13Proc. Arthropod. Embryol. Soc. Jpn. 49, 13–14 (2016)Ⓒ 2016 Arthropodan Embryological Society of Japan
ISSN 1341–1527

Entognathy Formations of Three Entognathan Orders: A Phylogenetic
Argument*Shigekazu TOMIZUKA1, 5), Makiko FUKUI2), Kaoru SEKIYA3)
and Ryuichiro MACHIDA4, 5)
Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305–8572, Japan
Graduate School of Science and Engineering, Ehime University, Matsuyama, Ehime 790–8577, Japan3)
Research Administration Office, University of Tsukuba, Tsukuba, Ibaraki 305–8577, Japan4)
Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305–8572, Japan
5)
Current address: Sugadaira Montane Research Center, University of Tsukuba, Sugadaira Kogen, Ueda, Nagano 386–2204, Japan
E-mail: allacmaf@gmail.com (ST)1)
2)

“Entognatha-Ectognatha System”, which is formulated
as “Entognatha (= Ellipura (= Protura + Collembola) +Diplura) + Ectognatha”, has been widely accepted as a mostreliable phylogeny of Hexapoda (Insecta s. lat.). However, it
has been recently challenged from various disciplines,
especially on the monophyly of and the interordinal
relationships of Entognatha. Entognathy has been regarded asa most reliable synapomorphy for three entognathan orders,Protura, Collembola, and Diplura. We compare the entognathy
formations of these three orders based on the knowledge
accumulated for the last couple of decades (on Protura: Fukui
and Machida, 2006, 2009, in prep.; Fukui, 2010; on Collembola:
Tomizuka and Machida, 2011, 2012, in prep.; on Diplura: Ikeda
and Machida, 1998, Sekiya and Machida, 2009, 2011, in prep.)to examine the homology of their entognathies, and discuss
the “Entognatha”.
The entognathy formation of Protura and Collembola arerevealed to closely resemble each other in major points, suchas concerning: 1) the origin of mouth folds, which are formedby the fusion and ventral extension of terga of intercalary andthree gnathal segments, and 2) the origin of the posterior limitof entognathy, which is accomplished by the fusion of (possibly
the labial tergal territories of) mouth folds in both sides.
However, the entognathy of Diplura is constructed in an
utterly different manner, which is characterized by: 1) themouth fold is formed by the fusion of ventrally extended tergaof intercalary and three gnathal segments and labial coxae, 2)
the rotation of labial appendages is involved in the entognathy
formation, 3) the posterior limit of entognathy is accomplishedby the fused labial subcoxae which form the postmentum, and4) the posteromedial area of mouth fold is partitioned as theadmentum, which is labial coxal in origin.
Thus, the manners of entognathy formation in Protura
and Collembola closely resemble each other, being named“Ellipura type”. The homology between their entognathies isstrongly supported, and the monophyly of Ellipura is well
supported as well. The manner of entognathy formation inDiplura is, however, much different from the Ellipura type,which can be called the “Diplura type”. Hence, the homologyof entognathies between Ellipura and Diplura is not always
verified, and the monophyly of Entognatha cannot always besubstantiated.
References
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* Abstract of paper read at the 50th Annual Meeting of the Arthropodan Embryological Society of Japan, July 3–4, 2014 (Fuchu, Tokyo).

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Tomizuka, S. and R. Machida (2012) Entognathy formation ofCollembola. Proceedings of the Arthropodan Embryological Societyof Japan, 47, 29–31.