Physico-chemical characteristics of waxes produced by the African honeybee, apis mellifera scutellata.

[摘要] In this dissertation the physical and chemical alterations induced bymastication and manipulation of wax by the worker bee in honeycombconstruction, and the subsequent contribution afforded the structural integrityof the nest, are elucidated.In comb building, the freshly secreted wax scales are mandibulated togetherwith a frothy salivary emulsion, and added piece-meal to form honeycomb.Textural modifications were revealed using X-ray crystallography. While virginscale wax is highly structured, with the crystallites aligned approximatelyperpendicular to the planar surface, comb wax has a random crystallographicarrangement. This reflects a disruption of the crystallite structure following themechanical insult of mastication. Chemical analyses included investigation ofboth lipid and proteinaceous elements. Lipid composition was evaluated byenzyme-catalyzed as well as thin-layer and gas-liquid chromatographicmethods. The results indicate a reduction in scale diacylglycerols with acorresponding increase in comb saturated monoaeylglycerols. Suchmodifications are highly suggestive of lipase activity within the salivaryaddition. The proteins of comb and scale wax were analyzedelectrophoretically, under reduced conditions. Each wax possesses uniquepolypeptide fractions, in addition to sharing common protein species, It isspeculated that those in common represent integral proteins, such as transportmolecules, while the disparities noted may be due to salivary enzymaticdegradation, or even glycosylation.The effects of these textural and chemical alterations on the mechanicalbehaviour of the waxes was assessed. Tensile tests were performed on avariety of scale and comb wax preparations over the range of temperatureslikely to impinge on the honeybee nest. These investigations reveal the specificstructural contributions made by each of the physico-chemical alterationsdescribed. Further, they demonstrate that while scales are ideal mouldingmaterials due to their high distensibility and low stiffness, the greaterresistance to deformation and lower potential for extension makes comb waxa superior structural material. The mechanical advantage for includingpropolis and cocoon silk within the comb structure was also investigated.Tensile testing indicates that the resultant composite material is structurallysuperior, largely due to the presence of silk reinforcement.

[发布机构] University of the Witwatersrand