Petrosia

Petrosia is a benthic genus of sponges belonging to the family Petrosiidae.

== Diet == They are filter feeders, and their diet is composed of microorganisms, including bacteria, fungi, plankton, and unicellular algae. Certain species can also absorb dissolved organic matter directly from the water. Other species host symbiotic cyanobacteria, which can provide additional nutrition via photosynthesis.