Carotenoid pigments have myriad functions in fish, including coloration and immunity. The “carotenoid trade-off hypothesis” posits that dietary limitation of carotenoids imposes constraints on animals to allocate to one function at the expense of another. This hypothesis rarely has been tested in fish. We quantified tissue carotenoids in breeding and non-breeding female convict cichlids in Lake Xiloa, Nicaragua. This species is reverse sexually dichromatic such that females possess carotenoid-based coloration that males lack. We also collected algae samples near nest sites to assess carotenoid availability, recorded water depth, and examined cichlids’ behavioral interactions with pair mates, conspecifics, heterospecific competitors, and predators. Each of these, we predicted, would mediate potential carotenoid trade-offs. We found that non-breeding females had significantly higher levels of carotenoids in their integument, liver, and gonads compared to breeding fish. We found that algae and total carotenoids declined with depth across our study transects at 9, 11, 13, and 15 m, but the concentration of carotenoids (ng carotenoid g−1 algae, or algal quality) did not vary with depth. Furthermore, relationships among carotenoid concentrations of the three tissue types did not vary with depth, and female color status (orange or not) was not affected by behavioral interactions with other community members, reproductive status, or water depth. Our results support previous studies showing that carotenoid pigmentation may serve a signal function that facilitates the establishment of non-breeding females within the breeding population. Our study also uncovered no evidence indicating that carotenoids are limiting in the diet of breeding female convict cichlids.

中文翻译：

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雌性罪犯慈鲷（一种反向性二色性鱼类）中类胡萝卜素的可用性和权衡

类胡萝卜素色素在鱼类中具有多种功能，包括着色和免疫。“类胡萝卜素权衡假设”假定类胡萝卜素的饮食限制对动物施加了限制，以牺牲另一种功能为代价分配给一种功能。这一假设很少在鱼类中得到检验。我们量化了尼加拉瓜西洛亚湖的繁殖和非繁殖雌性慈鲷的组织类胡萝卜素。该物种具有反向性二色性，因此雌性具有雄性所缺乏的基于类胡萝卜素的着色。我们还在巢址附近收集藻类样本以评估类胡萝卜素的可用性，记录水深，并检查慈鲷与配对、同种、异种竞争者和捕食者的行为相互作用。我们预测，这些中的每一个都会调节潜在的类胡萝卜素权衡。我们发现，与繁殖鱼相比，非繁殖雌鱼的外皮、肝脏和性腺中的类胡萝卜素含量明显更高。我们发现藻类和总类胡萝卜素在 9、11、13 和 15 m 处的研究断面随深度下降，但类胡萝卜素的浓度（ng 类胡萝卜素 g-1 藻类，或藻类质量）不随深度变化。此外，三种组织类型的类胡萝卜素浓度之间的关系不随深度变化，雌性颜色状态（橙色与否）不受与其他社区成员的行为互动、生殖状态或水深的影响。我们的结果支持先前的研究，表明类胡萝卜素色素沉着可能具有促进非繁殖雌性在繁殖种群中建立的信号功能。