Detritivory, coprophagy, and the evolution of digestive mutualisms in Dictyoptera
Detritivory, coprophagy, and the evolution of digestive mutualisms in Dictyoptera
复制标题
网翅目的碎屑、粪食和消化互利共生的进化
作者：
C. Nalepa;D. Bignell;C. Bandi
摘要：我们回顾了包括蟑螂和白蚁在内的现存有害食肉动物的文献，得出结论：食粪是导致双翅目主干类群后肠发酵系统进化的关键行为。共噬作用利用纤维素基底物上浓缩的微生物群体。这些微生物是潜在的互助者和食物，但它们也会启动纤维素的降解，解毒化感物质并软化底物，这一现象被称为“外瘤胃”。我们认为，复杂的后肠动物的进化是一个内化这种自组装的微生物群落的过程，伴随着宿主-微生物相互依赖、新生儿微生物接种来源和宿主社会行为的变化。当白蚁的祖先成为亚社会时，过程滋养松弛是从先前存在的种内食性行为进化而来的，因为氧单和超鞭毛虫包囊的生理学排除了它们通过成虫粪便中的包囊转移的可能性。利用鞭毛虫的营养阶段作为食物的好处加强了这种行为。这些鞭毛虫与双翅目昆虫谱系的联系是古老的，可能起源于石炭纪煤沼泽的外部瘤胃的一部分。
Summary: We review literature on extant detritivores, including cockroaches and termites, and conclude that coprophagy was the key behavior leading to the evolution of hindgut fermentation systems in the stem group of Dictyoptera. Coprophagy exploits concentrated microbial consortia on cellulose based substrates. These microbes are potential mutualists and food, but they also initiate degradation of cellulose, detoxify allelochemicals and soften the substrate, a phenomenon known as the "external rumen". We suggest that the evolution of a sophisticated hindgut fauna is a process of internalizing this self-assembled microbial community, accompanied by changes in host-microbe interdependence, the source of microbial inoculum for neonates, and host social behavior. Proctodeal trophallaxis evolved from pre-existing intraspecific coprophagous behavior when termite ancestors became subsocial, because the physiology of encystment in oxymonad and hypermastigid flagellates precludes their transfer via cysts in adult feces. The behavior was reinforced by the benefits of using the trophic stages of flagellates as food. The association of these flagellates with the dictyopteran lineage is an ancient one, and may have originated as part of the external rumen in the Carboniferous coal swamps.