A novel gene associated with intraspecific predation in Spodoptera litura larvae

We investigated the inheritance of cannibalistic behavior in larvae of the common cutworm, Spodoptera litura. The fact that artificial selection of non-cannibalistic animals over 17 generations resulted in decrease of their cannibalistic behavior is clearly the proof of their inheritance of this behavior. Average frequency of cannibalism in selected larvae (3.2%) was significantly lower than that in non-selected larvae (24.5%). We employed the differential display RT-PCR analysis to evaluate differences in gene expression in the brains between selected and non-selected lines, and identified one gene whose expression was significantly higher in non-selected line larvae than that in selected line larvae. The identified gene with 779 bp was a novel gene without a major sequence homology with any reported genes. This gene was expressed in several tissues, fat body, brain, and hemocytes, among which the highest expression was observed in the brain. Further, the expression of this gene was very low in the brain of normally fed larvae but starvation significantly enhanced its expression only in the non-selected larvae. These results imply the possibility that the gene identified in the present study contributes to initiating cannibalistic behavior of S. litura larvae although the detailed function of this gene is unknown at present.