Griffiths D J, Bryden M M, Kennaway D J
J Pineal Res. 1986;3(2):127-34. doi: 10.1111/j.1600-079x.1986.tb00735.x.
Blood was collected over a 24-h period from free-living adult Weddell seals that had been exposed to natural constant daylight for some 12 weeks. The plasma melatonin concentration was low throughout the trial (range of means: 30.8-70.4 pg/ml) with the exception of a 3-h period centered on 1700 h local time, when the plasma level rose to a mean of 131.8 pg/ml. The pineal gland of the Weddell seal is thus capable of transient bouts of activity during constant and bright daylight, a situation usually inhibitory to the function of the gland. It is suggested that circadian fluctuations in the intensity of constant light entrain variation in the pineal gland functioning of this seal during summer.
在24小时内，从自由放养的成年威德尔海豹身上采集血液，这些海豹已经暴露在自然恒定光照下约12周。在整个试验过程中，血浆褪黑素浓度较低（平均范围：30.8 - 70.4 pg/ml），但在当地时间1700时为中心的3小时时间段除外，此时血浆水平升至平均131.8 pg/ml。因此，威德尔海豹的松果体在持续明亮的日光下能够出现短暂的活动，而这种情况通常会抑制该腺体的功能。有人认为，夏季恒定光照强度的昼夜波动会使这种海豹松果体功能产生相应变化。
