osculum

noun3

1. •
   A small opening or orifice.
2. •
   The main opening in a sponge from which water is expelled.

   • Oscula are also thought to arise initially from a single porocyte (Weissenfels, 1980), but how they coordinate with other porocytes to form a larger osculum is still unclear. — 2012
3. •
   (no longer used) One of the suckers on the head of a tapeworm.