キタカワゲラ亜目の比較発生学的研究（昆虫綱・カワゲラ目）

筑波大学 (University of Tsukuba)201

キタカワゲラ亜目の比較発生学的研究（昆虫綱・カワゲラ目）

筑波大学 (University of Tsukuba)201

First instar nymphs of two peltoperlid stoneflies (Insecta, Plecoptera, Peltoperlidae)

The first instar nymphs of two peltoperlid stoneflies, i.e., Microperla brevicauda Kawai, 1958 of Microperlinae and Yoraperla uenoi (Kohno, 1946) of Peltoperlinae, were examined and described. Additionally, the phylogeny and groundplan of the first instar nymphs of Peltoperlidae and Plecoptera were considered. The first instar nymphs of M. brevicauda have a slender body with a prognathous head of typical shape; they represent a groundplan in Plecoptera. On the other hand, the first instar nymphs of Y. uenoi have a broad, cockroach-like body with an orthognathous and shortened head, the latter being regarded as a potential autapomorphy of Peltoperlinae. Such differences in body shape between the subfamilies are speculated to arise from heterochrony. The three-segmented cerci of Y. uenoi are characteristic to Systellognatha, whereas the four-segmented cerci of M. brevicauda were independently acquired within Microperlinae. The structure and distribution pattern of chloride cells in the first instar nymphs of Plecoptera were also discussed. The presence of coniform chloride cells is a potential groundplan of Arctoperlaria. One to two pairs of chloride cells are distributed on the first nine abdominal segments of M. brevicauda; this represents a groundplan character of Systellognatha. On the other hand, one to four pairs of chloride cells are found on the second to ninth abdominal segments of Y. uenoi; this distribution pattern may be an apomorphic groundplan of Peltoperlinae

Egg structure and embryonic development of arctoperlarian stoneflies: a comparative embryological study (Plecoptera)

Egg structure and embryonic development of nine arctoperlarian stoneflies from nine families, i.e., Scopuridae, Taeniopterygidae, Leuctridae, Capniidae, and Nemouridae of Euholognatha, and Perlidae, Chloroperlidae, Perlodidae, and Peltoperlidae of Systellognatha were examined and compared with previous studies. The primary aim of this study was to use embryological data to reconstruct the groundplan and phylogeny of Plecoptera and Polyneoptera. Euholognatha has eggs characterized by a thin, transparent chorion, while the eggs of Systellognatha are characterized by a collar and anchor plate at the posterior pole. These features represent an apomorphic groundplan for each group. The embryos form by the concentration of blastoderm cells toward the posterior pole of the egg. Soon after the formation of the embryo, amnioserosal folds form and fuse with each other, resulting in a ball-shaped “embryo-amnion composite” that is a potential autapomorphy of Plecoptera. As an embryological autapomorphy of Polyneoptera, embryo elongation occurs on the egg surface, supporting the affiliation of Plecoptera to Polyneoptera. After its elongation on the egg surface, the embryo sinks into the yolk with its cephalic and caudal ends remaining on the egg surface. This unique embryonic posture may be regarded as an apomorphic groundplan of Plecoptera. Arctoperlarian plecopterans perform three types of katatrepsis: 1) the first type, in which the embryo’s anteroposterior and dorsoventral axes change in reverse during katatrepsis, is found in Capniidae, Nemouridae, Perlidae, Chloroperlidae, and Perlodidae, and this sharing is symplesiomorphic; 2) the second one, in which the embryo’s axes are not changed during katatrepsis, is found in Scopuridae, Taeniopterygidae, and Leuctridae, and this may be regarded as synapomorphic to them; 3) the third one, in which the embryo rotates around its anteroposterior axis by 90° during katatrepsis as known for Pteronarcyidae, is found in Peltoperlidae, and this type may be synapomorphic to these two families