Douglas R H, Wagner H J
Cell Tissue Res. 1982;226(1):133-44. doi: 10.1007/BF00217088.
The retinal rods, cones and epithelial pigment of most lower vertebrates display rhythmic photomechanical (retinomotor) migrations in response to changes in ambient lighting conditions. This study examines the extent of these migrations in the absence of the daily changes in illumination (constant darkness and constant light) in three species of teleosts. Salmo trutta, a crepuscularly active fish, showed two peaks of light adaptation occurring around dawn and dusk when kept in constant darkness. Tinca tinca, a nocturnal species, also showed an endogenous rhythm during extended periods of darkness, but, unlike Salmo trutta, it was light-adapted throughout what would normally have been "day". At the maximal extent of migration under conditions of continual darkness, the pigment migrated 59% as much as it did during a normal light/dark cycle. Nannacara anomala, a tropical diurnally active species, showed a similar but more pronounced rhythm than Tinca tinca for all 3 days of experimental darkness, behaving essentially identically to fish exposed to a light/dark cycle. Nannacara anomala also displayed a weak rhythm when kept in constant light. It is concluded from these and previous results that the pattern of endogenous photomechanical movement depends both on the activity pattern of a species and on the constancy of the lighting conditions to which it has been exposed during its lifetime.
大多数低等脊椎动物的视网膜视杆细胞、视锥细胞和上皮色素会根据环境光照条件的变化进行有节律的光机械（视网膜运动）迁移。本研究考察了三种硬骨鱼在没有每日光照变化（持续黑暗和持续光照）的情况下这些迁移的程度。褐鳟是一种晨昏活跃的鱼类，在持续黑暗环境中时，其在黎明和黄昏左右出现两个光适应峰值。丁鱥是一种夜行性物种，在长时间黑暗中也表现出内源性节律，但与褐鳟不同的是，在正常情况下本应是“白天”的时间段内它都处于光适应状态。在持续黑暗条件下迁移到最大程度时，色素迁移的量是在正常光/暗周期中迁移量的59%。九间始丽鱼是一种热带昼行性物种，在实验黑暗的所有3天中，其表现出与丁鱥相似但更明显的节律，与暴露于光/暗周期的鱼类基本相同。九间始丽鱼在持续光照条件下也表现出微弱的节律。从这些以及之前的结果可以得出结论，内源性光机械运动模式既取决于物种的活动模式，也取决于其一生中所暴露的光照条件的稳定性。
