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Haga Y.,Tokyo University of Marine Science and Technology | Kondo H.,Tokyo University of Marine Science and Technology | Kumagai A.,Tokyo University of Marine Science and Technology | Satoh N.,Mariculture Fisheries Research Institute | And 2 more authors.
Aquaculture | Year: 2015

Cysteine sulfinic acid decarboxylase catalyzes reaction of decarboxylation of cysteine sulfinic acid into hypotaurine. This step is considered as a rate limiting step of taurine biosynthesis in animals. Because of lower CD activity, marine fish has limited ability of de novo taurine synthesis and requires taurine in food. However, if we can develop a method to control CSD activity in marine fish, supplement of taurine to diet of marine fish is not necessary. In order to develop this technique, we have to isolate CSD from marine fish. This study, thereby, is conducted to isolate CSD from red sea bream Pagrus major and yellowtail Seriola quinqueradiata. We also analyze the expression of CSD in red sea bream, yellowtail, Japanese seabass Lateolabrax japonicus, and barfin flounder Verasper moseri. Total RNA was extracted from liver of red sea bream and yellowtail. Primers are designed against sequence of highly conserved region of reported CSD in other animals for RT-PCR. 776. bp and 725. bp partial CSD sequences were successfully cloned from red sea bream and yellowtail. By 5' and 3' RACE methods for cloned partial CSD sequences, total length of CSD (1882. bp and 1821. bp) from red sea bream and yellowtail was determined. Classification of deduced amino acid sequence revealed that red sea bream and yellowtail CSD showed 88.8% homology similar to Nile tilapia, platyfish, etc. Domain analysis shows that pyridoxine binding region was conserved in CSD from both species.Expression analysis of CSD from red sea bream, Japanese seabass, barfin flounder and yellowtail indicated that CSD is expressed in a variety of tissues but commonly in the liver and pyloric ceca of all species examined. Additionally, strong CSD expression was observed in the heart in all species examined except for Japanese seabass. © 2015 Elsevier B.V.

Kobayashi Y.,Hokkaido University | Takatsu T.,Hokkaido University | Yamaguchi H.,Wakkanai Fisheries Research Institute | Joh M.,Abashiri Fisheries Research Institute | Joh M.,Mariculture Fisheries Research Institute
Fisheries Science | Year: 2015

To characterise food-habit differences in Pseudopleuronectes herzensteini juveniles we compared diets, prey diversity and nutritional states between two groups, i.e., one in the Sea of Japan and the other in the Sea of Okhotsk around northern Hokkaido, Japan. Juveniles were collected with a sledge net along the sea bottom at depths of 8–50 m in August 2010 and 2011. In the Sea of Japan, 63 were analysed (23 in 2010 and 40 in 2011). In the Sea of Okhotsk, 88 were analysed (55 in 2010 and 33 in 2011). There were no differences in standard lengths of juveniles (the Sea of Japan: 27.0 mm in 2010 in median; 28.8 mm in 2011; the Sea of Okhotsk: 28.3 mm in 2010; 29.2 mm in 2011) or in bottom water temperatures at the study sites. However, stomach content volume and Fulton’s condition factor K were higher in the Sea of Okhotsk than in the Sea of Japan. High feeding intensities in the Sea of Okhotsk may have led to a higher nutritional status in fish collected from this sea. In both seas, the diet comprised mainly harpacticoid copepods, gammarids and polychaetes, with some additional bivalves being observed in the Sea of Japan. The value of the prey-diversity index (Δ*) was lower when the K value of juveniles was higher. © 2015, Japanese Society of Fisheries Science.

Joh M.,Abashiri Fisheries Research Institute | Matsuda T.,Mariculture Fisheries Research Institute | Miyazono A.,Abashiri Fisheries Research Institute
Journal of Fish Biology | Year: 2015

Otolith microstructure of reared and wild cresthead flounder Pseudopleuronectes schrenki larvae and juveniles was used to investigate the daily periodicity of ring formation, morphological change and unique otolith structure related to important life events. By comparing microstructural features of P. schrenki with those reported for other flatfish species, it was shown that there may be microstructural features that are common to all flatfishes. In the sagittae and lapillus, a check (a distinct ring) was formed in the centre of otoliths at c. 6 days post hatching, and the daily formation of rings observed outside the check was confirmed. During metamorphosis, accessory primordia (AP) of otolith growth were formed on the outer edge of the sagittae, and the shape of the sagittae became more complex. No AP was formed on the lapilli, however, and otolith rings were concentrically formed throughout the larval and juvenile (≤51·6 mm standard length, LS) stages. It is proposed, therefore, that lapilli are more appropriate than sagittae for analysis throughout the larval and juvenile (≤51·6 mm LS) stages. During metamorphosis, unique rings that are relatively wide and show weak contrast are formed on lapilli (metamorphosing zone, MZ). Hence, the duration of metamorphosis, larval duration and the days of juvenile life can be estimated by the number of rings within the MZ, using rings from the check to outermost ring of the MZ, and that of rings formed outside MZ, respectively. The formation of AP on sagittae as well as the absence of AP, bilateral asymmetry and the formation of a unique structure during metamorphosis on lapilli have also been reported for other flatfishes. © 2014 The Fisheries Society of the British Isles.

Kayaba T.,Kushiro Fisheries Research Institute | Wada T.,Fukushima Prefectural Fisheries Experimental Station | Murakami O.,Mariculture Fisheries Research Institute | Sawaguchi S.,Seikai National Fisheries Research Institute | Kawabe R.,Nagasaki University
Fisheries Research | Year: 2015

For conservation and management of fish stock, reliable reproductive parameters, especially information on the spawning period, are greatly needed. Until now, the spawning period of male fish was estimated mainly using the gonadosomatic index (GSI) and microscopic observation of the testes. However, these methods pose the problem of estimation accuracy and handiness for analysis, respectively. To identify biological characteristics that would allow accurate determination of spawning periods, we investigated the seasonal development of testes and sperm ducts in our model fish, the barfin flounder Verasper moseri. GSI (testis weight. ×. 100/body weight) reached a maximum during November-December; however, this peak period occurred approximately two months before the onset of spawning. In contrast, the sperm duct index (SDI) (sperm duct weight. ×. 100/body weight) sharply rose from February to March when spermiation and sperm release actively proceeded. On comparing the SDI of all gonadal development phases, it was found that only the fish that underwent spawning had significantly enlarged sperm ducts due to sperm accumulation. This finding strongly suggested that sperm duct volume is an adequate indicator for accurately identifying spawning period in male fish. Moreover, analysis using SDI takes less effort for sample processing, suggesting to be practical for continuous monitoring of stock assessment. © 2015 Elsevier B.V.

Yoshikawa N.,Kyoto University | Matsuda T.,Mariculture Fisheries Research Institute | Takahashi A.,Kitasato University | Tagawa M.,Kyoto University
General and Comparative Endocrinology | Year: 2013

Barfin flounder larvae exhibit unique black coloration, as well as left-right asymmetry in juvenile stage as in other flatfish. In this study, we first assessed the changes in melanophores with development and then investigated their responsiveness to melanin-concentrating hormone (MCH) during metamorphosis. Larval-type melanophores appeared on both sides of the body before metamorphosis, whereas adult-type melanophores appeared only on the ocular side after metamorphosis. Even in the individuals of this species displaying black coloration, the density of larval-type melanophores was similar to that in transparent larvae of other species. However, unlike in transparent larvae, larval-type melanophores completely dispersed in the black larvae of this species. Therefore, the black coloration during larval stages was mainly due to dispersion, and not the density, of larval-type melanophores. In vitro MCH treatment revealed, for the first time, the responsiveness of melanophores in larval stages. On the ocular side, larval-type melanophores aggregated against MCH during larval stages, while, in the larvae at later metamorphic stages and in juveniles, larval-type melanophores did not aggregate, although aggregation of adult-type melanophores was noted. In contrast, on the blind side, the responsiveness of larval-type melanophores to MCH was consistently present from larval to juvenile stages. The metamorphic transition of MCH responsiveness from larval- to adult-type melanophores only on the ocular side suggests the larval (therefore, immature) nature of the blind side skin. We propose that the inhibited development, and thus the retention of the larval-type skin leads to the formation of the blind side characteristics and is the central mechanism for the flatfish asymmetry. © 2013 Elsevier Inc.

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