Sponges pt.1

A yellow tube sponge (Aplysina fistularis) growing on a Caribbean coral reef. Photo taken by Dr. Alex Mustard. More can be found at www.amustard.com

“Oooooooooooh! Who lives in a pineapple under the sea? SPONGEBOB SQUAREPANTS!”

Actually, pineapples are terrible places for sponges to live. If SpongeBob wanted the best place to survive and be successful, he would have lived on top of Patrick’s rock. I know, I know, it’s a show for kids and therefore isn’t accurate, but what better way to introduce the topic than with a relevant pop culture reference?

I just have to say that sponges are weird.

Like coral, they were first thought to be plants, which to be fair is quite understandable. Sponges don’t possess appendages, eyes, noticeable mouths, or reproductive parts, so if I had come across my first sponge without knowing its biology, I would have thought it was a plant too.

Sponges are the simplest multi-cellular creatures of the animal kingdom, and they’re so cool that they have their very own phylum, Porifera. In fact, sponges are so unique that they have no other close relatives.

Like other marine invertebrates, such as coral, barnacles, and oysters, sponges will permanently attach themselves to hard surfaces like rocks or shipwrecks. Some species of sponge will even burrow themselves into whatever substrate they want to call home. Once they’ve attached, there’s no second guessing, so hopefully they picked a good spot!

Unlike coral, sponges are a bit hardier and have fewer requirements to be successful. Sponges can live in a variety of different places that vary in temperature, salinity, and depth. About 2% of sponges can live in freshwater!

Sponges can be found almost everywhere: on rocks, shipwrecks, and coral reefs; they can be found in the tropics and higher attitudes, though a good portion of them live in Antarctic waters. Unlike coral, sunlight is a limiter for sponges. Too much sunlight exposure can be harmful for sponges, so they tend to prefer caves, crevices, and other places that don’t get a lot of direct sunlight.

However, there are a lot of sponges that live in areas with a few feet or less of water above them and in direct sunlight. These sponge species possess a special relationship with a species of algae that will dwell in the sponge. The sponge protects the algae from herbivores while the algae secretes pigments in the outer most layer of the sponge. These pigments act like sunscreen, thereby helping to protect the sponge from the sun.

Like most animals, a good place for a sponge to live will have a steady supply of food. Areas with strong tidal currents can support large sponge populations because all that water movement brings in extra food. Like whale sharks, sponges are filter-feeders, but how they feed is a bit more complicated. I will therefore have a whole post dedicated to how sponges eat!

For being the simplest multi-cellular animals you can find, sponges can be very complicated. I’ve barely scratched the surface of what make sponges unique and what they can do for their environments. But like all things, it wouldn’t be fun or interesting if it were easy!

Sources and fun links for those who want to dive right in to sponges:
Ocean: The Definitive Visual Guide made by the American Museum of Natural History
https://www.britannica.com/animal/sponge-animal#ref32631
http://www.oceanicresearch.org/education/wonders/sponges.html
http://tolweb.org/treehouses/?treehouse_id=4291
https://oceanservice.noaa.gov/facts/sponge.html