Creature of the Month

Tube Sponge 
Acervochalina sp

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Sponges are amongst the simplest members of the animal kingdom.  They have no digestive, nervous or
circulatory systems for example.

The lack of sophistication in sponges has been shown in a classic experiment.  A sponge was pushed through fine silk to completely break it down.  However, it soon succeeded in reassembling itself.

A sponge feeds by drawing water into its central cavity through its pores - the tiny holes covering its body.  The filtered water leaves through the big outlet pores.

With their varied colors and intricate shapes, sponges add beauty to the reef or rock.  Some sponges are greenish, violet or pinkish in color because they harbor symbiotic algae.  The more symbionts and light, the stronger the color.   When there is low light these sponges are a much paler color - almost white.

The sponge uses the algae as a source of oxygen, a
screen against sunlight and as a food source.  It
provides the algae with a secure habitat.

The picture on the left shows a Tube sponge, Acervochalina species. This sponge can produce a chemical which is highly toxic to Pocillopora and Acropora corals.  Photo copyright Tim Nicholson.
Taken at Gota Baraka, Egyptian Red Sea.

The two pictures on the right were taken in Roatan Honduras.  You can see that sponges can get very large as shown in the upper picture.   The lower picture is looking down into the sponge. 

Further Reading:
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Great British Marine Animals, Paul Naylor
http://www.scubatravel.co.uk/britishmarine.html

The Red Sea in Egypt Part II, Farid S Atiya