Embryological study of Protura : Comparative embryological reconstruction of hexapod phylogeny

Protura具有许多与多足类动物共有的特征，是最原始的六足类群之一，因此该六足类群对于阐明六足类起源、更高层次的系统发育和地面平面是最重要和最有趣的。比较胚胎学方法是考虑此类系统发育的最有前途的方法之一。然而，六足动物的微小尺寸（平均1毫米）使其胚胎学研究绝对困难，而且我们对Protura的胚胎学知识仍然完全缺乏。此外，我们甚至对proturans的生态和生命周期也知之甚少，我们甚至无法孵化proturans。为此，我策划了Protura的胚胎学研究，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aceretomid proturan Baculentulus densus（Imadate，1960）为材料，首先确定了采样的年龄，并检查了女性生殖系统的季节变化。结果，我成功地估算出该物种的生命周期：它的生命周期为两年，繁殖季节为冬末初春。接下来，我尝试改进proturans的培养方法。经过多次试验，我以磨碎的枯叶为基质进行孵化，获得了良好的结果，并成功地维持了成虫数月之久。相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，我还对古颌动物等无翅目动物进行了胚胎学研究，特别是颌附肢的系列同源性和六足动物胚胎膜的进化转变。获得的结果已作为两篇原始论文（正在出版）和两篇口头报告发表。

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.