Marine Biology Department, Centre Scientifique de Monaco, 8 Quai Antoine Ier, MC-98000, Monaco, Monaco.
Sci Rep. 2017 Sep 11;7(1):11210. doi: 10.1038/s41598-017-10348-4.
Calcareous octocorals are ecologically important calcifiers, but little is known about their biomineralization physiology, relative to scleractinian corals. Many marine calcifiers promote calcification by up-regulating pH at calcification sites against the surrounding seawater. Here, we investigated pH in the red octocoral Corallium rubrum which forms sclerites and an axial skeleton. To achieve this, we cultured microcolonies on coverslips facilitating microscopy of calcification sites of sclerites and axial skeleton. Initially we conducted extensive characterisation of the structural arrangement of biominerals and calcifying cells in context with other tissues, and then measured pH by live tissue imaging. Our results reveal that developing sclerites are enveloped by two scleroblasts and an extracellular calcifying medium of pH 7.97 ± 0.15. Similarly, axial skeleton crystals are surrounded by cells and a calcifying medium of pH 7.89 ± 0.09. In both cases, calcifying media are more alkaline compared to calcifying cells and fluids in gastrovascular canals, but importantly they are not pH up-regulated with respect to the surrounding seawater, contrary to what is observed in scleractinians. This points to a potential vulnerability of this species to decrease in seawater pH and is consistent with reports that red coral calcification is sensitive to ocean acidification.
钙质八放珊瑚是生态上重要的钙化生物，但相对于石珊瑚而言，人们对其生物矿化生理学知之甚少。许多海洋钙化生物通过在钙化部位上调 pH 值来促进钙化，以对抗周围海水的影响。在这里，我们研究了形成硬骨珊瑚和轴向骨骼的红色八放珊瑚 Corallium rubrum 的 pH 值。为了实现这一目标，我们在载玻片上培养微菌落，便于对硬骨珊瑚和轴向骨骼的钙化部位进行显微镜观察。最初，我们广泛描述了生物矿化和钙化细胞在其他组织中的结构排列，然后通过活体组织成像测量 pH 值。我们的结果表明，发育中的硬骨珊瑚被两个珊瑚骨母细胞和一个 pH 值为 7.97 ± 0.15 的细胞外钙化介质所包围。同样，轴向骨骼晶体被细胞和一个 pH 值为 7.89 ± 0.09 的钙化介质所包围。在这两种情况下，与消化腔中的钙化细胞和流体相比，钙化介质的碱性更强，但重要的是，它们没有相对于周围海水进行 pH 值上调，这与在石珊瑚中观察到的情况相反。这表明该物种对海水 pH 值下降的潜在脆弱性，这与红珊瑚钙化对海洋酸化敏感的报告一致。
