Shizuoka Prefectural Research Institute of Fishery

Yaizu, Japan

Shizuoka Prefectural Research Institute of Fishery

Yaizu, Japan
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Sano K.,Sophia University | Kawaguchi M.,University of Tokyo | Yoshikawa M.,Shizuoka Prefectural Research Institute of Fishery | Iuchi I.,Sophia University | Yasumasu S.,Sophia University
FEBS Journal | Year: 2010

A fish egg envelope is composed of several glycoproteins, called zona pellucida (ZP) proteins, which are conserved among vertebrate species. Euteleost fishes synthesize ZP proteins in the liver, while otocephalans synthesize them in the growing oocyte. We investigated ZP proteins of the Japanese eel, Anguilla japonica, belonging to Elopomorpha, which diverged earlier than Euteleostei and Otocephala. Five major components of the egg envelope were purified and their partial amino acid sequences were determined by sequencing. cDNA cloning revealed that the eel egg envelope was composed of four ZPC homologues and one ZPB homologue. Four of the five eel ZP (eZP) proteins possessed a transmembrane domain, which is not found in the ZP proteins of Euteleostei and Otocephala that diverged later, but is found in most other vertebrate ZP proteins. This result suggests that fish ZP proteins originally possessed a transmembrane domain and lost it during evolution. Northern blotting and RT-PCR revealed that all of the eZP transcripts were present in the ovary, but not in the liver. Phylogenetic analyses of fish zp genes showed that ezps formed a group with other fish zp genes that are expressed in the ovary, and which are distinct from the group of genes expressed in the liver. Our results support the hypothesis that fish ZP proteins were originally synthesized in the ovary, and then the site of synthesis was switched to the liver during the evolutionary pathway to Euteleostei. © 2010 The Authors Journal compilation © 2010 FEBS.


Sano K.,Sophia University | Kawaguchi M.,Sophia University | Yoshikawa M.,Shizuoka Prefectural Research Institute of Fishery | Kaneko T.,University of Tokyo | And 3 more authors.
FEBS Journal | Year: 2011

We purified eel hatching enzyme (EHE) from the hatching liquid of Japanese eel Anguilla japonica belonging to Elopomorpha to a single band on SDS/PAGE. TOF-MS analysis revealed that the purified EHE contained several isozymes with similar molecular masses. Comparison of the egg envelope digestion specificities of the purified EHE and of recombinant EHE4, one of the EHE isozymes, suggested that the isozymes contained in the purified EHE were functionally the same in terms of egg envelope digestion. By electron microscopy, the egg envelope became swollen after treatment with the purified EHE. The EHE cleavage sites on the zona pellucida (ZP) protein of the egg envelope were located in the N-terminal repeat regions. In previous phylogenetic analysis, we suggested that fishes included in Elopomorpha, as basal teleosts, possess a single type of hatching enzyme genes, and that fishes in Otocephala and Euteleostei gain two types of hatching enzyme genes called clade I and II genes by duplication. Further, the clade I enzymes, zebrafish hatching enzyme (ZHE1) and medaka high choriolytic enzyme (HCE), swell the egg envelope by cleaving the N-terminal regions of ZP proteins, while the clade II enzyme, medaka low choriolytic enzyme (LCE), solubilizes the swollen envelope by cleaving the site at the middle region on the ZP domain. In this evolutionary scenario, our findings support that hatching of Japanese eel conserves the ancestral mechanism of fish egg envelope digestion. The clade I enzymes inherit the ancestral enzyme function, and the clade II enzymes gain a new function during evolution to Otocephala and Euteleostei. Embryo of Japanese eel, an early species in Teleostei, has only a single type of hatching enzyme (EHE). At hatching, a part of egg envelope is softened by EHE. The cleavage sites of EHE are located in the N-terminal repeat regions, not in ZP domain. This manner of EHE is the ancestral form of egg envelope digestion in teleostean evolution. © 2011 FEBS.


Hiratsuka S.,University of Shizuoka | Hiratsuka S.,Shizuoka Prefectural Research Institute of Fishery | Honma H.,University of Shizuoka | Saitoh Y.,University of Shizuoka | And 3 more authors.
Journal of Nutritional Science and Vitaminology | Year: 2013

The effects of dietary sialic acid in dams on the learning abilities of their pups after weaning were investigated using rats deficient in n-3 fatty acids. Nine-week-old female Wistar rats were fed an n-3 fatty acid-deficient diet for 3 wk and were mated at 12 wk of age. During pregnancy and lactation, the female rats were fed the n-3 fatty acid-deficient diet, and were given water or water containing 1% N-acetylneuraminic acid (NANA) ad libitum. After weaning, the learning abilities of the pups were evaluated using a novel object recognition test. The recognition index of pups nursed by dams fed on water containing 1% NANA (NANA-intake dams) was significantly higher than that of pups nursed by dams fed only on water (NANA non-intake dams). There were no significant differences in the total sialic acid or docosahexaenoic acid contents in the cerebral cortex or hippocampus of pups nursed by dams fed on either type of water. The total dimethylacetal (DMA, from plasmalogen) level in the cerebral cortex of pups nursed by NANA-intake dams was significantly higher than that of pups nursed by NANA non-intake dams. These results suggest that dietary sialic acid in dams during pregnancy and lactation might be beneficial for the learning abilities of pups after weaning, which may be related to the plasmalogen level in the brain of pups.


Koizumi K.,Japan National Research Institute of Fisheries Science | Koizumi K.,Shizuoka Prefectural Research Institute of Fishery | Hiratsuka S.,Japan National Research Institute of Fisheries Science | Hiratsuka S.,Shizuoka Prefectural Research Institute of Fishery | Saito H.,Japan National Research Institute of Fisheries Science
Journal of Oleo Science | Year: 2014

The fatty acid compositions of the total lipids of three edible deep-sea fishes, Diaphus watasei, Diaphus suborbitalis, and Benthosema pterotum, were compared with those of a highly migratory fish, Katsuwonus pelamis, to clarify their lipid characteristics and nutritional value as seafood. The mean lipid contents in the three myctophids were markedly higher than was that of K. pelamis. All three myctophids had medium levels of 20:5n-3 (icosapentaenoic acid, EPA) and 22:6n-3 (docosahexaenoic acid, DHA) in their lipids, similar to those in surface pelagic fishes. The actual EPA and DHA amounts of the three myctophid fishes were higher than were those of K. pelamis. Therefore, the nutritional values of the myctophids as source for EPA and DHA are better than that of K. pelamis, and this fnding may introduce a new resource of healthy marine food from these under-utilized deep-sea fish species. © 2014 by Japan Oil Chemists' Society.


Unuma T.,Hokkaido National Fisheries Research Institute | Hasegawa N.,Hokkaido National Fisheries Research Institute | Sawaguchi S.,Hokkaido National Fisheries Research Institute | Tanaka T.,Shizuoka Prefectural Research Institute of Fishery | And 3 more authors.
Aquaculture | Year: 2011

The quality of eggs obtained from maturation-induced Japanese eel, Anguilla japonica, is unstable. One of the causes for low quality eggs is that females are artificially induced to ovulate at an inappropriate maturational status. Here we investigated the feasibility to use the morphological changes of lipid droplets in oocytes as a biomarker to show the optimum timing for injections of salmon pituitary extract (SPE) for priming and maturation-inducing steroid (MIS) for final oocyte maturation and ovulation. Various sizes of oocytes (700 to 1000 μm) were collected by cannulation from maturation-induced female eels during five days until ovulation. Morphology of the lipid droplets in these oocytes were classified into 10 stages mainly on the basis of their diameter, which increased with the progress of maturation as the droplets fused together. To assess the maturational status of each female, the lipid droplet stage was determined for 10 oocytes randomly chosen among the most advanced mode of developing oocytes and the median value was defined as the stage for the individual. Relationship between the lipid droplet stage at induction of ovulation and hatchability of the ovulated eggs was examined in 23 females, in which the hatching rate markedly fluctuated. Stages of females from which good quality eggs were obtained converged around stage 4 (five largest droplets, 55 to 70 μm) at priming with SPE, stage 6 (90 to 110 μm) at injection with MIS, and stage 7 (110 to 130 μm) at ovulation, while those of females from which low quality eggs were obtained showed distributions over broader ranges. Furthermore, 466 females were induced to mature and the lipid droplet stage at induction of ovulation was examined in 13 females from which high quality eggs (hatching rate >80%) were obtained. Most of the 13 females were at stage 3 (40 to 55 μm) or 4 when primed with SPE, at stage 6 when injected with MIS, and at stage 7 when they ovulated. These results suggest that the optimum stages for SPE priming, MIS injection, and ovulation are stages 3 to 4, 6, and 7, respectively, though the optimum stage for priming will be variable if the temperature and/or the time between priming and MIS injection is varied. We conclude that the lipid droplet stage can be used as a sensitive biomarker to show the optimum timing for inducing ovulation by hormonal treatments. © 2011 Elsevier B.V.


Unuma T.,Hokkaido National Fisheries Research Institute | Sawaguchi S.,Hokkaido National Fisheries Research Institute | Hasegawa N.,Hokkaido National Fisheries Research Institute | Tsuda N.,Hokkaido National Fisheries Research Institute | And 3 more authors.
Aquaculture | Year: 2012

To obtain fertilized eggs of the Japanese eel . Anguilla japonica, mature females are injected with maturation-inducing steroid (MIS) to induce final oocyte maturation and ovulation and then paired with mature males for spawning (induced spawning method) or stripped to collect eggs for insemination (stripping and insemination method). Progress of final oocyte maturation and ovulation and consequent egg quality are affected by the environmental water temperature. To detect the optimum temperature of the rearing water during artificial induction of ovulation by MIS injection, we investigated the effects of water temperature on ovulation, egg quality, and its deterioration due to over-ripening using the stripping and insemination method. Mature females injected with 17α-hydroxyprogesterone were stocked in tanks maintained at 17.5. °C, 20. °C, 22.5. °C or 25. °C. Earlier ovulation occurred at the higher water temperatures. Viability of the eggs that were collected from females immediately after observation of ovulation was similar at 20. °C and 22.5. °C but inferior at 17.5. °C and 25. °C. After eggs are retained in the body cavity for an hour, their viability was increasingly reduced due to over-ripening at the higher temperatures between 20. °C and 25. °C. Moreover, hatchability of unfertilized eggs placed in tubes and maintained at 15. °C, 17.5. °C, 20. °C, 22.5. °C or 25. °C for 3. h showed a time-dependent decrease due to over-ripening, which progressed slower at the lower temperature band between 20. °C and 25. °C. However, 15. °C and 17.5. °C did not delay the progress of over-ripening compared to 20. °C. We conclude that 17.5. °C and 25. °C are not appropriate for ovulation induction, because egg quality just after ovulation is lower than at 20. °C and 22.5. °C. In the stripping and insemination method, 22.5. °C is disadvantageous compared to 20. °C because of the faster progress of over-ripening, though this does not matter in the induced spawning method as spawning behavior and consequent fertilization are expected to occur at an appropriate timing after ovulation. © 2012 Elsevier B.V.


Yoshikawa M.,Shizuoka Prefectural Research Institute of Fishery
Journal of Fish Biology | Year: 2013

To assess the relationship between growth rate of body mass and sex in the Japanese eel Anguilla japonica in the early life stage; the growth rates of males and females were compared under experimental conditions. The mean growth rate of females was significantly slower than that of males. To assess the relative priority of growth rate and sex, growth was delayed by restricted feeding, resulting in a significantly higher proportion of females in the delayed than in the normal growth group. These findings indicate that the mean growth rate of A. japonica is slower in females than in males in the early life stage around sex determination and differentiation under experimental rearing conditions. Moreover, growth rate probably has priority over sex determination, with slow growth rate increasing the probability of being female. © 2013 The Fisheries Society of the British Isles.


In order to improve the hatching rate of eggs from artificially matured female eels, the environmental temperature during late stages of oocyte development was lowered from 20 °C (control) to 18 °C. Thus, female eels in which artificial maturation was induced at 20 °C using chum salmon pituitary extract (SPE) were transferred to water at either 20 or 18 °C at the beginning of the late stage of maturation. Biopsy by cannulation was carried out on the basis of an increase in body weight index (BWI; BWI = body weight × 100 / initial body weight). If the eel was judged to be nearing final maturation, a priming dose of SPE was administered, followed by a dose of maturation-inducing hormone (MIH). The average hatching rates of the eggs from the eels maintained at 20 and 18 °C were 16.6% (n= 10) and 45.9% (n= 11), respectively. The hatching rates at 18 °C were significantly higher than those at 20 °C. At 20 °C, the optimal timing of cannulation may often be missed due to both the rapid rate of oocyte development in the late stage and the unreliability of the BWI-based timing criterion. At 18 °C, rapid development of maturing oocytes in the late stage was prevented, and the optimal ovulation induction period was prolonged. Accordingly, the likelihood for optimal timing of cannulation was increased, as reflected in high hatching rates of fertilised eggs. On the basis of these results, a temperature of 18 °C in late stages of oocyte development is recommended to help in improving and stabilising the hatching rate. © 2012 Elsevier B.V.


Hiratsuka S.,Shizuoka Prefectural Research Institute of Fishery | Haneda Y.,Shizuoka Prefectural Research Institute of Fishery | Koizumi K.,Shizuoka Prefectural Research Institute of Fishery
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2016

The volatile flavor compounds in ordinary muscles with and without bleeding of skipjack tuna Euthynnus pelamis were analyzed by gas chromatograph-mass spectrometry (GC/MS) and compared. The contents of aldehydes and alcohols in ordinary muscle of skipjack tuna with bleeding were significantly lower (p <0.05) than those without bleeding. The aldehydes and alcohols were generated when the blood and lipid separated from the skipjack tuna were incubated in phosphate buffer (pH 6.0) for 2 days at 5°C. However, they were not generated in one side of blood and lipid. The aldehyde and alcohol levels both increased with blood concentration in the range from 0 to 100 μL by the reaction of 100 mg of lipid. These results suggest that the aldehydes and alcohols from the skipjack tuna might be generated by the reaction of blood and lipid. Moreover, the bleeding of skipjack tuna could be effective for reducing fish odor. © 2016 The Japanese Society of Fisheries Science.


Fujita D.,Tokyo University of Marine Science and Technology | Ishii R.,Tokyo University of Marine Science and Technology | Kanyama T.,Tokyo University of Marine Science and Technology | Abe M.,Shizuoka Prefectural Research Institute of Fishery | Hasegawa M.,Shizuoka Prefectural Research Institute of Fishery
Echinoderms in a Changing World - Proceedings of the 13th International Echinoderm Conference, IEC 2009 | Year: 2013

A tropical sea urchin, Diadema setosum has been known for more than a century on the Pacific coasts of Boso and Izu peninsulas in Japan. Around Okinoshima near the northernmost record of the species in Boso Peninsula, D. setosum inhabited the ditches and notches of cuesta-like rocks leaving Eisenia/Ecklonia forests on the top of ledges and formed patchy barrens on the boulders at 2 to 5 m in depth. When D. setosum was removed monthly from a quadrat, Eisenia forest was formed, while barren was maintained in a control. In Uchiura Bay on the Izu Peninsula, D. setosum formed a zoned barren (2 to 10 m in depth) on boulder beds, leaving shallower Sargassum and deeper Undaria/Eckloniopsis beds. Monthly removal of D. setosum from enclosed boulders and a large rock as well as transplantation of Sargassum onto suspended floats resulted in temporally limited success in algal restoration. © 2013 Taylor & Francis Group.

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