Yukimasa KOBAYASHI Nobuo SUZUKI Satoru SHIMIZU. Sialis sp. Photo by T. Suzuki

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1 Labial egg burster of Sialis japonica and its possible phylogenetic significance: A comment on the article by Ando et al. (1985) (Megaloptera; Sialidae) Sialis sp. Yukimasa KOBAYASHI Nobuo SUZUKI Satoru SHIMIZU Photo by T. Suzuki 51 st Annual Meeting, June 12 13, 2015 The Arthropodan Embryological Society of Japan

2 Egg burster () of Sialis was known first in four North American species (Evans 1972) stemma head S. hamata abdominal end S. occidens Sialis hamata Fully developed embryo S. rotunda S. californica Sialis, lateral view

3 Fine structure of Sialis (Canterbury & Neff, 1980) S. itasca S. iola micropyle is formed in the embryonic cuticle, and left on the split chorion after embryonic molt on hatching.

4 Ando, H., Miyakawa, K. & Shimizu, S. 1985: External features of Sialis mitsuhashii* embryo through development (Megaloptera, Sialidae) Fig. comb-like structure on labium comb-like structure P (*S. mitsuhashii: synonym of S. japonica) 10-day-old embryo 100 µm

5 Comb-like structure corresponds to known in preceding studies Ando et al. (1985) Canterbury & Neff (1980) But, strangely, Ando et al. did not refer to that point. Why??

6 Evans s study: PhD thesis Unpublished documentation

7 Corydalidae (Megaloptera): s were described in 1922 by Smith and in 1972 by Evans head Neohermes californicus Corydalus cornutus Orohermes crepusculus (Evans 1972) Chauliodes pectinicornis (Smith 1922)

8 Embryonic origin of in Sialis japonica (modified from Ando et al.) 4-day-old 6-day-old 8-day-old 9-day-old labrum mandible maxilla labium labial palpus labial palpus originates in the proximal parts of the fused labial appendages (original photos by Shimizu)

9 Distribution of s in Neuroptera State of :present :absent?: unexamined (Tree from Aspöck et al. 2012)???????? s have been known in 7 of 17 neuropteran families

10 of Osmylus fulvicephalus (Osmylidae: Neuroptera) by Hagen (1852) O. hyalinatus Photo by T. Suzuki tooth embryo ventral view lateral view Probably the first record of in insects

11 Neuropteran s in 6 other families A B C D E Sisyra Semidalis Coniopterigidae Sisyridae Sympherobius Hemerobius Micromus Hemerobiidae F G H I Nothochrysa Chrysopa Osymlops Nemoptera Chrysopidae Nymphidae Nemopteridae (A, B, C, D, F, I, Withycombe 1923; E, G, Smith 1922: H, New 1983)

12 Neuropteran s Probably widely distributed in this order Located on the ventral side of the head, between mandibles, but not on the head capsule Embryonic origin almost unknown But some authors seem to interpret it as belonging to the frontal region of a head capsule or to a labrum. e.g. Emden, 1946; Konopová & Zrzavý 2005

13 Emden s review (1946) on egg bursters Three types of s 1. Acral (frontal) s 2. Persistent acral (frontal) s 3. Persistent thoracoabdominal s Megaloptera Neuroptera

14 Labral ET of Chrysopa perla (Konopová & Zrzavý 2005) Chrysopa nigra Photo by T. Suzuki Chrysopa Chrysopa Sialis labrum labrum labrum labium Note the labral egg-tooth (arrow), from the caption of their Fig.8. But, according to its position and shape, we presume the egg burster to be derived from the labium as in the case of Sialis.

15 Neuropteran s: Probably derived form the labium A B C D E Sisyra Semidalis Coniopterigidae Sisyridae Sympherobius Hemerobius Micromus Hemerobiidae F G H I Nothochrysa Chrysopa Osymlops Nemoptera Chrysopidae Nymphidae Nemopteridae (A, B, C, D, F, I, Withycombe 1923; E, G, Smith 1922: H, New 1983)

16 Hexapod s: Known in 22 of 33 orders Most of s are located on the frons or clypeus, not on the labrum. frons clypeus labrum Trichopteran (Nemotaulius) Ephemeropteran (Potamanthus) (Konopová & Zrzavý 2005)

17 Labial s in Megaloptera and Neuroptera: A new type of in insects So for restricted to these two orders Potential synapomorphy of these orders Supporting the sister-group relationship of these orders in the controversial phylogeny of Neuropterida Raphidioptera Megaloptera Neuroptera Kristensen, 1991; Hünefeld et al. 2012; Beutel et al (Meg.paraphyletic) etc. Raphidioptera Megaloptera Neuroptera Kjer et al. 2006; Cameron et al; 2009; Haring & Aspöck 2004; Misof et al etc.

18 State of in Raphidioptera Photo by T. Suzuki Inocellia japonica fully developed embryo (Tsutsumi & Machida, 2006) An seems to be absent, but the detailed examination will be needed.

19 Problems to be solved Nature of in Sialis? Ando et al. regarded it as a dentate ligula. Probably correct, but need more detailed observations. Confirmation of embryonic origin of neuropteran In Raphidioptera, the has so far been unknown (Tsutsumi & Machida 2006). But more detailed SEM observations will be needed to confirm it.

20 Acknowledgements We cordially thank late Prof. Hiroshi Ando and late Dr. Kozo Miyakawa for leaving many SEM photos of Sialis to us in their will. We also thank Dr. Tomoya Suzuki for providing some photos of Sialis and Neuroptera for us.