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太平洋クロマグロ雌雄に特徴的な DNA 断片を検出する目的で AFLP 解析を行った。雌雄 4 個体ずつ計 8 個体よりゲノム DNA を調整し，64 プライマーセットで 2 次増幅した結果 1038 のバンドを検出し，内 183 が個体間で多型を示した。二次増幅を EcoRI+AGG と MseI+CAT プライマーで行った際に雄 32 個体中 29 個体，雌 32 個体中 3 個体において確認される 437 bp の断片を同定した。この断片を定量した結果，雄に於いて検出され易く，また断片の量も検出される雌より有意に（P

— Indoor and outdoor experiments were conducted to improve the rearing techniques for artificially hatched northern bluefin tuna Thunnus thynnus during growout culture. Collisions with the walls of tanks or nets caused mass mortality that occurs during growout. The period when collisions frequently occur and the types of injury caused by collision were examined in this study. Juveniles were reared in indoor tanks from 30 to 120 d after hatching, and in an open sea net cage from 42 to 150 d after hatching. Dead fish were collected and counted daily in both of the experiments. In the indoor experiment, the sampled fish were preserved in 10% formalin solution, and each of 10 specimens of about 30, 50, 70, 85, 100, 130, 160 and 225 mm in body length (BL) were examined using x-rays to detect injury of the bones. Juvenile and young adult bluefin tuna showed a reduction in numbers caused by collision with the tank or the net wall during the experiments. In the indoor tank, there were 1,200 fish on day 30 but only eight on day 120. The daily mortality increased from day 30 after hatching, when juveniles reached 50-mm BL and remained over 4%/d until day 60 when juveniles grew to 300-mm BL. The proportion of dead fish with injuries of bone, especially of the vertebral column and the parasphenoid, increased after fish reached 50-mm BL, and exceeded 60% in fish with BL 85 mm or greater. In the open sea net cage, there were 3,841 fish at the start of the experiment on day 42 and only 65 on day 150. In this experiment, the reduction was greatest from the start of the experiment until day 80, when fish grew to approximately 25 cm in total length. Significant bacterial, viral or parasitic diseases were not observed in these fish; the only findings were dislocations of the vertebral column and injuries to the upper and lower jaws. These results show that the loss of juvenile and young adult bluefin tuna was caused by collision with the tank or net wall that fatally damaged the bones of the vertebral columns and the parasphenoid.

マダイ仔稚魚に24時間の高水温,低水温,高塩分,低塩分およびアンモニアストレスをそれぞれ負荷し,半数致死レベルを求めて魚の発育に伴う各種環境ストレス耐性の変動様式を調べた。ストレス耐性は,どのストレスでもふ化直後は高く,ふ化後14から21日目の脊索屈曲期前後に有意に低下した。稚魚期(28日令)以降は,水温およびアンモニア耐性に明らかな回復がみられ,塩分耐性にも緩やかな回復が示された。以上の結果,マダイ仔稚魚のストレス耐性は,いずれも変態期に低下する様相を示し,この時期にみられる活動余地の低下が,各種環境ストレス耐性の低下原因の一つであることを示唆した。また,各種ストレスの24時間半数致死レベルが,ストレステストの負荷条件として利用できることを示唆した。

Nile tilapia were exposed to severe hypoxic conditions. The respiratory frequency (RF) of the fish reached a maximum level at approximately 10 mmHg PO2 and decreased gradually thereafter. The fish sank to the bottom and subsequently their respiration began to stop. The hypoxic conditions increased the hematocrit value. As RF decreased, plasma cortisol and glucose levels climbed drastically. Just before respiratory arrest, the ATP and the total adenylate (TA) concentrations were significantly depressed in the liver, kidney and ordinary muscle but not in the heart or gill. As RF decreased, ATP and TA in both the liver and kidney decreased rapidly. Cytochrome oxidase activity increased significantly in the brain, heart, gill and ordinary muscle until respiratory frequency peaked. However, from the peak RF, this activity decreased in the liver and kidney. Lactic acid levels in both ordinary muscle and liver increased markedly when the fish sank. These results indicate that the stress response to hypoxic conditions is induced markedly with the decreased RF. It is also suggested that the decreased energy status in the liver and kidney of tilapia occurs at the same stage as the metabolic depression in the whole body, without increases in the aerobic and anaerobic metabolisms.

Gustatory response of marbled rockfish Sebastiscus marmoratus was recorded from the facial nerve supplying the anterior palate. In amino acids, the lowest threshold was for L-proline at 10−6–10−5 M; in ATP-related substances, the value for inosine was approximately 10−5 M and in organic acids, the value for L-lactic acid was approximately 10−6 M. An almost complete self-adaptation was observed for stimulants after 5 s application. While a weak solution of L-lactic acid as adapting stimulus depressed the response to it completely, it did not appreciably affect the response to 10-times or more concentrated L-lactic acid solution. In contrast to a weak solution, a moderate solution caused a severe depression of the response to stronger solutions, resulting in a shift of the dose–response curve towards a high concentration range. Time for recovery from adaptation differed depending on chemicals and stimulus duration: for 10−4 M L-lactic acid, it took about 2.3 and 4.5 s for 1/2 recovery of response magnitude under unadapted condition from the adaptation after 1 s- and 5 s-stimulation, respectively. L-Lactic acid and L-alanine strongly depressed the response to each other, yielding a rightward shift of the dose–response curve. A similar profound cross-adaptation was also observed between inosine and 5′-inosinic acid. The possible role of gustation is discussed.

SUMMARY: An inhibitory effect of Kunitz and Bowman-Birk soybean trypsin inhibitors (K- and BB-SBTI) was investigated on tryptic and chymotryptic proteinases of a brood of tiger puffer Takifugu rubripes and yellowtail Seriola quinqueradiata. These assist to comprehend the differences in dietary soybean meal (SBM) utility by fish species and to develop low cost SBM diets with low contents of fish meal. The K-SBTI strongly inhibited tryptic proteinase and weakly inhibited chymotryptic proteinase from the hepatopancreas and intestine including pyloric ceca of the fishes. The BB-SBTI strongly inhibited both proteinases of the fishes. The K-SBTI inhibition for tryptic protease and the BB-SBTI inhibition for tryptic and chymotryptic proteases were relatively constant in tiger puffer with growth of 12–199 g bodyweight. In yellowtail with growth of 7–672 g bodyweight, the K-SBTI inhibition for tryptic protease and the BB-SBTI inhibition for chymotryptic protease were also relatively constant. The BB-SBTI inhibition for yellowtail tryptic protease typically fell in the stage from 7 g to 57 g bodyweight, and then decreased slightly or was maintained constantly. These results indicate that there are different inhibitory modes of K- and BB-SBTI and there is inter- and intraspecific diversity of tryptic protease conformation between the two species.

SUMMARY: The zero-year red sea bream Pagrus major were fed for 41 days on dry pellets containing 1% Teaflan (60% catechin) or Spirulina supplement. The effects of catechin and Spirulina on ascorbate absorption, lipid metabolism, and collagen synthesis were compared in relation to vitamin C nutrition. Total ascorbate concentrations in the serum and liver were increased significantly in the catechin-fed groups relative to the control, but Spirulina increased in value only in liver. Feeding with catechin and Spirulina depressed non-esterified fatty acid and total lipid in serum, respectively. Liver lipid was depressed by feeding catechin and Spirulina. Hepatic free carnitine and long-chain acylcarnitine contents were markedly higher in both catechin- and Spirulina-fed groups than in the controls. Hepatic carnitine palmitoyltransferase activity was markedly elevated in the Spirulina-fed group. In contrast, glucose-6-phosphate dehydrogenase and fatty acid synthase activities were not different among the groups. The collagen fraction soluble at 20°C was lower and the insoluble collagen fraction (not soluble at 70°C) was higher in catechin- and Spirulina-fed groups. These results suggest that dietary supplementation with catechin, as well as Spirulina, improved vitamin C metabolism in young red sea bream.

Control and stressed groups of juvenile Japanese parrot fish Oplegnathus fasciatus were fed diets (moist pellet) supplemented with 0, 75, and 300mg of ascorbic acid (AsA) per 100g. Fish in the stressed group were intermittently exposed to decreasing water oxygen levels every 3 or 4 days for 16 weeks. In the fish given a diet containing no AsA supplement, AsA-deficiency symptoms were manifest-ed earlier, and to a greater extent, in the stressed fish than in the non-stressed ones. Similarly, the growth of stressed fish fed on a diet supplemented with 75mg AsA per 100g was inferior to the growth of the control group, and in the stressed fish there was a reduction in AsA levels in the plasma, kidneys, and gills. On the other hand, fish fed on a diet supplemented with 300mg of AsA per 100g were barely affected by the stressor. These results indicate that, in Japanese parrot fish under these experimental conditions, ex-posure to intermittent hypoxic stress not only induced AsA-deficiency disease early, but also in-creased the AsA requirement. It was also shown that high doses of AsA increased the ability of these fish to resist the stressor.

Feeding stimulants for the marbled rockfish Sebasticus marmoratus were identfied by the omission test uding the synthetic extract of krill Euphausia pacifica. The fish were fed on a purifiedcasein diet supplemented with constituents of the extract for 6 days. The feeding stimulant activity was evaluated by the daily feeding rate. The nucleotide fraction of the extract was the most effective, followed by the amino acid fraction which showed a littel activity. Inosine had the highest activity among all constituents of the extract. With increasing supplementary level to the diet, amino acids such as L-alanine, L-methionine, L-serine and L-proline and nucleotides such as adenosine-5'-diphosphate, adenosine-5'-monophosphate and inosine-5'-monophosphate became positive. When inosine together with, L-alanine, L-methionine, L-serine and L-proline was supplemented to the diet, its activity for the fish was remarkably improved, becoming to the synthetic extract.

The effect of algae as feed supplementary was determined on yellow tail Seriola quinqueradiata in terms of serological parameters and proximate composition of the dorsal muscle. Fish of 144g in body weight were reared for 60 days in floating nets. Control group was fed on sand lance Ammodytes personatus.One percent of hot water-extract from Chlorella vulgaris (Chlorella-extract group) or 0.5% of kelp Laminaria digitata (kelp meal group) was supplemented to the above basal diet (sand lance). The supplementaries had no effect on body weight gain or feed conversion efficiency. The kelp meal depressed the lipid, non-protein nitrogen, and amino nitrogen levels in the serum, and elevated the muscle lipid level. Chlorella-extract, however, did not cause significant alteration in serum constituents and proximate composition of the muscle.After 60 days of feeding, the fish were kept in indoor tanks without feeding for 23 days. Body weight loss was not significantly distinct among the 3 groups. Nevertheless, the serum lipid and nonesterified fatty acid levels were characteristically changed under the starvation period in response to the dietary regimen. The muscle lipid loss was higher in the kelp meal group than the control group. Furthermore, the suppression of breakdown of muscle protein was found in the Chlorella-extract group and the kelp meal group.These results showed that the kelp meal contributed to accelerate the lipid deposition to the muscle and to mobilize the lipid to energy. The importance of algae supplement in yellow tail, was discussed in relation to improvement of lipid metabolism which had a close connection with the health condition of the fish.

Chromatophoroma in the croaker (Nibea mitsukurii) showed a unique geographic distribution. The contribution of environmental chemicals to the cause of chromatophoroma in the feral croaker is considered likely on the basis of the following results in our studies. 1) Chromatophoroma was induced in tank-reared N. mitsukurii by administration of certain kinds of known carcinogens such as 7,12-dimethyl-benz(a)anthra-cene, N-methyl-N'-nitro-N-nitrosoguanidine, and nifurpirinol. 2) Local accumulation of pigment-cell hyperplasia in the catfish (Protosus anguillaris) showed similar tendencies to those of chromatophoroma in N. mitsukurii. 3) Removal of contaminated sediment from the harbor and the river appeared to reduce the incidence from 47% in 1973–1983 to about 20% in 1985–1987. 4) Waste water from a factory located at the station where the incidence of the neoplasm was the highest contained mutagenic substances such as chloroacetones and glyoxals [5]. Exposure of catfish to the waste water induced pigment-cell hyperplasia on the skin. J Invest Dermatol 92:248S–254S, 1989

The visual cell morphology in 2-90mm long larvae and juveniles, and adult of the red sea bream Pagrus major was examined histologically. The visual system of the larvae is poorly developed at hatching, but becomes functional in 36 hours. At this time, the eyes are well pigmented, cones are formed, and optic nerves connect with the optic tectum. The visual cells of larvae smaller than 10.6mm are all single cones. At 11mm TL, the single cones fuse to form twin cones, and rods appear at the same time. Red sea bream shifts from a pelagic to a benthic habitat when about 12-15mm long. The observed increase in visual sensitivity at 11mm appears to be a preadaptation to life at greater depths. Likewise, the specialized retinal region for acute vision shifts from temporal to dorso-temporal at a length of 30mm, implying a change in visual axis from fore to lower-fore direction, and an adaptation to the change in diet from planktonic to benthic animals.