サザエの産卵と発生-1-

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The spawning behavior of the Topshell, Turbo cornutus SOLANDER was occasionally observed in the field, Kisami near the Shimoda Bay, Shizuoka Pref., in 12th July 1962. This is apparently the first record on the spawning behavior which has long remained unknown of the Topshell. (The seasonal change of maturation and the characteristics of egg and sperm were described by AMIO (1956)). The observation reveals (items 1-4) and suggests (items 5, 6) the following facts. 1. The Topshells spawn in mid-July, at the coast of Izu Peninsula. 2. The spawning place is the rocky zone of the coast. 3. Male and female jet the gonad contents into the sea, as already known in Haliotis gigantea (MURAYAMA, 1935), H. discus and H. sieboldii (INO, 1952). 4. The fertilized eggs are non-adhesive, and strongly demersal, about 0.26mm in dia-meter; free from the gelatinous coating seen in ovarian stage. 5. The spawning action may be stimulated by the extremes of water temperature. In fact, it appears to occur in concurrence with extremely rising from about 20°C up to about 25°C in surface water temperature (Fig. 1). 6. The eggs in natural environment seem to be fertilized in higher ratio (97%).