الفهرس 
Acknowledgements
MATERIALS AND METHODSOnly 14 pages are availabe for public view
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Abstract
Laboratory experiments were conducted to: (1) Evaluate the toxicity of selected common herbicides, acetochlor, pinoxaden, haloxyfop-p-ethyl, tralkoxydim, bispyribac-sodium, penoxsulam, quinclorac and bentazon in comparison with the pyrethroid insecticide deltamethrin against the early 4th instar larvae and pupae stages of C. pipiens in the laboratory, (2) Assess the predatory efficacy of Nile tilapia O. niloticus as a biological control tool against larvae and pupae of C. pipiens mosquito under laboratory condition, and (3) Investigate the toxicity effects of sub-lethal concentrations of selected common rice herbicides, acetochlor, halosulfuron-methyl, bispyribac-sodium, bensulfuron-methyl, quinclorac and bentazon on hematology and selected serum components of Nile tilapia fish.
Results were reported in accordance with the objectives outlined above as follows:
I. Toxicological Impacts of Some Herbicides and Deltamethrin on Larvae and Pupae of C. pipiens Mosquito under Laboratory conditions
1. Evaluation of the toxicity effects of some herbicides and deltamethrin insecticide on 4th instar larvae and pupae of C. pipiens under laboratory conditions
1.1. Toxicity impacts of eight selected herbicides (pinoxaden, haloxyfop-p- ethyl, tralkoxydim, bispyribac-sodium, penoxsulam, quinclorac, bentazon, and acetochlor) in comparison with a pyrethroid insecticide deltamethrin on the early fourth instar larvae of C. pipiens after 24, 48, and 72-h and on C. pipiens pupae after 24 and 48-h after exposure were detected in laboratory. All tested pesticides exhibited variable toxicity against the early 4th instar larvae and pupae of C. pipiens after exposure times. In addition, the toxicity of all pesticides against larvae and pupae of C. pipiens were increased drastically as exposure time increased especially after 72-h exposure for larvae and 48-h exposure for pupae.
1.2. Based on the estimated LC50 and LC90 values of the tested herbicides, results showed that deltamethrin insecticide was the most toxic pesticide against the 4th instar larvae and pupae of C. pipiens after exposure times followed by pinoxaden which
was the highest toxic herbicide against the 4th instar larvae and pupae of C. pipiens. Further, bispyribac-sodium, penoxsulam, tralkoxydim, haloxyfop-p-ethyl, and acetochlor exhibited moderate toxicity against the 4th instar larvae and pupae of C. pipiens after exposure time, while both bentazon and quinclorac were the least toxic compounds among the all tested pesticides on the 4th instar larvae of C. pipiens.
1.3. According to toxicity index values of the tested pesticides, for LC50 values, deltamethrin (100-fold) was more effective than all tested herbicides by 4.68-0.001- fold after 24-h exposure; by 2.19- 0.0001-fold, after 48-h exposure and by 0.174- 0.0002-fold after 72-h exposure for on the 4th instar larvae of C. pipiens, by 1.5 to 0.0004-fold after 24-h exposure and from 15.38 to 0.0003-fold after 48-h for pupae.
II. Evaluation of the predation potentiality of Nile tilapia (O. niloticus.) Juvenile on immature stages of C. pipiens L. under laboratory conditions
The predatory efficiency of Nile tilapia, O. niloticus juvenile was evaluated on the 3rd larvae and pupae of C. pipiens. mosquito under laboratory condition. The average daily consumptions of the Nile tilapia juvenile were 104.58±4.01 and 52.08±6.48 from the 3rd larvae and pupae of C. pipiens per day, with significant difference between them. Some factors have been found to effect on the predation potential of O. niloticus juvenile against the 3rd larvae and pupae of C. pipiens such as size of fish, time of predation, illumination time, and stages of prey.
1- Effect of light and darkness on the predatory efficiency of Nile tilapia fish on larvae and pupae of C. pipiens mosquito regardless of fish size
According to effect of light and darkness on prey consumption and regardless of the fish size, results indicated that the O. niloticus fish consumed in average 98.17±4.56 and 111.00±5.76 larvae/fish and 69.33±4.66 and 34.83±6.63 pupae/fish during the day time and night time, respectively.
2- Effect of fish size on the predatory efficiency against larvae and pupae of C. pipiens mosquito regardless of illumination condition
Fish size also affected the prey consumption, the average daily predation rate for the small O. niloticus sized fish (length 2.1-2.6 cm and weight 250-315 mg) and large size fish (length 2.5-3.2 cm and weight 365-420 mg) were 99.83±4.53 and 109.34±6.42 larvae/fish per day with no significantly difference between them and were 40.92±8.39 and 63.25±8.03 pupae/fish per day, with a significant different between them. Based on the daily consumption data, the large size of O. niloticus fishes devoured larger number of C. pipiens larvae and pupae than the small size fishes.
3- Effect of fish size and illumination condition (light and dark) on the predatory efficiency against larvae and pupae of C. pipiens mosquito
According to the effect of both fish size and illumination time (light and darkness time) on the predation potential of O. niloticus on the larvae and pupae of C. pipiens, results showed that the predation efficiency of small and large sized O. niloticus fish on 3rd larvae of C. pipiens was higher during the night time than the day time but both of them devoured more number of C. pipiens pupae during the day time than at the night time while in both cases the predation rates of fish during the night time and day time were increased as the size of Nile tilapia fish increased.
III. Toxicity Effects of Some Herbicides on Hematology and Serum Biochemistery in Juvenile of Nile Tilapia O. niloticus.
Exposure of O. niloticus juvenile to sub-lethal concentrations of acetochlor, bispyribac-sodium, bentazon, bensulfuron-methyl, halosulfuron-methyl, and quinclorac a common rice herbicides for 96 h resulted in important change in the hematological and biochemical variables of O. niloticus, as well as being gene toxicants to erythrocytes of the target species. As our knowledge, this is the first report on the toxicity effects of acetochlor, halosulfuron-methyl and bensulfuron-methyl on hematological and biochemical profiles of O. niloticus in the world.
1. Toxicity of some herbicides on O. niloticus hematological profile of blood
According to hematological profiles results indicated that the sub-lethal concentrations of acetochlor, bispyribac-sodium, bensulfuron-methyl, halosulfuron-
methyl and quinclorac caused significant reduction in erythrocyte count in exposed O. niloticus fish; acetochlor in hemoglobin level; acetochlor, bispyribac-sodium and halosulfuron-methyl in monocytes count; acetochlor, bispyribac-sodium and bensulfuron-methyl in eosinophils count; halosulfuron-methyl and bentazon in neutrophils count; and acetochlor, bispyribac-sodium and quinclorac in platelets count of fish exposed to herbicides compared to control group. In contrast, all tested herbicides induced significant increase in blood lymphocytes counts (except quinclorac) and in mean corpuscular volume (MCV) level (except both bensulfuron- methyl and quinclorac which observed non-significant increase) compared to untreated group. Based on the hematological results, acetochlor is considered the highest potent herbicides on hematological parameters of O. niloticus fish compared with others tested herbicides.
2. Toxicity of some herbicides on O. niloticus biochemical profile of blood
For biochemical profiles of O. niloticus, the results showed that a significant increase in cholesterol level in fish groups exposed to concentration of acetochlor, bispyribac-sodium, bensulfuron-methyl and quinclorac while other fish group exposed to concentrations of bentazon and halosulfuron-methyl observed non-significant increase in cholesterol level compared to unexposed fish. In fish group exposed to concentrations of acetochlor, bispyribac-sodium, bensulfuron-methyl and quinclorac showed non-significant increase in ceratin level but other fish group exposed to bentazon and halosulfuron-methyl showed significant decrease in ceratin level in comparison to the control group. Urea level was increased significantly in fish exposed to concentations of all tested herbicides except quinclorac which showed non- significant increment compared to the control fish group. In fish exposed to acetochlor concentration showed significant elevated in total protein level while fish exposed to bispyribac-sodium, bentazon, halosulfuron-methyl and quinclorac showed no significant elevation but the fish treated with bensulfuron-methyl induced no change in total protein level compared to control. Significant increase in levels of albumin, globulin and albumin/globulin ratio in fish group exposed to chronic concentrations of all tested herbicides except bentazon, halosulfuron-methyl and bensulfuron-methyl which showed non-significantly increase with only globulin as compared with control.
For liver enzymes, the activity of alkaline phosphatase (ALP) was increased significantly in fish group exposed to acetochlor, bispyribac-sodium, bentazon, bensulfuron-methyl and halosulfuron-methyl and non-significant increment only with quinclorac as compared to control. Alanine aminotransferase (ALT) level was increased significantly in fish exposed to acetochlor and bensulfuron-methyl, however, the fish group subjected to other tested showed no significant increase in activity of target enzyme relative to control group. There was also a significant elevate in the activity of aspartate aminotransferase (AST) in the fish treated with acetochlor whereas, the increase in the activity of this enzyme was no significant in the fish exposed to bispyribac-sodium, bentazon, bensulfuron-methyl and quinclorac. A reverse trend was detected in fish treated with halosulfuron-methyl which induced a non-significant decrease in the activity of aspartate aminotransferase in comparison to control. There was no significant elevation in serum glucose level in fish group exposed to chronic concentrations of all tested herbicides relative to unexposed fish group.
The blood smears of control fish showed normal structure of erythrocytes. The blood smear of exposed-herbicides showed poikilocytosis of erythrocytes (alteration of erythrocytes shape). The most effective herbicide wasacetochlor while the least effective one was bentazon