锯缘青蟹视网膜电图特性的昼夜节律变化

本文系统地分析了锯缘青蟹scylla serrata视网膜电图特性(敏感度、光谱敏感性和波形)的昼夜节律性变化。这种节律性可能主要是由于视网膜屏蔽色素位置的昼夜变化所致,但也可能存在另一种机制。

CIRCADIAN RHYTHMS OF THE ERG OF THE CRAB SCYLLA SERRATA

Circadian rhythms of the ERG were studied in the crab Scylla serrata under the constant dark-adapted condition. 1, The ERG sensitivity, defined as the reciprocal of the light intensity giving rise a 67 *V response, increases near dusk, keeps a rather high level during the night, and decreases near dawn. The sensitivity usually increases 2.5 to 4.0 log units from day to night, depending on the wavelength of the test flash. 2. During the night, the spectral sensitivity of the EEG has a maximum between 490 nm and 514 nm, and agrees well with the absorption spectrum of a rhodopsin pigment (AAAmax= 508 nm), calculated from the Dartnall nomogram. In contrast, the relative sensitivity, determined during the day, is higher than that during the night at wavelengths longer than 550 nm. 3. Cireadian change in waveform of the BEG is observed. The day response is fast and exhibits an initial on-transient. But, the night response of comparable amplitude is relatively slow, having a longer latency, without on-transient.These effects might be realized by circadian change in pigment migration. During the day, retinal screening pigments may take positions similar to the light-adapted ones, even in darkness, and thus screen the rhabdom to some extent. Similarly, selective absorption of screening pigments may be responsible for the relative elevation of sensitivity in the long wavelength region. Furthermore, some additional mechanism is needed to mediate the circadian change in waveform of the EEG.