Department of Biological Sciences, Florida Atlantic University, Boca Raton, Florida, 33431, USA.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2018 Dec;204(12):1007-1015. doi: 10.1007/s00359-018-1299-4. Epub 2018 Oct 26.
Hatchling marine turtles emerge at night from underground nests on oceanic beaches and then use visual cues to crawl from the nest site to the sea ("seafinding"). However, the light wavelengths (λ's) used to accomplish this orientation have not been thoroughly documented, nor do we understand why some λ's are favored over others. We measured nocturnal radiance on the horizon at 20 nm intervals between 340 and 600 nm at two nesting beach sites and then, under laboratory conditions, determined the lowest intensities of those λ's that induced green turtle and loggerhead hatchlings to crawl toward each light source (a low positive "phototaxis threshold"). Both species were similarly sensitive and were attracted to all λ's. Radiance measures at all λ's were greater toward the seaward horizon than toward the landward horizon, providing an important orientation cue regardless of variation in lunar illumination. Previous studies document that both species detect λ's longer than those that are most attractive. We hypothesize that seafinding is a specialized response mediated by cones that are sensitive to the shorter λ's (to minimize the effects of dark noise) but such as rods, are especially sensitive to low levels of nocturnal illumination.
幼海龟在夜间从海洋沙滩下的地下巢穴中孵化出来，然后利用视觉线索从巢穴爬向大海（“寻海”）。然而，用于完成这种定向的光波长（λ）尚未得到充分记录，我们也不了解为什么有些 λ 比其他 λ 更受欢迎。我们在两个筑巢海滩上以 20nm 的间隔测量了 340 到 600nm 之间的地平线夜间辐射亮度，然后在实验室条件下，确定了那些能诱导绿海龟和红海龟幼龟向每个光源爬行的最低强度（低正向“趋光性阈值”）。这两个物种的敏感性相似，都被所有 λ 吸引。所有 λ 的辐射亮度都朝向海的方向大于朝向陆地的方向，无论月光照射的变化如何，这都提供了一个重要的定向线索。先前的研究表明，这两个物种都能探测到比最有吸引力的 λ 更长的 λ。我们假设寻海是一种由对较短 λ 敏感的视锥介导的特殊反应（以最小化暗噪声的影响），但与视杆一样，对夜间低水平光照特别敏感。
