Effects of nutritional history on nitrogen assimilation in congeneric temperate and tropical scleractinian corals
Effects of nutritional history on nitrogen assimilation in congeneric temperate and tropical scleractinian corals
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营养史对同属温带和热带造石珊瑚氮同化的影响
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发表时间：
2004
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影响因子：
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通讯作者：
F. Lipschultz
中科院分区：
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作者：
G. Piniak;F. Lipschultz
众所周知，珊瑚的营养历史会影响代谢过程，如无机养分的吸收和光合作用，但它如何影响摄入猎物的同化效率或猎物氮在宿主和共生体之间的分配却知之甚少。将温带硬核珊瑚Oculina arbuscula及其热带同系物Oculina diffusa驯化为3种营养模式（每周饲喂2次、饥饿、添加无机营养剂饥饿），然后饲喂以稳定同位素示踪剂15N标记的nauplii Artemia。两种摄食珊瑚的同化效率均最低（丛木珊瑚为36-51%，白花珊瑚为38-57%），但与其他摄食珊瑚的同化效率无统计学差异。喂食和饥饿的珊瑚也有相似的NH4+排泄率。这与氮循环和保护模式预测的氮排泄减少和氨基酸分解代谢减少不一致。在珊瑚宿主组织中，采食4 h内摄入的15N约90%为tca不溶性（蛋白质和核酸）和乙醇溶性（氨基酸/低分子量化合物）。tca不溶池也是两种虫黄藻中标记的主要储存库（丛树花为40-53%，白花为50-60%）。然而，营养史对食饵15N在寄主和虫黄藻生化池中的分布没有影响。这一结果与氮守恒假说一致，因为优先的碳代谢将使饥饿对含氮生化库的影响最小化。
The nutritional history of corals is known to affect metabolic processes such as inorganic nutrient uptake and photosynthesis, but little is known about how it affects assimilation efficiency of ingested prey items or the partitioning of prey nitrogen between the host and symbiont. The temperate scleractinian coral Oculina arbuscula and its tropical congener Oculina diffusa were acclimated to three nutritional regimes (fed twice weekly, starved, starved with an inorganic nutrient supplement), then fed Artemia nauplii labeled with the stable isotope tracer 15N. Fed corals of both species had the lowest assimilation efficiencies (36–51% for O. arbuscula, 38–57% for O. diffusa), but were not statistically different from the other nutritional regimes. Fed and starved corals also had similar NH4+ excretion rates. This is inconsistent with decreased nitrogen excretion and reduced amino acid catabolism predicted by both the nitrogen recycling and conservation paradigms. In coral host tissue, ~90% of the ingested 15N was in the TCA-insoluble (protein and nucleic acids) and ethanol-soluble (amino acids/low molecular weight compounds) within 4 h of feeding. The TCA-insoluble pool was also the dominant repository of the label in zooxanthellae of both species (40–53% in O. arbuscula, 50–60% in O. diffusa). However, nutritional history had no effect on the distribution of prey 15N within the biochemical pools of the host or the zooxanthellae for either species. This result is consistent with the nitrogen conservation hypothesis, as preferential carbon metabolism would minimize the effects of starvation on nitrogen-containing biochemical pools.