The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Kohei Yamauchi - One of the best experts on this subject based on the ideXlab platform.
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Changes in Transcript Levels of Gill Cortisol Receptor during Smoltification in Wild Masu Salmon, Oncorhynchus masou
Zoological Science, 2001Co-Authors: Shinya Mizuno, Kazuhiro Ura, Akihiko Hara, Haruhisa Fukada, Naoyuki Misaka, Yoshifumi Onodera, Shinji Adachi, Kohei YamauchiAbstract:Abstract We developed a quantitative PCR assay to investigate transcript levels of gill cortisol receptor (CR) in masu salmon (Oncorhynchus masou). Using this system, we examined changes in transcript levels of gill CR during smoltification of wild masu salmon while tracking serum cortisol and growth hormone (GH) concentrations patterns. The masu salmon were parr in January and February, and thereafter smoltified, migrating from the river to the sea in May. Gill CR transcript levels were very low in January and February, but thereafter increased and reached a maximum in April (5 fold increase over levels observed in January). In May, when smolt enter the sea, the gill CR transcript levels decreased. Serum cortisol concentrations were also low from January to March and increased to the peak in April. These changes correlated well with changes in CR transcript levels from March to April. In contrast, serum GH concentration began to increase in January, peaked in March and decreased from March to May. These ...
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The effect of cortisol administration on blood plasma immunoglobulin M (IgM) concentrations in masu salmon (Oncorhynchus masou)
Fish Physiology and Biochemistry, 1994Co-Authors: Masaki Nagae, Kazuhiro Ura, Akihiko Hara, Hiroshi Kawamura, Shinji Adachi, Hirotoshi Fuda, Kohei YamauchiAbstract:Immunoglobulin M (IgM) is known as a main factor in the humoral immune system of teleosts. In the present study, the effect of cortisol on plasma IgM concentrations was investigated using a specific antibody to IgM in masu salmon ( Oncorhynchus masou ). Cortisol was orally administered each day for 2 weeks at a dose of 1 mg g^−1 in the diet, and for the following week the fish were fed a non-treated diet. Blood plasma samples were collected at 0, 1, 2 and 3 weeks after the initiation of treatment. Oral administration of cortisol elevated plasma cortisol concentrations to about 40 ng/ml for 2 weeks after administration and slightly reduced plasma IgM concentration; the suppression was statistically significant one week after the period of hormone administration. However, treatment with cortisol did not affect plasma concentrations of total protein or α1-protein, one of the major serum proteins, during the experimental period. These results indicate that cortisol specifically suppresses plasma IgM concentrations.
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Ultrastructural demonstration of salmon-type gonadotropin-releasing hormone (sGnRH) in the olfactory system of masu salmon (Oncorhynchus masou).
Neuroscience letters, 1994Co-Authors: Hideaki Kudo, Hiroshi Ueda, Hiroshi Kawamura, Katsumi Aida, Kohei YamauchiAbstract:Abstract Immunocytochemical and immunoelectron microscopic localization of salmon-type gonadotropin-releasing hormone (sGnRH) were observed in the olfactory system (olfactory epithelium, olfactory nerve and olfactory bulb) of masu salmon ( Oncorhynchus masou ) to investigate its possible involvement in the olfactory functions. sGnRH-immunoreactive (ir) bipolar neuron, which might be related to the terminal nerve, was located in dorsal portion of the olfactory nerve. sGnRH-ir gold particles were concentrated on electron-dense granule-like structures of 50 nm in diameter in fibers of the olfactory nerve close both to the olfactory epithelium and to the olfactory bulb. These findings suggest that sGnRH might participate in neurotransmisson and/or neuromodulation in the olfactory system of masu salmon. sGnRH would become a useful molecular marker for studying the olfactory imprinting and homing mechanisms in salmonids.
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Immunochemical studies on serum proteins in juvenile masu salmon, Oncorhynchus masou
Comparative Biochemistry and Physiology Part B: Comparative Biochemistry, 1994Co-Authors: Kazuhiro Ura, Akihiko Hara, Hiroshi Kawamura, Kohei YamauchiAbstract:Abstract Serum protein profiles of parr and smolt in masu salmon ( Oncorhynchus masou ) were analyzed by crossed immunoelectrophoresis (CIE) and two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (2D-SDS-PAGE) combined with Western blotting. Comparing with parr serum and smolt serum by CIE, three proteins were identified to be changed quantitatively. By 2D-SDS-PAGE combined with Western blotting, two proteins with molecular weights of 43,000 and 80,000, were identified as possible smolt-specific serum proteins, since they were not detected in parr.
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Serum thyroxine, estradiol-17β, and testosterone profiles during the parr-smolt transformation of masu salmon, Oncorhynchus masou
Fish Physiology and Biochemistry, 1993Co-Authors: Hideaki Yamada, Hiromi Ohta, Kohei YamauchiAbstract:Changes in serum thyroxine (T_4), estradiol-17β (E_2) and testosterone (T) levels during the parr-smolt transformation (smoltification) were investigated in the masu salmon ( Oncorhynchus masou ) in 1985 and 1987. T_4 showed a peak in levels at the early stage of smoltification and E_2 and T levels peaked almost at the same time. There were no significant differences between the concentrations of serum hormones in female and males. During smoltification, germ cells in the peri-nucleolus and spermatogonia stage were present in the ovary and testis, respectively. These results suggest that E_2 and T may be involved in smoltification in the masu salmon.
Koji Maekawa - One of the best experts on this subject based on the ideXlab platform.
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Factors affecting aggressive behaviour of spawning migratory males towards mature male parr in masu salmon Oncorhynchus masou.
Journal of fish biology, 2010Co-Authors: M. Watanabe, Koji MaekawaAbstract:This study examined whether dominant migratory males (adopting fighter tactics) of the masu salmon Oncorhynchus masou would more aggressively attack large mature male parr (adopting sneaker tactics) as large mature male parr are expected to have the potential to cause a greater decrease in fertilization success. The frequency of aggressive behaviour was not related to the body size of males, and it increased with the frequency of interactions with mature male parr. The fertilization success of mature male parr was much lower than migratory males, and no relationship was observed between fertilization success and aggressive behaviour. The low fertilization success of mature male parr, despite infrequent aggressive behaviour by migratory males, indicates that there might be little benefit for migratory males to attack mature male parr more aggressively according to their body size.
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LATITUDINAL VARIATION IN SEXUAL SIZE DIMORPHISM OF SEA-RUN MASU SALMON, Oncorhynchus masou
Evolution; international journal of organic evolution, 2006Co-Authors: Tsuyoshi Tamate, Koji MaekawaAbstract:Sexual size dimorphism (SSD), a difference in body size between the sexes, occurs in many animal species. Although the larger sex is often considered invariable within species, patterns of selection may result in interpopulation variation or even reversal of SSD. We evaluated correlations between latitude and female body size, male body size, and relative body size (male body size/female body size) in 22 populations (ranging from 37°N to 49°N) of sea-run masu salmon (Oncorhynchus masou) that spawn in rivers along the Sea of Japan coast. Male size and the relative body size increased with latitude, but female size did not correlate with latitude. In addition, increase in male size with latitude was sufficient to result in a reversal of SSD, the switch-point being around 45°N. We suggest that the positive correlation between latitude and male size is due to increasing operational sex ratios or sexual selection on sea-run male body size that result from sex-biased patterns of anadromy. In conclusion, our study provides the first example of predictable geographic variation in SSD shaped by apparent patterns of sexual selection.
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Differential energy allocation of alternative male tactics in masu salmon (Oncorhynchus masou)
Canadian Journal of Fisheries and Aquatic Sciences, 2002Co-Authors: Yusuke Koseki, Koji MaekawaAbstract:To compare energy allocation to gonad, relative to soma, between alternative male tactics (mature parr and migratory males) in masu salmon (Oncorhynchus masou), we quantified energy contents in som...
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Interpopulation variation in reproductive traits of female masu salmon, Oncorhynchus masou
Oikos, 2000Co-Authors: Tsuyoshi Tamate, Koji MaekawaAbstract:Several life history models predict that larger eggs and lower fecundity should be favored in a low-growth environment. We applied the model of Sibly et al. to seven Japanese populations of masu salmon (Oncorhynchus masou) in order to test the predictions that populations in which individual growth rate is low are characterized by larger eggs and lower fecundity. Two populations, Shumarinai and Shikaribetsu, had the lowest growth rates of individuals, largest egg sizes and lowest fecundities of all populations examined. In contrast, the Shiribetsu, Chitose and Uono populations had highest growth rates of individuals, smallest egg sizes and highest fecundities. The Shibetsu and Toya populations were intermediate between these two groups. The gonadsomatic index (GSI) of the Shumarinai and Shikaribetsu populations was smaller than that of all other populations. Correlation analysis indicated that populations with lower individual growth rates had larger eggs and lower fecundities. The results were consistent with the predictions of the Sibly et al. model: increased egg size which results in decreased fecundity is probably an adaptation to low-growth environments. Therefore, in masu salmon, growth differences among populations may explain interpopulation variation in egg size and fecundity.
Hiroshi Ueda - One of the best experts on this subject based on the ideXlab platform.
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Diurnal changes in salmon GnRH secretion in the brain of masu salmon (Oncorhynchus masou)
General and comparative endocrinology, 2013Co-Authors: Kosuke Fukaya, Masafumi Amano, Hiroshi UedaAbstract:The day–night changes of salmon GnRH (sGnRH), which is secreted from various brain regions, were analyzed in maturing and matured masu salmon (Oncorhynchus masou). In maturing males, the levels of sGnRH secreted from the olfactory bulb (OB), terminal nerve (TN), and ventral telencephalon and preoptic area (VT+POA) were all significantly higher during midnight than daytime. However, the contents of sGnRH in the pituitary gland during midnight were not higher than those during daytime. In maturing females, the levels of sGnRH secreted from the VT+POA were higher during midnight than daytime, and the contents of sGnRH in the pituitary gland were also higher during midnight. In matured fish, the levels of sGnRH secreted from the OB, TN and VT+POA during midnight were significantly higher than those during daytime. There were also no significant differences in the contents of sGnRH in the pituitary gland. These results suggest that a short photoperiod may be involved in diurnal secretion rhythms of sGnRH in various brain regions and the pituitary gland.
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Effects of aggressive interaction on downstream movement and olfactory function in masu salmon, Oncorhynchus masou
Aquaculture, 2012Co-Authors: Shih-pin Lee, Hiroshi UedaAbstract:In the present study, behavioral, electrophysiological, and molecular biological experiments were developed to examine the role of aggressive interaction ("fighting experience") on downstream movement and olfactory function in relation to smoltification in hatchery-reared one-year-old masu salmon (Oncorhynchus masou). Individual salmon that lost the fighting contest in April and May moved downstream earlier than the winners. The olfactory response to salinity sensitivity of the losers, measured by electro-olfactogram to 10^[-1] M sodium chloride, was significantly higher than that of the winners during the period from April to June. In May, the olfactory response to imprinting activity of the losers, previously exposed for one week to 10^[-4] M L-glutamic acid was significantly high, and the salmon olfactory imprinting-related gene was also highly expressed. During the smoltification period, losing the aggressive interaction might exert strong influences on downstream movement and olfactory function in masu salmon. The present newly developed experiments provide new evidence for evaluating the relation between the aggressive interaction and the smoltification in masu salmon
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Effects of aggressive interaction on downstream movement and olfactory function in masu salmon, Oncorhynchus masou
Aquaculture, 2010Co-Authors: Shih-pin Lee, Hiroshi UedaAbstract:Abstract In the present study, behavioral, electrophysiological, and molecular biological experiments were developed to examine the role of aggressive interaction (“fighting experience”) on downstream movement and olfactory function in relation to smoltification in hatchery-reared 1-year-old masu salmon ( Oncorhynchus masou ). Individual salmon that lost the fighting contest in April and May moved downstream earlier than the winners. The olfactory response to salinity sensitivity of the losers, measured by electro-olfactogram to 10 −1 M sodium chloride, was significantly higher than that of the winners during the period from April to June. In May, the olfactory response to imprinting activity of the losers, previously exposed for 1 week to 10 −4 M l -glutamic acid was significantly high, and the salmon olfactory imprinting-related gene was also highly expressed. During the smoltification period, losing the aggressive interaction might exert strong influences on downstream movement and olfactory function in masu salmon. The present newly developed experiments provide new evidence for evaluating the relation between the aggressive interaction and the smoltification in masu salmon.
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effects of external and surgically implanted dummy radio transmitters on mortality swimming performance and physiological status of juvenile masu salmon Oncorhynchus masou
Journal of Fish Biology, 2009Co-Authors: Yuya Makiguchi, Hiroshi UedaAbstract:The effects of external and surgically implanted radio transmitters on juvenile masu salmon Oncorhynchus masou were examined. External attachment of transmitters significantly decreased the survival of fish and caused a decreased critical swimming speed compared with surgical implantation. Although plasma cortisol, plasma glucose and haematocrit values did not differ significantly among groups, it appeared that the most suitable transmitter attachment method for juvenile O. masou may be surgical implantation.
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site fidelity of and habitat use by the formosan landlocked salmon Oncorhynchus masou formosanus during typhoon season in chichiawan stream taiwan as assessed by nano tag radio telemetry
Zoological Studies, 2009Co-Authors: Yuya Makiguchi, Liao Linyan, Y Konno, Hisaya Nii, K Nakao, Gwo Jinchywan, H Onozato, Huang Yiishing, Hiroshi UedaAbstract:Site fidelity of and habitat use by the Formosan landlocked salmon (Oncorhynchus masou formosanus) during typhoon season in Chichiawan Stream, Taiwan as assessed by nano-tag radio telemetry. Zoological Studies 48(4): 460-467. Movements of (time-series horizontal position) and habitat use by adult Formosan landlocked salmon (Oncorhynchus masou formosanus) were examined in a Taiwanese stream, (Chichiawan Stream) using nano-tag telemetry in summer (typhoon season) 2007. A great flood caused by a typhoon occurred during the tracking period in this study, but the flood did not change the positions or habitat use by the adult salmon. Ten tagged fish predominately used microhabitats near boulders and made frequent short movements of < 200 m between habitats. Our results suggest that adult salmon are basically sedentary in summer, but undertake small-scale movements to secure food. In conclusion, this study provides useful information for the conservation of the Formosan landlocked salmon by showing that boulders in streams may serve as refuges from floods brought by typhoons.
Tsuyoshi Tamate - One of the best experts on this subject based on the ideXlab platform.
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Latitudinal variation in egg size and number in anadromous masu salmon Oncorhynchus masou.
Journal of fish biology, 2009Co-Authors: Kentaro Morita, Tsuyoshi Tamate, Y. Sugimoto, Y. Tago, T. Watanabe, H. Konaka, M. Sato, Y. Miyauchi, Kazumasa Ohkuma, Toru NagasawaAbstract:Latitudinal variation in egg size and number in anadromous masu salmon Oncorhynchus masou was examined. Relatively greater variation in egg size occurred among rivers than among females within rivers or within females. Egg size was generally greater and egg number generally lower at more northerly latitudes.
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LATITUDINAL VARIATION IN SEXUAL SIZE DIMORPHISM OF SEA-RUN MASU SALMON, Oncorhynchus masou
Evolution; international journal of organic evolution, 2006Co-Authors: Tsuyoshi Tamate, Koji MaekawaAbstract:Sexual size dimorphism (SSD), a difference in body size between the sexes, occurs in many animal species. Although the larger sex is often considered invariable within species, patterns of selection may result in interpopulation variation or even reversal of SSD. We evaluated correlations between latitude and female body size, male body size, and relative body size (male body size/female body size) in 22 populations (ranging from 37°N to 49°N) of sea-run masu salmon (Oncorhynchus masou) that spawn in rivers along the Sea of Japan coast. Male size and the relative body size increased with latitude, but female size did not correlate with latitude. In addition, increase in male size with latitude was sufficient to result in a reversal of SSD, the switch-point being around 45°N. We suggest that the positive correlation between latitude and male size is due to increasing operational sex ratios or sexual selection on sea-run male body size that result from sex-biased patterns of anadromy. In conclusion, our study provides the first example of predictable geographic variation in SSD shaped by apparent patterns of sexual selection.
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Interpopulation variation in reproductive traits of female masu salmon, Oncorhynchus masou
Oikos, 2000Co-Authors: Tsuyoshi Tamate, Koji MaekawaAbstract:Several life history models predict that larger eggs and lower fecundity should be favored in a low-growth environment. We applied the model of Sibly et al. to seven Japanese populations of masu salmon (Oncorhynchus masou) in order to test the predictions that populations in which individual growth rate is low are characterized by larger eggs and lower fecundity. Two populations, Shumarinai and Shikaribetsu, had the lowest growth rates of individuals, largest egg sizes and lowest fecundities of all populations examined. In contrast, the Shiribetsu, Chitose and Uono populations had highest growth rates of individuals, smallest egg sizes and highest fecundities. The Shibetsu and Toya populations were intermediate between these two groups. The gonadsomatic index (GSI) of the Shumarinai and Shikaribetsu populations was smaller than that of all other populations. Correlation analysis indicated that populations with lower individual growth rates had larger eggs and lower fecundities. The results were consistent with the predictions of the Sibly et al. model: increased egg size which results in decreased fecundity is probably an adaptation to low-growth environments. Therefore, in masu salmon, growth differences among populations may explain interpopulation variation in egg size and fecundity.
Hiroyuki Kawachi - One of the best experts on this subject based on the ideXlab platform.
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Molecular identification of biwa trout (Oncorhynchus masou rhodurus) using PCR-RFLP method.
Journal of food science and technology, 2019Co-Authors: Chihiro Matsumoto, Yukino Kyota, Shunya Yamanaka, Naoki Murakawa, Ryutaro Kikunaga, Yoshihiro Yamada, Hiroyuki KawachiAbstract:Polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) analysis was used to identify meat from biwa trout (Oncorhynchus masou rhodurus), amago trout (Oncorhynchus masou ishikawae), yamame trout (Oncorhynchus masou masou), and rainbow trout (Oncorhynchus mykiss). PCR amplification was conducted using primers flanking conserved regions of NADH dehydrogenase subunits 4 and 5 (ND4–ND5) (2848 bp) and ND1 (1091 bp) genes of mitochondrial DNA following restriction digestion with the enzyme HaeIII. Although the segments of ND4–ND5 and ND1 genes showed intraspecies variation, the generation of DNA fragments larger than 300 bp and 160 bp following cleavage by HaeIII of ND4–ND5 and ND1, respectively, was efficient to differentiate the four species. Furthermore, this method was successful in species identification even when using PCR-amplified products obtained from thermally processed biwa trout samples. This sensitive technique can be utilized to reveal commercial fraud, where biwa trout is adulterated with meat from cheaper counterparts.
