報告書番号

U97077

タイトル（和文）

ヒラメ全雌種苗の生産－雌雄の成長差と水温の生理的性発現に与える影響－

タイトル（英文）

FEMINIZED SEEDLING PRODUCTION IN JAPANESE FLOUNDER -DIFFERENCE IN GROWTH RATE BETWEEN MALE AND FEMALE,AND EFFECT OFTEMPERATURE ON PHENOTYPICAL SEX DETERMINATIO-

概要 （図表や脚注は「報告書全文」に掲載しております）

全雌化による成長の速いヒラメ種苗の生産を目的として，生理的性発現への水温影響を明らかにするとともに，水温制御条件での雌雄の成長差を検討した。（１）遺伝的全雌種苗を孵化後４３日目から５０日間，１６，１８，２０，２４，２８度で飼育した結果，１８および２０度では９０％以上が生理的雌を発現したが，２８度ではすべて生理的雄となった。（２）水温２０～２５度で１０ヶ月飼育した両性生殖種苗の平均体重は，生理的雄４７３ｇに対して雌５７８ｇであった。（３）雌性発生倍数体の孵化後９６日目から２０７日目における水温２３度での成長速度は，生理的全雌群が全雄群を上回った。以上から，稚魚期に１８～２０度で飼育することによって生理的雌の出現率が向上できることが明らかになった。また，水温制御条件での生理的雌の成長の優位性が確認された。

概要 （英文）

THIS STUDY EXAMINED:(1) THE EFFECT OF WATER TEMPERATURE AT THE JUVENILE STAGE ON PHENOTYPIC SEX DETERMINATION OF THE JAPANESE FLOUNDER,AND (2) DIFFERENCES IN GROWTH RATE BETWEEN PHENOTYPIC MALES AND FEMALES UNDER TEMPERATURE-CONTROLLED CONDITIONS. (1) GYNOGENETIC DIPLOID FLOUNDERS WERE REARED AT 16 DEGREE,18 DEGREE,20 DEGREE,24 DEGREE AND 28 DEGREE FROM 43 TO 92 DAYS AFTER HATCHING. ALMOST ALL THE FISH BECAME PHENOTYPIC FEMALES AT 18 DEGREE AND 20 DEGREE (100% AND 94%,RESPECTIVELY),BUT BECAME PHENOTYPIC MALES AT 28 DEGREE. (2) NORMAL FLOUNDER SEEDLINGS (BISEXUAL DIPLOID) WERE REARED IN A CLOSED RECIRCULATING SYSTEM AT A TEMPERATURE RANGE OF 20 DEGREE TO 25 DEGREE. THE 5G SEEDLINGS GREW TO 578-G PHENOTYPIC FEMALES IN 10 MONTHS AND 473-G PHENOTYPIC MALES IN 10 MONTHS. (3) PHONOTYPIC FEMALES AND MALES OF GYNOGENETIC DIPLOID FLOUNDERS WERE REARED AT 23 DEGREE FROM 96 TO 390 DAYS AFTER HATCHING. THE GROWTH RATE OF PHENOTYPIC FFEMALES WAS HIGHER THAN THAT OF PHENOTYPIC MALES UNTIL DAY 207 AND THEN THERE WAS NO DIFFERENCE. THESE RESULTS SHOW THAT TEMPERATURE CONTROL BETWEEN 18 DEGREE TO 20 DEGREE INTHE JUVENILE STAGE IS ESSENTIAL FOR FEMINIZED SEEDLING PRODUCTION,AND FEMINIZED SEEDLINGS HAVE A BETTER GROWTH RATE THAN NORMAL SEEDLINGS.

報告者

キーワード