Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-STAR), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan.
Biogeochemistry Research Center, Research Institute for Marine Resources Utilization (MRU), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan.
PLoS One. 2022 Aug 4;17(8):e0272032. doi: 10.1371/journal.pone.0272032. eCollection 2022.
The hadal amphipod Hirondellea gigas is an emblematic animal of the Pacific trenches, and has a number of special adaptations to thrive in this 'extreme' environment, which includes the deepest part of the Earth's ocean. One such adaptation that has been suggested is the presence of an 'aluminum gel shield' on the surface of its body in order to prevent the dissolution of calcitic exoskeleton below the carbonate compensation depth. However, this has not been investigated under experimental conditions that sufficiently prevent aluminum artefacts, and the possibility of other elements with similar characteristic X-ray energy as aluminum (such as bromine) has not been considered. Here, we show with new electron microscopy data gathered under optimized conditions to minimize aluminum artefacts that H. gigas actually does not have an aluminum shield-instead many parts of its body are enriched in bromine, particularly gastric ossicles and setae. Results from elemental analyses pointed to the use of calcite partially substituted with magnesium by H. gigas in its exoskeleton, in order to suppress dissolution. Our results exemplify the necessity of careful sample preparation and analysis of the signals in energy-dispersive X-ray spectroscopic analysis, and the importance of analyses at different electron energies.
深渊端足目动物 Hirondellea gigas 是太平洋海沟的标志性动物，为了在这种“极端”环境中茁壮成长，它有许多特殊的适应性，包括地球海洋的最深处。有人提出，其体表存在一种“铝凝胶屏蔽”，以防止碳酸钙补偿深度以下方方解石外骨骼的溶解。然而，在足以防止铝伪影的实验条件下，尚未对此进行研究，也没有考虑到其他具有与铝相似特征 X 射线能量的元素（如溴）。在这里，我们通过在优化条件下收集的新电子显微镜数据表明，H. gigas 实际上没有铝屏蔽——相反，其身体的许多部位富含溴，特别是胃骨和刚毛。元素分析结果表明，H. gigas 在其外骨骼中使用了部分被镁取代的方解石，以抑制溶解。我们的结果说明了在能量色散 X 射线光谱分析中仔细准备样品和分析信号的必要性，以及在不同电子能量下进行分析的重要性。
