HAHN, DA; University of Florida: Characterization of hexameric storage proteins during development and reproduction in the flesh fly, Sarcophaga crassipalpis.

Unlike vertebrates, insects are capable of accumulating substantial amino acid reserves and do so primarily in the form of hexameric storage proteins. Documenting the allocation of amino acids to current utilization versus storage for later use is fundamental to understanding the regulation of nitrogen metabolism in insects. I have identified the major storage proteins in the flesh fly, Sarcophaga crassipalpis, and described their phenology during immature and reproductive development. S. crassipalpis contained two storage proteins, one homologous to the Larval Serum Protein-1 (scLSP-1) and one homologous to LSP-2 (scLSP-2) characterized in other flies. scLSP-1 was present in the hemolymph throughout the feeding phase of the third instar, after which it was taken up into the fat body upon wandering. Larvally-derived LSP-1 stores were primarily depleted during the larval-pupal transition and during pharate adult development, and were not detectable in adults. scLSP-2 was present in the hemolymph early during the third instar feeding stage but was taken up by the fat body prior to the onset of wandering and utilized during pupation and pharate adult development. scLSP-2 was also present in substantial amounts in the blood of adult females. While detectable in adult males, levels of scLSP-2 were significantly lower than in females. This suggests that scLSP-1 provides amino acid stores to support the significant tissue remodeling and growth that occurs during metamorphosis and pharate adult development. In contrast, the developmental profile and adult sex differences in scLSP-2 suggests roles in both development and reproduction. Future investigations will focus on understanding the role of these proteins in direct development, seasonal developmental arrest, and reproduction.