Life history adaptations of larvacean tunicates to environmental variability

我的长期目标是确定冷海浮游动物对环境条件的整体适应能力。这一点很重要，因为适应决定了关键的生活史特征，如年龄和成熟时的大小、繁殖力(即产蛋率)和死亡率，这些共同决定了季节和年际周期的补充和丰度。生活史特征受到巨大的选择压力和快速进化变化的影响。我的指导性概念模型是进化论中经典的生活史优化模型，在该模型中，关键性状受到生理权衡的影响，其中许多与体型有关。例如，生活史理论预测，体型越大，生育能力就越强，从而终生健康状况也就越好。然而，如果增加体型需要更长的发育时间，从而增加被吃掉的可能性，那么增加繁殖力可能会通过权衡来阻止。 在这项提案中，我概述了未来五年的两个目标：(1)确定冷洋幼虫的生殖分配和繁殖力；(2)确定它们的最佳年龄和成熟时的大小。生殖分配将以各种方式确定，包括投资于鸡蛋的脂肪和脂肪酸的数量。一种假说认为，幼虫是非常熟练的卵大小操纵者，这是因为一种新的机制，即在生命周期的很晚阶段选择成熟的卵，以响应食物质量。目前尚不清楚这种情况是如何发生的。在第二个目标中，我将确定幼虫的最佳年龄和成熟时的大小，并测试经典优化理论和一个新的基于温度的机制模型的预测。从本质上讲，我将回答这个问题，即幼虫是在固定大小的情况下繁殖，还是在固定的年龄繁殖。这项研究将有助于将海洋浮游动物的研究超越过去的生物地球化学方法，进入生活史理论的背景下。这将有利于学术和政府部门的海洋科学家、政府监管机构以及渔业和水产养殖。

My long term goal is to determine whole-organism adaptations of cold ocean zooplankton to environmental conditions. This is important because adaptations determine key life history traits, such as age and size-at-maturity, fecundity (i.e. egg production rate), and mortality, which together determine seasonal and interannual cycles of recruitment and abundance. Life history traits are subject to intense selection pressure and rapid evolutionary change. My guiding conceptual model is the classical life history optimization model from evolutionary theory, in which key traits are subject to physiological trade-offs, many related to body size. For example, life history theory predicts that increased body size results in increased fecundity and thus increased lifetime fitness. However, increased fecundity may be prevented by trade-offs if increased body size requires increased development time resulting in increased probability of being eaten. In this proposal I outline two objectives for the next five years; (1) to determine the reproductive allocation and fecundity of cold ocean larvacean tunicates, and (2) to determine their optimal age and size-at-maturity. Reproductive allocation will be determined in various ways, including the quantity of lipids and fatty acids invested in eggs. One hypothesis is that larvaceans are highly adept clutch size manipulators, due to a novel mechanism of selection of eggs for maturation very late in the life cycle in response to food quality. How this occurs is not known. In the second objective, I will determine the optimal age and size-at-maturity of larvaceans, and test predictions from classical optimization theory and a new, temperature-based mechanistic model. In essence, I will answer the question of whether larvaceans reproduce at a fixed size, or at a fixed age. This research will contribute to moving research on marine zooplankton beyond the biogeochemical approach of the past and into a life history theoretical context. It will be of benefit to marine scientists in both the academic and government sectors, government regulators and fisheries and aquaculture.