Complex sentence: Host fish include the sailfish, the white marlin, the black marlin, the striped marlin and the swordfish; all these fish swim faster than does the remora, and it is not clear how the remora attaches to the host in the first place.
Split into simpler sentences: Host fish include the sailfish, the white marlin, the black marlin, the striped marlin and the swordfish. All these fish swim faster than does the remora, and it is not clear how the remora attaches to the host in the first place.