ウシエビ血球の形態および構造を光顕・電顕観察に基づいて記載した。パン酵母を血リンパ中に接種したところ, 血球および定着性食細胞の食作用, ノジュール形成および包囲化により除去された。これらの反応はほぼエビの全身で認められ, 酵母接種直後から1時間後にかけ血リンパ中の血球数の顕著な減少が認められた。Vibrio harveyiを血リンパ中に接種したところ, その98％が3時間以内に除去された。また, 顆粒球がフェノールオキシダーゼ活性を有することが確認された。

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2000年8月, タイのウシエビ種苗生産場で卵および幼生に真菌症が発生した。罹病卵および幼生からの分離菌はその形態学的特徴からLagenidium thermophilum に同定された。本分離株の発育温度と塩分耐性は過去にノコギリガザミから分離されたL. thermophilum 株の性状とよく似ていた。また, 本株は遊走子を用いた人為感染試験でウシエビの幼生に病原性を有することが確認された。これはタイにおけるウシエビからのL. thermophilum の初めての分離例である。

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　タイ国の伝統的な薬草ハーブ Clinacanthus nutans エタノール抽出物の坑ウイルス効果を調べた。 抽出物を希釈後, イエローヘッドウイルス（YRV）と25℃で2時間混合した。 この混合液をウシエビ（Penaus monodon）に注射し調べたところ, 供試した C.nutans の抽出液は YRV に対し坑ウイルス効果を示し, その効果は1μg/mlの濃度から認められた。 抽出物の坑 YRV 効果は経口投与においても得られ, C.nutans 抽出液は本病の制御に有効であることが示された。

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Genetic variability of wild and cultured shrimp populations in Thailand was studied by the microsatellite DNA technique. In wild populations from the Gulf of Thailand, South Thailand, and South Myanmar, high genetic variability was detected. Mendelian inheritances were evaluated in juveniles from 4 farms. In three of the farms, more than 4 genotypes were identified, indicating that the farms did not use single parental line. Genetic approaches are required to achieve stable production rates in shrimp cultures.

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The selenium distribution in the exoskeleton (abdominal pleuron) as an inedible tissue and the ordinary muscle of several species of shrimps (Kuruma prawn Marsupenaus japonocas, Northern shrimp Pandalus eous, Whiskered velvet shrimp Pleoticus muelleri and prawn Penaeus monodon) in clustacea, which have been known to be useful as the scavenger of heavy metals, was investigated in order to clarify the possibility of the available utilization of selenium from those tissues, in relation with the mercury distribution involving the tissues. As a result, each selenium and mercury level in the exoskeleton of all subjected species, except prawn, was about the same and low compared with that involving muscle, respectively. Moreover, from the selenium molar fraction involving exoskeleton, the low oxidation states of selenium species was almost predominant in all subjected species, as not in the case of involving ordinary muscle, suggesting that a little Se(VI) species as metabolized in living body after eating exists in the exoskeleton. On the other hand, the Se/Hg (the molar ratio of selenium to mercury) as an indicator of the safety of marine products was also extremely high compared with that involving ordinary muscle, except prawn, suggesting that the exoskeleton will be usually inedible but significantly safe tissue in which low levels of heavy metals such as mercury will tend to accumulate, as in the case of a preceding paper. These findings suggest that the available utilization of selenium will not be expected from the exoskeleton, including the improvement of the environment.

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　タイのyellow　head　diseaseに罹病したウシエビから,　封入体を形成しない新しいバキュロ様ウイルスが検出された。鰓やリンパ様組織の壊死巣に長さが150～200nm,　径が40～50nmで3層の膜からなるエンベロープに包まれた桿状のウイルス粒子が観察された。感染実験の結果から,　本ウイルスは今までにウシエビにみられたウイルスのうち病原性の強いものと考えられる。

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　タイのウシエビ幼生, アルテミアおよび飼育水からスウォーミング細菌の発育を阻止する細菌45株を分離した。同様の材料から得られた50株の Vibrio 属細菌に対する発育阻止能を二重平板法を用いて調べたところ, 45株中27株が強い阻止能を示し, それらはまた魚介類病原細菌を含む多くの Vibrio 属細菌の参考株に対しても抗菌作用を示した。生科学的性状および DNA の GC ％から, これらの27株はいずれも Alteromonas 属類似細菌と考えられた。

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Southeast Asia is a significant area for world shrimp culture. However, in recent years, the production of cultured shrimp has markedly decreased as a result of serious viral disease such as white spot syndrome (WSS) outbreaks. In the case of Malaysia, outbreaks of this disease have been a serious problem since 1996. As one of the preventive countermeasures against WSSV, virus inactivation has been carried out against kuruma prawn in Japan. In the recent studies, it became clear that there are differences among local strains of WSSV. Furthermore, kuruma prawn shows resistance against WSSV. For these reasons, methods to inactivate Malaysian isolates of WSSV were studied with prawn (Penaeus monodon). Viral inactivation was tested using the disinfectants formalin and ethanol, the halogenous disinfectants sodium hypochlorite and Isodine^R, and also using U.V. irradiation. These chemicals were mixed with the virus and injected into healthy prawns. As a result of these experiments, no mortality was observed at the concentrations of more than 0.25 ppm formalin, 0.5% effective chloride in sodium hypochlorite, and 2.5 ppm effective povidone-iodine in Isodine^R. From these results, sodium hypochlorite of halogenous disinfectants showed effective inactivation even at a low concentration (0.5 ppm). On the other hand, this virus was inactivated completely by U.V. irradiation at a dose of 3 × 10⁴ μW·sec/cm². These results were similar to the virus inactivation of a Japanese strain with kuruma prawn (Marsupenaeus japonicus).

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Carotenoid content and composition of commercial prawns Penaeus monodon exhibiting different body color were determined. A consistency was observed between the depth of body color of prawns and the carotenoid content of 2.3-33.1mg/100g in their exoskeleton. Astaxanthin was the major component in all the prawns, amounting to 86-98% of total carotenoids. Three forms of astaxanthin, namely diester, monoester, and free ones, were found. Cultured prawns accumulated preferentially astaxanthin monoester in their exoskeleton, when the total carotenoid content exceeded about 8mg/100g. Thus the external coloring in carotenoid-rich prawns may be due to interaction between the color of astaxanthin esters and that of carotenoprotein.

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　‘White spot disease’と診断されたクルマエビから初めてイエローヘッド病様ウイルスを見つけた。リンパ様器官, 肝膵臓の間質, 心臓, 鰓, 結合組織, クチクラ上皮, および造血組織に好塩基性封入体および肥大した核を持つ細胞が見られた。壊死細胞の細胞質にエンベロープを持つ, 長さ150～200, 幅40～50nmの桿状のウイルス粒子が確認されたが, 異常に長いウイルスも観察された。これらのウイルスの形態はイエローヘッド病のウイルスに類似する。

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In order to use shrimp meal (SM) made from headless shrimp waste as a protein source for poultry diets, chemical composition of SM and growth performance, dry matter (DM) digestibility and nitrogen (N) retention in broilers given diets containing SM ranged from 0% to 16% were measured. Comparing with the data in the previous reports, SM used in the present study was rich in fiber and ash, hence poor in CP. Amino acid profiles revealed that SM had lower concentration of methionine+cysteine, lysine, isoleucine, leucine, tryptophane than soybean meal. The results of orthogonal polynomials revealed that body weight gain, feed intake, feed efficiency, DM digestibility and N retention decreased with increasing levels of SM and the results of ANOVA showed that, in most case, these parameters did not change significantly when SM level was at and below 8%. However, these parameters in birds given 8% SM diets did not differ from those in birds given 12% and 16% SM diets. Taking this into account, the safer level to add SM to a broiler diet seems to be 4%. Decreased body weight gain may be resulted from decreased feed intake, feed efficiency and DM digestibility. In conclusion, it is suggested that SM can be used as a protein source in a broiler diet as far as it is included at and below 4%.

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A blue carotenoprotein fraction was liberated from the muscular epithelium of the prawn Penaeus monodon by extraction with a collagenase solution, leaving another carotenoid fraction in the tissue. Carotenoids in both fractions were analyzed and compared between dark gray prawns and blue ones. The main carotenoid in the carotenoprotein was free astaxanthin, of which content showed no significant difference between the two groups. The muscular epithelium after the removal of blue carotenoprotein turned red owing to the remaining carotenoids which were composed largely of astaxanthin esters. The total content of the remaining red carotenoids was about six-fold higher in the dark gray than blue group. Thus the different body color of cultured prawns is suggested to bedue to the varied composition of the blue carotenoprotein and red carotenoid fractions in the muscular epithelium.

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　PRDV と SEMBV は, 塩素処理によってそれぞれ5ppm・10分間, 10ppm・30分間で, またヨードによっては, いずれも10ppm・30分で不活化された。 PRDV は60分間（30℃）の乾燥や50℃（20分間）の熱処理および一重項酸素によって不活化された。 PRDV と SEMBV は12.5％および15％以上の塩化ナトリウムで不活化され, 海水中では, それぞれ5および7日間感染力を維持した。

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　オーストラリアにおける海面養殖の歴史は比較的浅いため, これまでに問題となったウイルス病はあまり多くない。 現時点における最大の脅威はバラマンディ仔魚におけるノダウイルスによる神経・網膜症である。 またヘルペスウイルスによると考えられる野生のピルチャード（イワシ類）の大量死は最近の大きな出来事である。 貝類には重要はウイルス病はないが, 養殖エビではパルボ様ウイルスおよびラブド様ウイルスなど4種のウイルスが観察されている。 mid-crop mortality syndrome (MCMS) が問題となっている。

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本研究では，産地や種類の異なる5種類のエビ背腸の内容物について，国産PSLシステムで光ルミネッセンス測定を行った。その結果，非照射試料のPSL積算発光量は下限しきい値（T₁　= 1000 counts/90 s）を下まわり，一方，1 kGy照射した試料は全て上限しきい値（T₂　= 4000 counts/90 s）を超えることが確認された。また，LEDによる光照射前後の発光量の増加とPSL発光の減少を評価パラメータとして用いても，非照射と1 kGy照射の試料との間に明確な差が確認された。 したがって，本PSL法はスクリーニング方法としてエビの照射履歴を検知することができる。

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In view of potential utilization of shrimp waste, shrimp chitin (SC) and shrimp chitin hydrolysate (SCH) were prepared from 3 kinds of shrimp species, namely: shrimp Penaeus monodon, endeavour shrimp Metapenaeus endeavouri and giant freshwater shrimp Macrobrachium rosenbergii. The effects of 5% SC and SCH (dry weight) on the state of water and on the denaturation of wanieso lizardfish Saurida wanieso myofibrillar protein (Mf) were evaluated based on changes in Mf Ca-ATPase activity and the amount of unfreezable water during frozen storage. Each effect was compared with those of Mf without additives (control) and Mf with glucose. The changes in Ca-ATPase activity of control and Mf with SC during frozen storage were exhibited biphasic pattern while those of SCH and glucose exhibited monophasic pattern. The amount of unfreezable water of Mf with SC was lower than that of control while those of Mf with SCH and glucose were higher than that of control. Present findings suggested that the preventive effect of SCH on freeze-induced denaturation of Mf is caused by the stabilizing the hydrated water molecule surrounding the Mf.

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The present study was conducted to measure the growth performance in growing broilers given shrimp meal (SM) made of heads of (Penaeus monodon) (BT) and white leg (Litopenaeus vannamei) (WL) shrimps. Forty-two male broiler chicks (8 days old, Ross 308) were randomly divided into 7 dietary groups (control, 5% BT, 10% BT, 15% BT, 5% WL, 10% WL and 15% WL) having similar body weight (6 birds per diet). Metabolisable energy and CP were adjusted to about 3,180 kcal/kg and about 235 g/kg, respectively, and other nutrients were formulated to meet or slightly exceed the requirements. Diet and water were provided ad libitum during the experimental period (8 to 21 days old). The results revealed that body weight gain decreased in BT groups with increasing level of SM (P<0.05), and feed intake decreased slightly with increasing level of SM in diets. As the result, feed conversion ratio also deteriorated with increasing level of SM. Similar trend was observed in WL groups, but the adverse effects of SM were milder comparing with BT groups. Nitrogen retention in both BT and WL groups tended to decrease with increasing level of SM. Chitin digestibilities in WL groups were greater than the corresponding values in BT groups. In conclusion, it is suggested that WL heads can be more nutritious SM for broiler diets than BT heads.

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We isolated 27 strains of marine crustacean-pathogenic Peronosporomycetes from various infected marine crustaceans collected in Japan, Thailand, Vietnam and the Philippines, and identified them morphologically. The internal transcribed spacer (ITS) l region of the nuclear rRNA gene of the 27 strains and 12 reference strains of six peronosporomycete species isolated from marine crustaceans were sequenced. The phylogenic relationship inferred from the sequences corresponded well to the morphological identification, indicating that sequencing of the ITS1 region is a useful tool for identification of marine crustacean-pathogenic Peronosporomycetes. Nauplii of brine shrimp Artemia salina were experimentally challenged by bathing in zoospore suspensions (1 × 10⁴ zoospores/mL, 25°C) with 18 strains belonging to nine species in four genera. The 48-h mortalities varied from 1.1% to 99.4% among the species, though all the strains were isolated from diseased animals.

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In this study, we have developed a DNA vaccine encoding viral envelope protein VP28 of penaeid rod-shaped DNA virus (PRDV, = WSSV). Protective efficacy of the DNA vaccine against PRDV was confirmed at 7 days post vaccination in kuruma shrimp Penaeus japonicus. The VP28 transcript derived from the vaccine was detected in various tissues at 1, 3 and 7 days post vaccination. Moreover, notable up-regulated expression of Rab7, penaeidin, lysozyme and crustin genes was observed upon DNA vaccination. These results suggest that the DNA vaccine significantly increased the protection and innate immune responses in kuruma shrimp against PRDV.

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冷凍流通している輸入エビのサルモネラ汚染が判明したことから，冷凍保存下のエビにおけるサルモネラの生残性を検討した．ブラックタイガーに血清型WeltevredenおよびSenftenbergを体表および体内の2方法で接種した．冷凍保存温度は -10℃，-20℃ および -30℃ の3温度で，保存期間は12週間とした．その結果，冷凍保存温度が低下するほど，また，体表接種より体内接種の方がサルモネラの生残性が高かった．さらに，S. SenftenbergはS. Weltevreden より高い生残性を示した．サルモネラはエビで冷凍保存された場合，特に -30℃ ではその接種菌数が長期間維持されることが確認できたことから，エビを解凍するときにはサルモネラの存在も考慮に入れ，衛生的な取扱いが必要である．

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