Maternal food restriction during pregnancy affects offspring development and swimming performance in a placental live-bearing fish

How pregnant mothers allocate limited resources to different biological functions such as maintenance, somatic growth, and reproduction can have profound implications for early life development and survival of offspring. Here we examined the effects of maternal food restriction during pregnancy on offspring in the matrotrophic (i.e. mother-nourishment throughout gestation) live-bearing fish species Phalloptychus januarius (Poeciliidae). We fed pregnant females either with a ‘low-food’ or ‘high-food’ ration for six weeks and quantified the consequences for offspring size and body fat at birth and one week after birth. We further measured fast-start escape performance of offspring at birth, as well as swimming kinematics during prey capture at zero, two, and seven days after birth. We found that the length of maternal food restriction during pregnancy negatively affected offspring dry mass and lean dry mass at birth, as well as body fat gain during the first week after birth. Moreover, it impacted the locomotor performance of offspring during prey capture at, and during the first week after, birth. We did not observe an effect of food restriction on fast-start escape performance of offspring. Our study suggests that matrotrophic poeciliid fish are maladapted to unpredictably fluctuating resource environments, because sudden reductions in maternal food availability during pregnancy result in smaller offspring with slower postnatal body fat gain and an inhibition of postnatal improving swimming skills during feeding, potentially leading to lower competitive abilities after birth.

妊娠母体如何将有限资源分配给维持代谢、体细胞生长与繁殖等不同生物学功能，对子代的早期发育与存活具有深远影响。本研究以胎生营养型（matrotrophic，即整个妊娠期由母体供给营养）的卵胎生鱼类詹氏扁胎鳉（Phalloptychus januarius，花鳉科Poeciliidae）为对象，探究妊娠期间母体食物限制对子代的影响。我们将妊娠雌鱼分为两组，分别以‘低食物量’与‘高食物量’的投喂量饲喂六周，并量化子代出生时及出生后一周的体型与体脂含量。此外，我们还测定了子代出生时的快速逃逸（fast-start escape）行为表现，以及出生后第0、2、7天时捕食过程中的游泳运动学（swimming kinematics）特征。研究发现，妊娠期间母体食物限制的时长会对子代出生时的干重与无脂干重产生负面影响，同时也会抑制子代出生后第一周的体脂积累。此外，母体食物限制还会影响子代出生时及出生后第一周内捕食过程中的运动能力。我们未发现食物限制对子代的快速逃逸行为表现存在显著影响。本研究表明，胎生营养型花鳉科鱼类对不可预测的资源波动环境适应性不足：妊娠期间母体食物可获得性的突然降低会导致子代体型更小、产后体脂积累速率更慢，同时抑制子代捕食过程中游泳能力的产后提升，进而可能降低子代出生后的竞争能力。