Effect of ascorbic acid supplementation on zootechnical performance,haematological parameters and sperm quality of lebranche mullet Mugil liza

The feed provided to breeding fish is one of the main factors influencing the quality of fish gametes. This study was carried out to evaluate the influence of ascorbic acid on growth, haematological parameters and sperm quality of Lebranche mullet males (Mugil liza). Six diets with different levels of ascorbic acid (0; 53; 107; 216; 482 and 708 mg/kg) were tested in triplicate for 75 days. During spermiation (first gonadal maturation), 144 individuals (205.7 ± 11.5 g and 25.7 ± 0.4 cm) were randomly distributed in 18 experimental tanks. Growth parameters were evaluated at the beginning and end of the experiment. Fish blood was collected to analyse glucose, total protein and erythrocyte count (EC) (n = 9). Fish (n = 12) from each treatment were euthanized to determine hepatosomatic index (HSI) and gonadosomatic index (GSI). Semen was collected to evaluate spermatic density, cell membrane integrity and sperm motility. No difference (p > .05) was found on growth parameters, GSI, HSI and total protein. However, EC was lower in fish fed without ascorbic acid (the control group). Ascorbic acid supplementation provided positive effects on sperm characteristics. Fish from treatments with 53 and 107 mg/kg presented the best results for motility time (133.30 ± 4.25 and 135.00 ± 2.77 respectively). Treatments with 107, 216 and 708 mg/kg provided the best results for motility rate (92.0 ± 2.9%, 93.0 ± 5.8% and 93.0 ± 5.8% respectively). Supplementation with 107 and 216 mg/kg provided the best results for plasma membrane integrity (70.12 ± 9.10% and 76.3 ± 3.1% respectively). Lower spermatic density was observed in fish without ascorbic acid supplementation, although no difference was found in sperm density among the treatments with ascorbic acid (p < .05). Considering these results, supplementation of dietary ascorbic acid between 107 and 216 mg/kg optimizes the spermatic quality in males of lebranche mullet.     

Effects of tidal flat reclamation on sediment quality and hypoxia in Isahaya Bay

• 1. Ariake Bay, which is located in western Japan, has a large tidal range (>6 m) and a vast tidal flat (200 km²). In the early 1990s, the government‐managed Isahaya Reclamation Project began in the western part of Ariake Bay. A 16‐km² area of tidal flat in the inner part of Isahaya Bay was destroyed through reclamation and separated from the sea by a dyke, which created land and a freshwater reservoir.
• 2. Since the initiation of the project, fishery yields around Isahaya Bay have dramatically decreased. The objective of this study was to clarify the relationship between the work associated with the Isahaya Reclamation Project and the recent environmental deterioration in Ariake Bay, with references to present sediment thickness and organic matter content, and hypoxic water distributions in Isahaya Bay.
• 3. The organic matter load from the reservoir has increased since the initiation of the reclamation project and has been associated with a thick layer of fine sediment at the bottom of Isahaya Bay. The thickness of fine sediment and the total organic carbon content were higher in Isahaya Bay than in the freshwater reservoir.
• 4. Based on measurements in August 2001, hypoxic water spread widely in and around Isahaya Bay; the lowest dissolved oxygen (DO) concentration (0.53 mg L^?1) was observed just outside the dyke. An analysis based on a two‐layered box model using data obtained in August 2001 showed that the DO consumption rate in the bottom layer was high (0.61 mg O₂ L^?1 day^?1), and that 22–41% of the total organic carbon load needed to induce the hypoxic water was derived from the reclamation area.
• 5. Our findings strongly suggest that enclosed seas may suffer from eutrophic and hypoxic conditions because of their low seawater‐exchange rate. A comprehensive conservation programme and environmental assessment including physical and material transport processes in the system is needed to manage the environment of the enclosed sea.

Copyright © 2005 John Wiley & Sons, Ltd.     

All-male Tilapia Hybrids of Two Strains of Oreochromis niloticus

Hybridization between Nile tilapia Oreochromis niloticus (Local and Stirling University strains) and blue tilapia O. aureus was found to be a tool to produce monosex populations. In order to select a purebred that produces all- or nearly all-male hybrids with high productivity, O. niloticus females and their diploid gynogenetics (meiogynes and mitogynes) were hybridized with O. aureus males. The sex ratio of progenies was evaluated from inter- and intraspecific crosses of two strains of Nile tilapia. Single-pair matings and group spawns under hatchery conditions showed no deviation ( P > 0.01) from the expected sex ratio of intraspecific crosses among two strains of Nile tilapia. However, a higher proportion of male progenies in blue tilapia was observed in group spawns in pond ( P < 0.004) and hatchery conditions ( P < 0.01). Only the Stirling strain and mitogynes produced all-male progenies under laboratory conditions. There were significant differences ( P < 0.05) in growth among hybrid progeny groups, when gynogens and their regular O. niloticus (Local strain) females were crossed with O. aureus males. Six-month hybrid offspring from mitogyne female parents grew better than those from regular and meiogyne female broods.     

Natural Stable Isotopes for Determination of Gastrointestinal Transit Time in Fish

This study evaluated the application of stable isotopes of carbon as an alternative and more accurate method to determine gastrointestinal transit time (GTT) in fish by comparing it to the inert marker method. The stable isotope method detects alterations of the normal carbon flow in a biological system by analyzing naturally occurring isotopes of carbon, contrary to studies based on conventional techniques that apply external markers to the diet to determine GTT through visual observation of the color change in feces. Therefore, 320 pacu, Piaractus mesopotamicus juveniles were reared in 32 tanks under two different temperatures (25 and 29 C). The pacu juveniles received two different diets, one based on ingredients derived from C₃ photosynthetic cycle plants and the other based on C₄ plant ingredients, both containing titanium oxide (TiO₂) as a marker. After 40 d, the isotopic signature of the diets was changed, and the marker was replaced by chromic oxide (Cr₂O₃). In the isotopic technique, the feces were analyzed to determine the exchange in the isotopic ratio of carbon δ¹³C. Both methods found that GTT was faster (nearly 6 h) in fish at 29 C when using the C₄/C₃ feeding strategy and slower in fish at 25 C using the C₃/C₄ strategy (15 h by inert marker and 18 h by the isotopic method). In conclusion, GTT determination in pacu juveniles using the stable isotope technique exhibits the same accuracy obtained with the inert marker method at temperatures suitable (nearly 29 C) for the metabolism of these animals.     

Distribution of a fish pathogen Listonella anguillarum in the Japanese flounder Paralichthys olivaceus hatchery

The present study was undertaken to investigate the distribution of Listonella anguillarum in a Japanese flounder (Paralichthys olivaceus) hatchery. A total of 2704 isolates were obtained from the developing fish, live diets and artificial feeds of Japanese flounder and their rearing water, 439 of which were identified as L. anguillarum by the combining incubation on thiosulfate-citrate-bile salt-sucrose (TCBS) agar at 35 °C overnight with polymerase chain reaction (PCR) detection for the VAH1 hemolysin gene. L. anguillarum was detected in all seven rotifer samples, with densities of 2.5 × 10³ to 4.6 × 10⁶ colony forming units (CFU) g^− 1. Both the analyzed samples of Nannochloropsis oculata contained this bacterium at densities of 1.6 × 10⁴ to 1.4 × 10⁵ CFU g^− 1. L. anguillarum was detected in only one of four samples of Artemia nauplii with a density of 4.8 × 10⁵ CFU g^− 1 (35%) and it was not detected in the two analyzed artificial feed samples. L. anguillarum was detected in 11 of 18 specimens of larval and juvenile Japanese flounder at densities of 5.0 × 10¹ to 7.4 × 10⁵ CFU g^− 1, while it was not detected in the two analyzed egg specimens of Japanese flounder. These results indicate that L. anguillarum associated with the developing Japanese flounder is likely derived from rearing water and live diets such as rotifers. Further, it is strongly suggested that L. anguillarum is a transient bacterium of the intestinal microflora for the Japanese flounder but is a permanently indigenous one for the Japanese flounder hatcheries.     

Multi-locus sequence typing of Salmonella enterica subsp. enterica serovar Enteritidis strains in Japan between 1973 and 2004

Salmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis) was responsible for a worldwide pandemic during the 1980s and 1990s; however, changes in the dominant lineage before and after this event remain unknown. This study determined S. Enteritidis lineages before and after this pandemic event in Japan using multilocus sequence typing (MLST). Thirty S. Enteritidis strains were collected in Japan between 1973 and 2004, consisting of 27 human strains from individual episodes, a bovine strain, a liquid egg strain and an eggshell strain. Strains showed nine phage types and 17 pulsed-field profiles with pulsed-field gel electrophoresis. All strains had homologous type 11 sequences without any nucleotide differences in seven housekeeping genes. These MLST results suggest that S. Enteritidis with the diversities revealed by phage typing and pulsed-field profiling has a highly clonal population. Although type 11 S. Enteritidis may exhibit both pleiotropic surface structure and pulsed-field type variation, it is likely to be a stable lineage derived from an ancestor before the 1980s and/or 1990s pandemic in Japan.     

Physiological characteristics of blue sac disease in chum salmon alevins

Fisheries Science - Blue sac disease (BSD) in salmonids results in the abnormal accumulation of ascites fluid and can often lead to mass mortality. However, the symptoms and causes of BSD remain...     

Affected homologous chromosome pairing and phosphorylation of testis specific histone, H2AX, in male meiosis under FKBP6 deficiency

A gene for FK506 binding protein 6 (Fkbp6) expresses during a specific stage of male and female meiosis. Disruption of the gene influences male reproduction, i.e. arrests spermatogenesis, but not female reproduction. Using the mouse model (targeted disruption), the role of the gene in homologous chromosome pairing has been demonstrated in a previous study. For further understanding the function of Fkbp6 in chromosome synapsis, we evaluated chromosome pairings during male meiosis in the as/as rat, a spontaneous null mutation, and compared them with those of the mouse model. Electron microscopy of the pachytene nuclei unveiled several types of abnormal chromosome pairing in the rat model, as shown in the mouse previously. The frequencies of aberrant pairings in the knockout mice and mutant rats were 42 of 67 nuclei (62.7%) and 20 out of 74 nuclei (27.0%), respectively. In order to clarify the mechanism of male specific infertility in Fkbp6 deficiency, the localization of gammaH2AX, a marker protein of XY chromosome inactivation during male meiosis, was examined. Immunostaining of gammaH2AX unveiled normal localization of the molecule to XY chromosomes (XY body) in both models, showing the independency of FKBP6 in sex chromosome inactivation. Besides the XY body, focal localization of gammaH2AX was observed in accordance with the unsynapsed chromosomes in both types of null animal. These results indicate the fundamental role of Fkbp6 in homologous chromosome synapsis during male meiosis. In conclusion, male specific infertility under Fkbp6 deficiency remains unsolved.     

Antinociceptive effect and acute toxicity of the Hyptis suaveolens leaves aqueous extract on mice

The aqueous extract of Hyptis suaveolens leaves was studied for their antinociceptive property in chemical and thermal models of nociception in mice. Oral administration of the aqueous extract (100, 200, and 400 mg/kg) dose-dependently reduced the number of writhings induced by acetic acid, decreased the licking activity of the early phase in formalin test and increased the reaction time in hot-plate test. The antinociceptive effect was significantly antagonized by naloxone (3 mg/kg; i.p.). Preliminary acute toxicity study showed that no animal death with doses up to 5 g/kg (p.o.).     

Quantitative structure-activity study of herbicidal N-aryl-3,4,5,6-tetrahydrophthalimides and related cyclic imides

The quantitative relationship between structure and inhibitory activity against the root growth of sawa millet of 30 N-aryl-3,4,5,6-tetrahydrophthalimides and 88 related N-aryl cyclic imide compounds (3-aryl-1,5-tetramethylenehydantoins, 4-aryl-1,2-tetramethylenetriazolidine-3,5-diones, and their thiocarbonyl analogs) was analyzed by means of physicochemical parameters of the aryl substituents and regression analysis. The results showed that, in each series of these classes of compounds, the position-specific steric effects of aromatic substituents, as represented by Verloop's STERIMOL values, are highly important in determining the inhibitory potency of the compound.