Embryological study of Protura : Comparative embryological reconstruction of hexapod phylogeny

原足纲是最原始的六足动物类群之一，具有许多与多足动物共有的特征，因此它对阐明六足动物的起源、高层系统发育和地面形体规划具有重要意义和意义。比较胚胎学方法是这种系统发育考虑中最有前途的方法之一。然而，六足动物的微小尺寸（约1毫米）使其胚胎学研究非常困难，我们对原足动物的胚胎学知识仍然完全缺乏。此外，我们对proturans的生态和生命周期知之甚少，甚至无法孵化proturans。因此，我策划了原tura的胚胎学研究，作为第一步，我试图阐明其生命周期，为其胚胎学研究奠定坚实的基础。以Imadate， 1960年的aceretomidproturan Baculentulus densus （Imadate, 1960）为材料，首先确定了样本的年龄，并检查了雌性生殖系统的季节变化。因此，我成功地估算出了该物种的生命周期：它的生命周期为两年，繁殖季节为冬末至早春。接下来，我尝试改进proturans的培养方法。经过多次试验，我用磨碎的枯叶作为基质，获得了良好的孵化效果，并成功地维持了几个月的成虫。有关研究的框架被概述为“在更高水平上阐明六足动物的系统发育”。在其框架内，我还对始祖鱼等无肢动物进行了胚胎学研究，特别关注了颌部附属物的序列同源性和六足动物胚膜的进化转变。获得的结果以两篇（已出版）论文和两篇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.