珍稀濒危动物穿山甲消化酶表达对其食性特化的适应机制

Pangolin is critically endangered species which has major medicinal value. It has high social attention. Ex-situ conservation and artificial domestication and breeding research should be urgently carried on to solve species protection and market demand problems. The species feeding habits is highly specialized. Human beings could not provide adequate natural food in long term and have to feed artificial diet in captivity. Previous research has shown that pangolins can not digest and utilize grains, vertebrates, eggs and dairy products, etc. But it can digest Tenebrio molitor and some other invertebrates better. Based on the general rule of animal’s digestive enzymes adapt to its dietary, we first proposed that pangolin may have formed specific digestive enzymes system to adapt to digest ants and termites. This specific system, however, may limit pangolin’s digestive ability of a variety of other substances. This study plans to use the proteomics technology to do large scale protein qualitative research (shotgun technology) and target verification of key proteins (PRM technology) of digestive juices from different parts of pangolin’s digestive organs, to analyze the kinds and secreting characteristics of main digestive enzymes of mouth, stomach and intestines, to verify whether the digestive enzymes play a key role in pangolin’s adaption to specialized diets but can not digest some artificial foods better. This study is expected to reveal the physiological mechanism of pangolin’s special feeding habits at the level of proteomics, and to rich the physiological evolutionary adaptive theory on animal’s feeding differentiation. This study can also provide more sufficient science evidence for selecting ingredients and optimizing composition of pangolin’s artificial food, and it is very helpful to solve the key technology problem of artificial food research and development for captive pangolin.

穿山甲是具有重大药用价值的极度濒危动物，急需开展驯养繁育研究解决物种保护及其市场需求问题。穿山甲食性高度特化，前期研究发现，其不能消化利用谷物、脊椎动物的肉、蛋以及乳制品等，但能较好的消化与蚁类相近的黄粉虫等无脊椎动物。基于一般动物消化酶表达适应其食谱的规律，我们首次提出，穿山甲可能形成了特异的消化酶系统以适应采食蚁类，却限制了对其他多种物质的消化能力。本项目拟采用蛋白质组学技术对穿山甲消化系统不同部位的消化液进行大规模蛋白质定性（shotgun技术）和关键蛋白进行靶向验证（PRM技术），分析其中主要消化酶种类及分泌特点，验证消化酶是否在适应其特化食性及不能很好消化某些人工食物中起到了关键作用。本项目有望从蛋白质组水平揭示穿山甲食性特化的生理机制，丰富动物食性分化的生理进化适应理论，并为穿山甲饲料原料选择及配方优化提供更充分的科学依据，解决当前圈养穿山甲所需的关键技术——人工饲料研制问题。

穿山甲是具有重大药用价值的极度濒危动物，亟需开展驯养繁育研究解决物种保护及市场需求矛盾。穿山甲食性高度特化，在圈养条件下，其不能很好的消化脊椎动物的肉、蛋及乳制品，但能较好的消化无脊椎动物饲料。基于动物消化酶表达适应其食谱的一般理论，我们开展了穿山甲消化酶表达谱、肠道菌群组成、对人工食物表观消化率及圈养维生素缺乏症的防治研究。结果发现，马来穿山甲唾液和肠液中均表达几丁质酶，尽管也表达蛋白酶，但多样性却比一般动物低，缺乏一些蛋白酶的表达；穿山甲肠道菌群与食蚁动物相近，且含有多种具备几丁质消化的类群。认为穿山甲消化酶表达及肠道菌群特点可能是对食蚁食性的进化适应。据此，我们选用无脊椎动物做主要原料配制的饲料，穿山甲进食后表观消化率较高，干物质消化率达72.16±2.74（n=6）；且在养殖中，发现当前配制的饲料仍存在不足，如维生素含量低，及时发现了圈养穿山甲维生素A和复合维生素B缺乏症。本项目揭示穿山甲食性特化的生理机制，丰富了动物食性分化的生理进化适应理论，为穿山甲饲料原料选择、配方优化提供更充分的科学依据，对于圈养穿山甲疾病防治具有重要意义。此外，尽管本项目已到期，但相关研究还在持续进行，后续仍会有成果产出。