I don't like the chances of survival of that parent marisa with that significant chunk out of its body. Still, no paste is coming out so it might just survive (I hope so since they appear to be fairly intelligent and nice considering you don't see them attacking each other as they lack their respective accessories).
These yukkuri only have the intelligence to recognize their own kind from their appearance. But there are case of couple who are separated by their owners but still able to recognize each others. There's also case where parents and child who lost their accessories because of human can recognize each others.
It's not explainable if this is simply because they are related by paste as family. Even now yukkuri are still a creature of mysteries.