Sulfur amino acid requirements of larvae of sitophilus oryzae (coleoptera: Curculionidae)

Abstract

1. 1. Larvae of the rice weevil, Sitophilus oryzae, had an absolute dietary requirement for l-methionine whereas l-cystine was not required for larval growth and development. 2. 2. l-cystine and l-homocystine spared suboptimal levels of l-methionine and the addition of l-cystathionine always improved the rate of larval development providing nutritional evidence for the presence of the cystathionine pathway in this species. 3. 3. Sitophilus oryzae utilized methionyl-amino acid peptides in lieu of dietary l-methionine and also utilized d-methionine but not as efficiently as l-methionine. 4. 4. Inorganic sulfate, in the form of MgSO 4, did not replace l-methionine nor did it spare suboptimal levels of l-methionine. 5. 5. The use of chlortetracycline in the amino acid diet to remove the symbiotic bacteria present in S. oryzae was not successful; concentrations that resulted in decreased numbers of bacteria resulted in larval and pupal mortality whereas concentrations that did not cause mortality did not remove the bacteria. As a result, the possible role of the symbiote in the metabolism of the sulfur amino acids was not determined.