Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)



Committee Chair(s)

William A. Brindley


William A. Brindley


Raymond T. Sanders


Ivan G. Palmblad


Vincent J. Tepedino


Elizabeth A. Boeker


Peter E. Wagner


The esterases and glutathione S-transferases of a solitary bee, Megachile rotundata (Fab.) (Hymenoptera: Megachilidae), the alfalfa leafcutting bee, were characterized by electrophoresis, substrate specificity, and inhibition studies. Comparisons were made between ages, sexes, and life stages for several classes of substrates and their isomers: aromatic, aliphatic, and thio-esters. Two esterases were found to be allozymes and variable between individuals and sexes. Adults typically possess an esterase that hydrolyzes fluorescent substrates, an organophosphate insensitive esterase, and a series of type 'B' esterases that are very sensitive to organophosphate inhibition. Electrophoretic patterns are different between adults and immatures and are probably related to differences in niche. Differences in substrate specificities, electrophoretic forms, and activities between the sexes is likely a function of reproduction and the fact that females are solely responsible for nest construction. Esterases not only function in detoxication but may have a raison d'etre in various aspects of nest, cell, and cocoon construction. Both esterase and glutathione S-transferase activity decrease with age, but decreases in male activity are significantly greater than in females. Km and Vmax were determined for p-nitrophenylacetate using a mixture of female esterases, and the inhibition constants and mechanisms were determined for four organophosphorus compounds. Their toxicities, ranging from greatest to least, were naled > paraoxon > trichlorfon > oxydemeton methyl. Glutathione S-transferase activity was also assayed over a range of natural product inhibitors (chalcones, flavones) and an herbicide (tridiphane). The alfalfa leafcutting bee is a better detoxifier than the honey bee, but how it, or any other pollinator, fits into plant allelochemic - insect herbivore theory is unclear.



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