不同食性蚂蚁颊下囊与消化道形态结构及细菌多样性比较研究

Ants are highly evolved social insects, which are far more abundant than most other insects in the world. Lots of ants established closely mutual commensal or symbiotic ties with other organisms, e.g., microbes, plants and hemipteran insects. Ants show significant diversification in feeding habits and nutrition niches during exploring and utilizing food resources. Morphological modification of infrabaccal pockets located in the preoral cavity together with alimentary tracts of ants are significant manifestations associated with differentiation of feeding habits and survival strategies of ants, and related microorganisms habored in the alimentary tracts play an important role in nutrition providing, immune responses, pathogen resistance, ecology and evolution of their hosts. However, documents on the morphological variations and bacterial community in infrabaccal pockets and alimentary tracts of ants are still limited, and this is particularly the case on ants occurring in temperate region. In addition, little is known about the similarities and differences in bacterial communities of the infrabaccal pockets and alimentary tracts of ants with different foraging habits and nutrition niches. For the current project we are taking our work further to solve the problems mentioned above by comprehensively using methods of comparative morphology and molecular biology. This project will focus on the dominant ants with distinctly diversified foraging habits and niches, representing the four different subfamilies in Qinling Mountains and adjacent areas. The morphology and ultrastructure of the infrabaccal pockets and alimentary tracts of different representative ants will be investigated to enlighten the correlationship between the morphological variations of related structures and feeding habits of ants. In addition, the gut microbiota of dominant ants will be investigated using 454 pyrosequencing to analyze its correlation with ant species, feeding habits, developmental stages and castes of related ants. Furthermore, we also aim to clarify the vertically transmitted endosymbionts in defferent ants by analyzing the coevolution between the bacteria in their eggs and the adult ants. The results of this project will hopefully further our understanding and provide new information on the coevolution of ants and related microbes, and will be informative for future studies on the effects of related endosimbionts to their hosts.

蚂蚁是高度进化的社会性昆虫，其食性和营养生态位在自然演化中产生了显著分化。口前腔的“颊下囊”和消化系统特化正是其食性分化和生存策略多样性的重要体现；消化道中一些微生物更对宿主蚂蚁的营养利用、免疫反应和繁衍具有重要影响作用。但蚂蚁的颊下囊和消化道结构变异及微生物组成研究仅限于部分热带种类，温带蚂蚁的颊下囊和消化道变异及微生物组成一直缺乏研究。本项目拟以秦岭森林生态系统中食性和生态位分化明显的代表性优势蚁种为研究对象，利用体视显微镜和电镜技术对其颊下囊、消化道形态结构进行研究，明晰其消化道结构分化与食性的相关性；采用454高通量测序技术对颊下囊和消化道细菌组成进行研究，分析细菌多样性与蚂蚁食性、发育阶段及成虫品级的相关性，并结合卵中细菌组成分析探究不同食性蚂蚁体内可垂直传播的共生细菌种类，为相关微生物与宿主蚂蚁的协同进化及其对宿主生长发育、种群繁衍的影响研究提供新的信息。

蚂蚁是高度进化的社会性昆虫，其食性和营养生态位在自然演化中产生了显著分化。口前腔的“颊下囊”和消化系统特化正是其食性分化和生存策略多样性的重要体现。本项目以秦岭森林生态系统中食性和生态位分化明显的代表性优势蚁种为研究对象，开展了不同亚科主要蚂蚁种类的食性、消化道结构比较形态学和肠道微生物组成特点研究。（1）明确了秦岭林区优势蚂蚁种类野外采集食物的类型及其比例，并结合稳定同位素分析，确定了它们在森林生态系统中的食性和营养级地位。（2）明确了三个亚科（蚁亚科、切叶蚁亚科和猛蚁亚科）代表性蚂蚁种类的消化道结构和形态差异，发现前胃在各亚科间形态分化明显，在亚科内种间变化较小。首次发现杂食性日本弓背蚁和肉食性爪哇厚结猛蚁颊下囊内表面存在特殊形态的过滤毛，种间差异显著；颊下囊具有极大的伸缩性，具有上午基本无内含物、而下午一般较为饱满的日规律。（3）传统的微生物培养方法结果表明，工蚁颊下囊中普遍存在放线菌、芽孢杆菌和酵母菌及其他优势菌群，且微生物的丰度和多样性水平明显高于嗉囊和中肠。肉食性爪哇厚结猛蚁颊下囊也分布有丰富的放线菌，其中链霉菌为优势菌群，对于多种林木病原真菌具有较高的抑菌活性。（4）高通量测序结果表明，不同亚科蚂蚁消化道和颊下囊细菌种类组成存在明显差异，蚁亚科蚂蚁的颊下囊和嗉囊普遍存在乳酸菌Lactobacillus和醋酸菌Acetobacter，与该类蚂蚁喜食半翅目昆虫的蜜露相适应；猛蚁亚科普遍存在Mesoplasma、Wolbachia、Spiroplasma和Serratia细菌，与该类蚂蚁的肉食和捕食性行为相适应；而切叶蚁亚科的菌群组成在种间变化较大，揭示了该亚科的复杂食性。此外，颊下囊细菌组成明显不同于相应的消化道，而与幼虫比较相似，该结构的潜在功能有待于进一步的揭示。以上研究结果为微生物与宿主蚂蚁的协同进化及其对宿主生长发育、种群繁衍的影响研究提供了新的资料，对深入揭示蚂蚁与微生物的关系具有重要的意义。