美国普渡大学Roger N. Bryant团队的一项最新研究报道了现代lucinid双壳类中基于无机硫酸盐的化学共生特征。相关论文于2023年8月16日发表于国际顶尖学术期刊《地质学》杂志上。

课题组开始使用现代的lucinid双壳类来评估这一预测，这是一个有用的测试案例，因为(1)所有现代属都有共生体，生活在硫化物沉积物中，以及(2)形态学证据表明，从最早的祖先lucinid开始，这就是事实。研究人员测量了一组现代天然lucinid光泽壳中的S物种形成、丰度和CAS-δ³⁴S值，此外还测量了作为对照的有和没有S-氧化共生体的底栖双壳类的值。

对于天然lucinids而言，CAS浓度至多为非共生的底栖双壳类的三分之一，CAS-δ³⁴S 值(9.2‰—18.5‰)低于现代海水(21‰)或底栖双壳类(20.8‰—21‰)。这些观察结果表明，具有共生体的lucinids将硫化物衍生的硫酸盐结合到它们的壳中，这是它们化学共生的直接结果。研究认为，天然 lucinid中 的 CAS ³⁴S 损耗的浓度和数量反映了环境中硫化物的浓度，并且可以有效地揭示化石中的化学共生现象。

据了解，以硫氧化细菌鳃为宿主的内共生体的双壳类可以栖息在低多样性、硫化物环境的生态位。然而，由于缺乏适用于化石的可靠方法，了解这种生命策略的历史受到限制。碳酸盐化石中与碳酸盐相关的硫酸盐 S 同位素比率(CAS-δ³⁴S)的测量，可以通过识别环境硫化物的共生驱动氧化作用来填补这一空白。

附：英文原文

Title: Inorganic sulfate-based signatures of chemosymbiosis in modern infaunal lucinids

Author: Roger N. Bryant, Jocelyn A. Richardson, Tara C. Kalia, Olivier Gros, Juan Lopez-Garriga, Clara L. Blttler

Issue&Volume: 2023-08-16

Abstract: Bivalves that host sulfur-oxidizing bacterial gill-hosted endosymbionts can inhabit low-diversity, sulfidic environmental niches. However, understanding the history of this life strategy is limited by the lack of a robust method that can be applied to fossils. Measurements of carbonate-associated sulfate S isotope ratios (CAS-δ³⁴S) in carbonate fossils could fill this void by fingerprinting symbiont-driven oxidation of environmental sulfide. We begin to evaluate this prediction using modern lucinid bivalves, a useful test case because: (1) all modern genera host symbionts and live in sulfidic sediments, and (2) morphological evidence suggests that this has been true since the earliest ancestral lucinids. We measured S speciation, abundance, and CAS-δ³⁴S values in the shells of a suite of modern infaunal lucinids, in addition to epifaunal bivalves with and without S-oxidizing symbionts as controls. For infaunal lucinids, CAS concentrations were at most one-third of those of non-symbiotic epifaunal bivalves, and CAS-δ³⁴S values were lower (9.2‰18.5‰) than in modern seawater (21‰) or epifaunal bivalves (20.8‰21‰). These observations indicate that lucinids with symbionts incorporate sulfide-derived sulfate into their shells as a direct consequence of their chemosymbiosis. We argue that both the concentration and the magnitude of 34S depletion in infaunal lucinid CAS reflect environmental sulfide concentrations and could viably reveal chemosymbiosis in fossils.

DOI: 10.1130/G51353.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G51353.1/627624/Inorganic-sulfate-based-signatures-ofredirectedFrom=fulltext