Sponges of the Petrosiidae family are massive, vase-shaped or volcano-shaped sponges, sometimes encrusting, bulbous, and less commonly branching growth forms. Massive sponges are found at almost every site on our Koh Lanta diving trips.
Around Koh Lanta, the most obvious family member is the Giant Barrel Sponge, which is found on all of our coral reefs.
The texture is usually stony and brittle due to most species having more spicules (very small sharp-pointed spines) than spongin, which is the fibrous substance found in the skeleton of many sponges.
The outer layer of massive sponges are covered in these small sharp pointed spines, which form a pattern of interlacing lines resembling a net. This covering creates a crust which gives the surface of the sponge a smooth appearance.