9Proc. Arthropod. Embryol. Soc. Jpn. 49, 9 (2016)Ⓒ 2016 Arthropodan Embryological Society of Japan
ISSN 1341–1527

Embryonic Development of Eucorydia yasumatsui Asahina (Insecta:Blattodea, Corydiidae)*Mari FUJITA1, 3) and Ryuichiro MACHIDA2, 3)
Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305–8572, Japan
Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305–8572, Japan3)
Current address: Sugadaira Montane Research Center, University of Tsukuba, Sugadaira Kogen, Ueda, Nagano 386–2204, Japan
E-mail: fujita@sugadaira.tsukuba.ac.jp (MF)1)
2)

In cockroaches or “Blattaria,” about 450 genera and 3,500
species have been described. The species vary enormously insize and anatomy, and range in habitat. It has long been known
that “Blattaria”, Isoptera and Mantodea are closely related,
and an assemblage of the “Blattaria”, Mantodea and Isopteraor the Dictyoptera is well supported to be monophyletic (e.g.,Kristensen, 1991; Klass and Meier, 2006). Recent phylogenetic
works based on morphological and molecular evidence
suggest a subordinate position of Isoptera in “Blattaria”, andthe monophyletic group including both is usually called“Blattodea”. Seven or eight principal lineages are revealed in“Blattodea”: Blattidae, Lamproblattidae, Tryonicidae,Nocticolidae, Corydiidae, Blaberoidea (an assemblage of“Blattellidae” and “Blaberidae”), Cryptocercidae, and Isoptera(e.g., Klass and Meier, 2006; Ware et al., 2008; Djernæs et al.,2012). However, the relationships among these blattodean
principal lineages have been highly controversial. Against
such a background, we have started a comparativeembryological study of Blattodea for reconstruction of its
groundplan and phylogeny. Many embryological studies havebeen conducted on Blattodea, but most of them concern theBlattidae and “Blattellidae” (e.g., Wheeler, 1889; Heymons,1895). As a first step of our studies, we have tackled theembryological study of Corydiidae, on which no embryologicalstudy has been made, using a Japanese corydiid, Eucorydia
yasumatsui Asahina.
The outline of embryonic development of Eucorydia
yasumatsui was described, focusing on the formation andgrowth of the embryo and blastokinesis as well as the behaviorof mycetome. Migrating to the egg surface, cleavage nuclei
form the blastoderm, of which posterior half is with a higher
cellular density. In the ventral side of the area of blastoderm
with higher cellular density, a pair of areas with higher cellularcondensation appears. After a while, the paired areas comenear and fuse with each other to form a heart-shaped embryo.

The embryo gradually elongates and anteriorly migrates
towards the middle of the ventral side. At this stage, anatrepsis
completes. Soon the segmentation and formation ofappendages occur. Masses of symbiotic bacteria, which arecalled “mycetomes”, migrate from both anterior and posterior
poles toward the center of the egg to fuse there. As katatrepsis
occurs, the serosa is concentrated toward the region justposterior to the developing head, forming the secondary
dorsal organ. The definitive dorsal closure proceeds, and theembryo acquires its definitive form. The embryo of E.
yasumatsui develops, keeping its original position on the eggʼsventral side without changing its anteroposterior axis
throughout development. That is, the blastokinesis in thecorydiid E. yasumatsui is of the “non-reversion type”.
References
Djernæs, M., K.-D. Klass, M.D. Picker and J. Damgaard (2012)
Phylogeny of cockroaches (Insecta, Dictyoptera, Blattodea), withplacement of aberrant taxa and exploration of out-group sampling.
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Heymons, R. (1895) Die Embryonalentwickelung von Dermapteren undOrthopteren

unter

Besonderer

Berücksichtigung

derKeimblätterbildung. Gustav Fischer, Jena.
Klass, K.-D. and R. Meier (2006) A phylogenetic analysis ofDictyoptera (Insecta) based on morphological characters.
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Wheeler, W.M. (1889) The embryology of Blatta germanica andDoryphora decemlineata. Journal of Morphology, 3, 291–386.

* Abstract of paper read at the 50th Annual Meeting of the Arthropodan Embryological Society of Japan, July 3–4, 2014 (Fuchu, Tokyo).