Kin Recognition and Egg Cannibalism by Drosophila melanogaster Larvae

Cannibalism is a widespread behavioral phenomenon that is often thought to be an adaptive plastic response to limited environmental resources. However, cannibalism can potentially come at a fitness cost to an individual if one consumes relatives, due to the potential loss of indirect fitness benefits. One way in which this cost could be avoided is by the selective avoidance of cannibalising kin in favour of consuming non-kin conspecifics through the use of kin recognition mechanisms. Here, we examined whether fruit fly (Drosophila melanogaster) 2nd instar larvae differ in their interactions with groups of related and unrelated eggs, and whether this is associated with differential rates of cannibalism. Our experiment revealed that, at this developmental stage larvae appear to be able to distinguish between full-sibling eggs and non-kin eggs, as they behaved differently towards these two groups. Larvae approached groups of unrelated eggs more frequently and spent more time overall associating with them than they did with groups of related eggs. Furthermore, larvae cannibalized unrelated eggs significantly more frequently than kin eggs. These results are consistent with a kin-selection behavioral strategy that maximizes both direct and indirect fitness benefits. We discuss these findings in the context of this species' natural history, and the potential mechanisms of kin recognition. This study contributes to the growing body of research examining the evolution of social behaviors using this model species.