Aphanius Dispar Trying To Mate With Swordtail?

[ladylouroll]

is it possible that my male Aphanius dispar is trying to mate with his only other tank mate a large female swordtail. he keeps resting on top of her and opening his mouth really wide over and over again. what else could this be? any ideas please? not that i think them breeding is even possible but my swordtail looks a bit umm... panicy i guess.

 

[BigC]

Killifish and Livebearers are very closely related (toothcarps) Whilst they will not cross breed due to obvious reasons, it is an interesting observation.
ATB
BigC

 

[ladylouroll]

they still keep doing it on and off. then bobby the swordtail will chase the dispar then the dispar will peck the swordtail then they leave eachother alone until the dispar decides to go pester bobby some more .