Embryological study of Protura : Comparative embryological reconstruction of hexapod phylogeny

原尾类是最原始的六足类类群之一，具有多足类的许多共同特征，因此，该类群对于阐明六足类的起源、更高层次的生殖发育和地面平面图都是最有意义和最有趣的。比较胚胎学的方法是最有前途的方法之一，这样的遗传学的考虑。然而，一分钟的大小（av。1 mm）的六足动物使其胚胎学研究绝对困难，我们对原尾虫的胚胎学知识仍然完全缺乏。此外，我们甚至对原尾虫的生态和生命周期都知之甚少，我们甚至无法孵化原尾虫。为此，本研究计划进行原尾类的胚胎学研究，首先阐明原尾类的生活史，为胚胎学研究奠定坚实的基础。本研究以一种拟除虫菊酯原尾类Baculentulus densus（Imadate，1960）为材料，首先鉴定了取样年龄，并考察了雌性生殖系统的季节变化。结果，我成功地估计了这个物种的生命周期：它的生命周期为两年，繁殖季节是冬末春初。接下来，我尝试改进原尾虫的孵化方法。经过多次试验，以磨碎的枯叶为基质，获得了较好的孵化效果，并成功地维持了几个月的成虫。本文的研究框架为“高水平的六足类成虫发生学的阐明”。在其框架内，我还进行了胚胎学研究的无翅类，如古颚类，特别提到的系列同源性的颚附属物和进化过渡的六足动物胚胎膜。所取得的成果已作为两份原始文件（印刷中）和两份口头报告发表。

The Protura, possessing many features shared together with myriapods, are one of the most primitive hexapod groups, so that this hexapod group is the most significant and interesting for elucidating hexapod origin, phylogeny in higher level and ground body plan. The comparative embryological approach is one of the most promising methods for such phylogenetical considerations. However, a minute size (av. 1 mm) of the hexapod makes its embryological study absolutely difficult, and our embryological knowledge on Protura remains to be utterly lacking. Moreover, we have little information even on the proturan ecology and life cycle, and we have been unable to even incubate proturans. For this reason, I planned the embryological study of Protura, and as the first step, I tried to elucidate the life cycle, to found a firm base for its embryological study.Using an aceretomid proturan Baculentulus densus (Imadate, 1960) as materials, firstly, I identified the age of samplings and examined the seasonal change of female reproductive system. As a result, I succeeded in estimating the life cycle of the species : it has a life cycle of two years, and its reproductive season is late winter to early spring. Next, I tried to improve the incubation method of the proturans. After many trials, I gained a good result of incubation by using milled dead leaves as a substrate, and I succeeded in maintaining adults over months.The frame work of the study concerned is outlined as "elucidation of hexapod phylogeny in higher level". Within its frame work, I also conducted embryological studies on apterygotes such as Archaeognatha, with special reference to the serial homology of gnathal appendages and the evolutionary transition of hexapod embryonic membranes. The results obtained were/are published as two original papers (in press) and two oral presentations.