Biodiversity and rarity distributions of native freshwater fish in an agricultural landscape: the importance of β diversity between and within water‐body types

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Supplemental effect of vitamin A in diet on the reproductive performance and egg quality of the Japanese flounder Paralichthys olivaceus (T & S)

This study investigated supplemental effects of vitamin A in diet on reproduction of Japanese flounder Paralichthys olivaceus (T & S). Broodstock were fed either a non‐supplemented diet (control diet; CD) or a vitamin A‐supplemented diet (supplemental diet; SD) 1 month before and during the spawning season. Both dietary groups began to spawn in mid‐January. At the beginning of spawning, no notable differences were found in spawning or egg quality between treatments. Egg production of the CD broodstock began to decrease from mid‐April and spawning stopped in late May, whereas the SD group continued to spawn until the end of June. Buoyant egg rate of the CD group was lower than that of the SD group throughout the spawning period. Hatching rate was not different between the CD and SD groups. The percentage of normal larvae in the CD group was significantly lower than in the SD group. It is concluded that a low vitamin A content in the diet has some negative effects on reproduction of flounder. The importance of supplementation of vitamin A in broodstock diet of the Japanese flounder is suggested.     

Identification of vitamin B12 and pseudovitamin B12 from various edible shellfish using liquid chromatography–electrospray ionization/tandem mass spectrometry

In this study, the vitamin B₁₂ contents were analyzed in the edible portions of various shellfish (bivalves and snails). High vitamin B₁₂ contents (30.5–53.3 μg/100 g wet weight) were detected in mussels, surf clams, bloody clams, and freshwater clams. However, scallops and abalone had extremely low vitamin B₁₂ contents (0.1–1.1 μg/100 g wet weight) which was attributed to only the muscle portions being edible. These results suggest that high levels of vitamin B₁₂ are accumulated in the viscera of shellfish. Vitamin B₁₂ levels were also significantly higher in bivalves than in snails. The corrinoid compounds purified from all bivalves were identified as “true” vitamin B₁₂ using liquid chromatography–electrospray ionization/tandem mass spectrometry. In edible snails, abalone, and pond snails, however, both vitamin B₁₂ and pseudovitamin B₁₂ (an inactive corrinoid) were observed to be the major and minor corrinoid compounds, respectively. Based on these results, we conclude that the whole bodies of these edible bivalves are excellent sources of vitamin B₁₂ for humans.     

Quality of eggs and spermatozoa of rainbow trout fed an n-3 essential fatty acid-deficient diet and its effects on the lipid and fatty acid components of eggs, semen and livers

ABSTRACT: The effect of an n-3 essential fatty acid (EFA) -deficient diet on spawning and on the lipid and fatty acid contents of eggs, semen and livers of rainbow trout Oncorhynchus mykiss was investigated. Fish were split into two groups and fed either of two diets for a period of 4 months prior to the start of the spawning season. The control group was fed a commercial diet, containing n-3 EFA, whereas the experimental group was fed an n-3 EFA-deficient diet. Fish were 3 years old at the time of spawning. Eggs and semen were stripped off five females and five males from each diet group and cross-fertilized. Two of the five males fed the deficient diet showed a lower sperm motility, resulting in slightly lower mean hatching rates when crossed with eggs of either group. Higher lipid contents in the EFA-deficient diet were reflected in the egg and semen lipid contents, whereas the lipid contents of male livers of both diet groups were higher than those of female livers. In livers and eggs, the main polar lipid was phosphatidylcholine accompanied by phosphatidylethanolamine in sperm polar lipids. The non-polar lipids of eggs were mainly triacylglycerols but in livers and semen, free fatty acids and free sterols were more abundant. Essential fatty acids, namely n-3 highly unsaturated fatty acids and linolenic acid, were generally lower in eggs, semen and livers sampled from the EFA-deficient diet group. These results indicate that the fertilization, eyed and hatching rates obtained from crossings with males fed the EFA-deficient diet were slightly lower because of the dietary effect on sperm motility. Moreover, lipids of eggs, semen and livers of male and female rainbow trout were influenced greatly by their dietary availability.     

The Effects of Salinity on Reproductive Performance of Florida Red Tilapia

The reproductive performance of yearling Florida red tilapia broodstock was studied in laboratory aquaria at salinities of 1 (freshwater), 9, 18, 27 and 36 ppt under controlled photoperiod (14 L:10 D) and temperature (28 C).
Spawning was observed at all salinities, although egg production per unit female weight at each spawn was significantly higher at 1 ppt than at higher salinities. An inhibitory effect of salinity on reproductive performance was evidenced by a trend toward lower fertilization, hatching, and survival of prejuveniles with increasing salinity. Fry production per unit female weight declined at salinities above 18 ppt. The results suggest that Florida red tilapia broodstock may be maintained under salinities as high as 18 ppt without impairing fry production, suggesting that hatchery production in brackishwater would be practical in areas where freshwater resources are limiting.     

Effects of dietary protein and lipid levels on growth performance and body composition of black sea bass Centropristis striata (Linnaeus 1758) during grow-out in a pilot-scale marine recirculating system

The influence of four formulated practical diets, with different protein and lipid levels, on the growth and body composition of black sea bass ( Centropristis striata L.) pre-adults was evaluated in a pilot-scale marine recirculating system. Four test diets were prepared with a combination of two protein levels (44% and 54%) and two lipid levels (10% and 15%). The diets were as follows: low protein and low lipid (LP:LL; 44:10), low protein and high lipid (LP:HL; 44:15), high protein and low lipid (HP:LL; 54:10) and high protein and high lipid (HP:HL; 54:15). Fish (mean weight=75.5 g) were fed the respective diets for 90 days. For fish fed LP:HL, body weight gain was significantly ( P <0.05) higher than fish fed LP:LL. Increasing the protein level from 44% to 54% did not produce a significant effect on weight gain at high lipid level. A significant ( P <0.01) interactive effect between dietary protein and lipid levels on the growth and feed utilization was observed. Total lipid content in the whole body, muscle and liver was significantly affected by the dietary lipid levels. The results suggested that a combination of 44% dietary protein and 15% lipid was optimal for the growth of black sea bass.     

Effect of dietary taurine supplementation on growth performance of yellowtail juveniles <Emphasis Type="Italic">Seriola quinqueradiata</Emphasis>

ABSTRACT:   The effect of taurine on growth of yellowtail juveniles Seriola quinqueradiata was investigated by a feeding experiment of diets containing various taurine levels. Test diets supplemented with 0, 0.5, 1.0, 1.5 and 2.0% of taurine were prepared. These diets were fed to yellowtail juveniles with an initial mean body weight of 0.5 g for 6 weeks. Supplementation of taurine in the diet of yellowtail improved their growth performance significantly ( P  < 0.05) over the initial 3-week period. The fish fed with the taurine-supplemented diet improved in percent gain and feed efficiency over both 3 and 6 weeks. Taurine content in the muscle proportionally increased with the dietary taurine level. The fish fed without supplemented taurine diet showed higher contents of serine in the muscle. With each increase in the inclusion level of taurine content in the diet, the concentration of serine in the muscle decreased. The cystathionine content in the muscle of each group was unchanged. These results suggest that taurine supplementation in the diet not only improves growth but also affects the sulfur amino acid metabolism of yellowtail juveniles.     

Gonadal development in early life stages of <Emphasis Type="Italic">Spratelloides gracilis</Emphasis>

ABSTRACT:   The gonad of Spratelloides gracilis was not sexually differentiated in the yolk-sac, preflexion, flexion and postflexion stages. Sexual differentiation and development of the ovary and testis started in the transition stage from larva to juvenile. In juveniles at the fin ray completion stage, the ovary and testis could be distinguished because the ovary contained germ cells initiating meiosis and the testis had blood vessels and a high density of somatic cells. The ovary further developed in larger juveniles to have oocytes of perinucleolus stage together with those of the chromatin nucleolus stage, and oogonium. However, in the testis of larger juveniles, primary spermatogonium began proliferation by meiosis. Sexual differentiation may be regarded as one of morphological and functional changes accompanying metamorphosis in S. gracilis . Some fish larger than the mature size of 60 mm standard length had advanced germ cells and functional gonads, others did not have functional gonads. The distal end of the immature gonads did not connect with a genital duct near the anus. These observations indicate that S. gracilis has large variability in size-at-maturity. The variability in size-at-maturity in S. gracilis , together with large variability in age-at-maturity, may constitute an ecological basis for an extended spawning season in S. gracilis .     

Post-antibiotic effect of orbifloxacin against Escherichia coli and Pseudomonas aeruginosa isolates from dogs

Orbifloxacin is a fluoroquinolone drug used widely in companion animal medicine. In this study, we firstly determined post-antibiotic effects (PAEs) and post-antibiotic sub-minimum inhibitory concentrations (MIC) effects (PA-SMEs) of orbifloxacin for two strains each of Escherichia coli and Pseudomonas aeruginosa from dogs, and these parameters were compared with those of enrofloxacin. At twice the MIC, the PAEs of orbifloxacin ranged from -0.28-0.93 h (mean, 0.29 h) for E. coli and -0.18-1.18 h (mean, 0.37 h) for P. aeruginosa. These parameters were not significantly different for E. coli and shorter for P. aeruginosa, compared to enrofloxacin (P < 0.05). Continued exposure to 0.1, 0.2, and 0.3 the MIC of orbifloxacin resulted in average PA-SMEs of 0.55, 1.11, and 2.03 h, respectively, for E. coli, and 1.04, 1.40, and 2.47 h, respectively, for P. aeruginosa. These PA-SMEs, which had no significant differences with those of enrofloxacin, were significantly longer than the corresponding PAEs (P < 0.05). These results suggest that the PA-SME of orbifloxacin for E. coli and P. aeruginosa can be meaningfully prolonged by increase of sub-MICs.