Ultrafast Underwater Traps

This video shows how the incredible traps used by bladderworts work. The narrator is hard to understand, but the video is worth watching.



When you study the living world, you can see how the Creator designed organisms to meet the needs of every ecosystem on the planet. Consider, for example, carnivorous plants. Plants form the foundation of many food webs. Using carbon dioxide and water, they convert the energy of sunlight into food for themselves, but they produce much more food than they need. As a result, they are used as a food source by many animals, which in turn are used as a food source by many other animals. Plants, therefore, are crucial to many ecosystems.

The food they make for themselves supplies plants with energy, but like all other organisms, plants need more than energy to live healthy and reproduce properly. They also need specific chemicals to build the molecules they need for survival. Most plants use their roots to absorb those chemicals from the soil. But what about places where the soil isn’t nutritious or it isn’t practical to absorb nutrients from it? Those ecosystems need plants as well, so there need to be plants that can survive in such places.

Enter the carnivorous plants. They capture and digest living organisms, but they don’t use those organisms for energy. Instead, the they use the organisms’ constituent chemicals as building blocks for all the elegant chemistry that they need to do. That way, they don’t have to absorb nutrients from the soil. Even the most barren soil can host carnivorous plants.

While all carnivorous plants are amazing in their own way, a recent study in The Proceedings of the Royal Society B has highlighted the amazing design of one type of carnivorous plant: the bladderwort (genus Utricularia).

Bladderworts capture organisms with incredibly designed suction traps. The traps look like tiny bladders, which is where the plants get their name. They are perhaps the epitome of carnivorous plants, because they do not have roots at all. As a result, they don’t need any kind of soil in which to grow. Many float in water with their bladder traps poised to catch the organisms that swim there. Others grow in moist soil or decomposing matter, catching the organisms that are found there.1

Interestingly enough, even though bladderworts have been studied extensively, no one had ever done an in-depth study of the specific way their suction traps work. That’s why Olivier Vincent and his colleagues decided to use high-speed photography and mathematical models to analyze them. The findings they report from their study demonstrate how intricately designed these marvels of nature really are.2

They find the trap operates with a mechanism that consists of two phases. In the first phase, a flexible “door” on the trap closes, making it watertight. Then, glands inside the trap actively pump water out of the trap, causing the walls of the trap to sink in, which stores elastic energy. This process takes about an hour, at which point the trap is set.

The “door” has tiny trigger hairs that protrude from it, and those hairs are incredibly sensitive. When an organism touches the hairs, the second phase of the mechanism begins. The door opens, and all that elastic energy stored in the walls of the trap suck water inside with an acceleration that is 600 times greater than the acceleration due to gravity. In other words, the trap pulls 600 g’s! Amazingly enough, this phase is completely passive. It works solely on the elastic energy that is stored in the first phase!

Even more impressive is the “backup plan” that is employed by every trap. The researchers watched a single trap for a period of 20 days, and over that time, they found that it opened 60 different times without a detectable trigger. The authors suggest that these “spontaneous suction” events allow the bladder to bring in nutrients even if there isn’t a trigger. After all, there is usually some useful matter floating in water, and there are always a few microscopic organisms that probably can’t trigger the door. If a trap has been set for a while and hasn’t been triggered, then, it spontaneously opens, hoping to catch something good among the things floating in the water. The authors suggest that bladderworts’ incredible success at living in nutrient-poor environments is the result of the fact that the traps employ both an active trigger and spontaneous suction.

The best way to see how incredibly well-designed these amazing plants are is to read what the authors suggest can be learned as a result of their work:

The remarkable valve mechanism of Utricularia should provide inspiration for a great variety of biomimetic applications, especially for new deployable materials and fluid-elastic structures designed to act repeatedly, such as in microfluidic devices.

Indeed, some of the best examples of human technology are the result of scientists and engineers copying the work of the Ultimate Designer!

REFERENCES

1. H. Lambers and Timothy D. Colmer, eds., Plant Ecophysiology – Root Physiology: from Gene to Function (Springer, 2005), p. 129.
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2. Olivier Vincent, et al., “Ultra-fast underwater suction traps,” Proceedings of the Royal Society B doi: 10.1098/rspb.2010.2292, 2011
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