Chemistry, biochemistry, and physiology of insect cuticular lipids

Abstract

The chemistry, biochemistry, and physiology of insect cuticular lipids are reviewed. The types of components present in cuticular extracts are described with special emphasis on the occurrence and identification of the di-and trimethylalkanes and the newly discovered tetramethylalkanes. The methods used in the extraction of cuticular components are discussed, including recommendations to standardize procedures. The structural elucidation of methylalkanes, particularly the mass spectral interpretation of multi-methylbranched alkanes, is reviewed. The biosynthesis of cuticular lipids is discussed with emphasis on the hydrocarbon components, describing elongation reactions and the origin of the methyl branches. The effects of environment and development on cuticular lipids are reviewed.

The molecular physiology of increased egg desiccation resistance during diapause in the invasive mosquito,Aedes albopictus

“…We found that fatty acyl coA elongase transcripts were more abundant in mature oocyte tissue under diapause inducing SD conditions relative to diapause averting LD conditions in replicate temperate (diapausing) but not tropical (non-diapausing) populations (figure 1). Because fatty acyl coA elongases encode proteins involved in the synthesis of very long chain surface lipids that are known to mediate desiccation resistance in a diverse group of insects (Blomquist et al 1987;Vaz et al 1988;Juárez 1994Juárez , 2004Yoder et al 1995;Benoit & Denlinger 2007;Juárez & Fernández 2007), we hypothesized that the increased transcript abundance of this gene might be related to the previously documented increased survival of diapause relative to non-diapause eggs under desiccating conditions (Sota & Mogi 1992). Consistent with this hypothesis, we found that in a temperate population, diapause eggs had approximately 30 per cent more surface lipids (more than 99% hydrocarbon) than nondiapause eggs, but that eggs from a tropical population reared under SD and LD conditions did not differ in surface lipid quantities (figure 2).…”

“…Fatty acyl coA elongases are involved in the formation of very long chain lipids which are known to affect water loss in insects (Blomquist et al 1987). Using a comparative approach and based on well-established functional considerations, we link this expression pattern to an increase in hydrocarbon quantity and a decrease in water loss rate in diapause relative to non-diapause eggs.…”

Age estimation of Calliphora (Diptera: Calliphoridae) larvae using cuticular hydrocarbon analysis and Artificial Neural Networks

“…However, to determine the age 25 of larvae can be challenging and often requires a highly knowledgeable forensic entomologist. The 26 post-feeding larvae also remain to be a problematic stage to age due to the lack of morphological 27 changes occurring with time [5] and therefore the analyst must rely heavily on growth charts. DNA- 28 based analyses have been applied to the field of forensic entomology for over a decade [6].…”

“…They have different functions in 33 different species of insects and previous studies have shown their use for age estimation [1,[13][14][15][16], 34 sex [17] and species identification [18][19][20]. 35 The two main factors believed to be influential for the composition of hydrocarbon pools are 36 development/genetic factors and physiological state/environmental conditions [21][22][23]. The changes 37 observed during the blowflies' development may be affected by the environment they are exposed 38 to.…”

“…CHCs have the advantage of 43 determining the age to the day, rather than to the life stage and compliment the current techniques 44 used in the field. For more information on CHCs, the reader is referred to the following references 45 [25][26][27]. and have the ability to learn the relationship between input and output data, making them well-55 suited to fast processing of large real-world datasets (e.g.…”