This happy little fellow made me laugh the moment I saw it. I like looking for subjects underwater that excite my imagination. I do not know what you see, but I thought of an orchestra conductor. How many other things can it make you think of?

I used a housed Nikon SLR camera and a 60mm macro lens, all kept watertight in a special underwater housing. Since red, then orange, then yellow colours are absorbed as light travels through water, I used a large underwater flash to make the sponge less cyan/green and more bright yellow/orange. I got down low, being careful not to bump into any living coral or reef creatures, so that I could aim upward. Then I tried over a dozen different lighting angles. In many of the photos it just looked like an ordinary sponge. It took over a dozen tries until my camera caught it the way my eyes saw it.

Besides looking like a singing penguin this is actually a small (about four inches high) yellow tube sponge commonly found throughout the reefs of the Cayman Islands. In shallower water, they often come in strange forms and I have photos of many odd shapes.

Sponges are very simple animals that live by filtering food and oxygen from the water. They do not have any organs like a heart or eyes, but are made up of several different types of cells that each serve a special function, but which all work collectively.

Sponges can be encrusting, or tall and thin, or shaped like barrels or vases. They have thousands of tiny pores (called ostia) that are lined with a most intricate structure (called a collar cell) that includes a long hair-like flagellum. This flagellum moves so quickly that it creates a current. The sum of millions of these collar cells creates a strong current so that a cubic foot of living sponge can filter over 5700 gallons of water a day. Most of the water around the Cayman Islands goes through a sponge – in through the ostia and out through larger openings (the oscula) usually at the top – every day. The hole that looks like an eye on my happy sponge is actually an osculum, and it was right where you see it now—I did not put it there with Photoshop.

There are many other cells that make up a sponge, including amoebocytes that capture tiny food particles, including bacteria, and carry them around to all of the cells of the sponge. Other cells make up “spicules” or crystals that provide a firm or spongy structure. And, of course, there are cells that provide for reproduction.
So why do we care about this little yellow sponge? Sponge filtration makes the water clearer so that corals get more sunlight which is necessary for their health. The myriad holes and openings of a sponge serve as home to millions of reef creatures from fish and crabs to tiny worms. They also harbour bacteria that can take part in important chemical activities (such as nitrification and carbon fixation) that help keep water properties properly balanced for life in the sea. 

If that is not enough, a recent study showed that sponge cells can detect a harmful genetic mutation and self-destruct before a neighbouring cell has to do it. Trying to figure this out may provide a breakthrough in our understanding and treatment of cancer. The genetic code for the sponge and for later animals has amazing similarities, so we have a lot to learn from an animal species that has been successful for over 600 million years. 

 Facts about sponges

    Sponges can contain 16,000 other animals inside of it.
    To prevent other sponges from attacking them, Sponges can produce chemicals to keep other sponges cells from growing
    The chemicals that a sponge produces are being used to find a cure for cancer and many other diseases.
    A new type of sponge is found every year.
    One of the largest sponges ever was almost 10 feet wide.
    Some sponges can be found thousands of feet below the ocean’s surface.
    In such places as the Caribbean Sea, sponges can actually filter all of the water in one day.
    When a part of a sponge breaks off, the broken part will form a new sponge.
    If you strain a sponge through a cloth it will form a new shape on the other side.
Sponges do not have organs; instead they are made up of special cells that carry out all the processes.