Embryological study of Protura : Comparative embryological reconstruction of hexapod phylogeny

原足目具有许多与多足类共有的特征，是最原始的六足类群之一，因此这个六足类群对于阐明六足动物的起源、更高层次的系统发育和地体平面是最有意义和有趣的。比较胚胎学方法是进行这种系统发育考量的最有前途的方法之一。然而，分钟大小(av.1毫米)的六足动物的胚胎学研究是绝对困难的，而我们对原尾目的胚胎学知识仍然是完全缺乏的。此外，我们甚至对原生动物的生态和生活史也知之甚少，甚至无法孵化原生动物。为此，我策划了普氏原虫的胚胎学研究，作为第一步，我试图阐明其生活史，为其胚胎学研究奠定坚实的基础。以一种尖端体目的原生巴氏杆菌(Baculentulus densus，Imadate，1960)为材料，首先确定了采样年龄，并考察了雌性生殖系统的季节变化。结果，我成功地估计了该物种的生命周期：它的生命周期为两年，繁殖季节为冬末至初春。下一步，我尝试改进原生动物的孵化方法。经过多次试验，我以碾碎的枯叶为底物进行孵化，取得了良好的孵化效果，并成功地维持了成虫数月之久。有关研究的框架被概括为《更高层次的六足动物系统发育阐明》。在其框架内，我还对无翼类进行了胚胎学研究，特别是下颌附肢的一系列同源性和六足类胚膜的进化转变。所取得的成果以两篇原创论文(印刷中)和两份口头报告的形式发表。

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.