I doubt it's genetic. I think she just can't hold so many pups at one time. I wonder if it had anything to do with feeding habits. I know myself and many other ray keepers tend to over feed their rays sometimes. The pregnant ray probably feels she can't hold so many pups and probably feels worse when she stuffs herself with food. I'm going to try something different this time. Instead of feeding my pregnant ray once a night and watching her stuff herself, I'm going to feed her a little bit in the morning and a little more in the evening. I'm thinking this will help the pups not feel so cramped after feeding. What do you guys think?