Descriptive analyses of differentially expressed genes during larval development of Calliphora vicina (Diptera: Calliphoridae).

The analysis of insect evidence is often used in death investigations as the development of necrophagous insect species can be used to determine a minimum post-mortem interval (PMImin). Usually, the PMImin estimations are based on the age estimation of larvae developed on the corpse. So far, age estimation mostly relies on length or weight measurement of the larvae. These measurements are then compared to species-specific reference growth data obtained from laboratory studies. However, length and weight do not always represent the best developmental markers to provide accurate and precise age estimates for PMImin calculation, especially for post-feeding third-instar larvae which decrease in size. Therefore, more growth markers are required to improve age estimation not only for post-feeding larvae but also for all larval stages. As the analysis of temporally regulated genes proved suitable for age prediction in blow fly pupae, we examined the gene expression patterns of six genes (15_2, 2014192, EcdR, AR, hsp90 and actin) during larval development of Calliphora vicina at three constant temperatures and analysed the effect of a combination of morphological and molecular age markers on statistical models of development. EcdR, AR and 15_2 showed reliable tendencies to classify the post-feeding stage more precisely, and inclusion of gene expression data in models of development improved the statistical fit of the model. Nevertheless, for depicting the first larval stages and for quantifying the onset of the post-feeding stage more accurately, results of this preliminary study should be supported by searching for more informative genes.