Sunday, August 25, 2013

Freshwater wonders, Pectinatella

Moss animals adrift.

Magnificent bryozoan Pectinatella magnifica Hoover Reservoir

A quiet stroll and careful observing along the suspended boardwalk over the shallow north extremity of Hoover Reservoir at Galena, Ohio on a calm-water day allows discovery of water life below the surface. More than Asian carp and bluegill ripple the mirrored surface. Periscoping softshelled turtles break the surface with the just the tips of their pointy snouts. Swimming water snakes spread serpentine ripples. And, most interesting, magnificent bryozoans, moss animals, bob near the shoreline and are seen attached to debris under the surface.

Magnificent bryozoan Pectinatella magnifica is native to North America east of the Mississippi River. They spread mysteriously, probably hitching rides on ducks' feet and on other waterfowl. They appear following warm weather as their plankton food, tiny free floating plants and animals, become abundant in the water column.

Magnificent bryozoans are colonial moss animals forming gelatinous masses attached to rooted plants and heavy debris under water, but larger masses break loose and bob in ripples as they move with the wind, collecting along leeward shores. The surface of a mass supports multitudes of tiny filter feeding animals called zooids. Clusters of animals can be seen in closeup images, a microscope is needed to see an individual zooid.

Pectinatella mass found forming on a holdfast, a flooded sapling.

Pectinatella closeup

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