Bladderworts – Carnivorous Aquatic Traps

Carnivorous plants are a curious collection of organisms that have evolved ways to trap insects and other animals to supplement the lack of nutrients in the habitats where they grow. The term itself seems counterintuitive when you think about it. We all learned that plants make their own food, using carbon dioxide from the atmosphere, water, and nutrients, powered by sunshine.

But not all habitats have enough nutrients to support everything a plant needs, such as healthy growth and enough resources to flower and produce seeds for the next generation. As it turns out, our world is rich in carnivorous plants species that use both passive and active traps to snare animal prey lured to them. The most commonly known of these are pitcher plants that use tapered tubes to trap prey and absorb nutrients after their death – a passive approach. Sundews are also passive in design, using sticky surface hairs that snare prey. https://ourmshome.com/sundews-botanical-flypaper/

Venus Flytraps are the most recognized terrestrial carnivorous plant with active traps – a highly modified hinged leaf that is triggered to close around prey that are lured there by the smell of nectar. But lurking in shallow water wetlands across the world are a group of plants that also use a sophisticated active trap – in the worldwide genus Utricularia. Along the Gulf Coast these plants live in shallow ponds, drains and ditches that retain water most of the year.

The name Utricularia is from the Latin word utriculus, a reference to a wine flask, leather bottle or bagpipe. These bladders are the means of trapping aquatic organisms and represent one of the most sophisticated structures in the plant world. Each bladder is an offshoot of the underwater “stems’ that are suspended in the water column. At the heart of the trap is a door that is triggered to open inward, within milliseconds, sucking in water and the unsuspecting critters that are attracted to them, by sugary substances, much like other carnivorous plants.

The neat part of the design is the way cells in the walls of the hollow bladders pump out water to create negative pressure that drives the rapid-fire action of the door, once triggered. The door quickly shuts, trapping prey within. Prey quickly suffocate. It has been shown that traps can be reset and operate more than once. In any case, these traps are quite effective, as evidenced by the dark black color of bladders as they fill with prey. Depending on the species of bladderwort and the size of their bladders, prey may include tiny crustaceans, mosquito larvae, newly hatched tadpoles and fish fry.

Apart from the flowers of these plants that rise above the water on slender stalks, much of this drama remains out of sight beneath the surface. But where these plants exist, they can be numerous and have a significant impact on small aquatic creatures. The species that inspired this story is known as Little Swollen Bladderwort. Its bright yellow flowers make it easy to spot this time of year, each held above the water surface on a pad of multiple, modified floating leaves.

And although the U.S. has several other aquatic species, there are also more than one that live in the saturated soils of local Wet Pine Savannas, where their bladders lie in the soil, trapping soil organisms like nematodes. Still out of sight, but effective. Their presence in these habitats is only known because of their bright yellow flowers that emerge from the soil.

We may not have Venus Flytraps in our part of the world, but we do have some of the most effective and sophisticated active carnivorous plants anywhere – if you know where to look.

Hope to see you in our great outdoors!