Do dung beetle larvae need microbial symbionts from their parents to feed on dung?

Abstract

Abstract Adult dung beetles eat small particles of their food using soft mouthparts, but their larvae have biting jaws with which they chew material in their natal brood ball. It was assumed that microbes supplied by the parents help breakdown food material in the brood ball, which was thought to act as a fermentation chamber. It has been generally accepted that larval dung beetles gain access to nutrients in the dung via symbionts. Various dung treatments used here, including heat sterilisation and anti‐microbials, suggest that the maternal contribution to the brood ball is a pre‐digested meal for the newly hatched larva, and that microbes from the parents are not involved in larval feeding within this group of dung beetles. However, manipulation of the dung by the mother supplied the larva with smaller dung particles from the unsorted dung, and an additional ‘maternal gift’ secretion may provide partially digested dung, both of which affect survival of the larva. This overturns the largely untested dogma that larval dung beetles depend on microbial symbionts from the adults for feeding, but confirms that adult ‘conditioning’ of the dung is important for the larva in selecting out larger dung particles from the brood ball.