Creepy creatures invade Wapsipinicon River
Drought brings seldom-seen bryozoa to Iowa
Creepy animate blobs have been showing up with increasing regularity this month along the Wapsipinicon River.
Slimy on the outside, firm to the touch, embossed with an alien geometric pattern, they resemble nothing so much as the stars of low-budget 1950s Japanese creature features.
On Wednesday evening the sight of seven of them along a half-mile stretch of the Wapsie prompted sufficient curiosity for a Google search of “freshwater gelatinous mass,” which yielded: Bryozoa, a colony of tiny, filter-feeding animals with the scientific name, Pectinatella magnifica.
These seldom-seen life-forms have suddenly become rather common, it seems, because of the drought.
“They don’t like current, and they like warm water. With the drought, we might have just the right combination for them to flourish this year,” said Dan Kirby, a Department of Natural Resources fisheries biologist at Manchester.
We do, in fact, said bryozoa expert Tim Wood, a biology professor at Wright State University in Dayton, Ohio.
The North American natives, whose populations vary greatly from year to year, “are doing well this year throughout the Upper Midwest and Canada,” said Wood, secretary of the International Bryozoology Association.
Wood said a typical specimen is a colony of many thousands of tiny animals that band together for their mutual welfare.
While the colony has no sensory organs or ability to move, it provides a physical structure that offers protection to the individuals and reduces their competition for space, Wood said.
“The colony creates its own current that draws in water, enabling each individual to be more efficient in filtering nutrients from the water,” he said.
With each individual capable of both sexual and asexual reproduction, “the colony can grow exponentially as it gets older,” Wood said.
Asked if the creatures have any negative aspects, Wood said, “They scare people.”
Wood said he recently read about a Florida retirement community that, upon discovering the creatures in their private lake, called upon local law enforcement to come out and shoot them.
Though they have been known to clog water intake systems, “they are pretty innocuous,” he said.
“They are interesting creatures that can really be very beautiful,” he said.
Kirby said he’s seen them in off-channel areas of the Mississippi River, but he could not recall seeing them in Iowa’s interior rivers.
DNR fisheries biologist Scott Gritters said he and his “Mussel Blitz” colleagues saw “a bunch of them on the Wapsie below Anamosa” during their annual research project last month.
Bill Kalishek, a DNR fisheries biologist at Decorah, said he recalls seeing them only when befuddled citizens would bring one in — always from the Wapsie — and demand to know, “What the hell is that?”“They are just one of the interesting ‘other’ life-forms that call our rivers home,” Gritters said.