I had guessed that they showed up as gender specific when dealing with solids. But that they could have also had some bit or part that would make the individual tend to lean more towards one gender over the other. But I would have loved to see one or more that would appear as both male and female.
As for reproduction, I had guessed that when they are all in the Great Link and it's time for a new individual to form then a little bit from two or more in the Link come together to form an 'infant'
Yeah you've nailed it Star_Trucker, that would explain bisexual reproduction.