Serosal Cuticle Research Articles

The embryology of Lytta viridana LeConte (Coleoptera: Meloidae). VI. The appendiculate, 72-h embryo

The embryology of L. viridana is continued to the 72-h stage, when a little over one-quarter of the embryonic period has elapsed. The origin of the segmental appendages, further development of the coelomic sacs and enteron rudiments, formation of the nerve ganglia, appearance of tracheal invaginations, migration of the germ cells, and secretion of the serosal cuticle are described. The embryonic origin of the labrum is preoral and preantennal, that of the antennae and deutocerebrum paraoral. The tritocerebrum is formed in a well-defined intercalary segment. The ventral musculature of the stomodaeum arises from intercalary mesoderm, the dorsal and lateral musculature from labral mesoderm. The outer sheaths of the Malpighian tubules are formed from mesoderm of the 10th abdominal segment, the musculature of the proctodaeum from the 11th segment. The pleuropodia differentiate rapidly and begin secreting. The germ cell rudiment subdivides into three to six pairs of germ cell clusters, which become arranged segmentally.

The Embryonic Development of Tribolium confusum1,2

The basic embryogeny is described and a chronology of developmental events at 25.5±1°C is presented. The fundamental developmental pattern is not unusual for a beetle. The more notable events and structures include an apparently sperm-filled tubular structure (possibly a micropyle) found on the chorion of some eggs. Peripheral energids of the presumptive blastoderm exhibit annular waves of mitoses. The mesenteron develops from a pair of posterior rudiments. An eosinophilic serosa secretes a thick external cuticle. The well-developed pleuropodia are believed to produce secretions that lyse the serosa and the serosal cuticle. Centrifuged eggs develop, indicating that the embryos have some regulative ability.

The egg shell of the house cricket (Acheta domesticus): an electronmicroscope study.

ABSTRACT Consecutive changes in two discrete layers of the egg shell of the house cricket, Acheta domesticus, have been claimed to control the uptake of water by the eggs. The development of the shell has been re-investigated with the electron microscope by examination of eggs at different stages of embryogenesis and of ovarioles containing oocytes at various stages of maturity. It is confirmed that fragmentation of the maternal epicuticle and deposition and resorption of the serosal cuticle are the only apparent changes in the shell during development. The existence of a serosal epicuticle is confirmed and a distinction is made between the serosal epicuticle and the vitelline membrane. Previously unreported features of the shell are (i) an outer zone of the maternal endocuticle which seems to be the most stable part of the maternal cuticle, (ii) a microlaminar organization within the scales of the maternal epicuticle, (iii) a vitelline membrane containing specialized regions, which remains distinct from the serosal epicuticle throughout development, and (iv) the osmiophilic character of the serosal epicuticle, its complex fine structure and its origin. Observations on eggs which had just begun to absorb water allow us to suggest that fragmentation involves a shrinkage of the material of which the scales are composed.

THE SURFACE STRUCTURE OF VARIOUS LAYERS OF THE HOUSE CRICKET EGGSHELL AS SEEN IN THE SCANNING ELECTRON MICROSCOPE

The scanning electron microscope has been used to look at the surfaces of various layers of the house cricket eggshell during development. The maternal shell of the ovarian and new-laid egg, the vitelline membrane, and the serosal cuticle have been examined.

Identification, estimation, and localization of catecholamines in eggs of the house cricket, Acheta domesticus (L.)

DOPA, DOPamine, and N-acetyl DOPamine have been identified as the only polyphenols to occur during embryogenesis of Acheta domesticus. The quantitative variation and histochemical localization of these substances indicate that they are involved in the development of the serosal cuticle. In view of the absence of melanogenesis during normal development and the probability that a tanning reaction is involved in the termination of the first phase of water absorption, it is suggested that N-acetyl DOPamine is the precursor of a tanning quinone. The other phenols are thought to be intermediates in its biogenesis. A relatively large amount of free DOPamine has been found in the extra-embryonic fluid of post-catatrepsis eggs. This is thought to originate from the digestion of the serosa and serosal cuticle, and by de-acetylation of N-acetyl DOPamine through the action of the hatching enzymes.

The egg of Tetrix (Tetrigidae, Orthoptera), with a discussion on the probable significance of the anterior horn

ABSTRACT The structure of the egg-wall of Tetrix vittata and the changes that occur in it during development are described. The chorion has a hollow layer held open by struts and freely permeable to both air and water. At the posterior end the struts become finer and the chorion then resembles that of the Acrididae. A thick serosal cuticle develops with a hydropyle at the posterior end. This cuticle is dissolved before hatching. The egg takes up water and increases its volume during development. There is a long horn with a hollow core at the anterior end of the egg. This horn is entirely chorionic and appears to provide the egg with an expansion chamber.

TYROSINASE AND THE STRUCTURE OF THE EGG SHELL OF ACHETA DOMESTICUS (L.)

The endochorion of the egg of the house cricket, Acheta domesticus (L.), is composed, in part, of imbricated scales. These scales are revealed in the pattern of melanization of the chorion that results on immersing eggs in aqueous tyrosine before they have begun to absorb water. Such treatment prevents the normal breaking up of the endochorion, but does not prevent water absorption or normal development of the eggs. Failure of the endochorion to fragment in the usual way affects the structure of the underlying lipoid layer of the serosal cuticle.

PERMEABILITY OF THE EGG SHELL OF ACHETA DOMESTICUS (L.), AND THE FATE OF THE VITELLINE MEMBRANE

The egg shell of Acheta domesticus (L.) is permeable to dyes in the interval between the fragmentation of the endochorion and the secretion of the lipoid layer of the serosal cuticle, i.e. at the beginning of the water absorption period. The vitelline membrane persists throughout the whole of embryonic development, lying between the aforementioned layers from the beginning of water absorption.

STRUCTURE AND FUNCTION OF THE EGG SHELL AS RELATED TO WATER ABSORPTION BY THE EGGS OF ACHETA DOMESTICUS (L.)

The shell of the newly laid egg of Acheta domesticus (L.) consists of the chorion, in which two layers can be distinguished: an outer exochorion, about 2.5 μ thick; and an inner endochorion, about 0.4 μ thick, which contains lipoid and a tyrosinase. At about the time water absorption begins, the endochorion breaks up, in a more or less regular way, into many small fragments; as a result, spaces are created in the endochorion, and it seems probable that it is this structural change which permits water to be absorbed by the egg. The breaking up of the endochorion appears to be due to phenolic tanning. Also at about the time water absorption begins, the newly formed serosa begins to lay down the serosal cuticle, first an outer lipoid layer, about 0.4 μ thick, which contains a tyrosinase; and then an inner layer, which is laid down continuously while the serosa exists, and which reaches, at the time water absorption ends, a maximum thickness of 8–10 μ. Thereafter the inner layer of the serosal cuticle is steadily resorbed up to the time the egg is hatched, and the vacated shell consists only of the chorion and the lipoid layer of the serosal cuticle. Water absorption appears to be brought to an end by the phenolic tanning of the lipoid layer of the serosal cuticle.