Yes, they are the same species, Horabagrus brachysoma, one of the most common aquarium catfish sold in the US.

We don't get here and/or I have never seen live a single nigricollaris, not to mention melanosoma:
http://www.planetcatfish.com/common/fam ... mily_id=39
Yes, my guys, despite the not-always-pleasant enforcement of the pecking order, keep together.