Abstract
Adaptive theory predicts that mothers would be advantaged by adjusting the sex ratio of their offspring in relation to their offspring's future reproductive success. In the present study, we tested the effect of housing mice under crowded condition on the sex ratio and whether the fat content of the diet has any influence on the outcome of pregnancies. Three-week-old mice were placed on the control diet (NFD) for 3 weeks. Thereafter the mice were allotted randomly to two groups of 7 cages each with 4, 6, 8, 10, 12, 14, and 16 mice in every cage to create increasing crowding gradient and fed either NFD or high fat diet (HFD). After 4 weeks, dams were bred and outcomes of pregnancy were analyzed. The average dam body weight (DBW) at conception, litter size (LS) and SR were significantly higher in HFD fed dams. Further, male biased litters declined with increasing crowding in NFD group but not in HFD. The LS and SR in NFD declined significantly with increasing crowding, whereas only LS was reduced in HFD group. We conclude that female mice housed under overcrowding conditions shift offspring SR in favor of daughters in consistent with the TW hypothesis and high fat diet reduces this influence of overcrowding.
Highlights
Trivers and Willard predicted that, the animals manipulate SR of their offspring when net fitness benefits conferred by investment in sons and daughters differ [1]
Numerous factors like maternal hormone levels [6,7,8,9,10], food abundance [11,12], mate quality [13], habitat quality [14], dominance status [15], and maternal condition [16] influence the offspring SR. This hypothesis holds true for species with a small litter size (LS) and depends on 3 assumptions [1]: 1) that the condition of the offspring at the end of the parental investment is correlated with the condition of the dam during parental investment; 2) that these differences in condition are carried over to adulthood; and 3) that the adult will be differentially advantaged in reproductive success through slight advantages in condition
Pratt and Lisk conducted two studies to show that dexamethasone and progesterone can prevent the SR deficit induced by social stress in golden hamsters [18,19]. We address one such problem by comparing the SR of two groups of mice (Mus musculus) that were maintained under increasing crowding conditions and fed either control diet (NFD) or high fat diet (HFD)
Summary
Trivers and Willard predicted that, the animals manipulate SR of their offspring when net fitness benefits conferred by investment in sons and daughters differ [1]. Regardless of their quality, daughters are more likely than sons to reproduce in many polygynous mating systems [2,3]. Numerous factors like maternal hormone levels [6,7,8,9,10], food abundance [11,12], mate quality [13], habitat quality [14], dominance status [15], and maternal condition [16] influence the offspring SR. Even after accumulation of large amount of experimental support, the exact genetic and physiological basis for SR bias is still far from understood
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