Quote Originally Posted by celticstarb View Post
What I find most interesting is that temperature variations, either up or down, can trigger spawning. Most aquatic amphibians require a temperature drop to breed, but clawed frogs will breed with a temp increase. In fact, I have had better luck with an increase.
It's not so surprising really. You have to bear in mind that most species of Xenopus don't originate from tropical regions of Africa but from regions that have more of a Mediterranean zone climate, similar to parts of California, with a seasonal variation of dry, hot summers and mild but cool and wet winters.

The description I gave above of my own experience of breeding them strongly suggests that what stimulated them to breed was the seasonal fluctuation in ambient air temperature and hours of daylight, which were more or less natural and not controlled. Hence, the onset of spring, with warmer temperatures and increasing hours of daylight, created the right conditions to trigger egg laying.