Decline in Offspring Viability as a Manifestation of Aging in Drosophila Melanogaster

Abstract

Abstract. The evolutionary explanation of senescence proposes that selection against alleles with deleterious effects manifested only late in life is weak because most individuals die earlier for extrinsic reasons. This argument also applies to alleles whose deleterious effects are nongenetically transmitted from mother to progeny, that is, that affect the performance of progeny produced at late ages rather than of the aging individuals themselves. We studied the effect of maternal age on offspring viability (egg hatching success and larva-to-adult survival) in two sets of Drosophila melanogaster lines (HAM/LAM and YOUNG/OLD), originating from two long-term selection experiments. In each set, some lines (HAM and YOUNG, respectively) have been selected for early reproduction, whereas later reproduction was favored in their counterparts (LAM and OLD). In the HAM and LAM lines, both egg hatching success and larval viability declined with mother's age and did so with accelerating rates. The hatching success declined significantly faster with maternal age in HAM than in LAM lines, according to one of two statistical approaches used. Egg hatching success also declined with maternal age in YOUNG and OLD lines, with no difference between the selection regimes. However, the relationship between mother's age and offspring larva-to-adult viability differed significantly between these two selection regimes: a decline of larval viability with maternal age occurred in YOUNG lines but not in OLD lines. This suggests that the rate with which offspring viability declines with mother's age responded to selection for early versus late reproduction. We suggest broadening the evolutionary concept of senescence to include intrinsically caused declines in offspring quality with maternal age.

The song of the old mother: Reproductive senescence in female drosophila

“…Generally measured as total adult offspring, fertility decreases with increasing maternal age ( 16,27,60,81 , although only 27 controls for male age). In the later study, young (3 d pe) females produced, on average, >250 offspring over 6 d while older females (28 d pe) produced >60% fewer offspring over the same duration.…”

“…27 A similar trend is observed as parental age increases: offspring of old (15 d pe) parents had »3% lower viability than offspring of young (1 d pe) parents, 16 and additional studies found a negative relationship between parental age and offspring viability. 60,81 One study failed to detect a difference in offspring viability between old parents (males and females >25 d pe) and young parents (>5 d pe), although the offspring of old parents developed significantly (16.4%) more rapidly than young parents. 82 Fertility is studied more precisely by observing the effects of female age on offspring viability at different life history stages including embryonic, larval, pupal, and adult.…”

“…The degree to which maternal age affects these life stages varies. 16 Embryonic viability (often measured as percentage of eggs hatching) is high (>80%) when females are <7 d pe and decreases by 9-65% as females age (>23 d pe) ( [14][15][16]59,74,81 , although only 59 controls for male age). This developmental stage best predicts overall offspring viability.…”

“…This developmental stage best predicts overall offspring viability. 81 However, failure of eggs to hatch can be due to fertilization failure and/or embryonic death. The relative contributions of these 2 factors have not been reported.…”

Quantitative genetics of age at reproduction in wild swans: Support for antagonistic pleiotropy models of senescence

“…It is often witnessed in laboratory conditions (e.g., see refs. [2][3][4] and, more rarely, in nature (5-7). For evolutionary biologists, the evolution of decreased performance and increased mortality with age, which should at first sight be counterselected, is a puzzle.…”