Aarhus Institute of Advanced Studies, Aarhus C, Denmark.
Zoophysiology, Department of Biology, Aarhus University, Aarhus C, Denmark.
J Physiol. 2022 May;600(9):2245-2266. doi: 10.1113/JP282351. Epub 2022 Apr 5.
The cost of reproduction greatly affects a species' life history strategy. Baleen whales exhibit some of the fastest offspring growth rates in the animal kingdom. We quantified the energetic cost of gestation for southern right whales (Eubalaena australis) by combining whaling catch records of pregnant females with photogrammetry data on southern right whale mothers and calves from two breeding grounds in Argentina and Australia. The relationship between calf birth size and maternal length was determined from repeated measurements of individual females before and after giving birth. Fetal growth was determined from generalized linear models fitted to fetal length data from whaling operations between 1961 and 1967. Fetal length was converted to volume and mass, using the volume-to-length relationship of newborn southern right whales calves, and published tissue composition and energy content estimates. Fetal maintenance costs (heat of gestation) and the energy content of the placenta were predicted from published relationships and added to the fetal growth cost to calculate the total cost of gestation. Our findings showed that fetal growth rates and birth size increased linearly with maternal length, with calves being born at ∼35% maternal length. Fetal length increased curvilinearly through gestation, which resulted in an exponential increase in fetal volume and mass. Consequently, the cost of gestation was very low during the first (0.1% of total cost) and second trimester (4.9%), but increased rapidly during the last trimester (95.0%). The heat of gestation incurred the highest cost for pregnant females (73.8%), followed by fetal growth (21.2%) and the placental energy content (5.0%). KEY POINTS: Baleen whales exhibit some of the fastest fetal growth rates in the animal kingdom. Despite this, the energetic cost of gestation is largely unknown, as well as the influence of maternal body size on fetal growth rates and calf birth sizes. We combined historical whaling records and drone photogrammetry data to determine fetal growth rates and birth sizes in southern right whales (Eubalaena australis), from which we estimated the cost of gestation. Calf birth size, and consequent fetal growth rates, increased positively with maternal body size. The cost of gestation was negligible for southern right whale females during the first two trimesters, but increased rapidly during the last trimester. These results show that late gestation incurs a significant cost for baleen whale females, and needs to be accounted for in bioenergetic models.
繁殖成本对物种的生活史策略有很大影响。须鲸表现出动物王国中最快的后代生长速度之一。我们通过结合南露脊鲸（Eubalaena australis）雌性怀孕的捕鲸记录和来自阿根廷和澳大利亚两个繁殖地的南露脊鲸母亲和幼鲸的摄影测量数据，量化了南露脊鲸的妊娠期能量成本。通过对分娩前后个体雌性的重复测量，确定了幼鲸出生大小与母体长度之间的关系。从 1961 年至 1967 年的捕鲸作业中获得的胎儿长度数据，利用广义线性模型确定了胎儿生长情况。利用新生南露脊鲸幼鲸的体积与长度关系，以及已发表的组织组成和能量含量估计值，将胎儿长度转换为体积和质量。根据已发表的关系预测胎儿维持成本（妊娠期热）和胎盘的能量含量，并将其添加到胎儿生长成本中，以计算妊娠期的总费用。我们的研究结果表明，胎儿生长速度和出生大小与母体长度呈线性关系，幼鲸出生时约为母体长度的 35%。通过妊娠期，胎儿长度呈曲线增加，导致胎儿体积和质量呈指数增长。因此，妊娠的前三个月（占总成本的 0.1%）和第二个三个月（4.9%）期间，妊娠成本非常低，但在最后三个月（95.0%）期间迅速增加。妊娠期的热量消耗对怀孕的雌性来说是最高的（73.8%），其次是胎儿生长（21.2%）和胎盘的能量含量（5.0%）。关键点：须鲸表现出动物王国中最快的胎儿生长速度之一。尽管如此，妊娠期的能量成本以及母体体型对胎儿生长速度和幼鲸出生大小的影响仍不清楚。我们结合历史捕鲸记录和无人机摄影测量数据，确定了南露脊鲸（Eubalaena australis）的胎儿生长速度和出生大小，并据此估算了妊娠期成本。幼鲸出生大小和随后的胎儿生长速度与母体体型呈正相关。在妊娠的前两个三个月，南露脊鲸雌性的妊娠成本可以忽略不计，但在最后三个月迅速增加。这些结果表明，妊娠晚期对须鲸雌性来说是一个重大的成本，在生物能量模型中需要考虑这一点。
