Powers M K, Barlow R B, Kass L
Department of Psychology, Vanderbilt University, Nashville.
Vis Neurosci. 1991 Sep;7(3):179-89. doi: 10.1017/s0952523800004016.
A circadian clock modulates the structure and function of the lateral eyes of Limulus polyphemus, greatly increasing their sensitivity at night. During the mating season, male Limulus are visually attracted both day and night to females and objects that resemble females. This paper asks how well Limulus can see day and night, and whether the circadian changes in retinal sensitivity might influence the ability of these animals to find mates. We recorded the visual behavior of male and female horseshoe crabs in the vicinity of an object--a cement hemisphere (29.5 cm diameter) similar in size and shape to a female horseshoe crab--placed in a mating area near Mashnee Dike, Bourne, Massachusetts. Males oriented toward this target from an average distance of 0.94 m during the day and 0.88 m at night; and females appeared to avoid the target. We conclude that males can see potential mates at night almost as well as they can during the day. Apparently the circadian changes in the retina help compensate for the daily changes in illumination in the animal's normal environment. This study provides the first evidence for a role of visual circadian rhythms in an animal's natural behavior.
昼夜节律时钟调节美洲鲎侧眼的结构和功能，极大地提高其在夜间的敏感度。在交配季节，雄性美洲鲎在白天和夜晚都会被视觉吸引到雌性及类似雌性的物体那里。本文探讨了美洲鲎在白天和夜晚的视觉能力如何，以及视网膜敏感度的昼夜变化是否会影响这些动物寻找配偶的能力。我们记录了在马萨诸塞州伯恩市马什尼堤坝附近交配区域放置的一个物体（一个直径29.5厘米、大小和形状与雌性美洲鲎相似的水泥半球）附近雄性和雌性鲎的视觉行为。白天雄性从平均0.94米的距离朝向这个目标，夜晚从平均0.88米的距离朝向这个目标；而雌性似乎会避开这个目标。我们得出结论，雄性在夜间几乎能像在白天一样看清潜在配偶。显然，视网膜的昼夜变化有助于补偿动物正常环境中光照的日常变化。这项研究首次证明了视觉昼夜节律在动物自然行为中的作用。
