Potamon fluviatile crabs' unusual size, up to , and longevity (up to 15 years) are also interpreted as evidence of a long-established population, by analogy with island gigantism. On the island of Malta, "Potamon fluviatile" is rare and restricted to a few locations in the west of the island. On Gozo, there is a single population which inhabits a stretch of river only long. In the Balkan Peninsula, "Potamon fluviatile" is known to occur in Croatia, Montenegro, the Republic of Macedonia, Albania and Greece. There are four species of "Potamon" in the Balkans, and "P. fluviatile" is replaced by "Potamon ibericum" in
Something Is Out There worsened. The series was canceled after only six one-hour episodes were broadcast, with two additional episodes produced but not broadcast at the time except in isolated cases in the US. Due to its short run, the series is not often found in syndication, but the Sci-Fi Channel did include it as part of a rotation of short-lived series, including broadcasting the previously unaired episodes. An edited down version of the miniseries has aired as a syndicated television movie. Originally conceived by Frank Lupo in 1987 with the title "Invader", NBC ordered a four-hour mini-series for broadcast on May 8, 1988