这种乌贼背上有一些感光装置，可以测量有多少月光或星光照在它背上，

Then it has detectors on its back so it can sense how much starlight or moonlight is hitting its back.

虽然苏丹几乎站着不动, 但我很开心地长时间骑在它背上.

Although Sultan seldom budged , I spent many hours just happily sitting on his back.