マダカアワビ稚貝の殻表に形成される日周期的成長線の検証  [in Japanese] Validation of daily-formed growth increments on the shell surface of the young giant abalone, Haliotis madaka  [in Japanese]

マダカアワビHaliotis madakaの殻表に日周期的に形成される成長線の存在を証明する実験を行った。種苗生産した稚貝をalizarin complexone (ALC)溶液へ14日間の間隔を空けて2回浸漬した。蛍光顕微鏡による観察の結果,殻の断面に認められた2重蛍光標識間の平均成長線数は13.7本(観察個体数21,標準偏差1.7本)で,標識間の経過日数と一致した。天然海域への放流再捕個体の成長線の計数から逆算推定した放流時の殻長は,実測値とほぼ一致した。以上から,マダカアワビ殻表の成長線は日周期的に形成されると結論した。

To validate the daily formation of growth increments on the shell surface of the giant abalone, Haliotis madaka, double time-reference marks were incorporated on the shells of the juvenile abalones reared in aquaria by immersing the abalones in alizarin complexone (ALC) solution at an interval of 14 days. Double fluorescent marks of ALC were observed on the cross section of the shells under fluorescent microscopy. The mean number of growth increments on the shell surface between the two marks was 13.7 (N = 21, S.D. = 1.7), which corresponds with the time interval in days between the two marks. Release-and-recapture experiments into the natural sea showed that the shell lengths at release estimated by counting growth increments from the edge toward the apex of the shell of recaptured juveniles were in accordance with the actual shell lengths at release. It was concluded that the growth increments on the shell surface of the abalone were formed daily.