Proximate Factors Affecting Vertical Migrations in Mesopelagic Organisms

本提案旨在继续该实验室正在进行的关于触发水中生物垂直迁移的近似因素的研究。虽然这种现象被认为是地球上主要的行为模式之一，并且对海洋生态系统的结构有深远的影响，但人们对提示这种行为的日常时间的因素知之甚少。过去三年进行的研究已经明确地排除了关于光的特征可能导致这些迁移的假设之一。这些研究表明，在黄昏时发生的光谱分布的变化并不是触发这些迁移的诱因。此外，对近紫外光的光敏性并不是垂直迁移甲壳类动物的共同特征，因此，紫外光在大多数物种中引发这些迁移的作用也被低估了。该提案将继续解决在黄昏时是什么因素导致缅因湾海洋学家峡谷中上层生物垂直迁移的问题。潜在的线索将被解决：1)暴露于绝对光强的阈值，2)跟踪等值体，3)下行光的相对增加或减少，以及4)光强变化率是否对迁移速度有影响。其中一些迁徙物种的视觉生理也将被检查，以确定是否1)不同物种之间的光感受器敏感性存在差异，这可能与它们的迁徙模式的差异有关，以及2)是否内源性的光感受器敏感性节律存在于中远洋物种中，这可能与迁徙生活方式有关。将动物分布模式的现场和网络研究与它们的光感受器生理学研究相结合，将对确定哪些近似因素在控制中上层领域垂直迁移的每日时间方面发挥重要作用作出重大贡献。

This proposal seeks to continue ongoing studies by this laboratory of proximate factors triggering vertical migrations in midwater organisms. While this phenomenon is known to be one of the dominant behavioral patterns on earth, and has a profound influence on the structure of marine ecosystems, little is known about the factors which cue the daily timing of this behavior. Studies conducted in the last three years have definitively eliminated one of the hypotheses regarding which characteristic of light might cue these migrations. These studies demonstrated that it is not the change in the spectral distribution of light, which occurs at twilight, that is serving as a trigger to cue these migrations. In addition, photosensitivity to near-UV light was not found to be a common characteristic of vertically migrating crustaceans, and therefore, the role of UV light in triggering these migrations in most species has also been discounted. This proposal will continue to address questions about what factors at twilight are cueing vertical migrations in mesopelagic organisms in Oceanographer Canyon in the Gulf of Maine. Potential cues that will be addressed are 1) exposure to a threshold value of absolute light intensity, 2) tracking of an isolume, 3) relative increase or decrease in downwelling light, and 4) if the rate of change in light intensity has an effect on migration speeds. The visual physiology of some of these migrating species will also be examined to determine if 1) there are differences in photoreceptor sensitivity between the various species that can be correlated to differences in their migration patterns, and 2) if endogenous rhythms in photoreceptor sensitivity are present in mesopelagic species that can be correlated to a migratory lifestyle. Combining in situ and net studies of animal distribution patterns with studies of their photoreceptor physiology will make a significant contribution to determining what proximate factors are important in controlling the daily timing of vertical migrations in the mesopelagic realm.