Hong Kong Corals & the Associated Marine Life

> Other marine organisms

Sponges are the oldest and the simplest living group of multicellular organisms. They are sedentary filter-feeders, which can filter water equal to 4-5 times of their volumes every minute. Water is pumped from inhalant pores on the surface and led to the inner canals which are lined with cells (known as choanocytes) of whip-like tails. Rhythmic beating of these tails pumps water through the body in one direction. At the same time, food particles and oxygen in the water are filtered out and the leftover will finally be expelled through exhalent pores.

In the world, there are estimated to be 2500-9000 species of sponges and less than half of these have been described so far. Hong Kong's sponge fauna has been poorly investigated. Sponges vary greatly in forms and sizes, from thin encrusting sheets to large barrels or vases. It is difficult to identify them from photographs. The main key for identifying this organism is the size, type, distribution and arrangement of the supporting spicule.