Cheng Yuan-Cheng, Xie Cai-Han, Chen Yu-Chen, Fuh Nien-Tse, Chuang Ming-Feng, Kam Yeong-Choy
Department of Life Science, Tunghai University, Taichung, 407224, Taiwan.
Department of Life Sciences and Research Center for Global Change Biology, National Chung Hsing University, Taichung, 402202, Taiwan.
Front Zool. 2024 Jun 19;21(1):16. doi: 10.1186/s12983-024-00537-z.
Parental care benefits offspring but comes with costs. To optimize the trade-off of costs and benefits, parents should adjust care based on intrinsic and/or extrinsic conditions. The harm to offspring hypothesis suggests that parents should invest more in younger offspring than older offspring because younger offspring are more vulnerable. However, this hypothesis has rarely been comprehensively tested, as many studies only reveal an inverse correlation between parental care and offspring age, without directly testing the effects of offspring age on their vulnerability. To test this hypothesis, we studied Kurixalus eiffingeri, an arboreal treefrog with paternal care. We first performed a field survey by monitoring paternal care during embryonic development. Subsequently, we conducted a field experiment to assess the prevalence of egg predators (a semi-slug, Parmarion martensi) and the plasticity of male care. Finally, we conducted a laboratory experiment to assess how embryo age affects predation by P. martensi.
Our results showed that (1) male attendance and brooding frequency affected embryo survival, and (2) males attended and brooded eggs more frequently in the early stage than in the late stage. The experimental results showed that (3) males increased attendance frequency when the predators were present, and (4) the embryonic predation by the semi-slug during the early was significantly higher than in the late stage.
Our findings highlight the importance of paternal care to embryo survival, and the care behavior is plastic. Moreover, our results provide evidence consistent with the predictions of the harm to offspring hypothesis, as males tend to care more for younger offspring which are more vulnerable.
亲代抚育对后代有益，但也有成本。为了优化成本与收益的权衡，亲代应根据内在和/或外在条件调整抚育行为。后代伤害假说认为，亲代应该对年幼后代比对年长后代投入更多，因为年幼后代更易受到伤害。然而，这一假说很少得到全面检验，因为许多研究仅揭示了亲代抚育与后代年龄之间的负相关关系，而没有直接测试后代年龄对其脆弱性的影响。为了验证这一假说，我们研究了艾氏姬蛙，一种有雄性抚育行为的树栖蛙类。我们首先通过监测胚胎发育期间的雄性抚育行为进行了一项野外调查。随后，我们进行了一项野外实验，以评估卵捕食者（一种半蛞蝓，褐云玛瑙螺）的普遍性以及雄性抚育行为的可塑性。最后，我们进行了一项实验室实验，以评估胚胎年龄如何影响褐云玛瑙螺的捕食行为。
我们的结果表明：（1）雄性的陪伴和抱卵频率影响胚胎存活；（2）雄性在早期比晚期更频繁地陪伴和抱卵。实验结果表明：（3）当有捕食者时，雄性增加陪伴频率；（4）半蛞蝓在早期对胚胎的捕食明显高于晚期。
我们的研究结果突出了雄性抚育对胚胎存活的重要性，并且抚育行为具有可塑性。此外，我们的结果提供了与后代伤害假说预测相符的证据，因为雄性倾向于更多地照顾更易受伤害的年幼后代。
