Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa.
Department of Anatomy and Physiology, University of Pretoria, Onderstepoort 0110, South Africa.
Biol Lett. 2018 May;14(5). doi: 10.1098/rsbl.2018.0150.
Elevated prolactin (PRL) has been associated with the expression of social and cooperative behaviours in a number of vertebrate species, as well as suppression of reproduction. As social mole-rats exhibit both of these traits, PRL is a prime candidate in mediating their social phenotype. While naked and Damaraland mole-rats (NMRs and DMRs) have evolved eusociality independently within their family, both species exhibit an extreme skew in lifetime reproductive success, with breeding restricted to a single female and one or two males. Non-breeding NMRs of both sexes are physiologically inhibited from reproducing, while in DMRs only the non-breeding females are physiologically suppressed. Newly emerging work has implicated the dopamine system and PRL as a component in socially induced reproductive suppression and eusociality in NMR, but the DMR remains unstudied in this context. To investigate evolutionary convergence in the role of PRL in shaping African mole-rat eusociality, we determined plasma PRL concentrations in breeders and non-breeders of both sexes, comparing DMRs with NMRs. Among samples from non-breeding NMRs 80% had detectable plasma PRL concentrations. As a benchmark, these often (37%) exceeding those considered clinically hyperprolactinaemic (25 ng ml) in humans: mean ± s.e.m.: 34.81 ± 5.87 ngml; range 0.00-330.30 ng ml Conversely, 85% of non-breeding DMR samples had undetectable values and none had concentrations above 25 ng ml: 0.71 ± 0.38 ng ml; 0.00-23.87 ngml Breeders in both species had the expected variance in plasma PRL concentrations as part of normal reproductive function, with lactating queens having significantly higher values. These results suggest that while elevated PRL in non-breeders is implicated in NMR eusociality, this may not be the case in DMRs, and suggests a lack of evolutionary convergence in the proximate control of the social phenotype in these mole-rats.
催乳素（PRL）水平升高与许多脊椎动物物种的社会和合作行为表达以及生殖抑制有关。由于社会性掘穴滨鼠表现出这两种特征，因此 PRL 是介导其社会表型的主要候选者。虽然裸滨鼠和东非多毛滨鼠（NMR 和 DMR）在其家族内独立进化出真社会性，但这两个物种的终生繁殖成功率都存在极端偏向，繁殖仅限于一只雌性和一到两只雄性。两性非繁殖的 NMR 从生理上被抑制繁殖，而在 DMR 中只有非繁殖的雌性受到生理抑制。新出现的研究表明，多巴胺系统和 PRL 是 NMR 中社会诱导生殖抑制和真社会性的一个组成部分，但在这种情况下，DMR 仍未被研究。为了研究 PRL 在塑造非洲掘穴滨鼠真社会性方面的作用的进化趋同，我们测定了两性繁殖者和非繁殖者的血浆 PRL 浓度，并将 DMR 与 NMR 进行了比较。在非繁殖的 NMR 样本中，有 80%可检测到血浆 PRL 浓度。作为基准，这些通常（37%）超过人类中被认为是临床高催乳素血症（25ng/ml）的水平：平均值±标准误：34.81±5.87ng/ml；范围 0.00-330.30ng/ml 相反，85%的非繁殖 DMR 样本未检测到值，且没有浓度超过 25ng/ml：0.71±0.38ng/ml；0.00-23.87ng/ml 两种物种的繁殖者的血浆 PRL 浓度都有预期的变化，这是正常生殖功能的一部分，哺乳期的蚁后具有显著更高的浓度。这些结果表明，虽然非繁殖者中催乳素水平升高与 NMR 的真社会性有关，但在 DMR 中可能并非如此，这表明这些掘穴滨鼠的社会表型的近因控制在进化上没有趋同。
