摘要
一般研究中,通常将类似澄江动物群或关岭动物群为代表的生物软体印痕化石保存归因为与缺氧环境等有关的特异条件。本文关注到通常与化石降解和埋藏有关的缺氧环境推测并没有表达机理和成立条件;生物体内自身携带大量的微生物可能对生物的降解作用需要得到重视。为证实水体中氧气含量与生物非矿化组织印痕保存间的关系,本文通过设计条件控制(太湖银鱼,30℃,无菌纯净水、无外界微生物)进行有氧和缺氧环境的对比实验。该条件下的模拟对比实验研究证实:1)总体来说生物降解过程在有氧和缺氧环境下具有相似的降解速度;2)两者的降解实验在前期有短暂的差异,而144小时(6天)后有氧和无氧环境具有基本一致的降解速度和程度,其中较多样本6天后在缺氧环境的降解速度略高于有氧环境,短时间(6天)的降解差异是否会造成矿化差异有待研究;3)生物体本身携带的以肠道微生物为主的好氧和兼性厌氧微生物,足以使生物以蛋白质为代表的器官结构产生相似的破坏性降解,在本研究中是主要的降解因素;4)实验中所检出的生物体肠道内普遍存在的兼性厌氧微生物,可能是导致有氧和缺氧环境具有相似降解过程的主要原因;5)生物降解过程早期由于蛋白质的降解,微环境趋向于弱碱性而非一般推测的酸性;6)在实验设定条件下的有氧环境和缺氧环境对化石的形成和保存的早期过程相似,其他理化条件下的降解过程和结论需要进一步实验证实。
The fossil record of non-biomineralized orga-nisms,as in the Chengjiang fauna（Burgess Shale type preservation） and Guanling fauna（lagerstatte）,provides extremely important evidence to understand the anatomy of early animal life.It is widely believed that their preservation condition resulted from anoxic environments of deposition.However although the decay process in animals is clearly related to the physic-chemical conditions of depositional setting,it is also related to microbes,especially to intestinal ones.This research reports experiments to compare oxic and anoxic decay of a small fish under controlled conditions at 30°C.The experiments demonstrated that the speed of decay was fairly similar during several days between the oxic and anoxic conditions,but was faster in the oxic environment during the first 6 days,after which time it became similar in both environments and subsequently became faster in anoxic conditions.The main decay microbes were Stenotropho-monas maltophilia,Klebsiella sp.,Enterobacter cloacae,Pantoea sp.（identified by 16 Sr DNA BLAST） in most living animals and appear to play a major role in protein decay.The widespread occurrence of facultative anaerobes in the intestines of animals is sufficient to explain the broad simila-rity of results in the experiments between anoxic and oxic conditions.Notably the pH of both of these microenvironments rose in the duration of the experiments,in contrast to the general idea of increasing acidity through microbial activity,but is consistent with other experimental studies of decay amongst fish.The interaction and balance between decay and soft-body mineralization involved in fossilization requests additional experimentation,especially regarding an examination of physical-chemical conditions including in particular the materials and structures in the microenvironment of animal external and internal surface.
出处
《古生物学报》
CAS
CSCD
北大核心
2011年第4期526-538,共13页
Acta Palaeontologica Sinica
