Wednesday, August 4, 2010

Bladderworts: Pretty, But Deadly Adirondack Natives

What child hasn’t read about carnivorous plants? Usually by the time we are in 4th or 5th grade, someone we know has discovered the Venus Fly Trap, that classic carnivore of the floral world. But one needn’t travel to the tropics, or even The South, to discover the joy of plant carnivory. Right here in the Adirondacks we have pitcher plants and sundews, two carnivores that are popular in their own right. But we also have bladderworts, smaller and less unusual (at least on the surface – they look like snapdragons), but no less deadly. These are plants worthy of our attention.

New York is home to fourteen species of bladderworts, four of which are threatened and one that is endangered. Some species float in the water, while others are “rooted” in the soil at the water’s edge (bladderworts don’t technically have roots). Most sport bright yellow flowers that rival birdsfoot trefoil for brilliance, but two come in shades of pale purple, making them a delightful find.

Bladderwort – the name is bound to make one chuckle. It sounds funny and brings some funny images to mind. “Wort” comes from the Anglo-Saxon language, and it simply means “plant.” The “bladder” part of the name does not refer to an excretory system, however. If one pulls up a bladderwort, one will see all sorts of little pouches, or bladders, clinging to the plant. These bladders are the dangerous part of the plant.

Bladderworts come in two basic varieties up here: free-floating aquatics and terrestrial. Despite the name, terrestrial species (which make up about 80% of the world’s bladderwort species) are actually not growing high and dry – they are found in saturated, water-logged soils. This is because bladderworts must have water in order to get their food.

In a nutshell, here’s how it works. The bladders, which look kind of like little helmets, are more or less flat when they are set. When they are set, they are in a state of negative osmotic pressure. Across the opening to the outside world, each bladder has what is essentially a lid. Attached to the lid are the trigger hairs. When a small creature brushes by the trigger, a lever-like action takes place. Where the hair attaches to the bladder, it levers an opening in the seal around the lid. Once this seal is broken, the vacuum is released, the lid flies open, and the surrounding water (and its contents) are sucked into the bladder. When the bladder is full, the lid closes and calmness is restored…at least in the water. All of this happens in the tiniest fraction of a second.

Meanwhile, within the bladder, dire things are happening. Digestive enzymes and bacteria get to work on the prey. Prey items vary in size and species depending on the species of bladderwort involved. The free-floating bladderworts have larger bladders and can take on larger prey, sometimes capturing fish fry, mosquito larvae and even small tadpoles. More likely, however, they are eating things like water fleas and nematodes. The terrestrial species, with their smaller bladders, are consuming things like protozoans and rotifers, microscopic creatures swimming through the watery soil.

The rate of digestion depends on the size of the prey. Some food can be digested quickly, in a matter of minutes, while other items take hours, or even days, to be consumed. When the food had been completely reduced to soup, special cells extract the slurry, transporting it into the stem of the plant, once more creating a vacuum in the bladder. The trap is now reset and ready for its next victim.

While reading up on the digestive habits of these plants, I found myself grateful that they are so small. Can you imagine a bladderwort large enough to engulf a human? No body of water would be safe for swimmers! This could be the stuff of horror movies (giant bladderworts grow near nuclear reactors…swimmers and watercraft are warned to stay out of the water…)!

Science fiction aside, these are some pretty interesting, and highly sophisticated, plants. Bladderworts can be found in many of the Adirondack’s lakes, ponds, bogs, and even along streams and rivers. While they tend to prefer acidic water, some do very well in more alkaline conditions. If you are paddling along and see what look like bright yellow snapdragons sticking above the water’s surface, you have probably found a free-floating species. Reach in and lift out the leafy mass to see the bladders, but be sure to return it to its watery home when you are done.

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Ellen Rathbone

Ellen Rathbone is by her own admission a "certified nature nut." She began contributing to the Adirondack Almanack while living in Newcomb, when she was an environmental educator for the Adirondack Park Agency's Visitor Interpretive Centers for nearly ten years.

Ellen graduated from SUNY ESF in 1988 with a BS in forestry and biology and has worked as a naturalist in New York, New Jersey, and Vermont.

In 2010 her work took her to Michigan, where she currently resides and serves as Education Director of the Dahlem Conservancy just outside Jackson, Michigan.

She also writes her own blog about her Michigan adventures.





4 Responses

  1. Woodswalker says:
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