Changes in distribution of dietary α-tocopherol at 100 mg per 100 g of diet to organic tissues and to serum lipoproteins were investigated on Japanese flounder Paralichthys olivaceus. α-tocopherol had been transported to and preserved more positively in the gonad during the reproduction period. During maturity serum α-tocopherol had partly combined with the vitellogenin-like parts that diminished after the spawning period. Conversely, serum α-tocopherol after the spawning period partly combined with lipoprotein that increased after the spawning period. The prosperity and decline of different types of lipoproteins induced α-tocopherol distribution changes at the end of the spawning period.

抄録全体を表示

As an experimental model of heterosis in fish, the present study examined the amount of heterosis in salinity tolerance in four crosses between guppy strains having various kinships. Salinity tolerance was measured as survival time after transfer from fresh water to 35 ppt seawater. The amount of heterosis, expressed by the difference between the means of the parents and their F₁ hybrids in every pair, was larger in the strain combinations having distant kinship than in those having close kinship. The result indicates that the average amount of heterosis is dependent on the magnitude of kinship between the strains. The average survival times of the F₁ hybrids did not correlate with those of female parents, male parents, or mid-parent values but correlated closely with the average amount of heterosis in the four strain combinations, indicating that the average phenotypic value of the F₁ hybrids is not influenced by that of their parents but is dependent on the average amount of heterosis brought by the strain combination. Within each strain combination, variance in the amount of heterosis among pairs was larger in the strain combinations having close kinship than in those having distant kinship. These results indicate that the amount of heterosis was larger and more uniform in the strain combinations having distant kinship than in those having close kinship. The present study experimentally demonstrates that the strain combination having distant kinship is more useful for genetic improvement utilizing heterosis in fish.

抄録全体を表示

The anal fin of the medaka Oryzias latipes is sexually dimorphic, with mature males developing a larger anal fin than females. To determine the functions of the male anal fin during mating, an anal fin-removal experiment was conducted. Males were mated with females in successive treatments in which different portions of the anal fin were removed. Male medaka with half of their anal fin removed fertilized a significantly lower proportion of eggs than did males with a normal anal fin. The results show that the anal fin in male medaka is important for efficient fertilization, suggesting selection for a larger anal fin.

抄録全体を表示

Development of skin lectin and the lymphoid tissues were studied in the leptocephalus larvae of the Japanese eel Anguilla japonica. The specimens ranging in total length from 11 to 58 mm were captured at 12-19°N, 131-137°E and at 21-23°N, 123-128°E in the Pacific Ocean. The skin of leptocephali contained extremely active lectin which agglutinated rabbit red blood cells the same as adults. Club cells, known as lectin secreting cells, were also recognized in the epidermis of leptocephali, although the shape was not an elongated club form but oval. The cells were confirmed to contain lectin in the secretory vacuole by an immunofluorescence technique. The lectin in the cells was also recognized in the 8 days post-hatch preleptocephalous larvae, which was obtained from an artificially spawned eel, suggesting the importance of the lectin in the early larval development. In contrast, lymphoid tissues concerning immune functions showed delayed development with the exception of the thymus. No blood cells were seen in the kidney and spleen, even in a large specimen. Only a few undifferentiated leukocyte-like cells could be observed; some of them showed phagocytic figures. The thymus along with many thymocytes could be seen in the smallest leptocephalus of total length (TL) 11 mm. T cells may have a function in defense mechanisms during the leptocephalus stage, although other immune cells were still underdeveloped.

抄録全体を表示

In this study, the effects of weekly and biweekly administrations of salmon gonadotropin fraction (sGTH), via an emulsion prepared with lipophilized gelatin (LG emulsion), on the induction of vitellogenesis in the Japanese eel were compared to determine the adequate intervals of hormone administration. The effectiveness of simultaneous administration of sGTH and 17α-hydroxyprogesterone (17αP) using LG emulsion for the induction of final maturation and ovulation was also examined. Immature female Japanese eel (cultured eel and silver eel) were administered sGTH with LG emulsion weekly (2 mg/kg BW) or biweekly (4 mg/kg BW). In the fish injected biweekly with LG emulsion containing sGTH, biweekly cyclic fluctuations in the body weight (BW) and plasma levels of testosterone, estradiol-17β and sGTH II were repeated in response to the injection of sGTH. It took a longer period for the biweekly injected fish to complete vitellogenesis compared with the fish injected weekly. The weekly injections of sGTH were more effective than the biweekly injections in inducing vitellogenesis in the Japanese eel. The LG emulsion containing sGTH in the aqueous phase and 17αP in the oil phase was prepared. Hormone releasing properties were investigated by monitoring plasma profiles of hormones in immature eel. Significant differences in the plasma profiles of sGTH II and 17αP were not observed between simultaneous administration of sGTH and 17αP and single administration of sGTH or 17αP. Following induction of vitellogenesis, females that exhibited a rapid increase of BW and had oocytes at migratory nucleus stage were injected with sGTH and 17αP at the same time using LG emulsion. As a result, all females injected with sGTH and 17αP ovulated. Simultaneous administration of sGTH and 17αP can be useful for the induction of final maturation and ovulation in the Japanese eel.

抄録全体を表示

A marine plankton-net sample containing 18 genera with 26 species of diatoms and one genus with two species of dinoflagellate collected from the surface water of Seto Inland Sea was used for an enrichment culture under bubbling 10% CO₂ in air, and a 10% CO₂-tolerant microalga was isolated and identified as Thalassiosira weissflogii H1. There was no significant difference between the growth rates and maximum growth yields of this diatom under bubbling air, 5% CO₂ and 10% CO₂, but the growth rate and maximum growth yield under 20% CO₂ markedly decreased. The percentages of EPA and DHA for the total fatty acids in cells under 5-20% CO₂ were lower than those under air. However, the ratios of EPA to algal cells-dry weight under 5% CO₂, 10% CO₂ and 20% CO₂ were 0.76, 0.36 and 0.37 (% of dry weight), respectively, as compared with 0.18 under air. There was no significant difference in DHA contents (0.05 under air, 0.13 under 5% CO₂, 0.05 under 10% CO₂ and 0.09 under 20% CO₂), with or without bubbling CO₂. The polysaccharide content in the cells under 10% CO₂ was higher than that in the cells under air. This study is the first report on a highly CO₂-tolerant diatom.

抄録全体を表示

This study was undertaken to determine the availability of calcium (Ca) from seawater and from dietary tricalcium phosphate (TCP) in juvenile Japanese flounder Paralichthys olivaceus. Four semi-purified diets, supplemented with 0.2% Ca from Ca-lactate, no Ca supplement, and 0.2 and 2.5% Ca from TCP, were fed to duplicate groups of fish held in running seawater (26.5-29.0°C) for 10 weeks. The Ca unsupplemented diet gave significantly poor growth compared to the control diet with a 0.2% Ca supplement from Ca-lactate. A low Ca supplement from TCP to the diet gave comparable growth, however, a high Ca supplement from TCP resulted in significantly decreased growth and feed efficiency when compared with the control diet. A high level of Ca from TCP in the diet decreased Zn content of the bone. It is suggested that Ca from seawater is not adequately available to Japanese flounder and an easily digestible Ca supplement to the diet is necessary.

抄録全体を表示

Effects of culture conditions on the lectin level by a unicellular laboratory culture of Microcystis aeruginosa M228 (freshwater cyanobacterium) were investigated. The lectin level per cell at stationary phase increased two- or fourfold by lowering the light intensity from 45 or 90μE/m² per s to 12μE/m² per s, respectively, at 25°C as measured by the enzyme-linked immunosorbent assay method. The hemagglutinating activity against rabbit erythrocytes increased in response to the lectin level. The lectin level was threefold greater at 15°C than at 25°C, and nearly ninefold greater than at 30°C. Thus, although the specific growth rate of the cyanobacterium decreased with lowering light intensity and temperature, the lectin level per cell increased significantly. When the cyanobacterium was cultured at 15°C with a light intensity of 12μE/m² per s, the lectin level reached the maximum near the end of exponential phase, and then decreased toward stationary phase. The level near the end of exponential phase was nearly threefold greater than that of the culture incubated at 25°C with a light intensity of 45μE/m² per s. These findings show that the lectin production in M. aeruginosa M228 was induced by unfavorable conditions for the cell growth.

抄録全体を表示

Ultrastructural changes in gill chloride cells during smoltification were examined in wild and hatchery-reared masu salmon. On the filament, two types of chloride cells (α and β) and accessory cells were observed in wild fish from January (parr) to May (full-smolt), while only α and accessory cells (α-a cells) were observed in hatchery-reared fish from March (pre-smolt) to May (full-smolt). Among α-a cells of both types of fish, development of rough endoplasmic reticulum (ER) and Golgi apparatus was detected in pre-smolt before full-smolt. However, ultrastructural changes were not revealed in β cells of wild fish during smoltification. During smoltification, the α-a cell number increased and β cell number decreased. On the lamella, only one type of chloride cell was observed in both wild and hatchery-reared fish during smoltification. Their ultrastructural changes were almost the same as those in filament α-a cells, and their number declined during smoltification. Although there was almost no difference between changes in ultrastructure or in the number of chloride cells in both wild and hatchery-reared fish during smoltification, the chloride cell number of hatchery-reared fish varied widely in comparison to that in wild fish. The present study is the first report for wild salmonids of ultrastructural changes in gill chloride cells during smoltification, and indicated that there were some ultrastructural differences between gill chloride cells of wild masu salmon and hatchery-reared fish.

抄録全体を表示

In this study, ovarian development and vitellogenin levels were determined during the reproductive and non-reproductive molt cycles in the giant freshwater prawn Macrobrachium rosenbergii in order to examine the relationship between vitellogenesis and molting. During the reproductive molt cycle, the ovary developed synchronously with the advancement of molting stage. At molting stages B-C₀, the ovaries contained oogonia and oocytes at the previtellogenic and endogenous vitellogenic stages, and hemolymph vitellogenin levels were relatively low (2.4-3.0 mg/mL). At stage C_1, yolk accumulation commenced in oocytes at the endogenous vitellogenic stage, after which oocytes entered the exogenous vitellogenic stage. Vitellogenin levels increased (4.9 mg/mL) at this stage. During premolt stages D₀-D₃, vitellogenin titers were high (4.7-7.3 mg/mL), and gonadosomatic index (GSI) increased rapidly due to the yolk accumulation in the oocytes. Following ecdysis, yolk accumulation was completed at stage A₀, and oviposition occurred. Entering stage A, vitellogenin levels became low (0.6-1.3 mg/mL). In contrast, throughout the non-reproductive molt cycle, GSI remained low, and oocytes did not develop beyond the previtellogenic or endogenous vitellogenic stage. Some atretic oocytes at the exogenous vitellogenic stage were observed in a few females. During the non-reproductive molt cycle, vitellogenin levels did not show distinct changes in relation to the molt cycle.

抄録全体を表示

The genetic effects of hatchery release on natural populations were studied using simple mathematical models. We focused on the effect of sex differences in the number of released fish, the contribution to natural reproduction of released fish and/or in the fitness of released fish. A method for reducing introgression is discussed and we showed that the former two factors may reduce introgression, although the most effective bias for reduction depends on stocking density and fitness. We also showed that the dynamics can have multiple stable equilibria, which may result in irreversible introgression due to high stocking density in a single year.

抄録全体を表示

Effects of salmon calcitonin on calcium physiology of the otolith, rib bone, pharyngeal bone, and scale were examined in fed and starved goldfish Carassius auratus. Fish were intraperitoneally given salmon calcitonin at a dose of 10 ng/g body weight four times every other day. They were then incubated in ⁴⁵Ca-containing water for 24 h to examine the effect of the hormone on calcium deposition on these tissues. Another group of goldfish was incubated in ⁴⁵Ca-bone water for 2 days to prelabel the tissues with ⁴⁵Ca. Then they were kept in ⁴⁵Ca-free water for 8 days, during which they were given calcitonin four times every other day. The effect of calcitonin on calcium release from the tissues was examined by analyzing the prelabeled radioactivity. Calcitonin had no effect on plasma calcium concentrations or on calcium deposition in any of the tissues in fed fish. In starved fish, however, calcitonin increased calcium deposition on the rib bone, pharyngeal bone, and scale. In the starved fish, plasma calcium levels were not affected by the hormone, but plasma ⁴⁵Ca activity was lower in the calcitonin-treated group than in the control group. Calcitonin had no effect on calcium release from the bone and the scale, but reduced radioactivity in the otoliths of fed fish. These results suggest that calcitonin functions as an accelerator for calcium deposition on the bone and the scale in starved goldfish.

抄録全体を表示

To obtain useful information about the mechanism of the induction of gynogenesis in the Pacific abalone, nuclear behavior in normal and gynogenetic eggs was examined during meiosis and first cleavage. After its incorporation into the egg cytoplasm, the UV-irradiated sperm nucleus gradually dispersed and eventually developed into the male pronucleus, behaving like a normal sperm until contact with the female pronucleus. At mitotic prophase, the male pronucleus in the gynogenetic eggs did not form chromosomes like the female pronucleus, but became a dense chromatin body, which did not participate in karyokinesis. At completion of cytokinesis of the first cleavage, the UV-irradiated sperm nucleus was seen in the cytoplasm of one of the two blastomeres near the cleavage furrow. As a clear haploid mode was observed in the frequency distribution of chromosome numbers in gynogenetic larval cells, it is suggested that the paternal genome in the gynogenetic eggs does not contribute to the next generation.

抄録全体を表示

The changes in chemical constituents and physical indices during the processing of dried-seasoned squid using neon flying squid Ommastrephes bartrami and Argentina squid Illex argentinus were investigated. After processing, carbohydrate increased largely in the semi-dried meat and final product, but the increase of reducing sugar occurred only in the final product. An increase in b* value was found during the semi-drying process, implying the occurrence of browning formation. The trimethylamine oxide (TMAO) levels in the two squid were similar, but a marked reduction of TMAO was observed only in the processing of the neon flying squid. The initial amount of free amino acids (FAA) was 7445 ± 326 and 6392 ± 819 mg/100 g of carbohydrate-free dry meat in neon flying squid and Argentina squid, respectively. Proline and taurine were the most predominant constituents. No significant change in the total FAA was found during the processing of Argentina squid. However, the total FAA decreased greatly in neon flying squid. The reductions of FAA were primarily due to the boiling process, followed by the semi-drying process. Two taste amino acids (glutamic acid and alanine) increased in the final product, suggesting that they were supplemented in the seasoning for improving flavor quality. The initial level of adenosine triphosphate and its related compounds (ARC) in neon flying squid was higher. After processing, the total ARC increased significantly in the semi-dried meat and final product, which was associated with the increases of inosine and hypoxanthine.

抄録全体を表示

Lipid classes and fatty acid compositions of the muscles and eggs of wild and cultured sweet smelt in Korea from different habitats and fish culture farms were compared. Non-polar lipid (NL) content was in proportion to total lipid (TL) content and higher in the cultured fish muscles and eggs than in the wild fish. Phospholipid (PL) content showed almost no difference between the wild and cultured fish muscles. The fish eggs contained approximately three times as much PL as the fish muscles. The prominent NL classes of the fish muscles were triglyceride (TG) and free sterol (ST), and additionally, sterol ester (SE) was one of the prominent NL classes in the fish eggs. Each of the cultured fish muscles or eggs had proportions higher in TG and lower in ST compared with those of wild fish, respectively. These NL class proportions in fish muscles showed almost no difference in association with their wild habitats, fish culture farms as well as sex, while those in the fish eggs differed significantly. The PL class proportions of the fish muscles were similar in all samples, except those of the fish cultured in Miryang City. The wild fish muscles were rich in 16:1n-7, 18:3n-3 and 20:5n-3, whereas the fatty acid proportions showed almost no differences between fish habitats. The cultured fish muscles were rich in 18:1n-9, 18:2n-6, and 22:6n-3, in which the fatty acid proportions showed significant difference between fish farms due to different diets.

抄録全体を表示

The study describes the occurrence and characterization of an enzyme in the myofibrillar fraction from walleye pollack muscle which is responsible for the reduction of trimethylamine-N-oxide to dimethylamine and formaldehyde. The enzyme, trimethylamine-N-oxide demethylase (TMAOase), activity was optimal at pH 7.0-7.5 and was inactivated above 30°C. The apparent activation energy was 30.7 and 55.9 kJ·mol^-1·deg^-1 above 15°C and in the range of 0-15°C, respectively. Above 0°C, dimethylamine formation increased depending on the rise in temperature, although below 0°C, it slightly increased at -20°C than at 0 and -4°C. The NaCl reduced TMAOase activity at higher concentrations. The enzyme in the myofibrillar fraction required a cofactor system containing Fe²⁺, ascorbate, and cysteine for full activation.

抄録全体を表示

To clarify the cause of the marked difference in rigor mortis progress between cultured red sea bream and Japanese flounder, and as a part of a study program, we examined the properties of sarcoplasmic reticulum (SR), aiming at Ca²⁺ for both fish species. These results showed both the rigor mortis progress and caffeine contracture in cultured red sea bream was markedly faster in speed and considerably higher in the maximum level reached than that in cultured Japanese flounder. Both the Ca²⁺ uptake rate into SR and the Ca²⁺ release rate from SR were higher in cultured red sea bream than in cultured Japanese flounder. In addition, the SR Ca²⁺-ATPase activity was also higher in cultured red sea bream. Furthermore, the surface area percentage of SR per sarcomere was larger in cultured red sea bream than in cultured Japanese flounder. It was proposed that the differences in both biochemical properties and minute structure of SR between the two fish species may together be implicated in the marked difference in rigor mortis progress between the two fish species.

抄録全体を表示

Japanese flounder Paralichthys olivaceus glyceraldehyde-3-phosphate dehydrogenase (GAPDH or G3PD) cDNA was cloned and sequenced. Japanese flounder GAPDH was found to consist of 333 amino acid residues and to exhibit a high degree of homology to previously reported GAPDH of vertebrates, in both the DNA and amino acid sequences. Curiously, Japanese flounder GAPDH was found to be more homologous to GAPDH of Xenopus, chicken and mammals than to that of rainbow trout. We developed primers for RT-PCR and used this method to amplify GAPDH mRNA from various tissues to determine whether it could be used as an internal standard. The GAPDH was expressed in all organs and tissues, and confirmed that it represents a good internal standard positive control for the study of gene expression.

抄録全体を表示

It has been reported that catch muscle type myosin is expressed in various tissues of scallop, including gonad, heart, foot and mantle. However, there has been no report about the isolation and identification of myosin from tissues other than the adductor muscle. We isolated myosin from the mantle pallial cell layer of scallop and compared the structure and the characteristics with those of striated and catch muscle myosins. Comparison among three kinds of myosins in cleavage patterns by trypsin and cyanogen bromide revealed that myosin in mantle pallial cell layer (pallial cell myosin) has a different structure from striated and catch muscle myosins. The Mg²⁺-ATPase activity of pallial cell myosin is significantly lower compared with those of striated and catch muscle myosins. The present results indicate the existence of the intrinsic myosin in mantle pallial cell layer.

抄録全体を表示

Adenosine deaminase was purified from the adductor muscles of the scallop Patinopecten yessoensis and the round clam Mactra chinensis to apparent homogeneity as judged by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE). SDS-PAGE and gel filtration showed that the enzymes were monomers with a molecular weight of 40000-43000. The optimum pH was in a slight alkaline range. The enzymes were active for adenosine and 2'-deoxyadenosine, but not for adenine, 5'-deoxyadenosine, or phosphorylated adenosines. The size, optimum pH, and substrate specificity of the purified enzymes were similar to those of adenosine deaminase in vertebrates. The antisera against adenosine deaminase from the adductor muscles of the scallop were cross-reactive with calf intestine adenosine deaminase as well as adenosine deaminase from the round clam adductor muscle, but inactive toward the adenosine deaminase fraction purified from the scallop mid-gut gland.

抄録全体を表示

Changes in the content of ATP, phosphoarginine (PA), and lactic acid (Lac) were determined in the muscles of three species of lobster during storage at 0, 5, and 10°C. The ATP equivalent (Eq) of each species was calculated to evaluate the initial degradation of ATP in the postmortem stage. Both ATP and PA decreased simultaneously with Lac accumulation in the muscle of every lobster. The contents of the three components in Japanese spiny lobster changed slowly at 0 and 5°C and rapidly at 10°C. In the case of rock lobster, the changes at 0°C were slowest, followed by 5°C, and those at 10°C were fastest. In contrast, the changes in the three components of American lobster muscle exhibited less dependency on the temperatures. The decreases in Eq at 0, 5, and 10°C for American lobster were largest of the three species. The change in Eq in the initial 24 h was larger than that in the second 24 h for every lobster. It is suggested that each species of lobster had its own relationship between the storage temperature and the rate of ATP production, and degradation.

抄録全体を表示

Common carp (Cyprinus carpio L.) were acclimated to 30°C from 20°C over 24 h and maintained at that temperature for 35 days. Changes in the expression of mRNA transcripts for fast myosin heavy chain (MyHC) isoforms, E12 of the E protein, and myogenic regulatory factors belonging to the MyoD (MyoD, myogenin, myf-5) and myocyte enhancer factor-2 (MEF2A, MEF2C) gene families were investigated in the fast myotomal muscle using northern blot analysis. Myofibrillar Mg²⁺-ATPase activity gradually declined over 21 days and was significantly different from the starting level after only 3-5 days. Over the same time period there was a dramatic decrease in the mRNA transcripts of the MyHC isoform predominantly expressed in cold-acclimated carp (10°C-type MyHC) and a significant increase in the transcripts of the MyHC isoform predominantly expressed in warm-acclimated carp (30°C-type MyHC). The levels of myogenin mRNA transcripts almost doubled over 3-7 days before declining to 30% of the starting levels for the remainder of the experiment. While the levels of E12 mRNA gradually decreased, MEF2A and MEF2C mRNA transcripts showed a significant decrease over 24 h and then stabilized at the lower levels. In contrast, the levels of MyoD mRNA were not affected by temperature acclimation. The possible role of myogenic regulatory factors in the expression of temperature-specific isoforms of MyHC in common carp is briefly discussed.

抄録全体を表示

Levels of phosphatidylcholine hydroperoxide (PC-OOH) in plasma, red blood cell (RBC), and livers of cultured and commercially available marine and freshwater fish were determined quantitatively by normal phase high-performance liquid chromatography (HPLC) equipped with a post-column detection system, using diphenyl-1-pyrenyl phosphine as a fluorescence reagent. The levels of plasma PC-OOH in non-aromatic fish, including yellowtail, amberjack, the Japanese flounder, sea bream, and rainbow trout ranged between 1.2 and 5.1 nmol/mL plasma. In contrast, the levels of PC-OOH in the plasma of aromatic fish, including the Japanese smelt, rainbow smelt, shishamo smelt, and sweet smelt were extremely high. The sweet smelt plasma contained the highest amount of hydroperoxide, amounting to 29.4 nmol/mL plasma. The levels of PC-OOH in non-aromatic fish RBC were low, ranging between 23.4 and 25.2 fmol/10⁵ RBC. In contrast, a large amount of PC-OOH accumulated in all of the aromatic fish RBC used in the present study, ranging between 122 and 419 fmol/10⁵ RBC. The PC-OOH levels in the sweet smelt and the Japanese smelt RBC were markedly high. The sweet smelt liver also contained a large amount of PC-OOH, amounting to 670 nmol/g tissue. This value was five times higher than those of some non-aromatic fish. Any marked difference in the contents of phospholipids and polyunsaturated fatty acids in the blood of sweet smelt and rainbow trout was not recognized. These results suggest that biogeneration of lipid hydroperoxide is an initial step in the development of certain volatile compounds in the aromatic fish.

抄録全体を表示

We examined the distribution of several cathepsins (cathepsins B, B-like, L and D, and latent cathepsin L) in red and white muscles among 24 species of marine and freshwater fish. All activities of cathepsins except cathepsin D of marine red-flesh fish were relatively higher than that of marine white-flesh fish and freshwater fish. The activity of cathepsin D was detected in red or white muscle of all fish, and no difference can be seen between fish species.

抄録全体を表示

Four kinds of non-muscle proteins, including liquid egg white, plasma protein concentrate, wheat gluten and whey protein concentrate were added as gelation aid materials to horse mackerel surimi. Decrease in on-set temperature of first heat gelation and resolution degree were observed in the surimi containing these non-muscle proteins. Addition of plasma protein clearly increased the surimi rigidity, reflecting its excellent thermogelation ability. Addition of the proteins also enhanced the gel strength and cooking tolerance of heated surimi products (kamaboko). Plasma protein effectively increased the gel strength of kamaboko, giving a firm and elastic gel, which still had high gel strength in cooking under 70°C. Addition of the proteins also inhibited the browning of kamaboko during cooking.

抄録全体を表示