Fertilization and Development of the Lancelets

点击翻译按钮获取中文摘要

In the collaboration research group, we are mainly in charge of collecting mature amphioxus, keeping and feeding them in the lab and supplying the materials such as sperm, eggs, embryos from various stages and tissues etc.for deferent purposes of research. During the amphioxus spawning seasons in 1995 and 1996, we collected 5 kg of the adult amphioxus each season and supplied enough experimental materials for observation and analysis almost everyday.Embryogenesis of amphioxus was observed and recorded. The eggs do not show conspicuous ooplasmic segregation. The embryos showed regulative development when one of two blastomers were isolated at the 2-cell stage. We had some trials to clone the amphioxus gene homolog of the homeotic gene LIM,which is related to eary embryogenesis, troponin T which is muscle protein and astacin-like protease which is related to haching embryo. Isolation of LIM homeobox gene is now under way by determining nucleotide sequence of the PCR products, followed by screening of the cDNA library, and troponin T is now screening of the cDNA library, but we have no clone of the hatching enzyme. It is hoped that we succeed in the cloning after reformation of the possible problems in the next time. The effects of ion channel antagonists on the motility of amphioxus sperm and motility of the sperm of which the plasma membrane was removed using detergent were investigated. Obtained resutls suggest that fertilization, development and sperm motility are similar to that of marine invertebrates. Genetical variety of rRNA gene (rDNA) repeated units was studied in amphioxus. We detected the variety of the length of the internal spacer region between 18S rDNA and 5.8S rDNA.