Occurrence and Function of the Provisional Embryonic Cuticle of a Lepidopteran

Sharan, R. K.

doi:10.1038/1871040a0

Cited by 1 publication

(1 citation statement)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The deposition of the larval cuticle has been described in the embryo of Drosophila melanogaster (Hilman and Lesnik, 1970), but it remains unclear whether or not embryonic cuticle(s) is (are) formed prior to it. On grounds of light microscopical observations, "provisional embryonic cuticle(s)" were described in the coleopteran Tenebrio molitor (Sharan, 1959), and the lepidopterans Chilo suppressalis (Okada, 1960) and Hyalophora cecropia (Mueller and Bucklin, 1965). So far, the present findings in Manduca sexta are the only ones that can be compared with the hemimetabolous species.…”

Section: Secretion Of Cuticles and Membranes By The Embryonic Integumentmentioning

confidence: 99%

Embryonic integument and “molts” in manduca sexta (insecta, lepidoptera)

Ziese

Dorn

2002

Journal of Morphology

View full text Add to dashboard Cite

In Manduca sexta the germ band is formed 12 h post-oviposition (p.o.) (=10% development completed) and is located above the yolk at the egg surface. The cells show a polar organization. They are engaged in the uptake and degradation of yolk globules, pinched off from the yolk cells. This process can be observed in the integumental cells during the first growth phase of the embryo that lasts until "katatrepsis," an embryonic movement that takes place at 40% development completed. At 37% development completed, the ectoderm deposits a thin membrane at its apical surface, the first embryonic membrane, which detaches immediately before katatrepsis. The second period of embryonic growth--from katatrepsis to 84 h p.o. (70% development completed)--starts with the deposition of a second embryonic membrane that is somewhat thicker than the first one and shows a trilaminar, cuticulin-like structure. Whereas the apical cell surface is largely smooth during the deposition of the first embryonic membrane, it forms microvilli during deposition of the second one. At the same time, uptake of formed yolk material ceases and the epidermal cells now contain clusters of mitochondria below the apical surface. Rough endoplasmic reticulum (RER) increases in the perinuclear region. The second embryonic membrane detaches about 63 h p.o. At 69 h p.o., a new generation of microvilli forms and islands of a typical cuticulin layer indicate the onset of the deposition of the larval cuticle. The third growth phase is characterized by a steady increase in the embryo length, the deposition of the larval procuticle, and by cuticular tanning at about 100 h p.o. Beginning at that stage, electron-lucent vesicles aggregate below the epidermal surface and are apparently released below the larval cuticle. Manduca sexta is the first holometabolous insect in which the deposition of embryonic membranes and cuticles has been examined by electron microscopy. In correspondence with hemimetabolous insects, the embryo of M. sexta secretes three covers at approximately the same developmental stage. A marked difference: the second embryonic cover, which in Hemimetabola clearly exhibits a cuticular organization, has instead a membranous, cuticulin-like structure. We see the difference as the result of an evolutionary reductional process promoted by the redundancy of embryonic covers in the egg shell. Embryonic "molts" also occur in noninsect arthropods; their phylogenetical aspects are discussed.

show abstract

Section: Secretion Of Cuticles and Membranes By The Embryonic Integumentmentioning

confidence: 99%