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

[1] Petrosia are well distributed from temperate zone waters to tropical and from intertidal zone to deep waters.

[2] The genus has almost cosmopolitan distribution.

[1] Sponges are effective filter feeders, and associated, undigested microorganisms can count up to 60% of the fresh weight of marine sponges.

[3] These microorganisms include bacteria, fungi, cyanobacteria and unicellular algae.