Not to be semantically confused with : Butterworts such as Common Butterwort (Pinguicula vulgaris) although they are in the same family (Lentibulariaceae) and are also Carnivorous, as are Bladderworts. Butterworts grow in damp places, but not in lakes and they do have green leaves which can photosynthesize and roots, so are not totally dependent on insects for nutrition.
Nor to be semantically confused with :
Bladder-sedge (Carex vesicaria),
Brittle Bladder-fern (Cystopteris fragilis),
Bladder Ketmia (Hibiscus trionum),
Bladderseed (Physospermum cornubiense), Bladder Campion (Silene vulgaris),
Bladdernut (Staphylea pinnata), Bladder Senna (Colutea arborescens),
Brittle Bladder-fern (Cystopteris fragilis) or other Bladder-ferns [plants with similar names belonging to differing families]
Bladderworts, lacking roots, are unable to obtain nutrients from the lake-bed, so must obtain nutrition elsewhere.
All Bladderworts are Carnivorous Plants, although they do have chlorophyll in the filigree fern-like green leaves below the surface of the water with which they can synthesize their own products. They obtain obtain other nutrients by the dissolution of insects and water-creatures and their subsequent absorption. Bladderworts are so called because they have tiny flask-shaped bladders along their underwater stems (which are fern-like with numerous compound branches).
When a tiny insect or other creature (such as zooplankton) touches some very sensitive hairs near the opening of the trapdoor on the underwater bladder, this small trapdoor abruptly opens and the insect is sucked in with the entering water. The trapdoor then quickly shuts again trapping the insect within. The insect is slowly dissolved by enzymes or bacteria whereupon the released nutrients are absorbed by the plant. This presumably consists of a lot of nitrogenous compounds which it may not be able to obtain in sufficient quantities from the water. The speed with which the trapdoor opens and then shuts beggars belief - it outpaces the closing of the traps in
Venus Flytrap! It happens faster than the blink of the eye uTube video of Bladderwort trap capturing underwater creature. The trapdoor then resets itself by closing and pumping the water partially out of it ready to suck in the next victim (or 'sucker') when the hair-trigger is set off (or'pulled').
Lesser Bladderwort is the smallest and thinnest of the Bladderworts. Some specimens have boyancy bladders only, others have some stems with bladders and green leaves which are without bristles. The upper lip of the flower is 3mm by 4mm long, the lower lip 7mm by 5-7mm, so sometimes square. It is a native plant occurring mostly in the north and the west and occupying boggy pools and ditches in the fens. It seems to like shallow pools in acidic uplands, but also occurs in other places. It is the most commonly occurring of 6 other Bladderworts which are uncommon to very rare.