User blog comment:IamJakuhoRaikoben/Chapter 401: Igneel vs. Acnologia, Review./@comment-4933386-20140923055319

Something I still don't understand, why is the dragon's slayers heart thumping when Acnologia arrived? How come Natsu, Gajeel and Wendy didn't do that during Tenrou Island Arc?

At first I thought it was due to dragon inside them, but Rogue and Sting felt it too, so that couldn't be valid. Unless their respective dragon didn't die.