Many people probably do not realize that right here in Indianapolis, we have a carnivorous plant. Nope, not a Venus flytrap or pitcher plant, but a fascinating one, nontheless. This one is called Common Bladderwort, Utricularia macrorhiza, and there is a bunch of it blooming right now at Southeastway Park in our pond.
Most people might walk right by this little beauty and not realize it is there. It is a very delicate plant with thread-like leaves and vivid yellow blossoms. It lacks roots and survives by free-floating near the surface of the water. It can thrive in areas that contain loose sediment that cannot support many aquatic plants. This one is tucked in among the Floating Pondweed, Potamogetan natans, which has the large oval leaves in the picture.
One is rewarded if they take a closer look. The blossom reminds me of a snapdragon. I love the intricate dark orange nectar guides towards the center of the flower. Articles I have read indicated this plant is pollinated by bees and moths.
Don't let the delicate looking flowers fool you. This is a very deadly plant if you are a tiny rotifer, crustacean or other microbe. Among the leaves are found miniscule pear-shaped bladders. A study showed that one plant with ninety bladders had 270 captured crustaceans!
One can see the bladders in the closeup shot above. The scientific name Utricularia means "little bag" referring to the bladders' shape and function. One may wonder how do the bladders work to capture prey? Each bladder has an opening that has a hanging flap. Surrounding the opening are bristles that serve as triggers. These hairs are baited with an edible mucus that attracts the tiny microbes. When a creature swims by and touches the sensitive hairs, the flap flies open and water rushes into the bladder sucking the unsuspecting prey with it. The door snaps shut and the animal is trapped. The door only swings inward, so the prisoner has no hope for escape. The prey eventually die and the bladderwort uses special digestive cells to produce enzymes that help digest the body. Because the door does not open outward, the parts of the animal that does not easily digest will remain within the bladder and scientists can analyze these to see what was captured.
Here is a website that shows the bladder magnified 100 times. The tiny hairs up close along with the opening of the bladder makes it look like some kind of sea monster. That is probably just what it looks like to a tiny rotifer swimming along, minding its business.
This plant has some other unique survival techniques. In the winter many plants will become dormant and grow back from their root system under the ground. Since the bladderwort does not have a root system it relies on a special overwintering bud called a turion. This is formed at the end of the vegetative shoots and when the plant dies back it falls to the bottom of the pond.
The fine thread-like leaves help the plant by providing a bigger surface area to obtain carbon dioxide. Plants need carbon-dioxide to produce their own food through photosynthesis. Carbon dioxide is scarce in the water, so having a large surface area allows the plant to obtain it more easily.
Bladderworts play an important role plant in the pond habitat. Not only do they feed on tiny microbes, but they also provide food and shelter for fish, frogs, turtles, larger crustaceans and water insects. With strategies to survive the winter, obtain food through flawless traps and through carbon dioxide collection, bladderwort is truly an amazing plant!