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Physical description of the trap Authorities on the genus, such as botanists
Peter Taylor and
Francis Ernest Lloyd, agree that the vacuum-driven bladders of
Utricularia are the most sophisticated carnivorous trapping mechanism to be found anywhere in the
plant kingdom. The bladders are usually shaped similarly to
broad beans (though they come in various shapes) and attach to the submerged
stolons by slender stalks. Bladders are hollow underwater suction cups, also known as utricles, that possess a valve with bristles that open and close. The bladder walls are very thin and transparent but are sufficiently inflexible to maintain the bladder's shape despite the vacuum created within. The entrance, or 'mouth', of the trap is a circular or oval flap whose upper half is joined to the body of the trap by very flexible, yielding cells which form an effective hinge. The door rests on a platform formed by the thickening of the bladder wall immediately underneath. A soft but substantial membrane called the
velum stretches in a curve around the middle of this platform, and helps seal the door. A second band of springy cells crosses the door just above its lower edge and provides the flexibility for the bottom of the door to become a bendable 'lip' which can make a perfect seal with the velum. The outer cells of the whole trap excrete
mucilage and under the door, this is produced in greater quantities and contains sugars. The mucilage certainly contributes towards the seal, and the sugars may help to attract prey. Terrestrial species, like
U. sandersonii have tiny traps (sometimes as small as 0.2 mm; 1/100") Additionally,
Utricularia traps often collect a diversity of microplankton and detritus. When this periphyton is dissolved into basic nutrients within the bladder environment, bacterial enzymes help aid in digestion. Therefore, carbon secretion and periphyton utilization in the utricles enable
Utricularia to live with relatively little competition. Mutualism could have been an important association in aquatic
Utricularia trap evolution as these microbes may have allowed these plants to acquire the needed nutrients when they lost their roots, as they may have had issues acquiring phosphorus. Phosphorus was found to be the most important factor in
Utricularia nutrition, which helps explain why
Utricularia bladders are found with a wide diversity of bacteria to aid in phosphorus digestion. Such decoupling would allow
Utricularia to optimize power output (energy × rate) during times of need, albeit with a 20% cost in energy efficiency. According to the ROS mutation hypothesis, the sequestration of these protons has cellular consequences, which could lead to nucleotide substitutions. Oxidative phosphorylation is an imperfect process, which allows electrons to leak into the lumen, and only partially reduce oxygen. This partially reduced oxygen is a
reactive oxygen species (ROS) which can be very harmful, unlike its fully reduced counterpart, the water molecule. When there is greater potential change between the lumen and intermembrane space, the leakiness of the electron transport chain also increases, therefore creating a higher production of ROS in the mitochondria of
Utricularia. ROS is harmful to cells, as it produces damage to nucleotides and helical DNA. Therefore, the increased cellular respiration of
Utricularia bladders combined with the unique sequestration of protons could lead to its high nucleotide substitution rates, and therefore its wide diversity. This structural evolution seems highly unlikely to have arisen by chance alone; therefore, many researchers suggest this key adaption in
Utricularia allowed for radical morphological evolution of relatively simple trap structures to highly complex and efficient snares. This adaptation may have enhanced the genus' fitness by increasing its range of prey, rate of capture, and retention of nutrients during prey decomposition.
Lloyd's experiments In the 1940s,
Francis Ernest Lloyd conducted extensive experiments with carnivorous plants, including
Utricularia, and settled many points which had previously been the subject of conjecture. He proved that the mechanism of the trap was purely mechanical by both killing the trigger hairs with iodine and subsequently showing that the response was unaffected, and by demonstrating that the trap could be made ready to spring a second (or third) time immediately after being set off if the bladder's excretion of water were helped by a gentle squeeze; in other words, the delay of at least fifteen minutes between trap springings is due solely to the time needed to excrete water, and the triggers need no time to recover irritability (unlike the reactive trigger hairs of
Venus flytraps, for example). He tested the role of the velum by showing that the trap will never set if small cuts are made to it; and showed that the excretion of water can be continued under all conditions likely to be found in the natural environment, but can be prevented by driving the osmotic pressure in the trap beyond normal limits by the introduction of glycerine.
Ingestion of larger prey Lloyd devoted several studies to the possibility, often recounted but never previously accounted for under scientific conditions, that
Utricularia can consume larger prey such as young tadpoles and mosquito larvae by catching them by the tail, and ingesting them bit by bit. Prior to Lloyd, several authors had reported this phenomenon and had attempted to explain it by positing that creatures caught by the tail repeatedly set off the trap as they thrash about in an attempt to escape—even as their tails are actively digested by the plant. Lloyd, however, demonstrated that the plant is quite capable of ingestion by stages without the need of multiple stimuli. '' is held aloft by a rosette of floats. He produced suitable artificial "prey" for his experiments by stirring
albumen (egg white) into hot water and selecting shreds of an appropriate length and thickness. When caught by one end, the strand would gradually be drawn in, sometimes in sudden jumps, and at other times by a slow and continuous motion. Strands of
albumen would often be fully ingested in as little as twenty minutes. Mosquito larvae, caught by the tail, would be engulfed bit by bit. A typical example given by Lloyd showed that a larva of a size at the upper limit of what the trap could manage would be ingested stage by stage over the course of about twenty-four hours; but that the head, being rigid, would often prove too large for the mouth of the trap and would remain outside, plugging the door. When this happened, the trap evidently formed an effective seal with the head of the larva as it could still excrete water and become flattened, but it would nevertheless die within about ten days "evidently due to overfeeding". Softer-bodied prey of the same size such as small tadpoles could be ingested completely, because they have no rigid parts and the head, although capable of plugging the door for a time, will soften and yield and finally be drawn in. Very thin strands of albumen could be soft and fine enough to allow the trapdoor to close completely; these would not be drawn in any further unless the trigger hairs were indeed stimulated again. On the other hand, a human hair, finer still but relatively hard and unyielding, could prevent a seal being formed; these would prevent the trap from resetting at all due to leakage of water. Lloyd concluded that the sucking action produced by the excretion of water from the bladder was sufficient to draw larger soft-bodied prey into the trap without the need for a second or further touch to the trigger levers. An animal long enough not to be fully engulfed upon first springing the trap, but thin and soft enough to allow the door to return fully to its set position, would indeed be left partly outside the trap until it or another body triggered the mechanism once again. However, the capture of hard bodies not fully drawn into the trap would prevent its further operation. ==Genetics==