Tetsuya Umino

Molecular characterization of peroxisome proliferator-activated receptors (PPARs) and their gene expression in the differentiating adipocytes of red sea bream Pagrus major

To investigate the molecular mechanism of fish adipocyte differentiation, the three subtypes of PPAR genes (alpha, beta and gamma) were characterized in a marine teleost red sea bream (Pagrus major). The primary structures of red sea bream PPARs exhibited high degrees of similarities to their mammalian counterparts, and their gene expression was detected in various tissues including adipose tissue, heart and hepatopancreas. During the differentiation of primary cultured red sea bream adipocytes, three PPARs showed distinct expression patterns: The alpha subtype showed a transient increase and the beta gene expression tended to increase during adipocyte differentiation whereas the gene expression level of PPARgamma did not change. These results suggest that they play distinct roles in adipocyte differentiation in red sea bream. In the differentiating red sea bream adipocytes, mammalian PPAR agonists, 15-deoxy-Delta(12,14)-prostaglandin J(2), ciglitazone and fenofibrate did not show clear effects on the adipogenic gene expression. However, 2-bromopalmitate increased the PPARgamma and related adipogenic gene expression levels, suggesting the gamma subtype plays a central role in red sea bream adipocyte differentiation and in addition, fatty acid metabolites can be used as modulators of adipocyte function. Thus our study highlighted the roles of PPARs in fish adipocyte differentiation and provided information on the molecular mechanisms of fish adipocyte development.

Parentage assignment of stocked black sea bream Acanthopagrus schlegelii in Hiroshima Bay using microsatellite DNA markers

The genetic contribution of 51 broodstock, comprising 29 females and 22 males, reared at Hiroshima City Marine Products Promotion Center for the production of stocked black sea bream was monitored during two consecutive years using seven microsatellite DNA loci. The high discrimination ability of these markers was reflected in the polymorphic identification content (PIC=0.831), the exclusion probability (Q≈1), and the low probability of identity index (I=3.635−10). The total number of breeders contributing to the mating process was estimated at 32 (62.7%) in 2000 and 30 (58.8%) in 2001. On pedigree reconstruction, 69.3% of the offspring were successfully assigned to a single broodstock pair. Loss of alleles accounted for 16.9% during seed production; nevertheless, 90.9% of males and 69.0% of females participated in the mating process. Based on microsatellite genetic tagging, 58.9% of the fish sampled during the two months after release were identified as hatchery stock, presenting no significant differences from wild conspecifics in either fork length or body weight.

Usefulness of Ascophyllum meal as a feed additive for red sea bream, Pagrus major

Abstract Based on previous results that dietary algae meal can improve the physiological condition of fish, the effects of dietary Ascophyllum meal supplementation (0, 2.5 and 5%) on body composition and physiological condition were examined in 0 year red sea bream. Muscle protein increased in response to the algae level. Response to air-dipping and recovery time from anesthesia with 2-phenoxyethanol were improved by feeding Ascophyllum meal. These results offer support for the use of Ascophyllum meal as a feed additive in fish diets.

Phylogenetic relationship of two Mola sunfishes (Tetraodontiformes: Molidae) occurring around the coast of Japan, with notes on their geographical distribution and morphological characteristics

Phylogenetic analyses were conducted using complete nucleotide sequences of the D-loop in the mitochondrial genome of Mola specimens, collected mainly in Japanese waters, to clarify the genetic features and distribution patterns of Mola sunfishes. Two significantly distinct groups (designated A and B) were present in the genus, with a considerable net nucleotide sequence divergence between the two (8.4%). The two groups occurred sympatrically around the Japanese coast, as previously suggested by Sagara et al. (2005). Group A occurred mostly on the Pacific coast of eastern Japan, while group B was widely distributed along the Kuroshio Current, strongly suggesting different migration routes for each group. The morphological characteristics of the two group specimens were differentiated via the head bump, body proportions and shape of the clavus. Through the addition of Mola sequence data taken from outside Japan to our phylogenetic analyses, three independent groups, including groups A and B, were found, each with a wide geographical distribution, which suggests the presence of at least three independent species within the genus Mola.

Growth performance in clonal crucian carp, Carassius langsdorfii. Effects of genetic difference and feeding history

Abstract Clonal crucian carp was used to assess the relative importance of disproportional food acquisition and genetic differences in ‘growth depensation’ i.e. increased variation in size-frequency distribution over time. When larval feeding was limited on the 5th, 9th, and both the 5th and 9th days after hatching in a clonal population, subsequent growth was significantly retarded compared to the group recently unlimited food (control). Suppression of growth due to limited feeding was greater when food deprivation occurred on the 5th day than when it occurred on the 9th day, suggesting that short-term disproportional feeding has a greater effect the closer it is to first-feeding. When larvae of two genetically different clones were reared together up to larval development (day 1 to 30), growth was significantly different between them. Heritability for total length was estimated as 0.257 at a low stocking density ( n = 200) and 0.584 at a high stocking density ( n = 300). Genetic factors may, thus, determine not only growth but also competitive ability in social interactions. When two strains equalized for initial size were reared to the juvenile stage (day 90 to 150), no growth differences were observed. The extent of genetic control of growth performance may differ between the developmental stages.

Effects of Ascophyllum and Spirulina Meal as Feed Additives on Growth Performance and Feed Utilization of Red Sea Bream, Pagrus major

養魚飼料への藻類添加は生理状態の向上に有効であることが明らかにされているので、本研究ではマダイについて Ascophyllum と Spirulina の効果をみた。対照区には配含飼料に5%のセルロース、Ascophyllum 区、Spirulina 区にはそれぞれ藻類の粉末を5%添加した。初期体重85gのマダイ1年魚を77日間飼育し、成長、飼料利用率、生物学的性状、体成分に及ぼす効果をみた。いずれの藻類の添加においても成長、飼料効率、タンパク質効率、筋肉タンパク質蓄積量が向上し、筋肉成分では脂質蓄積量に増加がみられた。Spirulina の投与では悪影響は認められず、各項目においてAscophyllum より優れた効果を示し、これまでに報告された藻類に匹敵するか、もしくはそれ以上の効果を示した。

New Host Records for Lernaea cyprinacea (Copepoda), a Parasite of Freshwater Fishes, with a Checklist of the Lernaeidae in Japan (1915-2007)

The lernaeid copepod Lernaea cyprinacea Linnaeus, 1758, was found attached to three species of freshwater fishes, the barbell steed Hemibarbus labeo (Pallas) (Cyprinidae), the dark chub Zacco temminckii (Temminck and Schlegel) (Cyprinidae), and the Amur catfish Silurus asotus Linnaeus (Siluridae) from Hiroshima Prefecture in Japan. The findings from Hemibarbus labeo and Zacco temminckii represent new host records for L. cyprinacea, while Silurus asotus is a new host in Japan. Based on the literature published for 93 years from 1915 to 2007, a checklist of three species of lernaeid copepods (Lernaea cyprinacea, Lernaea parasiluri, Lamproglena chinensis) from Japan is given, including information on the synonym(s), host(s), site(s) of infection, and distribution. The checklist shows that in Japan L. cyprinacea has been reported from 33 or 34 species and subspecies of fishes belonging to 17 families in 10 orders and also from 2 species of amphibians from 2 families in 2 orders.

Mapping quantitative trait loci for egg production traits in an F2 intercross of Oh-Shamo and White Leghorn chickens

We performed quantitative trait locus (QTL) analyses for egg production traits, including age at first egg (AFE) and egg production rates (EPR) measured every 4 weeks from 22 to 62 weeks of hen age, in a population of 421 F(2) hens derived from an intercross between the Oh-Shamo (Japanese Large Game) and White Leghorn breeds of chickens. Simple interval mapping revealed a main-effect QTL for AFE on chromosome 1 and four main-effect QTL for EPR on chromosomes 1 and 11 (three on chromosome 1 and one on chromosome 11) at the genome-wide 5% levels. Among the three EPR QTL on chromosome 1, two were identified at the early stage of egg laying (26-34 weeks of hen age) and the remaining one was discovered at the late stage (54-58 weeks). The alleles at the two EPR QTL derived from the Oh-Shamo breed unexpectedly increased the trait values, irrespective of the Oh-Shamo being inferior to the White Leghorn in the trait. This suggests that the Oh-Shamo, one of the indigenous Japanese breeds, is an untapped resource that is important for further improvement of current elite commercial laying chickens. In addition, six epistatic QTL were identified on chromosomes 2, 4, 7, 8, 17 and 19, where none of the above main-effect QTL were located. This is the first example of detection of epistatic QTL affecting egg production traits. The main and epistatic QTL identified accounted for 4-8% of the phenotypic variance. The total contribution of all QTL detected for each trait to the phenotypic and genetic variances ranged from 4.1% to 16.9% and from 11.5% to 58.5%, respectively.

A Checklist of the Parasites of Eels (Anguilla spp.) (Anguilliformes: Anguillidae) in Japan (1915-2007)

1915～2007年の93年間に出版された文献に基づき, 日本産ウナギ属魚類3種(ウナギAnguilla japonica, オオウナギAnguilla marmorata, ヨーロッパウナギAnguilla anguilla)の寄生虫に関する情報を2つのリスト(寄生虫-宿主リスト, 宿主-寄生虫リスト)に整理して目録を作成した。ウナギとオオウナギは在来種であり, ヨーロッパウナギは国外からの移入種である。本目録には, 44種の寄生虫(繊毛虫類6種, 微胞子虫類1種, ミクソゾア類6種, 吸虫類7種, 単生類7種, 条虫類3種, 線虫類7種, 鉤頭動物4種, ヒル類2種, カイアシ類1種)に加えて, 学名がまだ決定していない寄生虫の情報が含まれる。寄生虫-宿主リストでは, 各寄生虫は高位分類群ごとに配列され, 最新の学名, シノニム, 寄生部位, 地理的分布および報告者の情報が示されている。上記44種のうち, ウナギから43種, オオウナギから1種, ヨーロッパウナギから10種の寄生虫が報告されている。単生類のGyrodactylus anguillaeと線虫類のRaphidascaris acusはヨーロッパウナギとともにヨーロッパから, またGyrodactylus nipponensisもインド・西太平洋地域から持ち込まれたと推察されている。ウナギから報告された寄生虫のうち, 8種は海産または汽水産で, 2種(Tubulovesicula anguillae, Pseudodactylogyrus kamegaii)の成虫がウナギに特異的に寄生しているため, 海洋と汽水域において, ウナギはそれら寄生虫の固有宿主の役割を果たしていると言える。

Effects of Feeding Regime on Biometric Parameters and Hepatic Enzyme Activities of young Red Sea Bream, Pagrus major

体重5.1gのマダイ幼魚を5群に分けて、3つの群は日間給餌頻度を2回、4回、6回とし、49日間飽食させた。他の2群には日間給餌回数2回の飽食量相当分を4回、6回に分けて投与した。飽食給餌では給餌頻度の増加と共に摂取量、脂肪組織、筋肉脂質が上昇した反面、飼料効率、比肝重量は低下した。4回飽食の場合、腸管長は最も短く、肝臓脂質合成酵素、アミノ基転移酵素活性は高かった。一方、2回分の飽食量を4回、6回に分けて給餌した場合、脂質蓄積に変化はなかったが給餌回数の減少と共に腸管は伸張し、肝臓の糖新生関連酵素、解糖酵素活性は低下し、脂質合成関連酵素が向上した。飼料効率、脂質蓄積、腸管長、酵素活性からみて1日2回の飽食給餌が最適であることが判明した。