Effects of modern drainage systems on the spatial distribution of loach in rice ecosystems

• 1. Although rice fields support many aquatic species, recent agricultural intensification in Asia has led to loss of biodiversity, such as freshwater fish, in exchange for increased agricultural productivity. In Japan, modern drainage systems have been introduced in recent decades.
• 2. This study investigated the effects of several aspects of modern drainage systems on the spatial distribution of dojo loach Misgurnus anguillicaudatus, a dominant fish species in Japanese rice fields.
• 3. Multimodel inference approaches and hierarchical partitioning were used to estimate the direction and degree of the effect of each system on the spatial distribution of dojo loach.
• 4. Three variables related to modern drainage systems (gaps between fields and ditches, the type of drainage ditch, and the presence of underground drainage pipes), flooding dates, and spatial autocovariates showed significant influence on the abundance of loach. In particular, gaps had the largest impact among all the variables on loach in the later part of the survey (June).
• 5. Based on the results, the effectiveness of several conservation methods implemented for paddy‐dwelling fish in Japan was discussed. The knowledge will be a guide to the appropriate conservation of freshwater fish in Asia and other countries.

Copyright © 2011 John Wiley & Sons, Ltd.     

Development of new self-feeding system for mass rearing of ayu <Emphasis Type="Italic">Plecoglossus altivelis altivelis</Emphasis> under artificial and natural light-dark cycles

Self-feeding of grouped ayu Plecoglossus altivelis altivelis was examined under an artificial light-dark (LD) cycle and natural day length using a trigger with a photosensitive sensor. In Experiment 1, approximately 15 juvenile fish (mean body weight, 0.6 g) were kept in 60-L glass tanks (four tanks) under LD 12∶12 (lighting period 06∶00–18∶00 hours) and self-feeding and locomotor activities were simultaneously recorded. Self-feeding was detected within one day and feeding activities were strongly synchronized to the LD cycle, with almost strictly diurnal feeding (98.2%). Although locomotor activities in the upper part of the tank were also greatest during the light phase (76.8%), the activity profiles were different from those of self-feeding, suggesting the validity of the photosensitive sensor. In Experiment 2,25 fish (mean body weight, 15 g) were kept in outdoor 1000-L tanks (four tanks) under natural day length and water temperatures in May, and self-feeding was recorded from mid-August. Stable self-feeding was observed from early September in all the tanks. Nearly all food demands were diurnal, and usually crepuscular. Somatic growth was seen in all tanks. These results demonstrate that the self-feeding system using a photosensitive sensor is applicable for grouped juvenile ayu as small as 0.6 g and adult fish reared under natural conditions.     

Effects of feeding time on approaching behavior to food odor in goldfish

ABSTRACT:   Effects of feeding time on approaching behavior to food odor in goldfish Carassius auratus were examined using the Y-maze flow-through system to test whether the behavior differed according to feeding time and experimental time. Fish were fed at 08.00, 12.00 or 16.00 hours once a day or three times (08.00, 12.00 and 16.00 hours) a day for at least 3 weeks under a natural photoperiod, and at 22 ± 2°C, preference reactions to food odor were tested at 08.00, 10.00, 12.00, 14.00 and 16.00 hours. The fish fed once a day showed significant positive approaching behavior only at the time when they were normally fed. The fish fed three times a day showed no significant positive approaching behavior. These results suggest that goldfish can remember when food is available and/or that there exists a mechanism to inhibit approaching behavior when food is not available.     

Thermal stress responses of a sterile mutant of Ulva pertusa (Chlorophyta)

SUMMARY: The thermal stress responses of a sterile mutant of the marine alga Ulva pertusa were investigated at 20°C and 30°C. The amounts of the photosynthetic pigments, β-carotene, chlorophylls a and b , lutein, neoxanthin, and violaxanthin, were 1.4–2.4 times higher in the 30°C-cultivated alga than in the 20°C-cultivated alga. The free amino acids, asparagine, aspartic acid, glutamine, glutamic acid, glycine, and serine, were abundant in the 20°C-cultivated alga, and increased 1.9–10.5-fold in response to thermal stress (30°C). Total carbon and nitrogen contents also increased in the 30°C-cultivated alga. Sodium dodecylsulfate-polyacrylamide gel electrophoretic patterns of total proteins extracted from both temperature-treated algae showed the increases of 20, 25, and 90 kDa proteins in the 30°C-cultivated alga. Isozyme assays for 20 enzymes showed a different banding pattern only in the case of glutamate dehydrogenase (GDH). Although it was observed that both temperature-treated algae possessed NAD⁺- and NADP⁺-specific GDH, the 30°C-cultivated alga had an additional NADP⁺-specific GDH (NADP-GDH). These results suggest that NADP-GDH compensates for the thermally induced decreases in nitrogen assimilation efficiency and thereby regulates nitrogen metabolism under conditions of temperature stress.     

The Immunomodulating Effect of Phlorotannins from a Brown Alga,Eisenia nipponica,on Mice Stimulated with Ovalbumin through T Cell Regulation

Plant Foods for Human Nutrition - The immunomodulating effect of phlorotannin was investigated in mice stimulated by ovalbumin. When analyzing the main components of phlorotannin concentrate (PTC)...     

Breeding of white-grained wheats for Japan

The possibility of breeding white-grained wheats tolerant to pre-harvest sprouting under Japanese humid weather conditions is discussed. New genetic dormancy sources, such as, AUS1408, 8019R1 and RyuuMai7, were evaluated for seed dormancy in different weather conditions. Some white-grained dormant wheats showed a strong dormancy similar to that of red-grained dormant wheats in a greenhouse trial, in the field their dormancy expression was much less than the red wheats. Three populations involving crosses with these new sources for winter wheat breeding were examined under repeated selection for seed dormancy. Some dormant white-grained lines, as judged under glasshouse conditions, were developed. Again the level of dormancy in these lines was not sufficient compared to red dormant varieties in field trial. In order to develop truly superior dormant white-grained materials, one population involving crosses with two dormant varieties, AUS1408 and 8019R1, was examined under repeated selection. From these materials we succeeded in breeding lines that had not only a good dormancy but also showed adaptation to Japanese weather conditions, including earliness, scab resistance and good seed appearance. However again the dormancy of these lines in field trial was not sufficient compared to that of red wheats and there was not a clear difference for seed dormancy between breeding lines and their parents. We conclude therefore that more work involving the use of new genetic sources or new breeding techniques, will be necessary for breeding advanced lines that maintain a sufficient tolerance to PHS in humid Japanese weather condition. This revised version was published online in August 2006 with corrections to the Cover Date.     

Inhibition of bacterial adhesion and salmonella infection in BALB/c mice by sialyloligosaccharides and their derivatives from chicken egg yolk

The effects of an egg-yolk-derived sialyloligosaccharide (YDS), asialo-YDS, and a sialylglycopeptide of YDS (SGP) on bacterial adhesion to intestinal epithelial cells and on Salmonella infection in BALB/c mice were examined. YDS, its derivative asialo-YDS, and SGP strongly inhibited the binding of Salmonella enteritidis but not E. coli K-88 to a human epithelial cell line, Caco-2. In a Salmonella infection experiment using BALB/c mice, oral administration of these reagents effectively prevented the bacteria from proliferating in spleen, as well as preventing lethality. An experiment using radioactive SGP orally administered to mice revealed that the compound was absorbed from the intestine into blood and eliminated via urine within 8 h. However, these reagents did not influence the production of TNF-alpha or NO. in culture macrophages. The results suggest that they inhibit Salmonella infection not by activating macrophages but by inhibiting the entry of bacteria through the gut, suggesting that YDS and its derivatives are useful for preventing Salmonella infection when ingested continuously.     

Investigation of genetic diversity and inbreeding in a Japanese native horse breed for suggestions on its conservation

Because native breeds can serve as genetic resources for adapting to environment changes, their conservation is important for future agroecosystems. Using pedigree analysis, we investigated genetic diversity and inbreeding in Japanese Hokkaido native horses, which have adapted to a cold climate and roughage diet. Genetic diversity was measured as the number of founders and the effective number of founders, ancestors and genomes. All metrics imply a decrease in genetic diversity. A comparison of these metrics suggested that pedigree bottlenecks contributed more than did random gene losses to the reduction of genetic diversity. Estimates of marginal contributions of ancestors suggest that the bottlenecks arose mainly because related stallions had been used for breeding. A tendency for an increase in inbreeding coefficients was observed. F‐statistics revealed that a small effective population size majorly contributed to this increase, although non‐random mating in particular regions also contributed. Because the bottlenecks are thought to have reduced the effective population size, our results imply that mitigation of bottlenecks is important for conservation. To this end, breeding should involve genetically diverse stallions. In addition, to prevent non‐random mating observed in particular regions, efforts should be made to plan mating with consideration of kinships.     

Dominant Characteristics Between <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis> and <Emphasis Type="Italic">Cyclotella</Emphasis> Sp. Accompanying Dilution Process in Eutrophic Lake

Although dilution of lake water has been used for improvement of water quality and algal blooms control, it has not necessarily succeeded to suppress the blooms. We hypothesized that the disappearance of algal blooms by dilution could be explained by flow regime, nutrient concentrations, and their interaction. This study investigated the effects of daily renewal rate (d), nitrogen (N) and phosphorus (P) concentration, and their interaction on the domination between Microcystis aeruginosa and Cyclotella sp. through a monoxenic culture experiment. The simulation model as functions of the N:P mass ratio and dilution rate (D) (calculated from d) was constructed, and the dominant characteristics of both species were predicted based on the model using parameters obtained in a monoculture experiment and our previous study. Results of monoxenic culture experiment revealed that M. aeruginosa dominated in all conditions (d = 5 or 15%; N = 1.0 or 2.5 or 5.0 mg-N L^?1; P = 0.1 or 0.5 mg-P L^?1) and the predicted cell densities were substantially correspondent to experimental data. Under various N:P ratios and D values, characteristics of domination for each species were predicted, indicating that Cyclotella sp. tended to be dominant under high P concentrations (P ≥ 0.36 mg-P L^?1) when the N:P ratio was less than 7.0, and M. aeruginosa could not form algal blooms at the N:P ratio ≤ 7.0 (N ≤ 0.7 mg-N L^?1). It was also suggested that the dilution rate leading to the Cyclotella sp. domination required 0.20 day^?1 or higher regardless of the N:P ratios.

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Graphical Abstract ? M. aeruginosa and Cyclotella sp. could be a superior competitor in nutrient-limited and nutrient-rich conditions, respectively. ? The simulation model in this study indicated that the predicted cell density and nutrient concentration were substantially correspondent to experimental data. ? The model predicted that Cyclotella sp. tended to be dominant at the P ≥ 0.36 mg-P L^?1 when the N:P ratio was less than 7.0, and M. aeruginosa could not form algal blooms at the N:P ratio ≤ 7.0 (N ≤ 0.7 mg-N L^?1).