Coastal BC Animals: Freshwater Sponge

Freshwater Sponge

Last summer I discovered an unusual growth on the steel cables used to anchor our float cabin to shore. I am not 100% sure about my identification, but I think it is correct. If anyone reading this post has other ideas I would love to hear them.

Freshwater sponge on steel anchor cables in Powell Lake, BC.

Freshwater Sponge (Spongilla lacutris) looks like a plant because of it's green branched structure, but it is a member of Phylum Porifera that includes fresh and salt water sponges. Sponges are part of the animal kingdom. While they may be capable of some movement, they are essentially stationary.

Water flowing through sponges provides them with and food, and carries away waste. Inside specialized cells with flagella (whip like appendages) keep water flowing. Sponges control the amount of water flowing by opening and constricting small pore openings. Sponges feed on bacteria, small bits of organic matter, and algae.

Freshwater Spongilla sponges reproduce asexually by forming buds (gemmules) prior to winter and these develop into adults in the spring. They also reproduce sexually in the summer with larvae moving about freely using cilia to reach their new habitat. They can be found in clean lake waters and slow flowing streams.

I've never seen freshwater sponges at the cabin before. I've watched them throughout the winter. I wonder if spring will bring more. And I wonder what effect they might be having on our steel cables. - Margy

References: Pioneer Union Elementary School District Virtual Zoo (online), A Snail's Odyssey: a journey through the research done on west-coast marine invertebrates (online), and The Phylum Porifera Project (online).