''Utricularia gibba'', commonly known as the humped bladderwort or floating bladderwort, is a small, mat-forming species of

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose nutrition and energy requirements are met by consumption of animal tissues (mainly mu ...

aquatic bladderwort. It is found on all continents except Antarctica. ''U. gibba'' has an exceptionally small

genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...

for a plant, despite having a typical number of

genes In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

. The sequencing of its DNA revealed only 3% repetitive DNA material.

Description

''Utricularia gibba'' is an aquatic carnivorous plant that belongs to the genus ''

Utricularia ''Utricularia'', commonly and collectively called the bladderworts, is a genus of carnivorous plants consisting of approximately 233 species (precise counts differ based on classification opinions; a 2001 publication lists 215 species).Salmon, B ...

'', or bladderworts. The

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

''gibba'' is Latin for "hump" or "swelling" – a reference to the inflated base of the lower lip of the corolla.Bruce Salmon (2001) ''"Carnivorous Plants of New Zealand"'' Ecosphere Publications It is a small- to medium-sized aquatic plant that can either be affixed to the substrate in shallow water or free-floating in the water column, however it will likely flower more if supported by a substrate beneath shallow water. It forms mats of criss-crossing, branching, thread-like

stolon In biology, a stolon ( from Latin ''wikt:stolo, stolō'', genitive ''stolōnis'' – "branch"), also known as a runner, is a horizontal connection between parts of an organism. It may be part of the organism, or of its skeleton. Typically, animal ...

s, each growing to approximately or longer and 0.2–1 mm thick. What are sometime described as leaves or leaf-like organs – the actual distinction is difficult in the reduced morphology – are numerous and scattered along the length of the stolons and are long with a very short dichotomous branching pattern toward the tip of anywhere from one to eight branches but usually not more than four. The bladder traps take the place of some of these distal branches on the leaf-like structures. The traps are ovoid and are attached to the leaf-like structure by a short stalk; each trap is 1–2.5 mm long and has two primary setiform branched appendages on top and some smaller appendages surrounded the entrance to the trap. The appendages are the trigger that sets the trap off and vacuums the prey that touched it into the bladder to be digested.Taylor, Peter. 1989. '' The genus Utricularia - a taxonomic monograph''. Kew Bullein Additional Series XIV: London.

Inflorescence In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a mai ...

s are erect and typically emerge from the water to about tall, though in some cases they can be submerged and produce cleistogamous flowers. Inflorescences can produce anywhere from one to twelve flowers but it is unusual to see anything other than two to six flowers per inflorescence. Individual flowers are yellow, often with reddish-brown nerves, and are split into two lips: the upper lip is almost circular and weakly separated into three lobes while the lower lip is slightly smaller, also circular, and has a rounded, bilobed swelling in the center. The

spur A spur is a metal tool designed to be worn in pairs on the heels of riding boots for the purpose of directing a horse or other animal to move forward or laterally while riding. It is usually used to refine the riding aids (commands) and to ba ...

is narrowly conical or cylindrical and curves down below the flower, varying in length from being just shorter than to noticeably longer than the lower lip. ''Utricularia gibba'' will flower throughout the year whenever conditions are favorable. Flowers, specifically the corolla, vary in size across this species' large distribution from .Schnell, Donald. 2002. ''Carnivorous Plants of the United States and Canada''. Timber Press: Portland, Oregon. pp. 369–370. The diploid chromosome number for ''U. gibba'' is 2n = 28.

Distribution and habitat

''Utricularia gibba'' has a vast geographic range and is native to the eastern United States, southeastern Canada, Central America, the Caribbean, the western Mediterranean, Southern Africa and southern India. It is considered an

invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

in Hawai'i, Australia, Japan, Brazil, New Zealand, Singapore, Serbia, Hungary and the United Kingdom. It grows in ponds and lakes or shallow water in ditches, pools, bogs, swamps, and marshes that may be still or slowly flowing. It can sometimes be found growing in deep water but will not flower unless the

inflorescence In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a mai ...

s are supported near the surface by living or dead vegetation. The waters in which it grows are typically poor in available

phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...

and

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

Genetic efficiency

In 2013, the

of ''U. gibba'' was sequenced. At only 82 megabases, the genome is exceptionally small for a multicellular plant and the main difference between other plant genomes and that of ''U. gibba'' is a drastic reduction in

non-coding DNA Non-coding DNA (ncDNA) sequences are components of an organism's DNA that do not encode protein sequences. Some non-coding DNA is transcribed into functional non-coding RNA molecules (e.g. transfer RNA, microRNA, piRNA, ribosomal RNA, and reg ...

. The discovery casts doubt on the idea that repetitive, non-coding DNA, popularly known as junk DNA, is necessary for life. ''Utricularia gibba'' and the

tomato The tomato (, ), ''Solanum lycopersicum'', is a plant whose fruit is an edible Berry (botany), berry that is eaten as a vegetable. The tomato is a member of the nightshade family that includes tobacco, potato, and chili peppers. It originate ...

split from a common ancestor approximately 87 million years ago. Since that time, both plants have experienced episodes of whole genome duplication (WGD) in which the plants' DNA content doubled in size. Since then, it has lost most unneeded DNA, unlike the tomato, and now has a genome only a tenth as long as the tomato's. Compared to ''Arabidopsis'', the introns of ''Utricularia gibba'' are somewhat fewer in number per gene, and conserved ''cis''-acting elements of its promoters are compressed. Most critical genes have returned to single copy status. However, the mitochondrial and

plastid A plastid is a membrane-bound organelle found in the Cell (biology), cells of plants, algae, and some other eukaryotic organisms. Plastids are considered to be intracellular endosymbiotic cyanobacteria. Examples of plastids include chloroplasts ...

genomes of ''U. gibba'' do not appear to be compressed relative to those of other angiosperms. The compression of its nuclear DNA is thought to have occurred via both numerous microdeletions and some large-scale recombinant deletions. The presence of numerous GC-rich sequences throughout the nuclear genome of ''U. gibba'' is considered to have created a molecular mechanistic bias in favor of deletions, but this does not preclude the presence of a selection pressure to preserve such deletions. Trap formation is induced in ''U. gibba'' by low phosphorus but not low nitrogen, indicating that phosphorus availability is more limiting in its environment. It had also been previously proposed that an increased mutation rate due to greater environmental mutagen exposure could have increased natural selection for loss of unneeded DNA, but no evidence for this was found in the relative mutational diversities of ''U. gibba'' and ''Arabidopsis''. It is possible that the genome duplication events and low-phosphorus environment acted in concert with one another: that the three whole genome duplications that occurred in ''U. gibba'' enabled the selective pressure of a phosphorus-poor environment to reduce total DNA without the deletion of important genes. Utricularia gibba and scenedesmus

Cultivation

''Utricularia gibba'' has the reputation of being one of the easier aquatic bladderworts to grow, often being described as a weed in cultivation. In his 1998 book '' The Savage Garden: Cultivating Carnivorous Plants'', Peter D'Amato advised that successful cultivation could be achieved with ''U. gibba'' floating in a small cup or bowl, within waterlogged

peat Peat is an accumulation of partially Decomposition, decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, Moorland, moors, or muskegs. ''Sphagnum'' moss, also called peat moss, is one of the most ...

, or even among the water-filled trays of other plants. It can also easily be grown in aquaria.D'Amato, Peter. 1998. '' The Savage Garden: Cultivating Carnivorous Plants''. Ten Speed Press: Berkeley, California. p. 231.

References

External links