サザエの産卵と発生-2-
スポンサーリンク
概要
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Experiments carried out during June ?? August in 1962 ?? 63, investigating the induction of spawning of Turbo cornutus SOLANDER, gave the following results. 1. Matured eggs cut out from ovary, could not be fertilized by insemination. These eggs (diameter 0.22 ?? 0.23mm), were covered with gelatinous coatings (diameter 0.41mm). It appeared that the penetration of the spermatozoa was obstructed by this coating. 2. Induction of spawning by adding NH4OH (1/1000 ?? 5/1000N) to sea water was not successful. The parent shells showed marked sensitivity to NH4OH, and were damaged by this concentration. 3. Stimulation by changing water temperature induced the discharge of the reproductive elements (Fig. 1, Plate I-1), and 95% of the eggs spawned were fertilized. 4. The fertilized eggs (diameter 0.26mm) were incubated at 25 ?? 26°C. The larvae were reared at 20 ?? 26.5°C, and fed with diatoms (mixture of Navicula, Nitzschia sp.). 5. The 1st cleavage occurred 30 minutes after fertilization. The 2nd cleavage, 90 minutes; the 3rd cleavage, 2 hours; and the 4th cleavage occurred 3 hours after fertilization. Trochophore (0.20 × 0.17mm) hatched in 11 hours. The larval shell of the veliger was completely formed (0.31 × 0.24mm), 27 hours after fertilization. On the peristomal part of the larval shell, a characteristic ring was formed. By 4 days, the larva had reached the benthic stage. By 5 days, the elongation of peristomal shell was clearly observed. After 41 days, the shell began to grow in a downwards spiral. After 100 days, the diameter of the shell had reached 3mm. The growth curve from egg to 100 days is shown in Fig. 3. The larval forms are shown in Fig. 2 and Plate I.