头足类生殖投入及其与环境响应—以阿根廷滑柔鱼为例

Cephalopods are the typical ecological opportunists, and highly sensitive to environmental fluctuations. With an exception of Nautilus, all the other species are characterized by short life-span and semelparous reproduction, and die after their spawning period. Then, the stock size depends on their recruitment, which in turn is determined by the level of reproductive investment that directed from the breeders. The level of reproductive investment in natural organisms is seen as a function of environmental influences, and reflects stock reproductive potential and subsequently the recruitment. Therefore, the researches on the reproductive investment are vital important in promoting fisheries development, and understanding the changes in reproductive investment responding to environmental influences is essential for predicting population dynamics and for informing management strategies. The reproductive investment, using the economic terms, has been referred to as ‘income breeding’ or ‘capital breeding’. The ‘income breeding’ species finance reproduction using concurrent energy intake, while the ‘capital breeding’ species pay for reproduction using stored energy. The Argentinean shortfin squid, Illex argetinus, is one of the three major fishing species in the distant water jigging fisheries of our country, and the development of this fishery is mostly dependent on the stock recruitment. The reproductive investment in I. argentinus was considered to be ‘income breeding’. However, recent researches in our laboratory have found that reproduction in I. argentinus was not entirely financed by energy acquired concurrently during the breeding season, where it seems to be more flexible in response to their living environment. Accordingly, our study will use I. argentinus as a model to study the reproductive investment and its response to external environment in cephalopods. We will apply the bio-marker technique of fatty acids to determine channel of energy sourcing for reproduction, as well as apply the technique of tissue energy density to analyze the reproductive energy accumulation. Meanwhile, in order to access the flexibility of reproductive investment linking to environment, we will use the mathematic models to test for relationships between reproductive investment and environmental variables experienced by the spawning individuals. And the main object of this study is to find out the likely pathway of adaptivity that the breeders allocate energy to reproduction under the possible environment pressure, which in turn will influence the subsequent recruitments in the following season. These lines in our study will enlarge the understandings of reproductive investment in cephalopods, and provide important theoretical visions for the stock biomass assessments and managements based on reproductive investment.

头足类是典型的生态机会主义者，对环境波动极为敏感。除鹦鹉螺属外，这些种类寿命短、终生一次繁殖，产卵后便死去，自然种群大小完全取决于补充群体。而生殖投入决定着补充群体大小，且与环境波动关系紧密。生殖投入研究对促进这些种类渔业发展具有重要意义。阿根廷滑柔鱼是我国远洋鱿钓渔业的主要钓捕对象，渔业发展与补充群体资源量息息相关。从经济学角度，生殖投入类型可以划分为收入型和资本型。前者来自即时的饵料摄食，后者则依赖储备能量。过去，阿根廷滑柔鱼被认为是收入型生殖投入。近来，本实验室发现其生殖投入表现出灵活性，能量积累与环境变化密切相关。基于此，本项目拟以该种为例，通过脂肪酸标记物法判别生殖投入途径来源，采用组织能量密度技术分析生殖能量积累，利用数学模型构建生殖投入与环境因子的关系，评估分析生殖投入的环境响应度，揭示生殖投入的环境适变性过程。研究结果将为基于生殖投入开展头足类资源评估管理提供重要的新思路。

头足类（除鹦鹉属外）均寿命短、终生一次繁殖产卵，产卵后便死去，自然种群大小取决于补充群体，后者则决定于生殖投入。阿根廷滑柔鱼是我国远洋鱿钓渔业的主要钓捕对象，渔业发展与补充群体资源量息息相关。为此，本项目研究以阿根廷滑柔鱼主要研究对象，利用组织能量密度测定技术分析生殖能量积累变化过程，确定了阿根廷滑柔鱼能量积累和生殖投入随着性腺发育增加显著，生殖能量积累在性腺发育成熟后处于最大值；利用脂肪酸、稳定同位素等生物化学标志物判别分析生殖投入途径来源，确定了阿根廷滑柔鱼的生殖投入类型为收入-资本混合型，即生殖能量以现场摄食饵料生物的吸收转化投入为主、在能量需求较大时以肌肉等存储能量转化投入为辅；在生殖能量积累中，阿根廷滑柔鱼转变食性增加较高营养层级饵料生物种类的摄食，以满足较大的生殖能量积累需求，而且生殖能量积累需求是促使其转变食性的关键因素；利用混合效应模型拟合分析生殖能量积累与栖息海域环境因子的关系，阐明了生殖投入主要受到水温、叶绿素a质量浓度等影响，并且这些环境因子对卵巢、输卵管和缠卵腺等性腺组织能量积累的影响作用存在组织特殊性，为后续构建生殖能量积累的环境模型提供了资料参考。以此为基础，项目拓展延伸了对茎柔鱼、鸢乌贼生殖投入的研究，获知了茎柔鱼具有阿根廷滑柔鱼相同的生殖投入方式，即收入-资本混合型；鸢乌贼的生殖能量来源倾向于外源性，即收入型。本研究将有助于进一步认知头足类尤其是阿根廷滑柔鱼、茎柔鱼等的能量积累及其生殖投入，为资源开发和资源养护提供了重要科学基础。