“Developmental and ecological benefits of the maternally transmitted microbiota in a dung beetle”

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Daniel B. Schwab, Hailey E. Riggs, Irene L. G. Newton, and Armin P. Moczek

Developmental and ecological benefits of the maternally transmitted microbiota in a dung beetle

Onthophagus gazella egg within the brood chamber of a brood ball. The dorsal closure of the brood ball has been parted to one side.
(Credit: Guillaume J. Dury)

Many organisms feed on nutritionally recalcitrant food sources throughout their development. As all animal species develop in the company of diverse microbial communities, understanding the benefits that these microbes confer to their hosts is increasingly the focus of investigation by developmental and micro-biologists.

During development and into adulthood, Onthophagus dung beetles feed primarily on the nutrient-poor dung of large herbivores, yet the mechanisms that enable dung beetles to subsist on dung are poorly understood. One long-standing but never tested hypothesis posits that microbial symbionts, which are passed from mother to offspring in some dung beetle species, may confer benefits to developing beetles that enable them to grow and develop normally. Through a step-wise series of experiments involving the removal of environmental and maternal sources of microbiota, a team of researchers at Indiana University, including Daniel Schwab, Hailey Riggs, Irene Newton, and Armin Moczek, show that maternally transmitted microbiota are highly beneficial to larval Onthophagus gazella, enhancing developmental and fitness-related outcomes such as adult body size, developmental rate, and survival. Furthermore, they show that the extent to which larvae benefit from the presence of maternal microbiota is highly contingent on the environment in which larvae develop: When exposed to two ecologically relevant stressors, the benefits of maternal microbiota are enhanced relative to more permissive conditions.

Collectively, these results provide a first demonstration of the adaptive nature of symbiont provisioning in dung beetles, which may have contributed in part to the evolutionary success of this group. Read the Article