I haven't seen these before. But this appears to be a quick-disconnect hose connector which should work in a similar way others do. A part of this connector should move against another. I think you should be able to squeeze the top and the bottom of the connector together (towards each other) and one of them will move thus releasing the hose or a stub connected to the fixture above. Just need to figure out which is the movable holding collet, which is the stationary housing and which is the captive tube that should come out when you open it. They all have these essential parts.
Some quick disconnects require you to squeeze the collet so it deforms and releases plastic clips holding it. Are those brown plastic latches in the slots of the white outer part that looks like a collet? See you you can press on its sides so that the slots release the latches - it could work that way, too.