Cucumber question

[Ruth]

I had a tiger cucumber (and still do as far as I know) in my 230g tank. He has never harmed anything and takes pretty good care of my sandbed.
Last night when I was pulling the clumps of calurpa and grape calurpa that have taken over my sump out I noticed a brown lump - didn't think that much of it and just continued to harvest my algea. Anyway up pops another brown lump so I decide to examine it better. It is a tiger cucumber - about 5" long. I go back and find the other lump and sure enough - another cucumber about the same size. WTF? I don't know if there are any more in there or not.
So answer me this - how the heck to these things propogate? Is it possible that somehow a piece got broken off the one in the display and that formed another one that somehow migrated to the sump and further propogated in there?