Why Is My Molly Doing This To My Female Platy?

My black male molly has been doing this to my female Platy and I can't figure out why. The molly raises his dorsal fin all the way up and then spins around her in circles. The Platy is a female and doesn't bother any fish, she just swims around happily always looking for food. The molly never does this to the female mollies, the male platy or any of the other fish. Why does he single out this one Platy? Another thing I noticed is sometimes he will chase her with his nose right on her belly like he's waiting for fry food.

 

Seems to be attempting to breed with her.

 

Looks to me like he's courting her. I'm pretty sure Mollies can mate with Platies.

 

the sail on that molly is amazing!!

 

She's the biggest, fattest female present, and his instinct is to attempt to mate with her. However, he cannot do so, as they are not only genetically incompatible, his gonopodium lacks the correct structure to insert spermatophores in a Xiphophorus sp.

 

the sail on that molly is amazing!!

Thanks! He was my first molly. Started off pretty small but once he got big and I saw that sail I knew I needed some more so I got a couple females and hoping I can make some more like him.

She's the biggest, fattest female present, and his instinct is to attempt to mate with her. However, he cannot do so, as they are not only genetically incompatible, his gonopodium lacks the correct structure to insert spermatophores in a Xiphophorus sp.

That sounds like a good explanation to me, thanks for the info. Hopefully he'll loose interest in his forbidden romance and start focusing his efforts on the other mollies