Bladder traps


The principle of bladder traps has also been realised only by one genus, namely by bladderworts (Utricularia). Bladder traps are a highly refined and complex trap system. Bladderworts produce as traps small bladders, whose size vary considerably between different species. The diametre varies between 1 – 10 mm. In the bladders wall are small pumps installed, which pump water from the inside outwards, whereby a negative pressure is produced and the bladder is dented inwards. In addition, the bladder shows a small opening, which is closed by a valve. At the valve are several bristles, which release the trap in contact. If a prey (mainly wheel animals, water fleas and nematodes; by larger bladders also mosquito larvae) gets at a bristle, this acts as lever, with which the prey releases the valve from its anchor. Through the negative pressure the valve and with this also some water and the prey, which was in front of the valve, are sucked inwards. After a complete pressure balance the valve closes again. The whole process only takes 0.02 seconds and is therefore the second fastest movement in plant kingdom. Faster is only the Canadian bunchberry (Cornus canadensis), which catapults, in the case of contact, its pollen to the top within 0,3 ms. Then pumps begin again to suck water out and to renew thereby the negative pressure. Parallel other pumps secrete digestive enzymes, with which the prey is utilized.

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