ABSTRACT: Diel changes in feeding habits and the relative contributions of daytime and nighttime diets to the nutrition of the mysid Orientomysis mitsukurii in a sandy shore environment were determined by field sampling and additional laboratory experiments. O. mitsukurii was distributed just above the bottom during the daytime but a subpopulation swam up into the water column at night. Nighttime swimming activity was prevalent in small individuals but progressively decreased at larger body sizes, while the gut pigment contents of all mysid size classes consistently increased at night. Stomach content analysis revealed that O. mitsukurii individuals of all size groups ingested sedimented particulate organic matter (POM) containing large quantities of clay minerals during the daytime, whereas they mainly foraged on planktonic diatoms in the water column at night. Estimated in situ algal ingestion rates at night accounted for approximately 80-95% of the daily carbon assimilation. O. mitsukurii also exhibited high efficiency in grazing on planktonic diatoms in laboratory experiments. Conversely, daytime sedimented POM carbon accounted for only a minor proportion (5-20%) of the daily carbon assimilation. The utilisation patterns of the different food sources were confirmed by carbon and nitrogen stable isotopic signatures in the benthic community. Our results suggest that efficient utilisation of primary producers, such as planktonic diatoms, by O. mitsukurii is beneficial for maintaining the species’ high abundance from an ecological transfer efficiency perspective, and that sedimented POM is an alternative food source for securing the basic energy required for their survival, particularly when phytoplankton availability is low.

中文翻译：

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沙质海岸环境中食物来源的Diel变化及其对米氏东方定向菌营养的贡献

摘要：通过田间采样和其他实验室实验，确定了沙质海岸环境中Diel的摄食习惯变化以及白天和夜间饮食对mitsukuriit mitsukurii的营养的相对贡献。白天，O。mitsukurii刚好分布在水底上方，但晚上有一个种群游入水柱。夜间游泳活动在小个体中普遍存在，但在较大的体型下会逐渐降低，而所有迷路类体型的肠道色素含量在夜间持续增加。胃内容物分析显示三叶草各种规模的人白天都摄入含有大量粘土矿物质的沉淀颗粒有机物（POM），而晚上主要在水柱中的浮游硅藻上觅食。估计晚上的原位藻类摄入速率约占每日碳同化的80-95％。O.mitsukurii在实验室实验中，在浮游硅藻上的放牧也表现出很高的效率。相反，白天沉积的POM碳仅占每日碳同化的一小部分（5-20​​％）。底栖生物群落中碳和氮稳定的同位素特征证实了不同食物来源的利用方式。我们的结果表明，从生态传递效率的角度来看，mitsukurii菌对浮游硅藻等主要生产者的有效利用有利于维持该物种的高丰度，而沉积的POM是确保所需基本能源的替代食品来源生存，特别是在浮游植物可利用性较低的时候。