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Proc. Arthropod. Embryol. Soc. Jpn. 48, 39–41 (2017)Ⓒ 2017 Arthropodan Embryological Society of Japan
ISSN 1341–1527[SHORT COMMUNICATION]

Preliminary Note on the Embryonic Development of Eucorydia
yasumatsui Asahina (Insecta: Blattaria, Polyphagidae)*Mari FUJITA and Ryuichiro MACHIDA
Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305–8572, Japan
Current address: Sugadaira Research Station, Mountain Science Center, University of Tsukuba, Ueda, Nagano 386–2204, Japan
E-mail: fujita@sugadaira.tsukuba.ac.jp (MF)

Polyneoptera, comprising 11 orders, is a significant
group for reconstructing the groundplan and evolution ofNeoptera. However, for Polyneoptera, the ordinal divergenceof which can be traced back to ancient times, it is difficult toreconstruct not only the interrelationship between each order
but also their groundplan, as there are more than 20
phylogenetic hypotheses on the interordinal relationships
within the group itself, without any consensus (Klass, 2009).
In Polyneoptera, an assemblage of the Blattaria, Mantodea
and Isoptera or the Dictyoptera is well supported to bemonophyletic. However, the interrelationship between thethree ordinal constituents of Dictyoptera has not beenclarified despite numerous morphological and molecularphylogenetic studies, and a polyphyletic status has been often
suggested for Blattaria (Klass, 2009). Thus, Blattaria may be
the most significant group for reconstructing the groundplan
and evolution of Dictyoptera. Against such a background, wehave started a comparative embryological study of Blattaria.
As a first step, we have tackled Polyphagidae, often regarded
as one of the basalmost clades in Blattaria, using a Japanesepolyphagid, Eucorydia yasumatsui Asahina. Establishing aculture (Fujita et al., 2011), we could constantly collect eggs.
This preliminary note reports our recent findings on theembryonic development of E. yasumatsui.
Eucorydia yasumatsui cockroaches were collected in
Iriomote and Ishigaki Islands, Okinawa Prefecture. Out ofoothecae deposited, the eggs were taken in physiologicalsaline, and fixed in Bouinʼs fixative. The egg structures wereexamined with a differential interference contrast microscope(LEICA DM6000-B). For the examination of embryonicdevelopment, the eggs were stained with a DNA specificfluorescent dye, DAPI (4ʼ, 6-diamidino-2-phenylindole
dihydrochloride, 10 µg/ml), and observed under UV-excitation
with a fluorescence stereomicroscope (LEICA MZ FLⅢ).
Eggs are ellipsoidal about 1.5 mm long, provided with 10
to 15 funnel-shaped micropyles on the ventral side of theposterior region (Fig. 1). A small embryo forms on theposterior ventral side of the egg (Fig. 2A). The amnioserosal
fold has already started to be produced at this stage. Theembryo elongates and migrates on the egg surface towards
the anterior to the middle of the ventral side (Fig. 2B). At thisstage, the amnioserosal folds are closed, completely covering
the embryo. Soon the segmentation (Fig. 2C) and formation ofappendages (Fig. 2D) occur. With progressive development,
the embryo elongates, with its abdomen folding (Fig. 2D, E).
After a while, the amnioserosal folds open and are withdrawn.
The embryo appears again on the egg surface, and the serosa
is concentrated in the region just posterior to the developing
head, forming the secondary dorsal organ (Fig. 2F). The
definitive dorsal closure proceeds, and the embryo acquires
its definitive form (Fig. 2G). Throughout development, theembryo does not suffer from a reversion of the anteroposterior
axis.
Micropyles are reported to be found in a group in Blatta
orientalis (=Periplaneta orientalis) and Blattella germanica(Blattellidae) (Kadyi, 1879; Wheeler, 1889). Our study
revealed that in Eucorydia yasumatsui, 10 to 15 micropyles arelocated in a small area on the ventral side of the egg. It wasreported that in Isoptera, micropyles occur on the dorsal sideof the eggs (Mukerji, 1970). However, isopteran embryos are
known to suffer from a reversion of the dorsoventral axis
because of rotation of the embryos (Striebel, 1960), hence, it
is concluded that the isopteran micropyles originally taketheir position on the “ventral side” of the egg. Thus, we may
assert that the micropyles on the “ventral side” of the egg
should be part of the groundplan of the Blattaria and Isoptera
or Blattodea (=Blattaria＋Isoptera). In Mantodea, Iwaikawa
and Ogi (1982) reported that eggs of Tenodera aridifolia haveone micropyle at the center of the eggʼs anterior pole,encircled by several micropyles arranged circularly.
Therefore, the micropyles of Mantodea and Blattodea seem todiffer in their localization and arrangement. However, there* This article, which was accepted in 2012 and should have been published in 2013, was printed in 2017 being much delayed due to various circumstances.

40M.FUJITA AND R. MACHIDA

are some points to be re-examined in Iwaikawa and Ogiʼsdescription: for example, according to them, the mantodean
micropyles have an extraordinarily wide opening about 4 µm.

A careful re-examination of the egg structure for mantodeans
is needed.
In Eucorydia yasumatsui, a small embryo forms on theFig. 1 Eggs of Eucorydia yasumatsui Asahina. A. Micropyles are located on the ventral side of the eggʼs posterior region as encircled. B.
Micropyles (arrowheads), posterior to the bottom, differential interference contrast microscopy. Bars = A: 200 µm; B: 10 µm.

Fig. 2 Outline of the embryonic development of Eucorydia yasumatsui Asahina, A to G. White and black arrowheads respectively show theanterior and posterior ends of the embryo. A. Formation of the embryo. B. Elongation of the embryo. C. Segmentation. D. Formationof the appendages. E. Curvature of the abdomen. F. Formation of the secondary dorsal organ and definitive dorsal closure. G.
Acquisition of the definitive form.
An: antenna, E: eye, Em: embryo, HL: head lobe, L1–3: pro-, meso- and methathoracic legs, Lb: labium, Lr: labrum, Md: mandible,
Mx: maxilla, SDO: secondary dorsal organ. Bar = 500 µm.

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EMBRYONIC DEVELOPMENT OF POLYPHAGID EUCORYDIA

ventral surface of the egg, and gradually elongates, accompanied
by a sequential segmentation. The embryogenesis of thisinsect is categorized into the short germ band type. The
embryo develops on the original position on the eggʼs ventral
side without changing its anteroposterior axis throughout
development. That is, the blastokinesis in Polyphagidae is of
the “non-reversion type”. Blattella germanica (Blattellidae)
and Blabera cranifer (Blaberidae), both of which are membersof Blaberoidea, undergo blastokinesis of the “non-reversiontype” (Wheeler, 1889; Bulliére, 1969; Tanaka, 1976). On theother hand, Periplaneta spp. (Blattidae) and Blatta orientalis(Blattidae), which are included in the Blattoidea, haveblastokinesis of the “reversion type”, in which reversion of
the embryoʼs axis occurs (e.g., Heymons, 1895; Lenoirrousseaux and Lender, 1970). In the type of blastokinesis,Polyphagidae resembles not the Blattidae but the Blattellidae
and Blaberidae. This may be favorable to McKittrickʼs (1964)
classification system, in which Blattaria are divided into twogroups, Blaberoidea composed of Polyphagidae, Blattellidae
and Blaberidae, and Blattoidea including Blattidae. That is,two types of blastokinesis, a “reversion type” and a “nonreversion type”, may be understood as being characteristic ofBlattoidea and Blaberoidea, respectively. As for othermembers of Dictyoptera, Isoptera (Knower, 1900; Striebel,1960) and Mantodea (Görg, 1959) are respectively known toshow blastokinesis of the “reversion type” and “non-reversiontype”. Understanding that Isoptera and Blattoidea exhibit
blastokinesis of the “reversion type” and Mantodea andBlaberoidea that of the “non-reversion type” may be intriguingin the phylogenetic reconstruction of Dictyoptera.

Striebel, H. (1960) Zur Embryonalentwicklung der Termiten. Acta

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