The indispensable soma of Cardiocondyla obscurior ants

Abstract

The evolutionary mechanisms that shape aging in social insects are not well understood. It is commonly assumed that queens live long and prosperous, while workers are regarded as a short-lived disposable caste because of their low reproductive potential. Queens of the ant Cardiocondyla obscurior gain high fitness late in life by increasing investment into sexual offspring as they age. This results in strong selection against senescence until shortly before death. Here, we show that workers have the same lifespan and shape of aging as queens, even though workers lack reproductive organs and cannot gain direct fitness. Under consideration of the prevailing aging theories and the biology of the species, we hypothesize that programmed aging has possibly evolved under kin selection.

Queens control caste allocation in the ant Cardiocondyla obscurior

“…Additional aspects of the species's biology probably further spur overlap between individual and colony fitness. Cardiocondyla has a relatively low degree of size dimorphism between sexuals and workers [74,81], and queen and worker lifespans are identical [82], indicating that the costs of production and maintenance of the two castes are similar. This allows caste allocation to become independent of colony size [46], removing a putative constraint on sexual production [83].…”

Darwin’s “neuters” and the evolution of the sex continuum in a superorganism

“…Development takes ca. 30 days from egg laying to adult, queens mate within the first two weeks of their lives, start egg-laying within a further two weeks, and have the same pace (lifespan ∼28 weeks) and shape of aging as workers ( 26 , 59 ). Queens can be identified from late embryogenesis onwards by the presence of paired crystalline deposits associated with the developing ovaries ( 27 ).…”