Utricularia resupinata

“Utricularia resupinata B.D. Greene ex Bigelow” identifies the species’ scientific name with the first person to discover this flowering plant -- a Massachusetts lawyer named Benjamin Daniel Greene (1793–1862), whose finding was reported in what became the standard botanical resource for that time period, with the following brief note: “Greene, M.S. Greene’s bladder wort…A small delicate species with purple flowers, discovered by B. D. Greene, Esq. at [a pond in] Tewksbury. Middlesex Co, MA.”[17]^:10 American botanist, physician, and botanical illustrator Jacob Bigelow (1787–1879) published his first edition of Florula Bostoniensis in 1814 – a detailed survey of flora in the greater Boston region, adding neighboring New England states in later editions.

Holotype or specimen of Utricularia resupinate collected in 1961, housed in University of South Florida Herbarium

Two of Frank Tweedy’s bladderwort finds are currently in New England herbaria, one at Harvard University and the other at the University of Vermont, both collected in 1879 on the shore of Big Moose Lake, Herkimer County, NY.[18] A herbarium (plural herbaria) is a collection of plant specimens that have been preserved for scientific study.[19] A search of all herbaria for this species in the Mid-Atlantic Herbaria Consortium yields 609 finds, beginning with B.D. Greene’s specimen now displayed in the New York Botanical Garden, included on this list with his date of discovery, 1829. The rest of the collection ranges from then to the most recent specimen found at Lake Hartwell, S.C. on October 9, 2019, with this description: “A Colony growing en masse, on bank in area where lake waters have receded. Proliferous colony stretching far up the shore and in the turn of the cove. Leaves matted in mud, some plants producing early fruits. Flowers very pale pink.”[20]

One of the early students of Utricularia resupinata and its carnivorous family (Lentibulariaceae) was Mary Treat (1830-1923), a naturalist who made major contributions in botany and entomology. She spent many hours over her microscope observing the bladders or traps along its supporting system of stems, trying to discover how “these little bladders” trapped and digested their animal prey. It was originally believed that the series of bladders on the stems and roots “floated the plant.” Mary Treat was “one of the first scientists to suspect that the bladders were actually traps for tiny creatures rather than air floatation devices.”[21]

In a book titled Through a Microscope, Mary Treat contributed a whole chapter on the Utricularia genus, puzzling over the “wonderful” process by which these bladders worked:

I have found almost every swimming animalculæ with which I am acquainted, caught in these vegetable traps; and when caught they never escape. Their entrance is easy enough; there is a sensitive valve at the mouth of the bladder, which, if they touch it, flies open and draws them in as quick as a flash. These downward-opening bladders not only entrap animalculæ, but, more wonderful still, the strong larvæ of insects.[22]^:62–63

Mary also held a five-year correspondence with biologist Charles Darwin as he was researching carnivorous plants, debating the question of how insects entered these bladders, finally convincing him of her theory. She recounted this in the same chapter, and it is worth quoting at length for this back story from the early history of botany:

Those who have read Mr. Darwin’s very interesting book on Insectivorous Plants, will have noticed that he says the valve of Utricularia is not in the least sensitive, and that the little creatures force their way into the bladders -- their heads acting like a wedge. But this is not the case, as Mr. Darwin himself was convinced some years before his death. In his usual kind, gracious manner he admitted that he was wrong, and gracefully says the valve must be sensitive, although he could never excite any movement. In a letter to me bearing date June 1st, 1875, he says: "I have read your article (in Harper’s Magazine) with the greatest interest. It certainly appears from your excellent observations that the valve is sensitive...I cannot understand why I could never with all my pains excite any movement. It is pretty clear I am quite wrong about the head acting like a wedge. The indraught of the living larva is astonishing.”[22]^:69

Utricularia resupinata was moved to a new genus as the science of botany progressed, and New York Botanical Garden (NYBG) leader John Hendley Barnhart (1871-1949) categorized this species in 1913 under “Lecticula,” a section of the genus Ultricularia. He based this taxonomy change on its unusual stem bracts noted above: “Utricularia sect. Lecticula is a section in the genus Utricularia that was originally described as genus Lecticula in 1913 by John Hendley Barnhart. The two species in this section are small subaquatic carnivorous plants that are distinguished by the unique bracts, which are basifixed and tubular. Both species are native to North and South America.”[23] Botanist Norman Taylor (1900-1975) in association with the NYBG published Flora in the Vicinity of New York in 1915, reporting on Barnhart’s new category (and name) for Utricularia resupinata. Under the Lentibulariaceae or bladderwort family of plants, he identified three genera -- Vesiculina Raf., Utricularia L., and Lecticula Barnhart, with Utricularia resupinata printed with its new name in this third genus. The following comment described this section of the genus: “L. [Lecticula] resupinata (B.D. Greene) Barnhart. In sandy bogs and borders of ponds: Me. to Fla., west to Mish. Rare.”[24] Lecticula resupinata is thus a plant synonym for Utricularia resupinata.

Peter Geoffrey Taylor (1926-2011) put in 41 years of research and observation on the genus Utricularia. In 1989 he published The Genus Utricularia: A Taxonomic Monograph with Utricularia resupinata one of the 240 species in this genus, and now under its original name. Taylor illustrated 214 of these species in his book, considered to be ground breaking with its in-depth study of an entire genus: “Taylor's species list and classification are now generally accepted with some additions of newly described taxa and modifications based on phylogenetic studies.[25]

Mary Treat repeatedly observed the tiny bladders of the Utricularia genus under her microscope trap minute animal life as a mosquito larva, for example, triggered sensitive filaments at the mouth of the bladder, snapping it shut. But one mystery baffled her: “I soon became satisfied that the valve was very sensitive when touched at the right point, but to this day I cannot tell what the power is that so quickly draws the creatures within.”[22]^:68–69 Recent research based on phylogenetics has answered some questions and raised others. The Utricularia bladder has long fascinated scientists. “Although the Utricularia traps are the smallest among those of carnivorous plants, they are arguably the most sophisticated and intricate ones.”[5]^:640

Picture of bladders on stem of Lavender Bladderwort taken by Peter M. Dziuk in 2015

Czech Republic botanist Lubomir Adamec has summarized the extensive research that has recently been done with species in the Utricularia genus – with a focus on its carnivorous bladder. Three things are clear. This plant expends a tremendous output of energy through its string of bladders. “When a prey species touches sensory hairs situated on the trap door it opens, the small animal is aspirated into the trap and the door closes again. This process of firing is complete within 10 -- 15 ms [milliseconds] and is the most rapid plant movement known.”[5] The source of this ATP energy -- Adenosine triphosphate, the molecule for storing and transferring energy in cells -- is still an open research question. This Utricularia resupinata picture of two bladders on the plant's stem captures the luminescence of these bladders with their "trap door" and trigger filaments branching out.[26]

Second, not all of the minute animals sucked into the Utricularia traps are digested, because it has been found that some of the organisms in this “bladder soup” actually assist in prey decomposition, a process similar to what happens in an efficient septic system. “In spite of its tiny volume, the trap fluid in Utricularia plants is inhabited permanently by various commensal microorganisms -- bacteria, cyanobacteria, microfungi, algae, euglens, dinophytes, protozoa (ciliates) and rotifers -- which live in a mutualistic interaction with the plant.”[5] This “miniature food web” offers many ecological possibilities, with potential applications pending further research.

And third, the presence or absence of oxygen inside the bladder is a key part of this “sophisticated and intricate” process. “Therefore, captured organisms either die of O₂ deprivation and are prey, or are able to tolerate anoxia and are commensals. Utricularia traps likely kill their prey by suffocation.”[5] Lubomir Adamec's research summary while technical, invites the reader to draw on a knowledge of all the physical and life sciences.[5] An intricate collection of valves inside the bladder help govern this complex organ -- inviting the reader to appreciate its mechanics, the pumping of water in and out at high speed and pressure; its electro-chemistry, transferring enough voltage when triggered to perpetuate the process; and learning of the symbiosis of minute animal species inside this botanical bladder, either facilitating or becoming food for digestion.