Cuttlebone morphometry measurements

Changes in seawater carbonate chemistry that accompany ongoing ocean acidification have been found to affect calcification processes in many marine invertebrates. In contrast to the response of most invertebrates, calcification rates increase in the cephalopod Sepia officials during long-term exposure to elevated seawater pCO2. The present trial investigated structural changes in the cuttlebones of S. officinalis calcified during 6 weeks of exposure to 615 Pa CO2. Cuttlebone mass increased sevenfold over the course of the growth trail, reaching a mean value of 0.71 ± 0.15 g. Depending on cuttlefish size (mantle lengths 44-56 mm), cuttlebones of CO2-incubated individuals accreted 22-55% more CaCO3 compared to controls at 64 Pa CO2. However, the height of the CO2- exposed cuttlebones was reduced. A decrease in spacing of the cuttlebone lamellae, from 384 ± 26 to 195 ± 38 lm, accounted for the height reduction The greater CaCO3 content of the CO2-incubated cuttlebones can be attributed to an increase in thickness of the lamellar and pillar walls. Particularly, pillar thickness increased from 2.6 ± 0.6 to 4.9 ± 2.2 lm. Interestingly, the incorporation of non-acidsoluble organic matrix (chitin) in the cuttlebones of CO2- exposed individuals was reduced by 30% on average. The apparent robustness of calcification processes in S. officials, and other powerful ion regulators such as decapod cructaceans, during exposure to elevated pCO2 is predicated to be closely connected to the increased extracellular [HCO3 -] maintained by these organisms to compensate extracellular pH. The potential negative impact of increased calcification in the cuttlebone of S. officials is discussed with regard to its function as a lightweight and highly porous buoyancy regulation device. Further studies working with lower seawater pCO2 values are necessary to evaluate if the observed phenomenon is of ecological relevance.

伴随持续海洋酸化（ocean acidification）的海水碳酸盐化学变化已被证实会影响多种海洋无脊椎动物的钙化过程（calcification processes）。与大多数无脊椎动物的反应相反，头足类（cephalopod）乌贼（Sepia officinalis）在长期暴露于升高的海水pCO₂环境中时，其钙化速率会升高。本试验研究了暴露于615 Pa CO₂环境6周期间，S. officinalis钙化形成的乌贼骨（cuttlebone）的结构变化。在生长试验过程中，乌贼骨质量增加了7倍，平均值达到0.71±0.15 g。根据乌贼外套膜长度（44-56 mm），CO₂处理组个体的乌贼骨沉积碳酸钙（CaCO₃）量比处于64 Pa CO₂对照组的个体多22-55%。然而，CO₂暴露组的乌贼骨高度有所降低，这归因于乌贼骨薄片（lamellae）间距从384±26 μm减少至195±38 μm。CO₂处理组乌贼骨中更高的CaCO₃含量可归因于薄片和柱状壁厚度的增加，尤其是柱状壁厚度从2.6±0.6 μm增至4.9±2.2 μm。有趣的是，CO₂暴露个体的乌贼骨中非酸溶性有机基质（几丁质，chitin）的掺入量平均减少30%。S. officinalis及其他强效离子调节生物（如十足目甲壳类，decapod crustaceans）在暴露于升高的pCO₂环境时，其钙化过程表现出的明显稳定性，被认为与这些生物为补偿细胞外pH而维持的细胞外碳酸氢根离子浓度（[HCO₃⁻]）升高密切相关。本文讨论了S. officinalis乌贼骨钙化增加对其作为轻质、高孔隙度浮力调节装置功能的潜在负面影响。需要进一步研究更低海水pCO₂值下的情况，以评估观察到的现象是否具有生态相关性。