A coupler mechanism comprising plug and receptacle units sealably mates and de-mates first and second reservoirs. In the mating sequence, the plug and receptacle units are brought together so that their end-seals are pressed tightly against each other axially, thus forming a sealed barrier between the units and the outside environment. Once the face-to-face seal between the units has been established, further engagement displaces slidable seal elements laterally, thereby creating an opening between the reservoirs, the opening remaining sealed from the outside environment before, during and after mating. The sequence for demating the units is just the reverse of the mating sequence. One embodiment of the invention applies the aforementioned construction to harsh-environment electrical, fiber-optical, and hybrid electro-optical connectors.
