Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Tremough Campus, Penryn TR10 9EZ, UK.
J Insect Physiol. 2022 Nov-Dec;143:104452. doi: 10.1016/j.jinsphys.2022.104452. Epub 2022 Oct 26.
When the likelihood of reproducing successfully is low, any prior investment in developing oocytes may be wasted. One means of recouping this investment is oosorption - where ova are absorbed and resources salvaged so they can be re-allocated to other traits. Food-limited female speckled cockroaches (Nauphoeta cinerea) appear to use this strategy. However, it is unclear if total food intake or the availability of specific nutrients induces this process. Here, we used the geometric framework of nutrition to determine how protein, carbohydrate and energy intake affect levels of ovarian apoptosis and necrosis (controlled versus uncontrolled cell death) in the terminal oocytes of female N. cinerea. We then compare the effects of nutrient intake on apoptosis (a key step towards oosorption) and offspring production to better understand the relationship between diet, apoptosis and female fitness. We found that even when food was abundant, females experienced high levels of apoptosis if their diet lacked carbohydrate. Necrosis was reduced when energy intake was high, but largely irrespective of nutrient ratio. Offspring production peaked on a low protein, high carbohydrate nutrient ratio (1:7.96), similar to that which minimized apoptosis (1:7.34) but not in the region of nutrient space that minimized necrosis. Thus, females consuming an ideal nutrient blend for reproduction can invest heavily in their current brood without needing to salvage nutrients from developing ova. However, offspring production was more dependent on carbohydrate consumption than apoptosis was, suggesting that the importance of carbohydrate in reproduction goes beyond regulating oosorption. This reliance on carbohydrate for female reproduction may reflect the unusual reproductive and nutritional physiology of speckled cockroaches; attributes that make this species an exciting model for understanding how diet regulates reproduction.
当成功繁殖的可能性较低时，任何在卵母细胞发育上的前期投入都可能浪费。一种回收这种投资的方法是卵吸收——即吸收卵子并回收资源，以便将其重新分配给其他特征。受食物限制的斑胸草雀（Nauphoeta cinerea）似乎就采用了这种策略。然而，目前尚不清楚是总食物摄入量还是特定营养素的可用性诱导了这一过程。在这里，我们使用营养的几何框架来确定蛋白质、碳水化合物和能量摄入如何影响雌性 N. cinerea 终末卵母细胞中的卵巢细胞凋亡和坏死（受控与不受控的细胞死亡）水平。然后，我们比较了营养摄入对凋亡（卵吸收的关键步骤）和后代产生的影响，以更好地理解饮食、凋亡和雌性适合度之间的关系。我们发现，即使食物充足，如果雌性的饮食缺乏碳水化合物，它们仍会经历高水平的凋亡。当能量摄入高时，坏死会减少，但在很大程度上与营养比例无关。后代的产生在低蛋白、高碳水化合物的营养比例（1:7.96）达到峰值，与最小化凋亡（1:7.34）相似，但不在最小化坏死的营养空间区域。因此，消耗理想的繁殖营养混合物的雌性可以在不从发育中的卵子中回收营养的情况下，大量投资于当前的繁殖。然而，后代的产生比凋亡更依赖于碳水化合物的消耗，这表明碳水化合物在繁殖中的重要性不仅仅是调节卵吸收。这种对雌性繁殖的碳水化合物的依赖可能反映了斑胸草雀异常的生殖和营养生理学；这些特征使该物种成为理解饮食如何调节生殖的令人兴奋的模型。
