Swollen Bladderwort (Utricularia micropetala)

Description

Utricularia inflata, commonly known as the swollen bladderwort, inflated bladderwort, or large floating bladderwort, is a large suspended aquatic carnivorous plant that belongs to the genus Utricularia. It is a perennial that is native to the southeastern coastal plains of the United States. It has often been confused with U. radiata, which is similar but smaller than U. inflata. Since 1980, U. inflata has been reported to exist in locations beyond its traditional range, such as the Adirondack Mountains in New York, southeastern Massachusetts, and in Washington State. Studies on the populations in the Adirondacks suggest that an introduction of U. inflata to a location where it naturalizes can lead to altered sediment chemistry by reducing the net primary productivity of native species. It is also listed by the state of Washington as a problematic species because of the dense mat-forming habit of this aquatic Utricularia. It is one of the few carnivorous plants that can be invasive. Utricularia inflata is one of the larger suspended aquatic species in the genus Utricularia. Like all aquatic Utricularia, U. inflata has no true roots or leaves. The filiform stolons are the main vegetative "stem" of the plant and can be up to one meter long or longer but are only 1–2 mm thick. The stolons are glabrous with 1–5 cm between branched divisions. Occasionally the stolons will produce floating air shoots at the water's surface and tuber-like organs in the substrate. Its filiform leaf-like structures appear to be additional branches off the main stolon and are tiny, filament-like structures that are not true leaves, though the terminology is often disputed among experts. The leaf structures are numerous and anywhere from 2–18 cm long, originating from the stolon base into two primary and unequal segments, which are further divided extensively into additional segments. The stalked, ovoid traps, 1–3 mm long, are produced on the latter leaf segments and are very numerous. In its native range, U. inflata, a perennial species, can begin to flower in January and may continue through June. In this phase of its growth it produces the most visible and noticeable morphological features of the species: a floating spoke-like whorl of spongy structures at the water's surface that support the inflorescences, often called a "float". U. inflata typically produces 6 to 8 spokes on the float (sometimes anywhere from 5 to 10), with each spoke 3–10 cm long and up to 8 mm wide. The apical half of the spokes bear numerous, dichotomously branched leaf-like segments that can also possess some traps. The 20–50 cm long erect inflorescences are produced from the center of the floating whorl and are usually solitary or possess very few scapes for each whorl. An individual plant can produce several whorls and inflorescences, but they are typically distant from each other. The inflorescences produce 9-14 (sometimes 4-17) flowers with unequal calyx lobes, 3–5 mm long. The entire corolla can be 2-2.5 cm long and is bright yellow with brown-colored veins on the spur and brown markings on the lower corolla lobe. This species has a diploid chromosome number of 2n = 18 for the most common form and 2n = 36 for the larger tetraploid populations. The larger tetraploid "race", as Peter Taylor called it, can be up to twice as large as the regular diploid species. Populations of this race have been located in Florida.