Sponges are some of the oldest known multi cellular animal inhabiting the earth and have been around for over 500 million years.
They are one of the reefs most important sedentary inhabitants, filtering water through their porous bodies, ingesting nutrients as food and releasing essential nutrients back in the seas through their main cavity called the Osculum.
Sponges are diverse in their shapes and colours, ranging from encrusting layers over rocks with tubes of 1mm to huge volcanic like structures of over a 1.5 mtr. There are over 5000 species of Sponge found in salt water, from the very shallows out to the depths of the ocean floors. They prefer clearer waters as silt can clog their pores, suffocating the Sponge of oxygen and food.
Scientists regard Sponges as bit of a mystery; unlike other animals they lack true tissue, organs and nerve systems. Yet they are still able to react to environmental changes, restore broken parts and regenerate after damage and even grow new sponges from broken pieces.
Sponges can reproduce both asexually and sexually. When sperm is released into the water, nearby Sponges will absorb the sperm and fertilise their eggs. The eggs hatch and tiny larvae are released, these will then settle on the reef creating the beginnings of a new Sponge.
It is also been recently discovered that Sponges have to ability to sneeze! Not a traditional 'A-Choo' but when something odd has been detected by the Sponge and caused stimuli in the osculum, it can contract it's whole body and expel jets of water in a sneeze-like fashion removing the irritant.
Sponges of the Petrosiidae family are often huge, vase-shaped or volcano-shaped sponges, sometimes encrusting, bulbous, and less commonly branching growth forms. Around Koh Lanta, the most obvious family member is the Giant Barrel Sponge, which is found on all of our coral reefs. The texture of these sponges 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.