The male will get in an 'S' shape almost. He nudges the female sometimes, but sometimes they just swim along beside them in the 'S' shape prior to mating. Basically he bends his tail so that his caudal fin curves. In my opinion that is his showing off his colors and or size of tail to the female. The females usually try to avoid the male for a couple of times, but he almost always succeeds. The reason they seem to suddenly get pregnant is because they hold sperm for upwards of 6 months, automatically reinpregnating themselves after having a batch of babies. The males continue to breed with the females, but they essentially just keep her sperm storage at full capacity.
It is hard to notice the guppy mating dance if you don't pay special attention to the tank, because it is a minimal show. They are the "romeo fish"... charm their socks off and get what they want kinda thing, so it is a very quick process.
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I thought they were just BFFs LOL. Maybe Wanderlei is a Wanderleta.
