Meeting the photosynthetic demand for inorganic carbon in an alga–invertebrate association: preferential use of CO2 by symbionts in the giant clam Tridacna gigas
Meeting the photosynthetic demand for inorganic carbon in an alga–invertebrate association: preferential use of CO2 by symbionts in the giant clam Tridacna gigas
复制标题
满足藻类-无脊椎动物组合中对无机碳的光合作用需求：巨型砗磲中的共生体优先使用二氧化碳
DOI：
10.1098/rspb.2000.1031
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
D. Yellowlees
中科院分区：
文献类型：
--
作者：
W. Leggat;T. Rees;D. Yellowlees
与大多数海洋无脊椎动物排泄呼吸二氧化碳不同，巨蛤(Tridacna Gias)必须获得无机碳(Ci)才能维持其光合性甲藻的共生种群。它们满足这一需求的能力将反映在它们高光合作用期间血淋巴的Ci浓度上。血淋巴中的Ci浓度与照度成反比，最小Ci浓度在光照峰值时为0.75 mm，在黑暗中增加到1.2 mm。在血淋巴中盛行的峰值光照条件下，分离的虫黄藻的光合作用速率显着低于潜在的最大光合作用速率(Pmax)，表明虫黄藻在栖息地受到碳的限制。这与以往关于珊瑚共生的研究是一致的。Pmax不受pH的影响，但Ci的半饱和常数(K0.5(Ci))随pH的升高(6.5-9.0)而显著增加，而K0.5(Ci)在同一范围内仅略有下降。这些结果表明，与珊瑚中使用碳酸氢盐的共生体相比，文蛤中的虫黄藻使用二氧化碳作为其Ci的主要来源。讨论了它们的生理意义，并与珊瑚共生进行了比较。
Unlike most marine invertebrates which excrete respiratory CO2, giant clams (Tridacna gigas) must acquire inorganic carbon (Ci) in order to support their symbiotic population of photosynthetic dinoflagellates. Their capacity to meet this demand will be reflected in the Ci concentration of their haemolymph during periods of high photosynthesis. The Ci concentration in haemolymph was found to be inversely proportional to irradiance with a minimum Ci concentration of 0.75 mM at peak light levels increasing to 1.2 mM in the dark. The photosynthetic rate of isolated zooxanthellae under conditions that prevail in the haemolymph at peak light levels was significantly less than the potential Pmax (maximum photosynthetic rate) indicating that zooxanthellae are carbon limited in hospite. This is consistent with previous studies on the hermatypic coral symbiosis. The Pmax was not affected by pH but there was a dramatic increase in the half–saturation constant for Ci (K0.5(Ci)) with increasing pH (6.5–9.0) and only a small decrease in K0.5(CO2) over the same range. These results indicate that zooxanthellae in giant clams use CO2 as the primary source of their Ci in contrast to symbionts in corals, which use bicarbonate. The physiological implications are discussed and comparison is made with the coral symbiosis.