. Crayfish . One species of crayfish once occurred in the Netherlands. This has completely disappeared except for one isolated pond. We now have more than seven types of lobsters from abroad. Three types of them are doing well, we may already be talking about millions of copies. . Cute pets . My brother once brought marbled crayfish home from his son’s school aquarium. They had enough of those easy-to-keep critters anyway. I did not know the species and after investigation it turned out that no one knew the species; the animal was first discovered in an aquarium shop. Where he comes from is a mystery. The marbled crayfish is extra special, because he, or rather she, can reproduce without a man. So I was terrified that the marbled crayfish was going to be invasive here too. Fortunately it looked like a warm water species, but still; nature sometimes knows how to adapt surprisingly quickly. . Overland walkers . The red American crayfish (photo) can walk over land to colonize …