Thurau Emma G, Rahajanirina Andry Narcisse, Irwin Mitchell T
Department of Anthropology, The Graduate Center of the City University of New York, New York, USA.
New York City Consortium of Evolutionary Primatology (NYCEP), New York, USA.
Am J Primatol. 2021 Mar;83(3):e23239. doi: 10.1002/ajp.23239. Epub 2021 Feb 5.
Tannins, a type of plant secondary metabolite, are well-known for their ability to precipitate proteins and thereby reduce the protein available to consumers. Most primate studies have focused on condensed tannins (CTs) as they were thought to be the most effective type of tannin at preventing protein acquisition, but there is growing recognition that other types of tannins can bind to proteins, suggesting the division among tannin types is not as clear-cut as previously thought. Although previous studies have documented the presence of CTs in primate diets and primates' behavioral responses to them, our understanding of tannins remains limited because few researchers have used Sephadex column purification to accurately determine tannin concentrations, and few have used in vitro assays to determine available protein content and the tannins' effectiveness in binding protein. In this study, we documented diademed sifaka (Propithecus diadema) diet from June to August 2018 at Tsinjoarivo, Madagascar (in two forests with varying degrees of habitat disturbance) and quantified CT concentration and actual available protein in foods. Eleven of the fourteen top foods tested contained CTs (concentrations: 4.8%-39.3% dry matter). An in vitro assay showed available protein was strikingly low in six of the eleven top foods (e.g., little to no apparent available protein, despite high crude protein). Overall, our findings suggest sifakas acquire less protein than previously recognized and probably have adaptations to counteract tannins. Such studies of available protein are critical in understanding dietary constraints on sifaka populations and the evolution of their diet choice strategies; despite the conventional wisdom that leaves are protein-rich, folivorous primates may indeed be protein-limited. However, further studies are necessary to determine if sifakas have counter-adaptations to tannins, and if they absorb more protein than our analyses suggest, perhaps receiving protein that we were unable to detect with the current techniques (e.g., pollen).
单宁是一种植物次生代谢产物，以其沉淀蛋白质的能力而闻名，从而减少了可供消费者利用的蛋白质。大多数灵长类动物研究都集中在缩合单宁（CTs）上，因为它们被认为是预防蛋白质获取方面最有效的单宁类型，但人们越来越认识到其他类型的单宁也能与蛋白质结合，这表明单宁类型之间的区分并不像以前认为的那么明确。尽管先前的研究记录了灵长类动物饮食中CTs的存在以及灵长类动物对它们的行为反应，但我们对单宁的理解仍然有限，因为很少有研究人员使用葡聚糖凝胶柱纯化来准确测定单宁浓度，也很少有人使用体外试验来确定可利用蛋白质含量以及单宁结合蛋白质的有效性。在这项研究中，我们记录了2018年6月至8月马达加斯加齐乔阿里沃（在两个栖息地干扰程度不同的森林中）冕狐猴（Propithecus diadema）的饮食，并对食物中的CT浓度和实际可利用蛋白质进行了量化。测试的14种主要食物中有11种含有CTs（浓度：干物质的4.8%-39.3%）。一项体外试验表明，11种主要食物中的6种可利用蛋白质含量极低（例如，尽管粗蛋白含量高，但几乎没有明显的可利用蛋白质）。总体而言，我们的研究结果表明冕狐猴获取的蛋白质比以前认为的要少，并且可能有适应机制来对抗单宁。这种对可利用蛋白质的研究对于理解冕狐猴种群的饮食限制及其饮食选择策略的演变至关重要；尽管传统观点认为树叶富含蛋白质，但食叶灵长类动物实际上可能受到蛋白质限制。然而，有必要进一步研究冕狐猴是否对单宁有反适应机制，以及它们吸收的蛋白质是否比我们的分析结果显示的更多，也许它们能吸收我们目前技术无法检测到的蛋白质（例如花粉）。
