Just defending the mantis shrimp idea because I feel obligated. Not that I really thought he would get in...
1: there are plenty of other crazy things, and this is fantasy genre, so why shouldn't he breathe air?
2: Yes, that is believable for a mantis shrimp. Their tanks have to be made of special glass, and there are reports of them taking people's fingers off at the knuckle.
Also as far as that dragonfly, yea or any to the wind mage stuff?