The rich bounty of plants in the Pantanal all benefit from the snail's constant feeding and recycling.
But the snails' banquet comes with a price.
It's August, and the annual drought transforms the wetland into a vast grassy plain dotted with small, muddy pools.
The snails are left high and dry, exposed and tasty.
They make a meal for millions of predators, especially caimans.
The calcium in the snail shell helps the caimans to thicken their skins.
Being on the menu is bad enough, but to continue their vital role of recycling, the surviving snails have to overcome a much bigger challenge, one which puts the whole ecosystem of the Pantanal on a knife edge.
Heavy rains return to the highlands of South America.
The swollen rivers burst their banks and once again flooded across the grassy plains.
Surprisingly, this is the most dangerous time for the ecosystem.
