JapaneseJapaneseSociety Society ofSystematicof Systematic Zoology

stS#ifima"r",k//･tlt･ l2 (1976)

THEFORMATION OF GERM RUDIMENT AND EMBRYONIC MEMBRANES

IN THE PRIMITIVE , ENDOCLYTA EXCRESCENS BUTLER

(, MONOTRYSIA, ) AND ITS PHYLOGENETIC SIGNIFICANCEi)

By

Hiroshi ANDo

(Sug. adaira Biolesrical Laboratory, Tekyo Kyoiku Univer$ity)

Masahiro TANAKA

CIgano I,Iigh Sehool, Gifu)

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Introduction

The order Lepidoptera is one of the orders well studied from the embryological

standpoint, and so far as we knew, almost all the studies coneern the embryogenesis of

the higher suborder in this oraer and up to the present, no studies have been

done on the family Hepialidae belonging to the primitive suborder Monotrysia.

Vvre therefore decided to study tlie embryogenesis of the Munotrysia in detail, com- paring the results obtained with the embryolog}, of ditrysian Lepidoptera and Trichoptera. Endo(:l),ta,evcrescens BulrLEK is feund in Japan, is a rneinber of Hepialidae, and is

the Tnaterial ".hich we used for the present study.

We set out in the present preliniinary report the outline of the peculiar germ rudi-

ment formation in the primitive moth. Tlie full proce$s of the einbryonic development of

the species will be publishecl in future papers.

rvIaterials and tw'Iethods

The feinale of Endoc4),ta earcrescens BuTLER laid their eggs in October, and the eggs hibernated and the first instar larvae hatched out early in April the following year, t -...... ttt -ttttt tt ttttt tt t t ttttt tt t t

1) (r,ontributions from the Sugnrlair:i BiolL)gical I.aboratnrl' of Tokyo KyoiltLL IJ･niN,ersity, No. 38,

NII-Electronic Library Service JapaneseJapaneseSociety Society of Systematic Zoology

53 Proc. Jap. Soe, Syst. Zool. No. IL' (1976)

so that the egg-duration was about 170-180 days.

The eggs were fixed with CARNoy's fiuid for five to twenty minutes as prefixation, BOulN's after which they were perforated with a fine needle and transferred to alcoholic

fluid for fifteen to thirty minutes at Toom temperature. The eggs were cut into ten psm

thickness and stained with DELAFIELD's haematexylin and eosin.

Observation

The eggs of Endoclyta excrescens are ellipsoid in shape, and about O.7-O.75xO.65 mm in size just after oviposition. At about a half day after egg-laying, the conspicuously thick blastoderm is formed throughout the entire periphery of the eggs. The nuclei oi the blastoderm eelis are located in the outer part of each columnar cell and the numerous yolk spherules are found in the

inner part of eaeh one. At about two hours later, the differentiatien of the germ disk beglns, that is, in cross section, the lens-shaped thiclg region appears in the Testricted small area of the blastoderm

(Fig. 1-1). This region is the germ disk or embryonic area and the remaining region is

the rudimental serosal or extraembryonic area.

Soon after this, the central part of the germ disk commences to invaginate into the yolk, and, as a result of this invagination, the germ disk changes its form from a convex Iens- shape to a small concave one in cross section (Fig. 1-2). This round body is of the germ rudiment. With the lapse of time, it gradually inereases in size and invaginates more

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2

3

Fig. 1. For]nation of genn rudiment and embryonic envelopes eE Endoc(>'ta earci'escens, cross section, 1-5: suceessive stages (diagrammatic). a, amnion; ac, amniotic cavity; gd, germ dislt; gr, germ rudiment; ra, rudimental umnion; s, serosa ; arrow, invagination of germ disk.

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54 S4tzfi･fatt.･:ft-ts.,. 12 (1976)

deeply into the yolk (Fig. 1-3). Accompanying the progress of invagination, the opening

of the gerrn rudiment becomes narrower and narrower, finally closes and the sae-like round

germ rudiment is separated from the rudimental serosa at seventeen to ninenteen hours

after oviposition (Fig. 1--4).

Tlie round germ rudiment isolated in the yQlk changes its form into flatted round in cross

section (Fig. 1-5). The part fronting on the rudimental serosa or egg surfaee is the rudimen- tal amnion and the part fronting on the egg center is the future germ band, and the central cavity is a rudimcntal amniotic caviLy. As the germ rudiment continues to develop, it

continues to increase in size and the rudimental amniotlc part thin$ off, viz. the differentiation of the amnion begins, but at the same time the thickness of that part whlch Iater develops into the germ bancl remains the same during this time, i. e., about one day after oviposition.

Discussion

In the present study, it is not known whether a]1 the members og Monotrysia have round germ rudiments or not, but at least in Endoc4>it'a of Hepialidae the germ rudiment formation is of a peculiar type, as mentioned above. That of E. exci-esccns differs funda-

mentally from that of ditrysian Lepidoptera. IN(oreover, the embr},onic envelope fermation

of E. excrescens as shown in Fig. 1 is also entirely dif'ferent from that of the Ditrysia

which is generally known at the present time (ANDERsoN, 1972' ; ANDERsoN & NNrooD,

1968; CHRIsTENSEN, 1942,1943; JoHANNSEN, 1929; OKADA, 1960; TANAKA, 1970).

Recently MIyAKAWA (1973) studied the embryology of the caddisfly, SlenoPsy,che griseiPennis MAcLAcHLAN, Stenopsychidae, belonging to the primitive suborder Annulipalpia of the order TrichopteTa, and in the caddisfly he found that rouncl germ rudiments like

that of Endoclyta are formed by the invagination of the germ disk, and he also observed

embryonic envelope formation similar to that in E. excrescens. The similarites in the early

embryonic develepment in these two species show a elose afilnity between annulipalpian

Trichoptera and inonotrysian Lepidoptera.

In systematics, it is well known t]iat the order Trichoptera is akin to the order

Lepidoptera, howevcr, up to the present, there has been no evidenee in the forin of

embryological data, and for this reason we feel that the new embryological eL,idence

obtained in the present study may help to indicate the phylugenetical relationship bctween

these twe orders.

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Proc． Jap． Soc． Syst． Zool ． No ．12 （1976 ） 55

． 1 行 に つ れ 深 く な る 。 そ の た め ，今 ま で の 胚 盤 は 袋 状 翅 「1完 鬚 亜 11の ヒ ゲ ナ ガ カ ワ ト ビ ケ ラ Stenopsv）Fche

の rudiment に な る 入 口 の と に で さ た の MIYAKAWA 1973 germ Q 陥 閉 鎖 共 ， griseiPennis 襯 察 れ も （ ， ）

球 型 の germ rudiment は 漿 膜 か ら 離 れ て 卵 黄 中 に に 最 も類 似 し て い る 。毛 翅 口 と 鱗 翅 目 が 系 統 一L 近 い

沈 む 。羊 膜 は gcr 皿 rudi 皿 ent の 卵 表 に 面 した 部 分 位 置 を 占 め る こ と は 周 知 の こ と で あ る が ， こ の よ う

の の ま 日 で て い な い か ら ， 胚 帯 は 残 余 部 分 か ら 分 化 す る 。 な 発 生 学 一L 事 実 ； ，今 ま 知 ら れ 。

こ の よ う な ger 皿 rudinlent と 胚 膜 の 形 成 は ， 毛

Ijterature Cited ‘‘ ” ANDERsoN D ，T ． 1972 ， The development of Holometubdk 〕us hlsects． In DevelopInen副 Systems I ， ， − ed 三ted by S J ． CouNcE ＆ C ．H ． WADDINGTON ： 165 242 ， Academic Press， London ＆ New York ．

ANDERSON D ．T ．＆ E ．C ． WooD ，1968． The morphologicul busis uf embryQ 【1ic movcIIlelLt5 in the light ， ’ − aPple moth ’ 尸as ＞o ．stvt ］ttana WALK ． Az ‘Sl．」θ zイ ノ ． Zoo 〜． ： 76 ：／ 793 ． brown ， 即 γ海 i （ ） ，16 − CHRIsTENsEN ， P 、J．H ．，19 ・12． Embryologisclle un 〔l zy1 ．ologische Studicn tlber die erste und frUhe Eient ・ ’ wicklung bei Oi 90 ，icl a 〃 tigtta LINNE （Fani． Lynlalltrlidae， Lepidoptera） C ．A ，Reitzels Verla9 ： − ／ 223 ，Kopel ／hagCn ． − ． ／943 urld t“Lniiiioilb 重ldunsr 〔ler LepidopterL1 ， E ／tt ． M ‘ゼ♂． 23 ： 204 223 ・ CIIRIsTENSEN ， P ．J，H ， ．SerQsa ， ’’ ／ ，『’ ’ 0 ．A ． ユ929 ．Solne il1111c cmbry ｛mic developmellt Qf D 〜α ‘r iSltl x iア 8 illi‘ Ct FABR ・ JoHANNsEN ， ， phases 「 ・ − （Lepidol ユtera ）． ・ノo τ‘ノ ．ハforphol，，48 （2）： 493 54L ・ ．・ 『 ） 〃 ノ・ ．・ ri − M エYAKAw へ K ．，エ973． The emb ・ ydugy ・ f the caddisfiy ， Sten θ ／s！ ・海 9 ・ 〜∫砂 ・ 〜 MAcLAcHLAN （ユ 1 −− 〔， ）SyChidae 〃 舜 d ： 413 ehoptCr ．i ： Sten 1 ）． KO な ， 41 （ ） 425． − ’ ’ OKADA ， M ．，19flO ． Embry nic develoP エnent of the rice stem borer，（：ソul／o suPi η essa ／．is． LS‘ブ．ノぐ‘ψ ・了b 尺ソo ’ ・ − K ．／θ i／“it Da 〜gaktt ， Sec ． B ，9 （工ユ3）： 243 296 ． ・ ’ ・ TANAKA ， M ．，1970 ． EmbryQnic develQpnlellt Qf the rice web 、、 Qrm ， f lne−i ゾθ／θ ’llicl ノ‘ψ θ 〃 〜‘ α ZE τ，LER ．1， leTe ’ ’ ／ ． l alul formation ．△ ’E ntv 〃 io 〜og 〜st 19 2 3 ： 35 4L ln しコtlllese Fro 皿 fertilization to gerlll ） ， （ ノ ） （ JL1 w 三th ETigllsh Sllmlnary ．）

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