Recently a series of posts on one of my marine educator listserves highlighted strange blobs coming up on East coast beaches after Hurricane Irene. These blobs were sort of grey and shiny on the outside and had a bit of a stink when broken open. Guesses ranged from ambergris (the infamous whale puke worth hundreds of dollars and used for perfumes) to the lowly potato sponge.
And the winner was............ Potato Sponge! (image via Virginia Institute of Marine Science - click for info).
Sponges do not have what we call an "organ" level of organization. They have no brain, liver, heart, or stomach. Nor do they have a spleen or area named the "Isles of Langerhans," but I digress (extra points if you know what the spleen and Isles do). They have no legs, fins or jaws. They are magnificent filter feeding machines that keep the water clean and clear. A typical sponge can filter 4 times it's own volume every minute, and in many tropical reefs they are second only to coral in non-moving animal biomass.
Organizationally they are simply a group of cells that function very nicely together with a minimum of specialization. You can cut a sponge in as many pieces as you want and not really kill them. There are some cells that move water, some that secrete the "skeleton," and some that digest the food. They have one type of cell (the amoebocyte) that is Totipotent! It can go where needed, then morph into another type of cell - how cool is that! It can change into a type that creates skeleton, does reproduction, contracts (muscle like tissue), reserves food, or even creates slime (okay this does not seem so important, but really, without mucous your lungs would seize up).
Even the sponge cells that can't change into other forms as needed tend to be able to move about. What appears to be a non-moving blob-like body of a sponge can actually slowly shift and rearrange itself to a new shape to optimize filter feeding in the currents.
I want these sorts of cells in my body. I could sit on the couch, slowly morphing - not into a fat doughnut eating blob, but into 150 lbs of lean doughnut filtering tissue that looks like Brad Pitt (just don't ask me to move or think). I will have to check with my wife on this... I suspect I would have to filter more than doughnuts to be appreciated.
In the mean time, appreciate the sponges in the touch table and on the reef. This is just a small sample of what they can do. I have not even mentioned their defenses (there is a reason they are in the no touch section).
For a nice web site on sponges see: http://en.wikipedia.org/wiki/Sponge
The spleen gets rid of old blood cells, recycles the iron and holds some new blood in reserve - among other things.
The Isles of Langerhans is an area of the pancreas that secretes hormones such as insulin - but you knew this right? (I may have once, but it slipped(s) my mind).