Recent Advances in Insect Embryology in Japan
Edited by H. Ando and K. Miya.
ISEBU Co. Ltd., Tsukuba 1985

107

Determination and Formation of the Basic Body
Pattern in Embryo of the Domesticated Silkmoth,Bombyr mori (Lepidoptera, BOlnbycidae)

Keiichiro MIY A

Synopsis
The determination and establishment of basic body pattern of the Bombyx germ band are discussed
chiefly from the morphological point of view. The anterior-posterior and ventral-dorsal polarities are
distinguished easily in the newly laid egg by the shape and ultrastructures, but any genes concerned withthe anterior-posterior polarity have not been found and experiments for modification of long axis of theegg have not succeeded. The first step of establishment of anterior-posterior organization of germ band is
performed by the protrusion of cytoplasmic masses from the germband at the lateral extremities ofanterior and posterior parts, resulting in the pyriform germband. Then these cytoplasmic masses are
subdivided into the numerous cytoplasmic granules and incorporated by the yolk cells.
From the pyriform stage, the gastrulation begins at the central region of the presumptive head lobe as
an invagination and this process extends posteriorly. At the same time, several degenerating cytoplasmic
masses appear among the ectodermal cells and/or between" the ectoderm and the mesoderm and thesemasses also are protruded into the yolk. This phenomenon spreads posteriorly with the progress ofgastrulation and seems to indicate the first step of establishment of ventral-dorsal organization of
germband.

Introduction
The first experimental studies on embryogenesis of the domesticated silkm9th, Bombyx
mori, were performed by Takami with cauterization (1942-1946). In the series of studies herevealed that the rough range of embryonic and extraembryonic regions, and thepresumptive mesodermal and neural regions were predetermined in the newly laid egg. Then
Miya (1950, 1952) carried out several experiments on the differentiation of primordial germ
cells and the gonad formation using the similar technique and made clear the predetermination of germinal region and the relation between the segmental genital ridges and theprimordial germ cells. From these results, Kuwana and Takami (1957) made a fate map of

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Miya, K.

Bombyx egg at first, and recently this fate map was reconfirmed by Katsuki et al. (I 980)
with the analysis of mosaics induced by super·cooling method.
Furthermore, several genes related to the morphogenesis of embryo were found in
Bombyx and their genetical, morphological and biochemical studies have been carried out(see Tazima,1964). These genes are divided into two categories; the one is maternal·effectmutant and the eggs laid by the homozygous female represent all this phenotype, while theother affects the embryogenesis only in the homozygote after fertilization. "Kidney-shaped
egg" (ki) belongs to the first category and all ki/ki female moths lay kidney-shaped eggs, inwhich all embryos develop no mesodermal tissues either in ki/ki or ki/+ combination, and"E-alleles" belong to the second and are all concerned not only with extra markings andsupernumerary legs, but also with abnormalities of gonads and genital organs. Further, mostof them are lethal in homozygous condition. Although ki gene is being re-examined recently
from the morphological and biochemical points of view (Sakaguchi et al., 1982; Kawaguchi,
unpublished data; Miya, in press), E-alleles are not studied from the recent new viewpoint.
Since Yajima's epoch-making experiment (1960), induction of double-cephalon anddouble-abdomen by centrifugation in embryo of Ozironomus, problems on formation of theembryonic body pattern have been studies in dipteran insects with centrifugation andUV-irradiation, for example, in Smittia (Kalthoff et al., 1982) and Sciara (see Sander, 1983).
On the other hand, many genes relating to the morphogenesis of embryo are found in
Drosophila and their ahalysis are being performed vigorously (see Lewis, 1978; Sander,
1982, 1983). Comparing with the results obtained in Drosophila and other dipteran insects,
the studies on such phenomena in Bombyx seem to be far behind in this field, and hence inthe present review the author intends to re-examine the results obtained in Bombyx until
now and to make a basis for the future study.

Structure of Mature Egg and Determination of
Basic Body Pattern

1. The structure of mature eggs

As the details of structure of the mature Bombyx eggs were described in the recent
reviews (Miya, 1984a, b), only the brief description will be done in this paragraph from theviewpoint of determination of embryonic body pattern.
The mature egg is a flat spheroid, approximately 1.3 mm long, 1.0 mm wide, and 0.6 mm
thick. At the anterior end, there is a micropylar apparatus, and hence the anterior-posteriorpolarity of the egg is easily distinguishable. One side of the egg is more convex than theother, and the convex side is the ventral side of the egg, at which the germ anlage appears at
first. Thus ventral-dorsal polarity also seems to be determined during oogenesis (Fig. 1).
As shown diagrammatically in Fig. 1, the egg is covered with a thick, tough, and elastic
chorion, which is formed by the follicular epithelium at the last period of oogenesis. Beneaththe chorion there is a complex vitelline membrane, which consists of a very thin outermembrane, an electron-dense outer layer, and a thick inner layer containing the numerous
electron-dense irregular granules. As in the most insect eggs, the ooplasm of the Bombyx egg
is divided into a superficial layer, the periplasm, and inner endoplasm, which occupies theBasic body pattern in silkmoth embryo

109

Fig. 1. Diagrammatic figure of the mature Bombyx egg showing anterior-posterior polarity(top - bottom) and dorsal-ventral polarity (right -left).
ch chorion, en egg nucleus, mir micropylar region, per periplasm, sI
subcortical layer, vm vitelline membrane, y yolk system.

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Fig. 2. Diagrammatic figure of the anterior part of mature egg.
ch chorion, gr.z zone of granules, mat.p maturation plasm, mi micropyle, rer.z
zone of rough-surfaced endoplasmic reticulum, vm: vitelline membrane.

Basic body pattern in silkmoth embryo111

Figs. 3, 4. Electron micrographs showing zones of rough-surfaced endoplasmic reticulum (Fig.
3, rer.z) and granules (Fig. 4, gr.z).
lip lipid droplet, mit mitochondria, vm vitelline membrane. Scale: 2 jJ.m.

112

Miya, K.

Fig. 5. Electron micrograph of the anterior polar plasm, in which the egg nucleus shows
metaphase of the 1st maturation division.
ea dense organelles connecting with endoplasmic reticulum, gol: Golgi body, liplipid droplet, mit mitochondria, rer rough-surfaced endoplasmic reticulum, ys
small yolk sphere. Scale: 2 Mm.
Fig. 6. Electron micrograph of the ventral periplasm to which a large cytoplasmic masscontaining rough-surfaced endoplasmic reticulum (rer) attaches.
rg round granule with thick cortex, ys small yolk sphere, vm vitelline
membrane. Scale: 2 Mm.

Basic body pattern in silkmoth embryo

113

central part of the egg and contains yolk organelles in the meshwork. Another special layer,
the subcortical layer, lies adjacent to the periplasm. This layer seems to react sensitively tothe fixing conditions, and it appears to be thicker and more distinct in the eggs fixed after
removing the chorion.
Fig. 2 represents diagrammatically fine structures of the anterior part of the egg. The
surface of the micropylar region shows a petal-like pattern, and at its center the micropylar
canals open (Kanda et al., 1974; Ohtsuki, 1979). These pattern and canals are formed bythree types of cells: the micropylar channel-forming cells, the micropylar orifice-forming
cells, and the micropylar rosette-forming cells (Yamauchi and Yoshitake, 1984). In the
micropylar region the vitelline membrane becomes thicker than in the other regions, and the
periplasm lying under the micropylar canals indicates the peculiar structure, comparing withthe other egg regions. This periplasm consists of a relatively thick layer of ooplasm which
terminates in a series of small cone-like processes, from which short microprojections
protrude into the inner layer of the vitelline membrane. Stacks of endoplasmic reticulum(ER) develop well parallel to the surface of egg (rer. z). Fig. 3 shows the ultrastructure ofthis zone. Another ooplasmic zone encloses the ER zone, and in this zone many vesicles
containing electron-dense granules are observed and slender mitochondria are present
numerously(gr. z). Fig. 4 shows the ultrastructure of this granule zone. At the short distancedorsally from the micropylar region, there is the maturation plasm (mat. p), in which the egg
nucleus is in metaphase of the first maturation division. Fig. 5 shows the ultrastructure ofthis plasm, in which the chromosomes and spindle fibers are enclosed by concentric
circle-like stacks of rER.
In the periplasm of the other egg regions, there are no remarkable differences except theconfiguration of rER. In the newly laid egg many pyronin-positive granules were observed
attaching to the periplasm (Suzuki, 1969). These structures are constituted of large whorlsof r ER (Fig. 6, rer; Miya 1984b) and their distribution is limited to the ventral and lateralsides of the egg, the presumptive embryonic region (Kobayashi and Miya, unpublished data).
2. Source and supply of cytoplasmic components in the mature egg
The ovary of Bombyx belongs to the meroistic-polytrophic type and large amount ofcytoplasmic components of the egg cells, except for' the yolk substance, are produced in thenurse cells and supplied from them (Miya et al., 1969; Yamauchi et al., 1981). Table I showschanges of the cytoplasmic components in the nurse cells with the progress of oogenesis. Not
all, but almost all of them are supplied to the oocyte corresponding to the developmental
stages (Yamauchi et al., 1981).
Table 2 summarizes the source and route of supply of the cytoplasmic components in themature egg. Among them, the rER seems to have the closest relation to the maternal
informations for the embryonic body pattern, at least their expression. As indicated in Table
2, the rER lying under the micropylar region originates from the anterior polar plasm(Yamauchi, unpublished data) and that in the periplasm of the other egg regions is formed
from the annulate lamellae derived from the nuclear membrane of nurse cells at the last stageof vitellogenesis.

114

Miya, K.
Table 1. Stage-dependent changes of cytoplasmic components in nurse cells(Yamauchi et al., 1981)
Organelles

Previtellogenesis
Stage

Mitochondria'"
Ribosome'"
r-ER'"
Dense ground granules'"Golgi bodies'"
Annulate lamellae'"
Lipid droplets·
Glycogen granules·
Electron dense masses
DPmasses
Microtubules·
Pinocytotic vesicles
Vacuoles

++
++
+
+
+
+
++

+
+

Vitellogenesis

11

III

IV

V

VI

VII

VIII

++
++
+
+
+
+
++

++
++
+
+
+
+
++

+
++
+
+
+
+
++

+
++
+
+
+
+
+

+

+

++

+
+

+
+

+
+

++
+
+
+
++

+
++
++
+
+
+
+
++
++
+
+
++
++

++
++
++
+
+
++
+
+
++
+
++
++
+

++
++
++
+
+
+
+
+
++
+
++
+
+

... : inflow into oocyte, ++ : presence of larger amount

Table 2. Source and route of supply of cytoplasmic components in mature egg cell
EGG CELL

FOLUCLE CELLS

Yolk spheresa(proteid yolk) ( b )
c

-4--

_

Small yolk sphere ..._ _ _ __NURSE CELLSHEMOLYMPH..................................................................... .

-egg-spec~fic ·2

protem..... ?

Lipid droplets.....................................................................
4-(lipid yolk)
Glycogen granules)..._ _ _ _ _ ............................. _glycogen granules· 4 ".....- - - - - .....................................................................
Mitochondria _ - - - - - ............................. _mitochondria ·4,5
Ribosomes ...._ - - - - - - ............................. _ribosomes ·4,5
Rough-surfaced
endoplasmic reticulum(micropylar region) ....- - - (anterior polar plasm of oocyte)·6
nuclear membrane ~(other egg regions) ..._ _ _ ............................. _annulate lamellae
Golgi bodies •..... ?
Round granules withthick cortes ..._ _ _ _ _ ..... ?
4 ..
_ _ _ _ __

"1
·4
·7

vitellogenin·1,2(other proteins·2

Izumi et al. (1980),·2 Irie and Yamashita (1983),
Yamauchi et al. (1981),·5 Miya et al. (1969),
Yamashita and HasegaWli (1974).

"3"6

diglycerides ·3

trehalose ·7

Ichimasa (1977),
Yamauchi (unpublished data),

Basic body pattern in silkmoth embryo

115

3. Determination of basic body pattern of embryo
Fig. 7 represents the fate map of Bombyx egg (Kuwana and Takami, 1957). Because of
thick and tough chorion, it is impossible in the Bombyx egg that the detailed fate map ismade by the defect method with point irradiation of DV-light or others. Hence, Katsuki etal. (1980) analyzed the mosaic individuals induced by the super-cooling method introduced
by Tamazawa (1977) and made a more detailed fate map. This fate map coincides roughlywith the Takami's original one.
As to determination of the anterior-posterior polarity, there are a series of studies onmaternal-effect mutants in Drosophila, such as dicephalic (dic) and bicaudal (bic). Dic
females produce eggs with anterior markers at both poles and these eggs produce mostly"double anterior" embryos and occasionally a perfect double cephalon. Some egg follicles
from homo-zygous dic females carry nurse cells at the both poles of the oocyte instead of
only the anterior pole and this anomaly results from aberrant arrangement of the normal
number of nurse cells (Lohs-Schardin,1982). On the other hand, bicaudal homo-zygous
females produce eggs which develop double abdomen instead of normal larvae (NiissleinVolhard, 1979).
In the Bombyx egg, no maternal-effect mutant for the anterior-posterior polarity has
been found and experiments for modification of long axi!> of the egg have not succeeded.
The most characteristic structure in the mature Bombyx egg is the structure of the anteriorpart, that is, micropylar apparatus of chorion, ultra-structure of vitelline membrane andooplasm. These structures seem to relate with sperm entry into the egg and activation of theegg, considering their changes at sperm entry (Miya, 1984b). Though origin and function of
the granule zone existing in this region remain unsolved, this zone might have any relation toanterior determinants.
As to determination of the ventral-dorsal polarity, several interesting results are reported
in Drosophila. A maternal-effect mutant, dorsal (d!), affects determination of thedorsoventral coordinate and the ventral cells formed no mesoderm, but ventral hypodermis(Niisslein-Volhard et al. 1980). Recently, Anderson and Niisslein-Volhard (1984) reported
the experimental results on "dorsalized" embryos in Drosophila. Ten loci have been foundwhich were reqUired for the production of lateral and ventral pattern elements. The lack ofeach gene function in the mother resulted in an embryonic phenotype identical to thematernal-effect mutation dorsal. Injection of RNA isolated from wild-type embryos into themutant at six loci partially restored ventral-dorsal polarity. For the mutant snake, especially,
injection of poly (A) + RNA isolated from wild-type embryos restored a complete ventraldorsal pattern,
In the Bombyx egg, a similar maternal-effect mutant "kidney-shaped egg" (ki), wasfound by Suzuki (1932) and has been studied from genetical, embryological, andbiochemical points of view. The homozygous female moths lay eggs, the ventral side ofwhich is slightly concave showing kidney-like shape. The egg died both in homozygous orheterozygous state of ki gene without any mesodermal organs, namely the ki embryo wasconstructed with only ectodermal organs, such as epidermis, setae, mouthparts, and so on.
Furthermore, the nervous system could not be formed except the brain (Suzuki and
Ichimaru, 1955; Miya, in press).
Sakaguchi et al., (1982) observed oogenesis of the ki egg and reported that the ki follicle

116

Miya, K.

100r-------~-r~--------------~~~------

85
80
75
65

20~~._------~----_+------_4------~----~--

OL-------~~~~--------------~~~------­

~o

A

B

Fig. 7. The fate map of Bombyx egg (Reproduced from Kuwana and Takami, 1957).
A: lateral view, B: ventral view, Ab abdomen, Ex extraembryonic region, Gn
gnathocepha1on, Ms mesodermal region, Pc protocephalon, Th thorax.

100

7S

50

25

o
%

A

B

Fig. 8. Diagrammatic figures showing segregation of germ anlage from the extraembryonicblastoderm (A) and completion of the germ band and the serosa (B).
ex extraembryonic blastoderm, ga germ anlage, gb germband, se serosa.

Basic body pattern in silkmoth embryo

117

cells at the ventral side were narrower and longer than those at the other sides. Theysuggested that the ki gene affected the size and shape of follicle cells at the ventral side, thepresumptive embryonic region. However, the comparative studies of ultrastructure between
the normal and the ki eggs revealed that there were no remarkable differences in the egg cell
during oogenesis. Further, no differences could be detected between the normal and the ki
egg in the qualitative and quantitative changes of yolk proteins or their synthetic capacity
during oogenesis (Kawaguchi, unpublished data). Analysis of ki gene function might
contribute to the solution of ventral-dorsal polarity as a useful clue.
Establishment of Basic Body Pattern of Embryo
1. Anterior-posterior organization

Fig. 8 represents diagrammatically the eggs in which segregation of the germ anlage andthe extraembryonic blastoderm (A) and completion of the germband and the serosa (B)occur. The blastoderm cells existing in the embryonic region continue parallel divisions tothe surface of egg to increase cell popUlation and to form the germ anlage, and those in theother region become the extraembryonic blastoderm. The area of germ anlage coincides
roughly with the embryonic region represented in the Takami's fate map. As mentioned
above, many cytoplasmic masses containing large whorls of rER, attach to the periplasm ofpresumptive embryonic region in the newly laid egg. These stacks of rER break down toform numerous tubular and/or vesicular structures, but the direct relation between such
structural changes and the establishment of germ anlage does not yet confirmed.
Yajima's experiments in Chironomus suggested that the anterior-posterior polarity
predetermined during oogenesis could be changed before the establishment of protocephaliccaudal organization. Afterwards, the similar results have been obtained in Eucelis (Sander,1960), in Srnittia (Kalthoff, 1979) and so on. Ripley and Kalthoff (1983) reported that theanterior determinants were cytoplasmic ribonucleoprotein particles existing in a yolk-freecytoplasmic cone observed behind the anterior pole of newly laid egg, diffused posteriorly
with the progress of development, and then migrated into the periplasm of the anterior partof the egg.
In the Bombyx egg, such anterior determinants have not been found and any experiments
have not succeeded in changing the anterior-posterior polarity. Morphologically, theanterior-posterior organization of germband is not yet established until the early germband
stage, as shown in Fig. 8B. However, many cytoplasmic masses are protruded from thegermband into the yolk at the lateral extremities of anterior part at this stage (Fig. lOA).
This phenomenon seems to be the first process of anterior-posterior organization of
germband. As shown in Fig. 11, these cytoplasmic masses contain many usual cell organelles,
such as mitochondria, r ER, and ribosomes. Then the protrusion of cytoplasmic masses
occurs in the posteriormost region of germband, and consequently the anterior and posterior
parts of germband become visible, resulting in the pyriform germband (Fig. 9A).
At the pyriform stage an invagination occurs in the center of presumptive head lobe of
germband and it indicates the first sign of mesoderm differentiation (Figs. 9A, lOB). At thisstage the protruded cytoplasmic masses are subdivided into numerous cytoplasmic granules,
which are incorporated by phagocytotic activity of the yolk cells, as shown in Rgs. lOB and118

Miya, K.

A

c

B

Fig. 9. Diagrammatic figures of germband at the pyriform (A), the head lobe formation (B),and the early diapause (C) stages.

B

Fig. IO. Diagrammatic figures showing the cross sections through the anterior part of thegermband at the early germ band (A), the pyriform (B), the head lobe formation(C), the early diapause (D) stages.
am amnion, cg cytoplasmic granule, cm cytoplasmic mass, dc degenerating
cytoplasmic mass, ecd ectoderm, msd mesoderm, ph phagosome se serosa, yyolk system, yc yolk cell, arrow an invagination occurring at the central regionof the presumptive head lobe -=- the first sign of gastrulation.

Basic body pattern in silkmoth em bryo

119

Fig. 11. Electron micrograph showing the cytoplasmic masses protruded from thegermbandcm cytoplasmic mass, gb.c: germ band cell, mit mitochondria, rer roughsurfaced endoplasmic reticulum. Scale. 21lm.
Fig. 12. Electron micrograph showing the cytoplasmic granules.
cg cytoplasmic granule, gb.c germ band cell, gl glycogen granule, lip lipid
droplet, mit mitochondria, yc yolk cell, ys small yolk sphere . Scale. 21lm.

120

Miya, K.

Fig. 13. Electron micrograph showing degenerating cytoplasmic mass inserted between theectoderm and the mesoderm.
dc. degenerating cytoplasmic mass, ecd.c ectodermal cell, lip lipid droplet,
msd. c mesodermal cell, ys small yolk sphere. Scale: 2 pm.

12. The next stage is the head lobe formation stage, at which the anterior part of germ band
develops into a wide head lobe (Fig. 9B). The invagination becomes deeper and extends
posteriorly, and the invaginated cells segregate from the outer layer of germband, theectoderm, to differentiate to mesodermal cells (Fig. IOC). With the differentiation of
mesoderm, several degenerating cytoplasmic masses appear, inserted among the ectodermal
cells and/or between the ectoderm and the mesoderm, and then these masses also are
protruded into the yolk and subdivided into the numerous cytoplasmic granules (Figs. IOC,13, dc). This phenomenon spreads posteriorly with the progress of gastrulation .
From the above-mentioned results, the establishment of anterior-posterior organization in
the Bombyx germband seems to accompany the protrusion of cytoplasmic masses into theyolk at the lateral extremities of anterior part of germband, the presumptive head lobe, andthe posterior part, the presumptive telson. The formation of head lobe results in thesubsequent occurrence of an invagination at its center. This invagination is a first sign offormation of mesoderm, and then extends posteriorly (Figs. 9C, 10D). This process ofgastrulation seems to indicate the establishment of ventral-dorsal pattern elements.

Basic body pattern in silkmoth embryo

121

2. Ventral-dorsal organization
As mentioned above, the ventral-dorsal organization of germ band may be closely related
to the establishment of anterior-posterior organization, because the formation of head lobe
may trigger the initiation of gastrulation, which means the first step of establishment of theventral-dorsal body pattern.
The maternal-effect mutant, "Kidney-shaped egg", serves as a clue for such a suggestion.
In the ki germband, protrusion of cytoplasmic masses occurs at the lateral extremities ofanterior part of germband as in the normal egg and the anterior-posterior organization isestablished. However, as development proceeds, such protrusion of cytoplasmic masses
spreads not only to the middle part of anterior region, but also to the entire length ofgermband. Consequently, the normal head lobe is not formed in the anterior region of
germband and the process of gastrulation beginning as an invagination in the center of headlobe is inhibited, resulting in no differentiation of mesoderm (Miya, in press).
The similar result was obtained by centrifugation. Some abnormal embryos consisting of
only ectodermal tissues were induced in the eggs centrifuged at the early stages, because of
the inhibition of gastrulation by the effect of centrifugation (Miya, 1967, 1973). The resultson the ki germband and the experimental results suggest that the ventral-dorsal organizationin the Bombyx egg might be established through the process of gastrulation.

References
Anderson, K. V. and Niisslein-Volhard, c., 1984. Information for the dorsal-ventral patternof the Drosophila embryo is stored as maternal mRNA. Nature 311: 223-227.
Ichimasa, Y., 1977. Incorporation of palmitic acid-1- 14C into lipids of pharate adult tissueof Bombyx mori. J. Insect Physiol. 23: 883-887.
Irie, K. and Yamashita, 0., 1983. Egg-specific protein in the Silkworm, Bombyx mori:
Purification, properties, localization and titre changes during oogenesis and embryogenesis. Insect Biochem. 13:71-80.
Izumi S., Tomino, S. and Chino, H., 1980. Purification and molecular properties of vitellinfrom the silkworm, Bombyx mori. Insect Biochem. 10: 199-208.
Kanda, T,. Matsumura, H., and Ohtsuki, Y., 1974. Surface structure of silkworm (Bombyxmori) egg. I. Fine structure of micropylar apparatus. J. Sericult. Sci. Japan 43:379-383(J apanese with an English summary).
Kalthoff, K., 1979. Analysis of a morphogenetic determinant in an insect emrbyo (Smittia
Spec" Chironomidae Diptera). In "Determinants of Spatial Organization" (Subtelny, S.
and Konigsherg I. eds.) pp. 97-126, Academic Press, New York,_____ , Rau, K.-G., and Edmond, J. C., 1982. Modifying effects of UV irradiation on
the development of abnormal body pattern in centrifuged insect embryos (Smittiaspec.,
Chironomidae Diptera). Develop. Bioi. 91:413-422.
Katsuki, M., Murakami, A., and Watanabe, I., 1980. Fate mapping of some tissues in thegenetic mosaics of the silkworm, Bombyx mori. Zool. Mag. 89:269-276 (Japanese withan English summary).
Kuwana, J. and Takami, T., 1957. Insecta. In "Embryology of Invertebrata" (Kume M. andDann. K. eds.) pp.287-343, Baihukan, Tokyo (Japanese).
Lewis, E. B., 1978. A gene complex controlling segmentation in Drosophiola. Nature.276: 565-570.
Lohs Schardin, M., 1982. DicephaUc - a Drosophila mutant affecting polarity in follicle
organization and embryonic patterning. Wilhelm Roux's Archiv 191: 28-36.

122Miya, K.

Miya, K., 1950. Studies on the development of gonad of the silkworm, Bombyx mori L. I.
On the region and period of differentiation of germ cells. Trans. Sapporo Nat. Hist. Soc.
19: 1-4 (J apanese with an English summary).
____ , 1952. studies on the development of the gonad of the silkworm. IV. The
gonad-formation in the cauterized eggs of the silkworm, Bombyx mori L. Zool. Mag.
61: 13-17 (Japanese with an English summary).
____ , 1967. Some problems of developmental physiology in the silkworm egg. J.
Sericult. Sci. Japan 36: 293-296.
____" 1973. Analysis of early embryonic development of the silkworm, Bombyx mori bycentrifugation. I. Effects of centrifugation on the different developmental stages. J. Fac.
Agr., Iwate Univ.ll:213-229.
____ , 1984a. Physiology and biochemistry of the early embryogenesis. In "TheBiochemistry of the Silkworm" (Ito, T. ed.) pp.280-309, Shokabo, Tokyo (Japanese).
_ _ _ , 1984b. Early embryogenesis of Bombyx mori. In "Insect Ultrastructure" (King R.
C. and Akai, H. eds.) Vol. 2:49-73, Plenum Pub. Corp., New York.
_ _ _ , Kurihara, M. and Tanimura, I., 1969. Electron microscope studies on the oogenesisof the silkworm, Bombyx mori L. I. Fine structure of oocyte and nurse cells in the early
developmental stages. J. Fac. Agr., Iwate Univ.9:22l-237.
Niisslein-Volhard, C., 1979. Maternal effect mutations that alter the spasial coordinates ofthe embryo of Drosophila melanogaster. In "Determination of spatial organization"(Konigsberg, I. and Subtelny, S. ed.), pp. 185-211, Academic Press, New York.
_ _ _-Volhard, C., Lohs-Schardin, M., Sander, K., and Cremer, C., 1980. A dorso-ventral
shift of embryonic primordia in a new maternal-effect mutant of Drosophila. Nature
283:474-476.
Ohtsuki, Y., 1979. Silkmoth eggs. In "A General Textbook of Sericulture" (The Sericultural
Society of Japan ed.) pp. 156-173, Nihon Sanshi Shinbun-sha Tokyo (Japanese).
Ripley, S. and Kalthof( K., 1983. Changes in the apparent localization of anterior
determinants during early embryogenesis (Smittia spec., Chironomidae, Diptera).
Wilhelm Roux' Archiv. 192:353-361.
Sakaguchi B., Kawaguchi, Y., Suenaga, H., and Koga, K. 1982. The genetic control of egg
architecture in Bombyx mori. In "The Ultrastructure and Functioning of Insect Cells"(Akai H., King, R. C., and Morohoshi, S. eds.), pp. 17-20, The Society for Insect Cells
Japan.
Sander, K., 1960. Analyse des ooplasmatischen Reaktionssystems von Euscelis p/ebejus Fall.
(Cicadina) durch Isolieren und Kombillieren von Keimteilen. 11. Wilhelm Roux's Archiv
151 :660-707.
_ _ _ _, 1982. Some functional aspects of egg cell and blastoderm in dipteran insects. In"The Ultrastructure and Functioning of Insect Cells" (Akai, H., King R. c., andMorohoshi, S. eds.), pp. 45-48, The Society for Insect Cell Japan •.
_ _ _ _ , 1983. Extrakaryotic determinants, a link between oogenesis and embryonicpattern formation in insects. Proc. 19th Ann. Meet. Arthrop. Embryol. Soc. Japan pp.
1-12.
Suzuki, K., 1932. On the inheritance and abnormal development of embryo in mutant
strain, "kidney-shaped' . J. Sericult. Sci. Japan 3:316-326 (Japanese).
_ _ _-.,and Ichimaru, M., 1955. Embryological studies on the hereditary unhatched eggs
in the silkworm. Ill. on the development of the kidney-shaped eggs of the silkworm.
Memoir Fac. Educ., Kumamoto Univ. 2: 177 -197 (Japanese with an English summary).
_ _ _ _ , 1969. Distribution and change of pyronin-positive granules during the early
development in the silkworm, Bombyx mon L. B. A. thesis, Fac. Agr., Iwate Univ. pp.
1-30
Takami, T.) 1942. Experimental studies on the embryo formation in Bombyx mori. I. Zool
Mag. 54:337-343 (Japanese).
_____ , 1946. Experimental studies on the embryo formation in Bombyx mori. V.
Presumptive mesodermal and neural regions of the egg. Seibu tsu 1: 208- 211 (JapaneseBasic body pattern in silkmoth embryo

123

with an English summary).
Tamazawa, S., 1977. On the influences upon supercooling treatment to the silkworm eggs,
Bombyx mori L. 11. Androgenesis and mosaic induced by the low temperature
treatments. Res. Bull. Univ. Farm, Hokkaido Univ. 20: 145-152 (Japanese with an
English summary).
Tazima, Y., 1964. The Genetics of the Silkworm, Logos Press, London.
Yajima, H., 1960. Studies on embryonic determination of the harlequin-fly, Chironomus
dorsalis. I. Effects of centrifugation and its combination with constriction andpuncturing. J. Embryol. expo Morphol. 8: 198- 215.
Yamashita, O. and Hasegawa, K., 1974. Mobilization of carbohydrates in tissue of female
silkworm, Bombyx mori, during metamorphosis. J. Insect Physiol. 20: 1749-1760.
Yamauchi H., Kurihara, M., and Miya, K., 1981. E1ectrone microscope studies on theoogenesis of the silkworm, Bombyx mori L. IV. Ultrastructural changes of the nurse
chamber. J. Fac. Agr., Iwate Univ.15: 155-174.
_ _ _ _ _ , and Yoshitake, N., 1984. Formation and ultrastructure of the micropylar
apparatus in Bombyx mori ovarian follicles. J. Morphol. 179: 47-58.

Author's address:

Prof. K. Miya,
Laboratory of Applied Entomology,
Faculty of Agriculture,
Iwate University, Morioka 020, Japan