Purple Bladderwort's suction traps, hiding in plain sight
September 2, 2026
There is a carnivorous plant drifting in the small ponds of the Ossipee and Sebago country, and almost nobody who swims past it knows it is there. has no roots at all. It floats free just under the surface as a loose tangle of fine submerged stems, and strung along those stems are hundreds of hollow bladders, each one only a couple of millimeters across.Every bladder is a trap, and it works by suction. Glands in the bladder wall pump water out until the inside is held under negative pressure, with a small door sealed watertight against that pressure. On the outside of the door sit mechanosensory bristles. When a swimming animal brushes one, the bristle flexes, the door inverts from convex to concave, and at that instant it can no longer hold; it springs, and the inrush of water carries the animal inside. It is one of the fastest movements known in the plant kingdom.The rootlessness is the reason for all that machinery. With no roots to draw nitrogen and phosphorus from the sediment, the plant has to take them from the water column, and the bladders are how it does it, catching zooplankton and other microinvertebrates. That fits where the species turns up: nutrient-poor pond and lake margins, the tea-colored, low-fertility water this glaciated country is full of.Purple Bladderwort then complicates its own story. Its traps are not sterile prey chambers. They hold a dense resident community of algae, ciliates and bacteria, and the literature on this species suggests it has partly relaxed its reliance on catching and digesting animals, drawing instead on what lives inside the bladders. Darwin was already looking into those traps and finding tenants.Twenty-six records have been logged in the surrounding ponds and lakes over the past two years, and they cluster in late summer: three at Chocorua on August 17 of this year, one at West Newfield across the Maine line on August 15, and three at Sebago on August 14 the summer before, with another at Naples on August 9. It is a native plant here and carries no federal listing. To find it, wade a quiet pond edge, lift a strand of submerged stem out of the water, and look closely at what is hanging off it.
