Baghdasarian G, Muscatine L
Department of Organismic Biology, Ecology, and Evolution, University of California, Los Angeles, 90095-1606, USA.
Biol Bull. 2000 Dec;199(3):278-86. doi: 10.2307/1543184.
A wide range of both intrinsic and environmental factors can influence the population dynamics of algae in symbiosis with marine cnidarians. The present study shows that loss of algae by expulsion from cnidarian hosts is one of the primary regulators of symbiont population density. Because there is a significant linear correlation between the rate of algal expulsion and the rate of algal division, factors that increase division rates (e.g., elevated temperature) also increase expulsion rates. Additionally, 3H-thymidine is taken up to a greater extent by algae destined to be expelled than by algae retained in the host cnidarians. Taken together, data for rates of expulsion, rates of division at different temperatures, and uptake of 3H-thymidine suggest that dividing algal cells are preferentially expelled from their hosts. The preferential expulsion of dividing cells may be a mechanism for regulation of algal population density, where the rate of expulsion of algae may be an inverse function of the ability of host cells to accommodate new algal daughter cells. This kind of regulation is present in some cnidarian species (e.g., Aiptasia pulchella, Pocillopora damicornis), but not in all (e.g., Montipora verrucosa, Porites compressa, and Fungia scutaria).
多种内在因素和环境因素都会影响与海洋刺胞动物共生的藻类的种群动态。本研究表明，藻类从刺胞动物宿主中被排出从而导致藻类损失，是共生体种群密度的主要调节因素之一。由于藻类排出速率与藻类分裂速率之间存在显著的线性相关性，因此提高分裂速率的因素（如温度升高）也会提高排出速率。此外，与保留在宿主刺胞动物体内的藻类相比，注定要被排出的藻类摄取3H-胸腺嘧啶核苷的程度更高。综合来看，排出速率、不同温度下的分裂速率以及3H-胸腺嘧啶核苷摄取的数据表明，正在分裂的藻类细胞会优先从其宿主中被排出。优先排出正在分裂的细胞可能是一种调节藻类种群密度的机制，其中藻类的排出速率可能与宿主细胞容纳新的藻类子细胞的能力呈反比。这种调节存在于一些刺胞动物物种中（如美丽艾氏海葵、鹿角杯形珊瑚），但并非所有物种都有（如疣状蔷薇珊瑚、压缩孔珊瑚和盾形蕈珊瑚）。
