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ที่มา:KASETSART UNIVERSITY FISHERIES RESEARCH BULLETINหัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Study on the Larval Development of the Creeper Snail, Cerithium sp. Bruguiere) ผู้เขียน: กฤษณา รัตนอาภา,  ดร.ชลอ ลิ้มสุวรรณ, รองศาสตราจารย์ , ดร.นิติ ชูเชิด, รองศาสตราจารย์ สื่อสิ่งพิมพ์:pdf AbstractThe creeper snail {Cerithium sp.) is commonly found on muddy beaches in nature, but when it invades shrimp rearing ponds it can multiply very quickly. This study of the creeper snail's life cycle started with observing its mating behavior. Creeper snails began to lay eggs four days after they mated. The eggs came out in strings, appearing like gelatinous white threads attached to various surfaces. Females could lay one string of eggs per day, and another string 10 days later, for a continuous period after mating. The number of individual eggs per string was found to be 2,109 to 4,991. Each egg was a slender oval, about 170 microns long and 150 microns wide. The creeper snail started its life as a one-cell zygote. Cell division began at 2-7 hours. After the seventh hour, the embryo entered the blastula stage. The parts were difficult to differentiate in the gastrula stage. By hours 19-39 the embryo developed into a trocophore that looked like a top with cilia all around. By hour 40 the trocophore developed into the veliger stage, but it remained inside the egg until hour 73, at which time it hatched as a free-living veliger. In short, within about three days it then developed into a creeping larva which dropped to the bottom of the pond. Within about one month it grew a shell with five spirals. |