Behavioural Ecology, University of Bern, Hinterkappelen, Switzerland.
Département de Biologie et Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec, Québec, Canada.
Mol Ecol. 2018 Oct;27(20):4136-4151. doi: 10.1111/mec.14837. Epub 2018 Sep 22.
Juveniles of the cooperatively breeding cichlid fish Neolamprologus pulcher either consistently provide help in form of alloparental egg care ("cleaners") or consistently abstain from helping ("noncleaners"). These phenotypes are not based on heritable genetic differences. Instead, they arise during ontogeny, which should lead to differences in brain structure or physiology, a currently untested prediction. We compared brain gene expression profiles of cleaners and noncleaners in two experimental conditions, a helping opportunity and a control condition. We aimed to identify (a) expression differences between cleaners and noncleaners in the control, (b) changes in gene expression induced by the opportunity and (c) differences in plasticity of gene expression between cleaners and noncleaners. Control cleaners and noncleaners differed in the expression of a single gene, irx2, which regulates neural differentiation. During the opportunity, cleaners and noncleaners had three upregulated genes in common, which were implicated in neuroplasticity, hormonal signalling and cell proliferation. Thus, the stimulus in the opportunity was sufficiently salient. Cleaners also showed higher expression of seven additional genes that were unique to the opportunity. One of these cleaner-specific genes is implicated in neuropeptide metabolism, indicating that this process is associated with cleaning performance. This suggests that the two types employed different pathways to integrate social information, preparing them for accelerated reaction to future opportunities. Interestingly, three developmental genes were downregulated between the control and the opportunity in cleaners only. Our results indicate that the two behavioural types responded differently to the helping opportunity and that only cleaners responded by downregulating developmental genes.
幼年共生慈鲷鱼 Neolamprologus pulcher 要么一直提供亲代抚育卵的帮助（“清洁工”），要么一直不提供帮助（“非清洁工”）。这些表型不是基于可遗传的遗传差异。相反，它们是在个体发育过程中产生的，这应该导致大脑结构或生理学的差异，这是一个目前未经测试的预测。我们比较了清洁者和非清洁者在两种实验条件下的大脑基因表达谱，一种是帮助机会，另一种是对照条件。我们的目的是确定：（a）对照条件下清洁者和非清洁者之间的表达差异；（b）机会引起的基因表达变化；（c）清洁者和非清洁者之间基因表达可塑性的差异。对照条件下的清洁者和非清洁者在单个基因 irx2 的表达上存在差异，该基因调节神经分化。在机会期间，清洁者和非清洁者有三个共同上调的基因，这些基因涉及神经可塑性、激素信号和细胞增殖。因此，机会中的刺激足够显著。清洁者还表现出另外七个仅在机会中上调的基因的更高表达。其中一个清洁者特异性基因参与神经肽代谢，表明该过程与清洁性能有关。这表明这两种类型使用不同的途径来整合社会信息，为它们对未来机会的快速反应做好准备。有趣的是，仅在清洁者中，三个发育基因在对照和机会之间下调。我们的结果表明，两种行为类型对帮助机会的反应不同，只有清洁者通过下调发育基因来做出反应。
