Villain is 30/12. He once limped QQ in MP and checked behind on a 554 flop and paid off a turned straight for a small pot. Gives me the impression he doesn't know what he's doing. What's the optimal turn action?

Party Poker No-Limit Hold'em, $ BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

MP ($171)
Hero ($302.63)
Button ($115.70)
SB ($198.50)
BB ($189.20)
UTG ($214.20)

Preflop: Hero is CO with 8, A. SB posts a blind of $1.
1 fold, MP raises to $4, Hero calls $4, Button calls $4, 1 fold, BB calls $2.

Flop: ($17) A, 9, J (4 players)
BB checks, MP checks, Hero bets $12, Button folds, BB folds, MP calls $12.

Turn: ($41) 8 (2 players)
MP bets $45, Hero ???