サケ科魚類の稚仔魚期における腸内細菌叢の形成時期について

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Masu salmon Oncorhynchus masou and chum salmon O. keta were cultured from the stages of the fertilized egg to spring fry, and were used to know when the normal intestinal microflora was established. The microbial viable counts and the microflora of the egg surface, yolk sac, body surface, digestive tract, and intesinal contents of sac fry, advanced fry, and fingering were investigated. Simultaneously ambient water and their diets were also investigated microbiologically. The results obtained are summarized as follows. 1. The microbial viable counts on the surface of eggs were 10^3-10^6/g, and the microflora Flavobacterium/Cytophagaceae and Pseudomonas were dominant. 2. The yolk of alevin and sac fry were sterile, but from the body surface of sac fry 10^1-10^4/g viable microbial counts were obtained, the microflora were effected by the flora of ambient water, composed of Pseudomonas, Flavobacterium/Cytophagaceae, and Achromobacter. 3. The microbial viable counts in the whole digestive tract of sac fry and advanced fry were nil to 10^4/g, but the intestinal contents of advanced fry and fingering were 10^8-10^7/g. The microflora of the whole digestive tract of sac fry were effected by the flora of diet and ambient water, and were composed of Coryneforms and Pseudomonas. However, in later stages the microflora of the intestinal contents of advanced fry and fingering were mainly composed of Aeromonas as was the previous finding. 4. From the above results it was assumed that the normal intestinal microflora of salmonids were established when the yolk was absorbed and the digestive tract was activated, at the stage of advanced fry.サクラマスおよびシロサケを対象に，受精後胚胎期から稚魚に至る成長過程中において，卵表面，孵化稚魚の体表，臍ノウ内容物および消化管，浮上稚魚および春稚魚の腸内容物，飼育用水ならびに餌料について，それらの生菌数とその菌叢を比較観察して以下のごとき結果を得た。1. 胚胎期の卵表面からは発眼期を量高に，卵重量g当り10^3～10^6の範囲で生菌数が測定され，その菌叢はFlavobacterium/CytophagaceaeおよびPseudomonasが主体を成したが，その後前者の割合が経日的に漸増した。2. 孵化稚魚の臍ノウ内容物から細菌は検出されなかったが，体表からは体重g当り10^2～10^3の生菌数が測定され，その菌叢はPseudomonas，Flavobacterium/Cytophagaceaeを主体とし，飼育用水の菌叢に類似した。3. 孵化稚魚の消化管および腸内容物からは10^1～10^5/gの範囲で生菌数が測定され，その菌叢はPseudomonas，Coryneforms，Flavobaeterium/Cytophagaceaeなどが主体を成し，この時期では未だ飼育用水あるいは餌料の菌叢の影響が認められた。4. 臍ノウ吸収後の浮上稚魚および春稚魚の腸内容物からは，10^3～10^7/gの範囲で生菌数が測定され，またその菌叢は成長と共に徐々にAeromonasが主体を成すに至る傾向を示し，この時期にこれら魚類固有の腸内細菌が形成されることが観察された。
日本水産学会 = The Japanese Society of Scientific Fisheriesの論文

サケ科魚類の稚仔魚期における腸内細菌叢の形成時期について

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