Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2011
Publication Date: 6/1/2011
Citation: Yocum, G.D., Buckner, J.S., Fatland, C.L. 2011. A comparison of internal and external lipids of nondiapausing and diapause initiation phase adult Colorado potato beetles, Leptinotarsa decemlineata. Comparative Biochemistry and Physiology, Part B. 159(3):163-170. Interpretive Summary: The Colorado potato beetle, Leptinotarsa decemlineata (Say), is believed to have originated in southern Mexico and experienced a rapid range expansion beginning in the mid-1800s. L. decemlineata is now endemic in most of the potato growing regions in the northern hemisphere and is the major defoliator of potato in those regions. For an insect species to survive in any given geographic location, its life cycle must be tightly synchronized to all biotic and abiotic factors required for development and reproduction. Insects must also be able to survive predictable recurring periods of environmental stress, such as winter for temperate zone insects. Diapause is the chief physiological mechanism by which insects meet these two requirements for survival. Because of its central role enabling insect pests to survive and reproduce in a given area, an understanding of the mechanism of diapause is critical in the management of any agroecosystem. One of the chief characteristics of diapausing insects is the large metabolic reserves they accumulated prior to entering into diapause. These reserves need to be sufficient to last until the insect can resume feeding in the following spring. The chemical property of the reserves is also critical to insure the metabolic availability of the reserves under low-temperature conditions. In this investigation we characterized the lipid profiles of diapausing Colorado potato beetles and determined the major class of internal and external lipids.
Technical Abstract: The Colorado potato beetle, Leptinotarsa decemlineata, reared under diapause inducing conditions will emerge from the soil as an adult and enter the diapause initiation phase, a period where metabolic reserves are stockpiled before the beetles enter the nonfeeding diapause maintenance phase. Internal and external lipids were characterized during the diapause initiation phase (IP) and compared to the lipid profiles of nondiapausing adults. The primary internal lipids of both diapause IP and nondiapausing adults are triacylglycerols. Only trace amounts of internal lipids were detected in day 1 diapause IP adults. A dramatic increase in internal lipids was observed between day 7 to day 15 post-emergence in the diapause IP adults. The majority of the triacylglycerol isomers were identified as C50, C52 and C54 chain length by GC-MS. There were no observed differences in the isomeric distribution of the internal lipids between diapause IP and nondiapausing adults. External lipids were mainly methyl-branched alkanes containing a 25 to 53 carbon backbone. The quantity of external lipids increased from day 1 to day 7 post-emergence in both the diapause IP and nondiapausing adults, with the bulk of the increase occurring in the longer chain-length methylalkanes.