white shrimp in fishmeal reduction diets.     

草鱼胰岛素样生长因子1受体基因cDNA全序列的克隆及功能

本研究采用cDNA末端快速扩增法(RACE)克隆了草鱼(Ctenopharyngodon idellus)IGF-IR基因全长cDNA序列, 并对该基因在草鱼不同时期胚胎和成鱼不同组织中的表达进行了分析。序列分析表明, 草鱼IGF-IR基因cDNA序列全长5 741 bp, 包括5′端非翻译区822 bp, 3′端非翻译区581 bp, 开放阅读框4 338 bp, 共编码1 445个氨基酸。序列比对结果显示, 草鱼IGF-IR可能属于a型, 该基因编码的氨基酸序列与鲤(Cyprinus carpio)IGF-IRa、斑马鱼(Danio rerio)IGF-IRa和人类(Homo sapiens)IGF-IR的相似性分别为95%、93%和66%, 具有较高的同源性, 表明该基因在长期进化中具有较高的保守性。RT-PCR结果表明, 该基因从16 hpf(hours post fertilization)胚胎期到出苗期都有表达, 在成鱼大部分组织中均有表达。原位杂交结果显示, 草鱼IGF-IR mRNA在不同时期胚胎组织中广泛存在, 其中在脑部、脊索和尾部等生长旺盛组织的细胞中表达量较高。本研究为进一步探索草鱼IGF-IR基因在生长发育信号通路中的作用和育种提供了基础资料。

     

Neoechinorhynchus rutili (Müller, 1780) (Acanthocephala) in the whitefish Coregonm nasus (Pallas) sensu Svärdson from the Bay of Bothnia

Abstract. The occurrence of Neoechinorhynchus rutili (Müller, 1780) in the white-fish Coregonus nasus (Pallas) sensu Svardson from the Bay of Bothnia was investigated in 772 fish obtained as monthly or bimonthly samples during the period July 1975-January 1977.
In both years most parasites were found only in November and December. All of the 402 parasites found were immature and very small. Most of them were in the first third of the intestine, and only a few were attached to the mucosa. No encysted parasites were found in other any tissues. It is thus suggested that the whitefish of the Bay of Bothnia is only an accidental host for N. rutili .
A clear correlation was found between the importance of ostracods in the diet and the occurrence of N. rutili . The first intermediate host in the Bay of Bothnia was shown to be an ostracod, Candona neglecta (Sars.).     

Karyotype analysis of Oreochromis mortimeri (Trewavas) and Sarotherodon melanotheron (Rüppell)

The karyotypes of both Oreochromis mortimeri (Trewavas) and Sarotherodon melanotheron (Rüppell) are shown to consist of 22 pairs of chromosomes (2n = 44). In O. mortimeri, the karyotype is composed of 9 sm/st and 13 t chromosomes. In the case of S. melanotheron, the karyotype is composed of 15 sm/st, 2 m and 5 t chromosomes. The karyotypes of these species are therefore similar to those of the majority of other tilapia species, with that of S. melanotheron being considerably different from that previously reported for this species.     

Development of embryos in Mastacembelus mastacembelus (Bank & Solender, 1794) (Mesopotamian spiny eel) (Mastacembelidae)

In this study, the embryonic development of the eggs in the Mastacembelus mastacembelus (Bank & Solender, 1794) was examined. At the same time, possibilities of artificial breeding through artificial insemination were investigated. Artificial insemination was achieved by mixing the eggs of the mature female and sperm of the mature male samples caught with gill nets (22 × 22) in Ataturk Dam Lake in Turkey. To this end, first in a Petri dish (100 × 20), the testes were cut into small pieces with a lancet and the mixture of sperm–testes‐tissue was obtained. The fertilization rate of the eggs was found to be 80%. The diameter of the eggs ranged from 2.015to 1.147 mm. The perivitelline space formed 0.5 h after insemination. The first cleavage occurred at the animal pool 4 h after insemination. The oil droplets had fused to a single droplet 19 h after insemination. The blastoderm became an embryonic shield 30 h after insemination. The blastoderm covered almost half the egg 40 h after insemination and embryonic body was formed. The blastoderm covered almost the whole egg 50 h after insemination. Some somites were discernible 59 h after insemination. The embryonic body reached two‐third of the circumference of the egg 70 h after insemination. The tail bud began to separate from the yolk 77 h after insemination. A newly hatched larva was observed at 85 h after insemination.     

Nifurpirinol (Furanace; P-7138) related lesions on channel catfish Ictalurus punctatus (Rafinesque)

Abstract. Skin lesions developed on channel catfish, Ictalurus punctatus , exposed to 0-5 mg/1 Furanace for 4 or 14 days. Lesions developed 3 days after the 4-day exposure and on the eleventh day of the 14-day exposure. The lesions continued to develop after the fish were moved to untreated water. The lesions which began as dull areas of skin, sometimes resulted in erosion of skin and muscle which exposed the vertebrae. Bacteria were not isolated from the lesions except those with severely eroded muscle. The gills possessed lesions characteristic of a response to a toxic chemical agent.     

Use of MS‐222 (tricaine methanesulfonate) and propofol (2,6‐diisopropylphenol) as anaesthetics for the tetra Astyanax altiparanae (Teleostei,Characidae)

The aim of this study was to evaluate the anaesthetic effect of MS‐222 and propofol and determine their optimal concentrations for safe handling of the tetra Astyanax altiparanae in the laboratory. The fish were separated by length into three classes: I (1.5–5.0 cm), II (5.1–8.0 cm) and III (greater than 8.1 cm). Pilot tests were performed to evaluate the appropriate anaesthetic concentrations for inducing the five possible anaesthetic stages: I – sedation; II – light anaesthesia; III – deep anaesthesia; IV – surgical anaesthesia; and V – spinal collapse. After defining the maximum and minimum concentrations required to induce stage IV anaesthesia, the animals were exposed to five intermediate concentrations (n = 10 fish/concentration) of each anaesthetic for 15 min. The animals were then transferred to clean water to evaluate the time required for recovery. In addition, blood glucose levels were measured for class II and class III fish subjected to the previously defined ideal concentrations for each of the tested anaesthetics (n = 10 fish/treatment). Both evaluated substances are suitable to anaesthetize A. altiparanae. The optimal MS‐222 concentration was 90 mg L^?1, and this result was similar for all three size classes. The optimal propofol concentrations for inducing surgical anaesthesia in the size classes I, II and III were 0.22, 0.23 and 0.27 respectively.     

Sperm quality analysis of normal season (NG) and out-season by photoperiod manipulation (PG) of male rainbow trout broodstock (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>)

Sperm quality parameters in rainbow trout (Oncorhynchus mykiss) were investigated during normal season spawning (November–January) and out-season spawning (July–August) treated with artificial photoperiod manipulation. Normal spawning males (n?=?15) were kept in an open concrete pond under natural condition. Out-season spawning males (n?=?15) were treated with artificial LED light (50 lm/m²) in a closed concrete pond. In these two experimental groups, five fish were used in each of three spawning periods. The mean weight and body length of males (2?+ years, n?=?30) were 1213.43?±?39.43 g and 45.08?±?0.62 cm, respectively. Sperms were collected from July to August 2016 in the out-season spawning or photoperiod-manipulated group (PG) (water temperature 14.21?±?0.31 °C) and from December 2016 to January 2017, in the normal season spawning group (NG) (water temperature 8.81?±?1.03 °C). Volume of sperm, osmolality of seminal plasma, density of sperm, percentage of motile spermatozoa (MOT), curvilinear velocity (VCL), and duration of motility were measured for each male. Seminal plasma osmolality, density of sperm, and the motility of duration were 358.47?±?37.24 and 308.87?±?44.09, 4.37?±?2.10 and 9.8?±?1.56, and 8.8?±?2.42 and 24.6?±?6.76 in PG and NG, respectively. Fertilization rate was 37.79?±?9.37% and 94.51?±?1.33% in PG and NG, respectively. Sperm quality parameters showed significant differences in most of the cases (p?<?0.05) and fertilization rate at eyed egg stage (150–160 degree-days) was significantly higher in normal season spawning group than the photoperiod-manipulated group (p?<?0.05). Though the rate of fertilization was low in out-season, it was able to get enough gametes in summer using only artificial light having no changes in other parameters.     

Freshwater habitat associations between pink (Oncorhynchus gorbuscha), chum (O. keta) and Chinook salmon (O. tshawytscha) in a watershed dominated by sockeye salmon (O. nerka) abundance

To understand the interplay between habitat use and contemporary anadromous Pacific salmon, Oncorhynchus spp., distributions we explored the habitat associations of three species, pink (O. gorbuscha), chum (O. keta) and Chinook salmon (O. tshawytscha) in streams of the Wood River system of Bristol Bay, Alaska, where sockeye salmon (O. nerka) are numerically dominant. We developed models to investigate the occurrence of nondominant salmon in relation to habitat characteristics and sockeye salmon density, using four decades of salmon presence and abundance data. The frequency of occurrence and abundance of nondominant species increased with watershed drainage area and stream depth and decreased with sockeye salmon density. The range of occurrence varied from nonexistent to perennial for the other species in sockeye‐dominated streams. Increasing watershed area resulted in larger stream habitat area and deeper habitats, allowing for the sympatric occurrence and persistence of all salmon species. The relationships between habitat and the presence of these Pacific salmon help define their requirements but also remind us that the patterns of presence and absence, within the overall ranges of salmon species, have yet to be fully understood.     

Histopathology caused by Caligus epidemicus Hewitt (Copepoda: Caligidae) on captive Acanthopagrus australis (Günther) (Pisces: Sparidae)

Abstract. Highest densities of copepodids (≤5.3 cm ^-2), chalimus (≤8.5 cm ^-2) and redundant filaments (≤6.7 cm^-2) of Caligus epidemicus were found on the anterodorsal and anteroventral flanks, head and pectoral fins of Acanthopagrus australis (Günther). Copepodids eroded the epidermis and usually attached their frontal filament to the basement membrane on the inter-ray region of fins, as well as the fin rays or scales. Chalimus stages were associated with a healed epidermis and little tissue response. The most extensive tissue response was associated with the redundant frontal filament, and was characterized by infiltrating macrophages, multinucleated giant cells, and epidermal and fibroblast proliferation. No significant pathology could be attributed to either pre-adult or adult copepods.     

Stock–environment–recruitment models for North Atlantic albacore (Thunnus alalunga)

Different stock–recruitment models were fitted to North Atlantic albacore (Thunnus alalunga) recruitment and spawning stock biomass data. A classical density dependence hypothesis, a recent environmental‐dependence hypothesis and a combination of both were considered. For the latter case, four stock–environment–recruitment models were used: Ricker, Beverton‐Holt, Deriso's General Model (modified to take into account environmental effects) and conditioned Neural Networks. Cross‐validation analysis showed that the modified Deriso model had the best predictive capability. It detected an inverse effect of the North Atlantic Oscillation (NAO) on recruitment, a Ricker‐type behaviour with density dependent overcompensation when environmental conditions are unfavourable and a Beverton–Holt‐type behaviour towards an asymptotic recruitment carrying capacity with favourable environmental conditions. The Neural Network model also detected that under favourable environmental conditions high spawning stock biomass does not necessarily have a depensatory effect on recruitment. Moreover, they suggest that under extremely favourable environmental conditions, albacore recruitment could increase well above the asymptotic carrying capacity predicted by Beverton–Holt‐type models. However, the general decrease in spawning stock biomass in recent years and increasing NAO trends suggest that there is low probability of exceptionally large recruitment in the future and instead there is a danger of recruitment overfishing.     

Partial replacement of fishmeal by brewer's yeast (Saccharomyces cerevisiae) in the diets of Thai Panga (Pangasianodon hypophthalmus × Pangasius bocourti)

Feeding trials were carried out to evaluate the efficacy of the replacement of fishmeal with brewer's yeast (Saccharomyces cerevisiae) in the diets of Thai Panga (Pangasianodon hypophthalmus × Pangasius bocourti). Thai Panga juveniles with an average initial weight of 36.4 ± 0.07 g were randomly stocked in cages (1 × 1 × 1.5 m³) at a rate of 40 fish per cage. Experimental diets were formulated to provide isonitrogenous (320 g kg^?1 CP) and isocaloric (15.30 kJ g^?1) diets, by increasing brewer's yeast levels to replace 30%, 45%, 60% or 75% of dietary fishmeal. The control groups were comprised of the commercial feed (CA) and the basal diet without brewer's yeast (CB). Fish were rearing for 9 months. The final weights, weight gains, specific growth rate and daily growth rate showed that brewer's yeast can be used effectively as a substitute for up to 45% of the fishmeal. The replacement of fishmeal by brewer's yeast did not affect the feed efficiency, blood haematology and meat quality (P > 0.05). Alternative complement activity (ACH50), lysozyme activity and total immunoglobulin (Ig) in the fish in groups that had replacement feed diets were significantly higher than those of control group. Replacing 45% of fishmeal with brewer's yeast can improve the growth performance and immune response of the Thai Panga.     

Cardiac function in juvenile salmon (<Emphasis Type="Italic">Salmo salar L</Emphasis>) in response to lipopolysaccharide (LPS) and inhibitors of inducible nitric oxide synthase (iNOS)

Salmon alevins responded to LPS with an initial increase in heart rate followed by a steady decrease over 2–3 days exposure and after 4 days heart rate had decreased significantly compared to control alevins. Effects of increasing concentrations of the inhibitor 1400W, which is highly specific for iNOS, were investigated in LPS exposed and control alevins. In alevins exposed to LPS for 4 days the heart rate increased a few seconds after addition of 1400W which was attributed to the vasoconstrictory effects of lowered levels of NO. In unexposed alevins application of the inhibitor 1400W resulted in decreased heart rate after about 30 min. A possible explanation for the decrease in heart rate resulting from an LPS challenge is that increased expression of iNOS produces increased NO levels and vasodilation. There is support for this idea since inhibition of iNOS using 1400W reverses this response. The results suggest that larval fish have at least some elements of a functional cytokine signalling system.