Int. J. Insect Morphol. & EmbryoL, Vol. 16, No. 1, pp. 91 to 94, 1987. 0020-7322/87 $3.00 + .00 Printed in Great Britain. Pergamon Journals Ltd.

SCIENTIFIC NOTE

PRIMARY D, ORSAL ORGAN IN EGGS OF PARNASSIUS GLACIALIS BUTLER A N D LUEHDORFIA JAPONICA LEECH

(LEPIDOPTERA • PAPILIONIDAE)

MASAHIRO TANAKA

Kan6 High School, Kan6 Nany6-ch6, Gifu 500, Japan

(Accepted 27 August 1986)

In Pterygota, the primary dorsal organs are found in the eggs of Brachyrhinus ligustici, Donacia crassipes, Euryope terminalis and Corynodes pusis (Coleoptera), Apis mellifica (Hymenoptera), Sciara coprophila (Diptera) and Endromis versicolora (Lepidoptera) (Johannsen and Butt, 1941). Although the embryogenesis of the Lepidoptera has beea well studied, only one paper concerning the primary dorsal organ of the moth, E. versicolora, has been published. This paper presents evidence for the formation of primary dorsal organs in Parnassius glacialis Butler and Luehdo,,fia japonica Leech.

The eggs of P. gd'acialis and L. japonica were obtained from pregnant females captured in Gifu Prefecture, Japan; the former were obtained during May of 1981 - 1984, and the latter during April of 1982- 1984. The eggs were fixed in Carnoy's fluid, for 30-40 min, or alcoholic Bouin's fluid, for 60 min. After fixation, the eggs, whose choria were removed, were dehydrated and embedded in paraffin. Sections, 8 #m thick were cut and stained with Delafield's hematoxyiin and eosin.

The duration of developmental period, from oviposition to completion of the fully grown embryo, of P. glacialis was about 24 days at 20-23°C, and that of L. japonica was about 14 days at 12- 15°C. Table 1 shows the chronology of early embryonic development of these species.

At about 20 hr after oviposition in P. glacialis and about 18 hr in L. japonica, the eggs develop into the cellular blastoderm stage, ti~at is, the whole surface of the egg is covered with the uniform blastoderm of one-cell layer, about 15/~m in thickness (Fig. 2). The yolk-mass is surrounded by a thin yolk plasmalemma and some of the yolk nuclei remain in the yolk.

In P. glacialis, immediately before the formation of ventral plate, the blastoderm cells, occupying the anterior region of the egg, increase in size, and then the cell boundaries disappear gradually. At the same time, the nuclei of enlarged blastoderm cells grow very large, 2 or more times in size of those of other cells, and these enlarged blastoderm cells divide amitotically, while the rest of other blastoderm cells remains unchanged. The cells resulting from amitotic divisions aggregate and form themselves into a discoidal syncytial cell-mass, lining the inner surface of the blastderm ir the anterior region of the egg (Fig. 4). This structure closely resembles the primary dorsal organ of Donacia crassipes (Hirchier, 1909), Sciara coprophila (Du Bois, 1932), and Brachyrhinus ligustici (Butt, 1936) or to the cephalo-dorsal body of Apis mellifica (Nelson, 1915). Therefore, I consider this peculiar cell- mass as the primary dorsal organ.

The lens-shaped primary dorsal organ of P. glacialis is composed of one or 2 cell-layers, deeply stained with hematoxylin and associated with the blastoderm cells. Each cell of the organ contains many yolk granules of varying size and its large elliptical nucleus, about 22 × 15 #m in size, contains many chromatin filaments.

In L. japonica, after the completion of cellular blastoderm, the blastoderm cells, situated at the anterior pole of the egg, increase in size, and then divide to form a cell-mass corresponding to the primary dorsal organ. The time and manner of formation of the dorsal organ in this butterfly are very similar to those of P. glacialis, but size and form are not similar.

In both species, at the next step of development, the extra-embryonic area becomes somewhat flattened to differentiate into the rudiment of serosa. During this course, the primary dorsal organ becomes more distinct, just under the dew.~loping serosa in the anterior region of the egg and the cell boundaries become clear. When the ventral plate i,; completely covered with the serosa, the primary dorsal organ is distinguished from other embryonic parts as an independent tissue, attaining its maximum size, closely adhering to the serosal cells (Figs. 5; 8; 9). In the light microscopy, the mature dorsal organ does not have a glandular appearance as observed in the organs of Collembola (Claypole, 1898; Philiptschenko, 1912; Tiegs, 1942a; Jura, 1965, 1967) and Campodea fragilis (Tiegs, 1942b); the ultrastructure of the organ will be examined in future. The cells of the dorsal organ of P. glacialis are arranged into one or 2 layers and those of L. japonica into 3 or more irregular rows (Fig. 8).

91

9 2 S c i e n t i f i c N o t e

A P PDO C[ )O SE

o ". : " " ' . ' . ' : . °'. *; ' . ." " " : ~ ' !.' . ; ' . . . . ' . ' . ' . ' . + . . : ' , . ' . ' ; ' : " • , , '+ .

; ' : " " ' : " ' " " ' ' ' ' ' ~ ' ' " ' " ' ' ' ' " C D ~

. • . : ; , .~ ~ S ? ..... ;.......... ..... .;.. . ;.: --;~\

" + " " . ' . : . . ' ~ " . ' . e ' , " : : • , ' . , I - • ". • , , " . ' l B

p p YN ~

" ::"" DC

~ yI N YG ~ ~ "

.+ . .:+:' "~.. ,+',~. : :,':., .: .':+~ ~ : .+.. .. :,,+.+,:

Y N

PDO

S E . . . . . . S E

Scientific Note 93

TABLE 1. TIME TABLE OF THE EARLY EMBRYONIC DEVELOPMENT OF Parnassius glacialis AND Luehdorfia japonica

Approximate age of eggs (hr)

P. glacialis L. japonica State of development ( 2 0 - 2 3 ° C ) ( 1 2 - 15°C)

Maturat ion and fertilization Cleavage Format ion of blastoderm and appearance of primary

dorsal organ Format ion of ventral plate and serosa Format ion of germ band Format ion of inner layer Segmentation of inner layer Disappearance of primary dorsal organ

0 - 1 0 - 1 2 - 1 6 2 - 1 4

17 - 20 15 - 18 21 - 25 19 - 23 26 - 35 24 - 28 70 - 80 40 - 45

9 0 - 96 48 - 55

The mature primar2¢ dorsal organ retains its structure for a while, but it begins to degenerate at the time when the germ band deeply sinks into the yolk. With the lapse of time, degenerating cells of the organ gradually lose the affinity for dyes, and the minute chromat in granules converge into one or more large globules (Fig. 6), and then the nuclear membrane disappears (Fig. 7).

In the eggs of Coleoptera (Hirschler, 1909, in Donacia; Paterson, 1931, in Euryope; 1936, in Corynodes; Butt, 1936, in Brachyrhinus), Hymenoptera (Nelson, 1912, 1915, in Apis) and Diptera (Du Bois, 1932, in Sciara), the primary dorsal organ appears as a mass of cells invaginating or projecting into the yolk on the dorsal side of the blastoderm or the rudimentary serosa. Though the location and the manner of formation of the primary dorsal organs in P. giacialis and L. japonica differ f rom those of Coleoptera, Hymenoptera , and Diptera, their origin, general structure and period of their existence closely resemble those o f these orders. Consequently, it is reasonable to consider the primary dorsal organ in P. glacialis and L. japonica as homologous to those in other pterygote insects.

Acknowledgements--I express my cordial thanks to Professor Dr H. Ando, Sugadaira Montane Research Center of Tsukuba University, and Professor Dr C. Jura, Jagiellonian University of Poland, for their comments and for critical reading of the manuscript .

REFERENCES

Bwyr, F. H. 1936. The early embryological development of the parthenogenetic alfalfa snout beetle, Brachyrhinus ligustici L. Ann. Entomol. Soc. Amer. 29:1 - 13.

CLAVPOLE, A. M. 1898. The embryology and o6genesis of Anurida maritima. J. Morphol. 14: 2 1 9 - 300. DE BoIs, A. M. 1932. A contribution to the embryology of Sciara. J. Morphol. 54:161 - 9 2 . HIRSCHLER, J. 1909. Die Embryonalentwicklung von Donacia crassipes L. Z. Wiss. Zool. 92: 6 2 7 - 7 4 4 . JOHANNSEN, O. A. and F. H. BUTT. 1941. Embryology of Insects and Myriapods. McGraw-Hill, New York. JURA, C. 1965. Embryonic development of Tetradontophora bielanensis (Waga) (Collembola) f rom oviposition

till germ band formation. Acta Biol. Cracow. Zool. 8:141 - 57.

FIGS. 1 -- 9.

FIGS. 1 -- 7. Format ion of primary dorsal organ in Parnassius glacialis. 1. Section of 25 hr-old egg. (Bar = 300 #mp. 2. Section through anterior pole of egg, at 20 hr after oviposition. (Bar = 50/~m). 3 - 7. Successive stages o f dorsal organ formation. 3, 4: At slightly later stage than that shown in Fig. 2. 5: At same stage shown in Fig. 1. 6: At 45 hr after oviposition. 7" At 60 hr after oviposition.

FIG. 8. Longitudinal section through anterior pole of egg of Luehdorfia japonica, at 30 hr after oviposition (Bar = 30/zm).

FIG. 9. Longitudinal section through anterior pole of egg of Parnassius glacialis, at 25 hr after oviposition. (Bar = 50 #m).

AP = anterior pole of egg; BC = blastoderm cell; CDO = cell of primary dorsal organ; DC = degenerating cell of primary dorsal organ; EBC = enlarged blastoderm cell; GB = germ band; NPD = nucleus of primary dorsal organ; NSE = nucleus of serosal cell; PDO = primary dorsal organ; PP = postericr pole of egg; SE = serosa; VM = vitelline membrane; YG = yolk granule; YN =

yolk nucleus; YP = yolk plasmalemma.

94 Scientific Note

JURA, C. 1967. The significance and function of the primary dorsal organ in embryonic development of Tetradontophora bielanensis (Waga) (Collembola). Acta Biol. Cracow Zool. 10:301 - 11.

NELSON, J. A. 1912. A peculiar structure in the embryo of the honey bee. Science. (Wash., D.C.) 35: 475. NELSON, J. A. 1915. The Embryology o f the Honey Bee. Princeton University Press, Princeton. PATERSON, N. F. 1931. A contribution to the embryological development of Euryope terminalis Baly, (Coleoptera,

Phytophaga, Chrysomelidae). Part I: The early embryonic development. South African J. Sci. 28:344 - 71. PATERSON, N. F. 1936. Observations on the embryology of Corynodes pusis (Coleoptera, Chrysoelidae). Q. J.

Microsc. ScL 78:91 - 132. PHILLIPTSCHENKO, J. 1912. Beitr~ige zur Kenntnis der Apterygoten. III. Die Embryonalentwicklung von lsotoma

cinerea. Z. Wiss. Zool. 103: 519-660. TInGs, O. W. 1942a. The "dorsal organ" of collembolan embryos. Q. J. Microsc. Sci. 83: 153-70. TIEGS, O. W. 1942b. The "dorsal organ" of the embryo of Campodea. Q. J. Microsc. Sci. 84:35-47.