Welcome back! We are now on day 5 since arriving in the Bonaparte Archipelago (Tuesday 8 December) and this is where we are.

Today  we are working north of Maret Island, in much deeper water (45+ metres deep) than yesterday. We have photographed sea floor habitats and critters along eight different 1.5 km transects with the AIMS towed video system, and collected 2 sled loads of critters from the sea floor to study.

 

A highlight for the day was getting a close-up look at several large sponges (see below) before we headed northward. So, today’s blog is all about sponges!

 

Yes, sponges do indeed live under the sea. But of course they do not live in a pineapple, and in fact, they are only sometimes yellow like SpongeBob SquarePants.

  
What is a sponge?

A sponge is an animal with no muscles, heart or lungs! A sponge’s body is basically a U-shape – often like a barrel or a glass (see below). Spongebob Squarepants (and other kitchen sponges you may have seen or used) are actually just small pieces of the real sponge they would have come from.

 

 

 

Even though it has no bones, a sponge keeps its shape because it is filled with a jelly-like substance called mesohyl within a skeleton made of fibers rather than bones. Water comes in and out of the sponge’s body through holes in its body walls called pores (see above). The water brings food (tiny bits of debris and plankton) to every part of the sponge, and the water takes away wastes. All the pieces that fit together to make the sponge can work together to squirt water out quickly, such as to prevent burial under sand.

What shapes can a sponge be?

Sponges can form into many interesting shapes. Some common ones include:

• Barrel

This type of sponge can grow up to 1.5 metres long – big enough for a person to stand inside it! The surface of these sponges often have deep ridges. 95% of all sponge species are of this type.

 

 

• Fan

This type of sponge can grow up to 1 meter long. They form a fan shape.

• Tube

Tube sponges are made up of thick tube-like structures that join at the base. They can grow up to 1 metre in length. They can chase away predators by squirting out toxic chemicals.

 

Watch this video of sponges near Maret Island

 

• How many barrel sponges do you see? Are they all the same kind? 

• Look closely to find the tube sponge towards the end of the video.

• Do you see any fish or other creatures near or on the sponges?

 

Sponges are home to many small critters

You most likely saw fish swimming near some of the sponges in the video. And if you looked very closely, you may have seen little animals crawling on them. In fact, sponges are a very important part of the sea floor as they provide food and homes to many different types of animals like fish, starfish, brittle stars, feather stars, crabs, and more. In fact, some microscopic organisms even live inside the tissues that make the sponge’s body walls and give the sponges their colour.

Look at the picture of a sponge below.  Can you see the crab living on it?  Can you see the pores?

 
Look at the sponge below closely.  This time can you see the pores? What about the central cavity? How many critters can you spot living on it?

Did you know…

• New medicines for treating HIV and breast cancer have been discovered from sponges.
• Sponges are common in Western Australia. 275 species of sponges have been found in the Damper Archipelago and 500+ at Ningaloo ReefNingaloo Reef.  
• This expedition is helping to figure out how many are found in the Kimberly region of Western Australia.
• Many types of fish, nudibranchs, star fish, turtles and other animals depend on sponges for food and shelter.
• Sponges are under threat from heavy fishing gear which drags along the sea floor and damages or kills them.

 

I hope you enjoyed this blog! See you next time.