Zen’ichiro Kawabata

Hiroshima University, Hirosima, Hiroshima, Japan

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Publications (22)27.89 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: To understand the differences in the stress sensitivities between domesticated Eurasian and Japanese indigenous strains of common carp (Cyprinus carpio Linnaeus 1758), we compared concentrations of cortisol released into the water in response to handling of the two types of strains. At 0.5 and 2 h after the handling treatment, the cortisol emission was greater from the Eurasian strain than from the Japanese strain. There were no differences between the strains in the cortisol levels after 4 to 24 h. We found that Eurasian strains exposed to the unnatural stressor (i.e., handling) exhibited a higher cortisol response than the Japanese strain.
    Ichthyological Research 01/2014; 61:165-168. · 0.90 Impact Factor
  • Zen’ichiro Kawabata
    Ecological Research 01/2011; 26(5):863-864. · 1.55 Impact Factor
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    ABSTRACT: The littoral zone of lakes and lagoons is often used by fish for feeding or reproduction. However, the large changes in temperature that are typical of natural environments, including the littoral zone, represent a potential stressor for fish. Despite the importance of this habitat, little is known about the effect of daily temperature fluctuations on the stress responses of fish. We monitored daily temperature changes in the near-shore and offshore regions of a natural lagoon between May and July 2008–2010. We observed large temperature fluctuations more frequently in the near-shore zone than the offshore zone. We then exposed common carp (Cyprinus carpio) to a temperature regime similar to that observed in the near-shore zone and measured the levels of cortisol released into the water. The rate of cortisol release increased when carp were exposed to an increase in temperature of ~0.6°C/h over a 5-h period. Conversely, there was no change in the rate of release when temperatures decreased. Our results highlight the importance of maintaining high temporal resolution when evaluating the stress response to daily fluctuations temperature. KeywordsCortisol–Fish–Non-invasive assay–Shore–Stress–Temperature
    Hydrobiologia 01/2011; 675(1):65-73. · 1.99 Impact Factor
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    Norio Yamamura, Arndt Telschow, Kimiko Uchii, Zen’ichiro Kawabata
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    ABSTRACT: In reproduction, many animal species migrate to local habitats that are appropriate for reproduction and for growth of newly born offspring. The examples are ubiquitous among crabs, freshwater fishes, amphibians, migratory birds, and sea animals. We propose a basic equation for population dynamics of such animals, assuming that the number of offspring is proportional to the area of the local breeding habitats as a first approximation. This equation is very simple to be solved analytically, and useful for representing environmental issues of habitat destruction and degradation. According to the equation, the adult density in breeding habitats increases temporarily during habitat destruction and returns to the original density afterwards. The temporal peak value is higher for a larger proportion of area with destruction, a higher temporal rate of destruction, and a higher survival probability of the adults. In contrast, habitat degradation results simply in a decrease of the adult density in breeding habitats. Using this equation, we will discuss the vulnerability of populations to epidemic diseases due to temporal local high densities with decreasing breeding habitats by human activities, exemplifying an outbreak of cyprinid herpesvirus 3 for wild carps in Lake Biwa. KeywordsBreeding habitat–Mathematical model–Temporal high density–Infectious disease–Cyprinid herpesvirus 3
    Ecological Research 01/2011; 26(1):181-189. · 1.55 Impact Factor
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    ABSTRACT: Lakeshore developments change the physicochemical properties of the underwater environment by altering shore morphometry, which may have significant effects on spatial variation and temporal stability in water temperature. Spatiotemporal temperature changes are costly to fish in terms of subsequent thermoregulatory behavior and acclimation; therefore, thermal conditions have a heavy impact on the biological function of fishes. Spatiotemporal variation and stability of water temperatures along cross-shore transects in the littoral zone (within 100m from shore) were monitored and compared on two lakeshores with different cross-shore depth profiles. One shore was associated with a retaining wall and a relatively deep, flat bottom (steep shore), whereas the other extended offshore at a gentle gradient (gentle shore). Water temperature was more spatially variable on the gentle shore than the steep shore [1.44±0.47 and 0.20±0.14°C (mean±SD), respectively], but a stable temperature range (i.e., the range of temperatures continuously observed on each shore for 48h) was maintained only on the gentle shore during seasonal temperature decline. These results suggest that gentle shores have higher potential to provide a wider range of thermal options, allowing fish to fine-tune thermoregulatory behavior and acclimate more efficiently to temperature changes.
    Limnology 01/2010; 11(1):71-76. · 0.88 Impact Factor
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    ABSTRACT: In reservoirs or lakes, mixing depth affects growth and loss rates of phytoplankton populations. Based on 1-year data from the Zeya reservoir, China, we scaled the mixing depth throughout a whole year by utilizing cluster analysis, and then investigated its influence on phytoplankton dynamics and other physical and chemical parameters. Over the whole year, all physical and chemical parameters except TN and temperature had significant correlations with mixing depth, indicating that mixing depth is one of the important driving factors influencing water environment. According to mixing depth, a year can be divided into three different periods, including the thermally stratified period, isothermally mixed period, and transition period between them. When considering the former two different periods separately, mixing depth had no correlation with the phytoplankton biovolume. However, over the whole year a significant correlation was observed, which indicated that the influence of mixing depth on phytoplankton growth in the Zeya reservoir still followed Diehl’s theory. Furthermore, according to the steady-state assumption, a unimodal curve (mixing depth—phytoplankton biovolume) with a significant peak appearing at a mixing depth of 2m was observed, closely agreeing with Diehl’ prediction.
    Limnology 01/2009; 10(3):159-165. · 0.88 Impact Factor
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    ABSTRACT: The influence of the size distribution of phytoplankton on changes in the planktonic food web structures with eutrophication was examined using natural planktonic communities in two world-famous lakes: Lake Baikal and Lake Biwa. The size distribution of phytoplankton and the ratio of heterotrophic to autotrophic biomass (H/A ratio), indicating the balance between primary production and its consumption, were investigated in the lakes of different trophic status. The results revealed that microphytoplankton (>20μm) in mesotrophic Lake Biwa, and picophytoplankton (<2μm) or nanophytoplankton (2–20μm) in oligotrophic Lake Baikal, comprised the highest proportion of the total phytoplankton biomass. The H/A ratio was lower in Lake Biwa (<1) than in Lake Baikal (>1). The low H/A ratio in Lake Biwa appeared to be the consequence of the lack of consumption of the more abundant microphytoplankton, which were inferior competitors in nutrient uptake under oligotrophic conditions but less vulnerable to grazing. As a result, unconsumed microphytoplankton accumulated in the water column, decreasing the H/A ratio in Lake Biwa. Our results showed that food web structure and energy flow in planktonic communities were greatly influenced by the size distribution of phytoplankton, in conjunction with bottom-up (nutrient uptake) and top-down (grazing) effects at the trophic level of primary producers.
    Limnology 01/2007; 8(3):227-232. · 0.88 Impact Factor
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    ABSTRACT: Trophic polymorphism was recently reported in introduced bluegill (Lepomis macrochirus) in Lake Biwa, Japan, where three morphs are specialized in benthic invertebrates (benthivorous type), submerged aquatic Trophic polymorphism was recently reported in introduced bluegill (Lepomis macrochirus) in Lake Biwa, Japan, where three morphs are specialized in benthic invertebrates (benthivorous type), submerged aquatic plants (herbivorous type), and zooplankton (planktivorous type). We evaluated the long-term effects of food resource utilization plants (herbivorous type), and zooplankton (planktivorous type). We evaluated the long-term effects of food resource utilization by these trophic morphs using stable isotope ratios, δ15N and δ13C. A significant difference in δ15N was found between the benthivorous and planktivorous types. The planktivorous type had the higher δ15N value, which corresponded with the value expected from its prey, zooplankton. The lower δ15N value of the benthivorous type would be derived from the lower δ15N values of benthic prey organisms compared to zooplankton. These results support previous findings that the benthivorousvorous and planktivorous types have different food resource utilization. In contrast, the δ15N and δ13C values of the herbivorous type were distinctly different from the expected values, indicating that this type was unlikely and planktivorous types have different food resource utilization. In contrast, the δ15N and δ13C values of the herbivorous type were distinctly different from the expected values, indicating that this type was unlikely to utilize aquatic plants substantially, contradicting the results of the dietary analysis. to utilize aquatic plants substantially, contradicting the results of the dietary analysis.
    Limnology 01/2007; 8(1):59-63. · 0.88 Impact Factor
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    ABSTRACT: We demonstrated the existence of the diversity of virus-like agents killing Microcystis aeruginosa in a shallow hyper -eutrophic pond in Japan, but without specific virus isolation, once in October and twice in December 2001. The pond water was treated by chloroform, filtered throughout GF-75 filter (0.3 µm), and then incubated with axenic M. aeruginosa for 7 days. The cell density of M. aeruginosa decreased ten-fold in the course of the incubation. Results suggested that the active agent for cell death was virus-like, based upon its size fraction (from 30 kDa to 0.3 µm), sensitivity on heat-treatment, and evidence of protein protection of DNA during our extraction procedure. From our results of pulsed field gel electrophoresis (PFGE) analysis, two or four different-sized DNA bands appeared from the culture lysate in each experiment. In total, ten different-sized bands (10-90 kb) were observed from the three sample dates, suggesting that multiple virus-like agents killing M. aeruginosa existed in this pond. To our knowledge, this is the first report of the existence of virus -like agents with different genomic size that kill M. aeruginosa .
    Journal of Plankton Research 01/2006; 28(4):407-412. · 2.44 Impact Factor
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    ABSTRACT: Seasonal changes in abundance of the testate amoeba Penardochlamys sp. and its food vacuole contents were investigated in relation to blooms of the cyanobacteria Microcystis spp. in a hypertrophic pond from April 1999 to March 2000. The behavior of the amoeba feeding on M. aeruginosa and M. wesenbergii was also observed in the laboratory. The amoeba was detectable from late May to November 1999 during the blooms of Microcystis spp. Cell densities of the amoeba fluctuated between 1.4 and 350 cells ml–1 with some sporadic peaks, which did not coincide with rapid decreases in the abundance of Microcystis spp. Food vacuoles contained only Microcystis cells; other prey items were not found, suggesting that this amoeba utilized only the cyanobacteria as food. The amoeba was frequently found attached to Microcystis colonies, but was not associated with other suspended particles. Observation of the amoeba feeding revealed the feeding mechanism and that the amoeba was able to graze on both species of Microcystis. These results suggest that the trophic coupling of these organisms is substantial, although grazing by the amoeba is not sufficient to regulate the dynamics of Microcystis populations in this hypertrophic pond.
    Limnology 01/2004; 5(2):71-76. · 0.88 Impact Factor
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    K Matsui, N Ishii, M Honjo, Z Kawabata
    Aquatic Microbial Ecology - AQUAT MICROB ECOL. 01/2004; 36:99-105.
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    FEMS Microbiology Letters 09/2003; 226(2):415. · 2.05 Impact Factor
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    ABSTRACT: A decrease in the abundance of virus-like particles (VLP) by heterotrophic nanoflagellates (HNF) was examined using size-fractionated water samples taken from a hypereutrophic pond in December 1999, and in March and July 2000. We recorded a considerable decrease in the abundance of VLP in the 5.0 µm filtrate relative to the 0.2–0.8 µm filtrates. Decrease rates of VLP were reduced in a parallel 5.0 µm filtrate treated with cycloheximide. The loss rates of VLP in 5.0 µm filtrate varied in each experiment, and a high rate of loss was found when the growth rate of HNF was high. These results suggested that HNF consumed the VLP and that HNF is an important factor for decreasing viral abundance in freshwater environments.
    Ecological Research 06/2002; 17(4):473 - 479. · 1.55 Impact Factor
  • Kazuaki Matsui, Man‐Sig June, Masaya Ueki, Zen’ichiro Kawabata
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    ABSTRACT: Changes of bacterioplankton diversity in lake water were followed in triplicate, continuous-flow experimental tanks. Most probable numbers (MPN) were obtained for 95 different carbon sources using BIOLOG plates and were used to characterize bacterioplankton diversity. During 70 days of incubation, MPN declined for 15 of the 95 substrates while three of 95 appeared to be newly used, indicating functional succession in the bacterioplankton. Total bacterial cell abundance was constant from day 7 to day 70 of the incubation period. The succession of species composition of phyto- and zooplankton was also observed and suggested some involvement by phyto- and zooplankton species in the changes of bacterioplankton diversity. Thus, BIOLOG-based MPN assays is a simple but sensitive method for characterizing the changes in the bacterioplankton carbon utilization profile and is also useful for tracing the functional succession of bacterioplankton diversity within a community.
    Ecological Research 03/2002; 16(5):905 - 912. · 1.55 Impact Factor
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    ABSTRACT: To diagnose the nutritional status of phytoplankton in Lake Baikal, surveys for the determination of concentrations of particulate carbon (PC), nitrogen (PN) and phosphorus (PP) and their ratios were conducted at six stations in March, June, August and October 1999. The concentrations of PC and PN were lower than, and those of PP were similar to, those in another mesotrophic lake except at the station near the mouth of the largest input river, Selenga River, of Lake Baikal. The PC : PN : PP ratio was 102 : 13 : 1, considerably close to the Redfield ratio. The ratio was constant against spatiotemporal changes. These indicate that phytoplankton in Lake Baikal were exposed to no deficiency in nitrogen nor phosphorus. From a viewpoint of the nutritional status of phytoplankton, Lake Baikal might be viewed as an ocean rather than as a lake.
    Ecological Research 02/2002; 17(2):135 - 142. · 1.55 Impact Factor
  • Zen’ichiro Kawabata
    Ecological Research 01/2002; 17(2):133-133. · 1.55 Impact Factor
  • K Matsui, M Honjo, Z Kawabata
    Aquatic Microbial Ecology - AQUAT MICROB ECOL. 01/2001; 26:95-102.
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    ABSTRACT: Mechanisms for coexistence among micro-organisms were studied by using a species-defined microcosm, consisting of the bacterium Escherichia coli, the ciliate Tetrahymena thermophila and the alga Euglena gracilis. These organisms were chosen as representative of ecological functional groups i.e. decomposer, consumer and producer, respectively. Direct and indirect interactions among these organisms were evaluated by comparisons of their population dynamics in culture with different combinations of the three species. There was an E. coli cell density dependent predator–prey interaction between T. thermophila and E. coli which was only established when there were more than 106 cells ml–1 of E. coli. Indirect interactions were evaluated from the cultivation of each organism in media containing metabolites of the others. Metabolites from each population strongly accelerated the growth of their own populations and those of the others except for the self-toxicity effect of E. coli metabolites. These observations suggested that not only the cell–cell contact of direct interactions, but also metabolite-mediated indirect interactions supported the maintenance of the populations of each micro-organism and their coexistence. In natural ecosystems, there are many interactions and it is difficult to evaluate all those regulating community dynamics. The gnotobiotic microcosm used in this study was shown to be suitable for examining the specific, species–species microbial interactions.
    Hydrobiologia 08/2000; 435(1):109-116. · 1.99 Impact Factor
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    ABSTRACT: Prompt and accurate methods for assessing the species composition of given areas are indispensable in addressing the rapid loss of biodiversity. Here, we propose a method for the surveillance of fish species composition in freshwater using environmental DNA as species markers. First, the applicability of the method was demonstrated through aquarium experiments. DNA was extracted from 120 ml aquarium water, and the degenerated primers targeting the fish mitochondrial cytochrome b gene were used for amplification. PCR-amplified fragments were analysed by random cloning, and all species reared in the aquarium were detected. Next, this method was applied to natural freshwater environments. Water samples were collected from three sites in the Yura River, Japan; DNA was concentrated from 2 l of environmental water, and then amplified and cloned. Up to four species of fish were detected by sequencing 47 randomly selected clones from a single water sample. Overall, the results were consistent with previous knowledge of fish habitat utilisation. Using this method, the surveillance of fish species composition can be conducted less laboriously than with traditional methods.
    Limnology 13(2). · 0.88 Impact Factor
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    ABSTRACT: To predict outbreaks of infectious disease and to prevent epidemics, it is essential not only to conduct pathological studies but also to understand the interactions between the environment, pathogen, host and humans that cause and spread infectious diseases. Outbreaks of mass mortality in carp caused by Cyprinid herpesvirus 3 (CyHV-3), formerly known as koi herpesvirus (KHV), disease have occurred worldwide since the late 1990s. We proposed an environment–KHV–carp–human linkage as a conceptual model for “environmental diseases” and specify research subjects that might be necessary to construct and shape this linkage.
    Ecological Research 26(6). · 1.55 Impact Factor

Publication Stats

109 Citations
27.89 Total Impact Points

Institutions

  • 2011
    • Hiroshima University
      Hirosima, Hiroshima, Japan
    • The University of Tokyo
      Edo, Tōkyō, Japan
  • 2007–2011
    • Research Institute for Humanity and Nature
      Kioto, Kyōto, Japan
  • 2000–2003
    • Kyoto University
      • Center for Ecological Research
      Kioto, Kyōto, Japan
    • Ehime University
      Matuyama, Ehime, Japan