Shells on shell

Here are (probably) spotted slipper shells living on a
Florida fighting conch. The slipper shells can't move much
in search of food, so they have modified their manner of
feeding to trap food with the mucus in the mantle.

Shells have all sorts of interesting behavior patterns.
Slipper shells have both male and female reproductive organs.
In general, the younger,more active slippers are male;
the older sedimentary slippers are female.
Slippers do not self-fertilize. Their male and female organs
operate at different times in their life cycle.