Bingham Brian L, Dimond James L, Muller-Parker Gisèle
Department of Environmental Sciences, Western Washington University, 516 High Street, Bellingham, WA 98225, USA
Shannon Point Marine Center, Western Washington University, 1900 Shannon Point Road, Anacortes, WA 98221, USA.
Proc Biol Sci. 2014 Aug 22;281(1789):20140548. doi: 10.1098/rspb.2014.0548.
Along the North American Pacific coast, the common intertidal sea anemone Anthopleura elegantissima engages in facultative, flexible symbioses with Symbiodinium muscatinei (a dinoflagellate) and Elliptochloris marina (a chlorophyte). Determining how symbiotic state affects host fitness is essential to understanding the ecological significance of engaging in such flexible relationships with diverse symbionts. Fitness consequences of hosting S. muscatinei, E. marina or negligible numbers of either symbiont (aposymbiosis) were investigated by measuring growth, cloning by fission and gonad development after 8.5-11 months of sustained exposure to high, moderate or low irradiance under seasonal environmental conditions. Both symbiotic state and irradiance affected host fitness, leading to divergent life-history strategies. Moderate and high irradiances led to a greater level of gonad development in individuals hosting E. marina, while high irradiance and high summer temperature promoted cloning in individuals hosting S. muscatinei and reduced fitness of aposymbiotic anemones. Associating with S. muscatinei may contribute to the success of A. elegantissima as a spatial competitor on the high shore: (i) by offsetting the costs of living under high temperature and irradiance conditions, and (ii) by promoting a high fission rate and clonal expansion. Our results suggest that basic life-history characteristics of a clonal cnidarian can be affected by the identity of the endosymbionts it hosts.
在北美太平洋沿岸，常见的潮间带海葵优美列指海葵（Anthopleura elegantissima）与马斯卡廷共生藻（Symbiodinium muscatinei，一种甲藻）和滨海椭圆绿藻（Elliptochloris marina，一种绿藻）形成兼性、灵活的共生关系。确定共生状态如何影响宿主适应性对于理解与不同共生体建立这种灵活关系的生态意义至关重要。通过在季节性环境条件下持续暴露于高、中或低光照8.5 - 11个月后测量生长、通过分裂进行克隆以及性腺发育，研究了宿主马斯卡廷共生藻、滨海椭圆绿藻或两种共生体数量均可忽略不计（非共生状态）时的适应性后果。共生状态和光照均影响宿主适应性，导致不同的生活史策略。中等和高光照条件下，宿主滨海椭圆绿藻的个体性腺发育水平更高，而高光照和夏季高温促进了宿主马斯卡廷共生藻个体的克隆，并降低了非共生海葵的适应性。与马斯卡廷共生藻共生可能有助于优美列指海葵作为高岸空间竞争者的成功：（i）通过抵消在高温和光照条件下生存的成本，以及（ii）通过促进高分裂率和克隆扩张。我们的结果表明，克隆性刺胞动物的基本生活史特征可能受到其宿主内共生体身份的影响。
