(Table 1) List of studied samples with vestimentiferan tubes

Vestimentiferan tube worms are prominent members of modern methane seep communities and are totally reliant as adults on symbiotic sulphide-oxidizing bacteria for their nutrition. The sulphide is produced in the sediment by a biochemical reaction called the anaerobic oxidation of methane (AOM). A well-studied species from the Gulf of Mexico shows that seep vestimentiferans 'mine' sulphide from the sediment using root-like, thin walled, permeable posterior tube extensions, which can also be used to pump sulphate and possibly hydrogen ions from the soft tissue back into the sediment to increase the local rate of AOM. The 'root-balls' of exhumed seep vestimentiferans are intimately associated with carbonate nodules, which are a result of AOM. We have studied vestimentiferan specimens and associated carbonates from seeps at the Kouilou pockmark field on the Congo deep-sea fan and find that some of the posterior 'root' tubes of living specimens are enclosed with carbonate indurated sediment and other, empty examples are partially or completely replaced by the carbonate mineral aragonite. This replacement occurs from the outside of the tube wall inwards and leaves fine-scale relict textures of the original organic tube wall. The process of mineralization is unknown, but is likely a result of post-mortem microbial decay of the tube wall proteins by microorganisms or the precipitation from locally high flux of AOM derived carbonate ions. The aragonite-replaced tubes from the Kouilou pockmarks show similar features to carbonate tubes in ancient seep deposits and make it more likely that many of these fossil tubes are those of vestimentiferans. These observations have implications for the supposed origination of this group, based on molecular divergence estimates.管栖须腕蠕虫（Vestimentiferan tube worms）是现代甲烷冷泉群落中的优势类群，成虫完全依赖共生硫化物氧化细菌获取营养。沉积物中的硫化物由名为甲烷厌氧氧化（anaerobic oxidation of methane, AOM）的生化反应生成。对墨西哥湾一处研究较为深入的物种的研究表明，冷泉生境的管栖须腕蠕虫通过类根系、薄壁且可渗透的后部管状延伸结构“开采”沉积物中的硫化物；这类结构还可将软组织内的硫酸盐及可能的氢离子泵回沉积物中，以提升局部甲烷厌氧氧化反应的速率。被发掘出的冷泉管栖须腕蠕虫的“根球”与碳酸盐结核紧密伴生，而碳酸盐结核正是甲烷厌氧氧化的产物。我们对刚果深海扇奎卢麻穴田（Kouilou pockmark field）冷泉中的管栖须腕蠕虫标本及其伴生碳酸盐开展了研究，发现活体标本的部分后部“根”状管结构被碳酸盐硬结沉积物包裹，而其余空标本则被碳酸盐矿物文石（aragonite）部分或完全置换。该置换过程从管壁外侧向内开展，并保留了原始有机管壁的精细残余结构。目前该矿化过程的机制尚不明确，但推测可能源自微生物对管壁蛋白质的死后降解，或是由甲烷厌氧氧化产生的高通量碳酸根离子在局部发生沉淀所致。产自奎卢麻穴的文石置换管与古代冷泉沉积中的碳酸盐管具有相似特征，这使得我们更有依据推断，这类化石管中有许多均属于管栖须腕蠕虫。基于分子分化估算得出的该类群起源推论，本研究的观测结果具有重要启示意义。