Natures wonders: speedy carnivorous bladderworts (Introduction)

by David Turell @, Thursday, September 21, 2017, 18:01 (753 days ago) @ David Turell

They use speed and suction to trap their prey:

https://www.sciencedaily.com/releases/2017/09/170921101733.htm

"The experiments described in the first article were conducted in close collaboration with colleagues from the Department of Animal Ecology, Evolution, and Biodiversity at the Ruhr University of Bochum, led by Prof. Dr. Ralph Tollrian. With the help of a high-speed camera, the researchers analyzed the "capture behavior" of the suction trap of Utricularia australis and possible escape attempts of one of its natural prey species, the water flea Ceriodaphnia dubia. They discovered that the fleas are sucked into the traps with 2800 times the acceleration of gravity and are decelerated inside the trap nearly as quickly. All of the trapping processes are too fast to allow the flea to make an attempt at escape.

***

"Comparative functional-morphological and biomechanical analyses on 19 bladderwort species conducted by the scientists revealed different trap entrance and trapdoor structures as well as several types of movement during suction that may be interpreted as adaptations to the different habitats the species occupy. One species, Utricularia multifida, has a trapdoor that does not move and likely traps prey according to a passive trapping principle instead of sucking it in."

From the study:

http://www.nature.com/articles/s41598-017-01954-3

"The aquatic bladderwort suction trap is a functionally resilient structure for reliably capturing zooplankton prey. It can be assumed that the only countermeasures of C. dubia to avoid capture by U. australis suction traps are encounter avoidance, a structural barrier making them unfit to pass the trap entrance, and/or an effective flight response. Encounter avoidance could, for example, be realized by an altered behavior in terms of swimming speed and/or an altered aggregation behavior, i.e. swimming in distance to plants. Such reactions are already described in the Daphniidae as inducible defenses against animal predators provoked by chemical cues. Also, inducible defense reactions like an alteration of the shape/dimensions of their bodies could support to impede suction, e.g. by increasing the body dimensions above the trap door diameter. Apparently, the mechanical contact to the trigger hairs and the process of trapdoor snap-buckling (which is accompanied by only small water displacements) do not induce flight responses of the prey. Probably, the timescales of both processes are too short to be processed fast enough by the animal’s nervous system. Also, we did not observe attempts of the animals to swim against the suction streams, which again would presuppose a processing and orientation of the body opposite to the torrent Utricularia produces. Evolving a fast enough sensory and reaction system triggered upon certain mechanical stimuli (trigger hair contact, sensing of a water flow field induced by snapping trapdoor) would probably allow for such a flight response. However, C. dubia is regarded as a slow swimmer and, especially, the reaction speed of the arthropod nervous system cannot be reduced unlimitedly (e.g. due to the absence of Schwann cells in arthropods)."

Comment: This cannot develop stepwise by chance evolution. The digestive enzymes must be developed and controlled so as not to self-digest the bladderwort itself.


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