Written By: Rich aka rsivertsen - Northwest New Jersey, (USA)
Growing Condition
First, the term “Aldrovanda Pond” is in itself misleading! When someone mentions the word “pond”, it invokes images of a fairly large body of free standing water, at least several meters in length, and a depth of about “knee deep” to “waist deep” or more; some place where you could float a small boat (rowboat, or inflatable), and go fishing or swimming. There are a few open areas like this in this site, an open pond, about waist deep, and about 10M wide; but you won’t find any Aldrovanda growing there! It’s too deep!
Aldrovanda ONLY grows in the very shallow margins, in ankle deep water, no more than 20 cm (6 inches) of free standing water, and the best strands are in areas where the water just barely covers them, 5 cm (2 inches); less is better. They are always found in very close proximity to large monocot plants that produce massive root systems, which provide a constant supply of CO2, and absorbs the excess nitrogenous matter given off by the Aldrovanda. These shallow areas also host the highest population densities of the zooplankton creatures.
The water tests moderately hard with neutral pH=7.0, and contains a conspicuous presence of clay. They actually seem to do better in very dirty water! After I walk around among them, my boots churn up lots of clay, and detritus, so much so, that the water becomes opaque, and I can’t even see the Aldrovanda strands anymore. Some places get so disgusting, that the water becomes a thin and soupy slurry of mud, clay and detritus. After a few days, when the water settles down, I notice these very same strands make a quantum leap in growth; some strands growing vertical, with their bottom ends still weighed down, stuck in the detritus.
This works on several levels. First it releases all those mineral rich nutrients from the clay based silt, and covers the strands with that mixture; next it flushes out all those critters that hide and live in the detritus, so that they wind up on the Aldrovanda, and become part of the menu; lastly, it warms up the water, as it absorbs more solar energy, heating it up, and causes the respiration rate of the zooplankton to increase, which increases the CO2 of the water.
It has also been a common misconception that Aldrovanda need highland temperatures year round. So tropical growers have them in air-con rooms! They can tolerate very warm, even hot water, which may be lethal for most fish, 95(F), (40C) is not unusual, and in fact, it is one of the factors that will cause them to produce flowers. In my ponds, if they have temps in the 90(F) for at least 2 weeks prior to the summer solstice (June 21), they will produce flowers in mid July, and often profusely at that.
They actually do better in warmer temps and can tolerate cooler conditions, but when the photoperiod drops to less than 8 hrs, combined with the cooler temps, they will go dormant, and form turions; I doubt that they will go dormant in tropical conditions when the photoperiod is essentially the same all year long, and the temps are well above those that which may induce them to form turions.
Growth
They grow incredibly FAST!! According to Lubomir Adamec, they can grow up to 3 new axils (whorls) per day, a full inch (2.5 cm) in length per day, and branch at least one (up to three) new apical growth points every 3 to 5 days, which means that they can double their population every week! They need a continuous supply of CO2 to meet this rapid rate of growth for its photosynthesis needs. They also trap, digest and consume more prey than it can use for its own immediate needs, and so it discharges the excess out into the water, where the roots of the monocot plants suck up that stuff like hungry vacuum cleaners! Without this relationship and balance, filamentous algae quickly moves in to take advantage of the nitrogenous matter, and eventually attacks the Aldrovanda and chokes it to death.
The more they eat, the faster they grow, and the more they multiply, and produce more branches and multiple apical growth points.
I took a few strands into my son’s university, and had a look-see with a decent dissecting microscope at his Biology Dept. The Dept Chair had the first look, and seemed astonished at what he saw. When I looked at them in a deep petri dish, I saw dozens of various small worms, perhaps some nematodes, small fresh water shrimp and several snails, who were pulling out the spent carcasses from the older traps, and copepods, apparently also grooming the strands of any algae, several rotifiers, daphna, hydras, a fresh water clam, some insect larvae and nymphs and many things we couldn’t identify. It was like a tropical rain forest canopy in miniature! Every strand was teaming with life like a busy downtown city street in rush hour. They may have an even more robust relationship with the creatures of the pond than previously realized!
Traps
They happen to be the only aquatic CP that can trap and consume even the largest stages of mosquito larvae.
The long hairs or bristles next to the traps also serve another interesting function; it allows them to survive out of water! When they are forced out of water, they abort forming traps, and their whorls collapse on top of each other forming a sheath around the center stem, and those bristles become loaded with tiny drops of dew every morning, which gets pulled into these hollow tubes (by capillary action) formed by the collapsed whorls, and stores enough moisture to sustain them an entire day out of free standing water. I was pretty amazed to see this one morning for myself when I wondered how these Aldrovanda stands managed to keep from dying when the water in the pond dried out. They take on a very different form of growth when they become “terrestrial” and look more like some species of Lycopodium rhizoids crawling in the moss and detritus.