Temperature, length and width of Tuberculodinium vancampoae (the resting cyst of Pyrophacus steinii) from surface sediments in the Omura Bay

Cyst forming dinoflagellates are useful in reconstructing past environments. For accuracy it is essential to know how environmental parameters such as salinity, temperature and light influence dinoflagellate cyst production and morphology. Here the effect of variation in these parameters on production and morphology of Tuberculodinium vancampoae (the resting stage of Pyrophacus steinii) is detailed. Encystment of T. vancampoae has been observed in all studied culture-experiments although only a few cysts are being formed at the limits of the temperature and salinity ranges (16.5°C, 34.8 °C and 20, 45 psu) with highest cyst production at 27 °C and 35 psu. Temperature clearly affects cyst morphology; cysts formed in cultures grown at 16.5 °C and 34.8 °C possess small, flattened processes. These cysts are not completely absent in cultures grown at intermediate temperatures but form only a minor part of the association. In previous studies, salinity has been found to influence the cyst morphology of several dinoflagellate species but this seems not to be the case for T. vancampoae. In this study there was no morphological variation related to salinity. High cyst production was observed in cultures grown under moderate to strong illumination but variation in illumination did not lead to morphological change. Our findings correspond to field observations where T. vancampoae has been observed in surface sediments of the sub-tropical to tropical regions characterised by mean sea surface temperatures between 12.7 °C and 29.5 °C, and sea surface salinities between 16.9 and 36.6 psu. In contrast to previous suggestions, T. vancampoae appears to be heterothallic rather than homothallic.产孢甲藻（dinoflagellate）在古环境重建中具有重要应用价值。为确保重建精度，明确盐度、温度、光照等环境参数对甲藻孢囊产出量与形态特征的影响至关重要。本研究详细阐述了上述环境参数的变化对Tuberculodinium vancampoae（Pyrophacus steinii的休眠阶段）的孢囊产出量与形态特征的影响。在所有开展的培养实验中，均观测到T. vancampoae的孢囊形成过程，但在温度与盐度范围的极限条件下（16.5℃、34.8℃以及20、45 psu）仅能形成少量孢囊，而在27℃、35 psu条件下孢囊产出量最高。 温度对孢囊形态具有显著影响：在16.5℃与34.8℃条件下培养得到的孢囊，具有短小扁平的突起结构。在中等温度条件下培养的样本中，此类孢囊并非完全缺失，但仅占孢囊群落的极小比例。 既往研究表明，盐度会影响多种甲藻的孢囊形态，但T. vancampoae并非如此；本研究未观测到与盐度相关的孢囊形态变化。 在中等至强光照条件下培养的样本中，孢囊产出量较高，但光照强度的变化并未引起孢囊形态的改变。 本研究结果与野外观测结果一致：在亚热带至热带区域的表层沉积物中，曾观测到T. vancampoae的存在，该区域的平均海表温度介于12.7℃至29.5℃之间，海表盐度介于16.9至36.6 psu之间。 与既往假说相悖的是，T. vancampoae实为异宗配合，而非同宗配合。