Table_1_Energy allocation trade-offs as a function of age in fungiid corals.xlsx

To compete effectively, living organisms must adjust the allocation of available energy resources for growth, survival, maintenance, and reproduction throughout their life histories. Energy demands and allocations change throughout the life history of an organism, and understanding their energy allocation strategies requires determination of the relative age of individuals. As most scleractinian corals are colonial, the relationship between age and mass/size is complicated by colony fragmentation, partial mortality, and asexual reproduction. To overcome these limitations, solitary mushroom corals, Herpolitha limax from Okinawa, Japan and Fungia fungites from Okinawa and the Great Barrier Reef (GBR), Australia, were used to investigate how energy allocation between these fundamental processes varies as a function of age. Measurements of the relative growth, biochemical profiles, fecundity of individuals of different sizes, and the settlement success of their progeny have revealed physiological trade-offs between growth and reproduction, with increasing body mass ultimately leading to senescence. The importance of energy allocation for reproduction led us to examine the reproductive strategies and sex allocation in the two studied species. In the present study, the smallest individuals of both species studied were found to invest most of their energy in relative growth, showing higher lipid and carbohydrate content than the later stages. In medium-sized corals, this pattern was overturned in favour of reproduction, manifesting in terms of both the highest fecundity and settlement success of the resulting brooded larvae. Finally, a phase of apparent senescence was observed in the largest individuals, characterized by a decrease in most of the parameters measured. In addition, complex reproductive plasticity has been revealed in F. fungites in the GBR, with individual females releasing eggs, embryos, planulae, or a combination of these. These data provide the most direct estimates currently available for physiological, age-related trade-offs during the life history of a coral. The unusual reproductive characteristics of the GBR F. fungites indicate previously unknown layers of complexity in the reproductive biology of corals and have implications for their adaptive potential across a wide geographical scale.

为有效开展生存竞争，生物体需在整个生活史中，调控可获取能量资源在生长、存活、维持及繁殖等生命活动中的分配策略。生物体的能量需求与分配模式随生活史进程动态改变，若要解析其能量分配策略，需明确个体的相对年龄。由于绝大多数石珊瑚（scleractinian corals）为群居类群，群体断裂、局部死亡及无性繁殖等过程会导致年龄与体量/大小间的关联难以厘清。为克服上述局限，本研究选取两类独居蘑菇珊瑚作为研究对象：分别为采自日本冲绳的长碟珊瑚（Herpolitha limax），以及采自冲绳与澳大利亚大堡礁（Great Barrier Reef, GBR）的蕈珊瑚（Fungia fungites），旨在探究上述核心生命过程间的能量分配如何随年龄发生变化。研究人员对不同体型个体的相对生长速率、生化谱特征、繁殖力，以及其后代的附着成功率进行了测定，结果揭示了生长与繁殖间存在生理性权衡：随着体型增大，生物体最终会走向衰老。鉴于繁殖相关的能量分配具有关键意义，本研究进一步考察了这两类研究物种的繁殖策略与性别分配模式。本研究发现，两类物种中体型最小的个体均将绝大多数能量投入相对生长，其体内脂质与碳水化合物含量高于后续生长阶段；中等体型的珊瑚则反转了这一分配模式，将资源优先投向繁殖，具体表现为最高的繁殖力以及其所育幼幼虫的最高附着成功率；而体型最大的个体则呈现出明显的衰老阶段，多数测定参数均出现下降。此外，研究还在澳大利亚大堡礁的蕈珊瑚（Fungia fungites）中发现了复杂的繁殖可塑性：单个雌性个体可释放卵子、胚胎、浮浪幼虫（planulae），或同时释放多种组合形式。本研究所得数据，是目前针对珊瑚生活史中年龄相关生理性权衡的最直接估算结果。澳大利亚大堡礁蕈珊瑚的特殊繁殖特征，揭示了此前未被认知的珊瑚繁殖生物学复杂性，同时也为其在广泛地理尺度下的适应潜力提供了重要启示。