The Southeast is a land dominated by rivers and home to a staggering variety of freshwater life forms and habitats.The region features some of the richest diversity of aquatic life of any temperate area in the world, rivaling the tropics.
So it shouldn’t surprise anyone thatwe are still learningabout what lies beneath the rippling waters that thread through this landscape.
Take, for instance, our emerging awareness of freshwater sponges in East Tennessee.
Although most of the 5,000 known sponges are found in marine environments, 150 species live in freshwater. East Tennessee is home to 11 of these freshwater sponge species, which are found in streams, rivers and lakes-any body of water that has relatively good water quality.
Freshwater sponge research has been limited in the past,butrecent discoveries are adding to the number of sponge speciesthat call this region home.
“Freshwater sponges have been overlooked because researchers have focused on other aquatic life forms, such as aquatic insects,” said Dr. John Copeland, professor of biology at Lincoln Memorial University in Northeast Tennessee.
Copeland recently began devoting time to researching freshwater sponges, heeding the advice of a former professor who advised him of the need back in the 1970s.
“When I first came to LMU, Dr. Louis Lutz was studying the spiny river snail in the Powell River, and he informed me that he was seeing a lot of freshwater sponges,” Copeland said. “He encouraged me to research them because he knew that nobody was looking at them. I am nearing retirement now, so I figured I better start.”
According to Copeland, the only documented research about Tennessee freshwater spongeswas published in 1943 by Clayton Hoff, a researcher from Quincy College in Illinois,who discovered four species of freshwater sponge while he was in residence at the Reelfoot Lake Biological Station during the summer of 1942.
Inthe past18 months, Copeland has possibly identified two new species of freshwater sponge in East Tennessee.He is working with two Italian researchers who are considered to be the world’s foremost experts on freshwater sponges to name the new species and publish descriptions.
For centuries, sponges were considered plants because of their primitive structure and lack of mobility. However, sponges are actually invertebrates (do not have a backbone) that grow on sturdy submerged objects in streams, rivers and lakes.
“Sponges are considered to be basal metazoans-they are at the very bottom of the animal kingdom,” Copeland said.
Sponges are filter feeders, obtaining their food from the flow of water through their bodies and from symbiotic algae. They have the unique ability to selectively choose what they are going to digest on any given day. This, of course, makes freshwater sponges especially sensitive to water conditions, so their presence indicates high water quality and low levels of pollutants.
“You can find them in very small streams that you can essentially hop across and in large rivers, such as the Conasauga and Hiwassee rivers,” Copeland said.
Freshwater sponges are more common and abundant than people realize, Copeland said. Part of the problem is that they can be easily confused with algae. The way to tell the difference is sponges have a coarse texture and are not slimy like algae.
In Tennessee, freshwater sponges come in a palette of colors, ranging from white to sandy to dark brown to green. They may be lobed, composed of finger-like projections or irregularly shaped; and they vary in size from a few millimeters to more than a meter across.
Freshwater sponges overwinter in a dormant state (called gemmules), and the best time of year to see them is during the summer and early fall, when they reach their maximum size. However, if you do spot one, Copeland said, let it be.
“There is nothing else like a sponge on planet Earth-they are truly fascinating creatures,” Copeland said.
Jenni Frankenberg Veal enjoys writing about the natural world and exploration opportunities found within the southeastern United States, one of the most biologically and recreationally rich regions on Earth. Visit her blog at www.YourOutdoorFamily.com.