Freshwater Sponge!

Photo: Wikimedia Commons, photographer unattributed

Orange and tubelike, a common antlers sea sponge, Axinella polypoides, grows among other sponges on the  sea floor, probably somewhere in the Indian or Pacific oceans. These strange organisms are familiar to viewers of Jacques Cousteau type shows, or people who are fortunate enough to dive in such places.

 Photo: John Pogacnik

While hopelessly landlocked in my office yesterday, I was texted a photo of a bizarre growth by John Pogacnik, who was, along with some others, exploring the Grand River. Neither he, I, or anyone he was with at the time recognized this thing. A quick bit of sleuthing by Judy Semroc led to Tim Wood of Wright State University, who was able to identify the organism. It is a freshwater sponge!

Dr. Wood studies freshwater bryozoans, which are in a different phylum than sponges, but he obviously doesn't ignore other strange underwater critters and pinned this one to the correct family, and even genus. It is a sponge in the genus Spongilla, and may be the species Spongilla lacustris.

This is a totally new one on me, and indeed the find offers me my first blogging foray into the Phylum Porifera, a group made up of simple filter-feeding animals. There may be as many as 10,000 species of sponges worldwide, and the vast majority of them live in oceans. I had no idea that we had freshwater sponges in Ohio; learn something new everyday!

Photo: John Pogacnik

This sponge is one of few cases - at least in these parts - where it would be easy to confuse the animal and plant kingdoms. One could be forgiven for thinking that this sponge is actually some sort of odd aquatic plant, when in reality it is a simple rather formless animal.

Sponges are all about water intake efficiency, and the need to constantly draw in H2O accounts for their long tubular growth habit. The innards are comprised of long channels, and external water is drawn in through openings called ostia. Lashlike flagella beat near the ostia, and draw in the water from which minute organisms, algae, bacteria and who knows what else are extracted and digested. Because of the need for clear water to feed in, sponges apparently fare poorly in waters that are excessively silted or otherwise polluted.

John and company found these sponges at Lake County Metropark's River Road property, an area known for its outstanding aquatic health. Not too far away is Ohio's only known site for riverweed, Podostemum ceratophyllum, an aquatic plant that only grows in high-quality streams. I'm sure it is no coincidence that these sponges are in the Grand River; another interesting piece of evidence that testifies to the topnotch ecological health of this State Scenic and Wild River.

Kudos to Lake County Metroparks, the Cleveland Museum of Natural History, Ohio Department of Natural Resources, Western Reserve Land Conservancy, Ohio Chapter of The Nature Conservancy, and everyone else who works to keep the Grand pristine. I wrote a piece about one of TNC's Grand River projects RIGHT HERE. Maybe few people would care about freshwater sponges, but I think they are quite cool indeed, and am glad that we still have streams that will support such life.

P.S.: If you know anything about the presence of these sponges in Ohio, please let me know.