Is that your name? I'm sorry I have all these questions coming through on Summitpost, but I feel I'm on the verge of enlightenment. How is the spread of the New Zealand snail related to humans? Do they lay eggs on a person's body, and then the eggs are deposited into the creek? I must do some more research. Your pictures are very interesting, Guido! Take care.
as far as I know, the snail attaches to the boots and any other clothing while you are in the water. If you don't clean them carefully afterwards there is a risk of spreading it to other areas. Apparently one single mud snail can have up to 40 million offspring in one year.