OPTIMISATION OF LABORATORY PROTOCOLS FOR THE HISTOLOGICAL STUDY OF TRIALEURODES VAPORARIORUM WESTWOOD, 1856 (HEMIPTERA: ALEYRODIDAE) GONADS – Part 1

"Many techniques for the histological study of the invertebrate gonads topography are described. For arthropods, a major drawback is the presence of the exoskeleton, which is a hardly permeable structure to the aqueous reagents with mechanical resistance also. Therefore, use of specific reagents and techniques, adapted for the study of their internal structures is a must. Several methods have been tested in this study like aqueous topographical fixation solutions based on picric acid (Bouin), mercury (II) chloride („Susa” Heidenhain) as well as alcoholic ones, picric acid (Duboscq-Brasil), mercury (II) chloride (Apathy) or acetic acid (Carnoy II) based. For the i) dehydration methods using absolute ethanol or 2-propanol, and ii) embedding ones the following methods were tested: paraffin with benzene, tert-butanol or pyridine as intermediary solvent (Gabe), paraffincelloidin double inclusion with diethyl ether: ethanol (1:1) as solvent (Pfuhl). After embedding and casting the paraffin blocks, these were cut at 5-10μ, the section ribbons were spread on distilled water and glued on slides with glycerol-albumine Mayer. For the double-embedded material, the sections were glued with Ruyter’s solution, with or without application of collodion. Heidenhain’s „Azan”, Mann-Dominici, Van Gieson and Gabe staining methods were used. For permanent slides, natural Canada balsam or artificial one “Caedax” were dissolved in xylene (mixture of isomers). Several procedures were tested for fixing solution, intermediary solvent, dehydrating, embedding and staining. The aim of this study was to optimise an efficient method in terms of results and reproducibility. Here, one of the successful methods is detailed (Heidenhain’s „Susa” fixation, ethanol dehydrating, paraffin embedding and Heidenhain’s „Azan” staining), to be followed by a series of optimized methods in future articles. The results obtained are reproducible, allowing the investigation methods of the structural modification of the white fly gonads induced by the chemical or biological control methods standardization. "