Yes Otos have spines. They've been known to kill angelfish who've choked on them.
There are some theories that most if not all catfish with spines carry some degree of poison (not too many studies have been done yet, but there was a writeup a few months ago in one of the hobby magazine subscriptions I get, can't remember which?) but most would not be toxic to humans unless a person just happened to have an allergic reaction. www.otocinclus.com
is a great site full of all kinds of tips on keeping and breeding otos, for anyone who may be interested.