الفهرس 
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Abstract
The Desert Locust S. gregaria (Forskal) is one of the most serious pests of crops. Therefore, it is necessary to prevent the spread and migration of these swarms in order to avoid their damage. However, the unconscious use of chemical pesticides in the control caused damage to the environment and humans. So, the current study was designed to evaluate the effect of chitin synthesis inhibitor (lufenuron) and rice bran extract (waste product) on embryonic development in the desert locust eggs as alternative agents that are safer for the environment and humans. The most important results obtained can be summarized as follows:
1. Biological effects:
Feeding application of different concentrations of lufenuron (25, 50, 100, 200 ppm) and rice bran extract (5, 10, 15, 20 x 103 ppm) against one day old of the 5th nymphal instar of S. gregaria females caused failure of ecdysis to adults and adult mortality, these effects increased significantly with the increase of tested compound concentrations, also a significant prolongation in the average duration of the treated 5th nymphs with lufenuron and rice bran extract comparing with the control.
In addition, lufenuron and rice bran extract treatment induced morphological aberrations, the most of adults which emerged have malformed wings, antennae and legs, sometimes the resulting adults failed in completely getting rid the last nymphal exuvia and unable to fly and move, some maturated females could not put their eggs in the sand but they laid them on the surface, so these eggs could not hatch.
On the other hand, the treatment of the newly moulted 5th nymphal instar of S. gregaria females with LC50 of lufenuron and rice bran extract induced a significant reduction in the average of oviposition period, life span of adults females, the total number of egg pods /female, the total number of eggs /pod, the percentage of fertility, and a significant prolongation in the pre oviposition period.
2. Biochemical effects:
Quantitative and qualitative analysis of the protein and determination of the total amount of DNA were studied to record the changes in protein content and the amount of DNA during embryonic development in normal desert locust eggs and affected eggs (which produced from females treated as one day old of the 5th nymphal instars with LC50 of lufenuron and rice bran extract) as an indicator of the effect of these factors on the biological processes and building the different tissues of embryo.
2.1. Quantitative determination of protein:
The results showed that the total protein content of normal eggs collected at 0 day old was (81.07 mg protein/gm eggs), after one day of oviposition increased significantly to (93.80 mg protein/ gm eggs). Then the protein content significantly declined sharply during the early incubation period (blastoderm, gastrulation, and the beginning of organogenesis stages) to become (38.74 mg protein/gm eggs) in the 4th day post oviposition (pop), the protein content increased significantly in the 7th, 11th & 12th days (pop) reaching (50.80, 46.77 & 73.19 mg protein /gm eggs) respectively, but it decreased significantly comparing with 0 day (pop).
Lufenuron affected eggs have significant reduction (p<0.05) in total protein content after the 0, 1st and 12th days of oviposition compared normal eggs. On other hand, the total protein increased significantly (p<0.05) at 4th & 7th days of oviposition, compared with normal eggs. At the 11th day of oviposition, there was no significant difference between control and lufenuron treatment.
The total protein content in rice bran extract affected eggs increased significantly (p<0.05) at 0 & 4th days old, compared with normal eggs. While the total protein content decreased significantly (p<0.05) after 1, 11 and 12 days of oviposition compared with normal eggs. At the 7th day of oviposition, there was no significant difference in total protein.
2.2. Qualitative determination of protein:
The changes in the protein patterns of electrophoresis of affected eggs by the treatment of one day old fifth nymphal instar of S. gregaria females with LC50 of lufenuron and rice bran extract compared with control normal eggs were studied during the embryonic stages.
In 0 day old eggs, control protein was separated by 12 types of molecular weights (13-250 kDa), while the eggs affected by the lufenuron and rice bran extract treatment were separated into (14 and 12) types of proteins with molecular weights (13-275 KDa and 13-325 KDa), respectively.
At one day old eggs , (12, 10 &14) types of protein bands with MWs (13- 325 kDa), (13- 115.3 kDa) and (12- 142.3 kDa) for (C) eggs and (L) & (R) affected eggs, respectively.
After four days of oviposition, the protein fractions were separated into 27 protein banding patterns fluctuated from 12 - 14 types of protein with molecular weights (12- 142.3 kDa), (13- 325 kDa) and (13- 325 kDa) for control and (L4) & (R4) treatment, respectively.
At 7 days old eggs, (11, 10 and 11) types of protein with molecular weights (12- 296.4 kDa), (12- 277.2 KDa), and (12- 277.2 kDa) for (C7) , (L7) and (R7) respectively.
In 11 days old eggs, (10, 11 and 13) types of protein with molecular weights (12 - 272.2 kDa) for normal eggs, (13 - 272.2 kDa) for lufenuron affected eggs, and (13 - 272.2 kDa ) for rice bran extract affected eggs.
After 12 days of oviposition, (12, 12, and 12) types of protein with molecular weights (12 - 280 kDa), (14 - 272.2 KDa) and (12 - 272.2 kDa) for normal eggs, lufenuron affected eggs, and rice bran extract affected eggs, respectively.
2.3. The level of DNA content:
At control, DNA level at 0 day old eggs, which was (20.4 µg /100 mg eggs) exhibited a significant increase during further embryonic development. The DNA concentration reached the highest level in the eggs of the 4th and 7th days old which recorded (44.2 µg/100 mg eggs & 42.3 µg/100 mg eggs), respectively. The 1st, 11th and 12th days old control eggs, showed a significant increase which recorded (35.5 µg /100 mg eggs, 30.9 µg/100 mg eggs & 38.7µg /100 mg eggs), respectively.
In lufenuron affected eggs, the DNA level decreased significantly in 0, 1 and 7 days (pop) and increased significantly in 4, 11 and 12 days (pop) compared with normal eggs. While it decreased significantly in 7 and 12 days (pop) (except the 4th day pop had no significant reduction) and increased significantly in 0, 1 and 11 days (pop) for rice bran extract affected eggs compared with normal eggs.
3. Histological studies of embryogenesis :
In the present study, histological sections and electron micrograph of eggs were examined as early as (0-5 hrs) after oviposition, to describe the structure and cleavage of the zygote. The major stages ”namely” blastoderm formation, gastrulation, segmentation and organogenesis were studied.
Cleavage started about 5 hrs post oviposition (pop) and is indicated by presence of cleavage nuclei. Cleavage nuclei increased in number by mitotic division until the blastoderm formation at 1 day (pop).
At the same time, dark granules begin to appear in the periplasm at the posterior pole of the egg forming pole cells. Some of cleavage nuclei migrate back into yolk as secondary vitellophages.
At about 2 days (pop), the blastoderm thickens forming the germ band. The germ band at this stage is differentiated into 2 layers of ectodermal and mesodermal cells. By the end of 2 days (pop) the embryonic envelopes, amnion and serosa are completed. At 3 days (pop), segmentation of the inner layer forming the head and thorax segments (mouth parts and three thoracic segments). The stomodeaum did not invaginate before presumptive anterior midgut rudiment cells, but they nearly invaginate at the same time. By 4 days (pop) the eye could be noticed and the brain appeared as two ganglionic masses separated by an esophagus. The dorsal ganglion is the superaesophageal ganglion. The ventral ganglion is a subesophageal ganglion. By 5 days (pop) trachea was noticed. The brain appears as 2 large interconnect cerebral lobes which enwrapped by a neurilemma.
4. Histopathological studies:
In both treatments, the most affected organs during the embryonic development stages were the brain and the alimentary canals. Eggs of 2 days old resulted from lufenuron treatment showed warped chorion, thinner & detached serosa and lysis of ooplasm. Some embryos were blocked at germ band formation. At 5 days old eggs, ruptured chorion, lysis of midgut yolk granules and degeneration of epithelial cells at both midgut & hindgut are observed. Also the crop structure appeared atrophied in the size. The brain become compressed and did not differentiate into known basic structure.
Rice bran extract affected eggs showed blocked development of some embryos at the cleavage stage. Eggs had lysis of yolk granules and disintegration of their content. At 5 days old affected eggs, midgut epithelial cells seem to be degenerated, yolk granules were deteriorated and dispersed, and some embryos had shrinkage & asymmetrical compound eyes. The brain loses its morphic nature, and appeared compressed & lysed.
5. Ultrastructural studies:
Electron micrograph of newly deposited eggs showed that, the chorion consists of several easily distinguishable layers. The inner one is endochorion and the outer exochorion. The vitelline membrane is the inner most chorionic layer.
In electron micrographs of 30 hrs old eggs of S. gregaria, cleavage nuclei of different shapes can be observed migrating to the periphery of the egg. Secondary vitellophages and primary vitellophage were also observed. After a set of mitotic division, the blastoderm cells arranged in a linear manner adjacent to stripe formed of microtubules.
Electron micrographs of 5 hrs old eggs affected of treatment with LC50 of lufenuron showed signs of deterioration, chorion exhibit abnormal appearance, some cleavage nuclei have abnormal appearance and short pattern of microtubules is obvious. Eggs affected of treatment with LC50 of rice bran extract showed signs of deterioration including vacuolation and lysis of cell components leaving cavities within the ooplasm. Blastoderm is disintegrated and failed to arrange. Vacuolated cytoplasm and irregular shape of cleavage nuclei were observed in both treatment.