Hydrilla
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''Hydrilla'' (waterthyme) is a
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
aquatic plant Aquatic plants are plants that have adapted to living in aquatic environments (saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that ...
, usually treated as containing just one species, ''Hydrilla verticillata'', though some botanists divide it into several species. It is native to the cool and warm waters of the
Old World The "Old World" is a term for Afro-Eurasia that originated in Europe , after Europeans became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia, which were previously thought of by the ...
in Asia, Africa and Australia, with a sparse, scattered distribution; in Australia from
Northern Territory The Northern Territory (commonly abbreviated as NT; formally the Northern Territory of Australia) is an states and territories of Australia, Australian territory in the central and central northern regions of Australia. The Northern Territory ...
,
Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...
, and
New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...
.Flora Europaea
''Hydrilla''
/ref>Flora of Taiwan
''Hydrilla''
Australian Plant Name Index
''Hydrilla''
/ref> The stems grow up to 1–2m long. The
leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...
are arranged in whorls of two to eight around the stem, each leaf 5–20 mm long and 0.7–2 mm broad, with serrations or small spines along the leaf margins; the leaf midrib is often reddish when fresh. It is
monoecious Monoecy (; adj. monoecious ) is a sexual system in seed plants where separate male and female cones or flowers are present on the same plant. It is a monomorphic sexual system alongside gynomonoecy, andromonoecy and trimonoecy. Monoecy is conne ...
(sometimes
dioecious Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...
), with male and female
flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...
s produced separately on a single plant; the flowers are small, with three sepals and three petals, the petals 3–5 mm long, transparent with red streaks. It reproduces primarily
vegetatively Vegetative reproduction (also known as vegetative propagation, vegetative multiplication or cloning) is any form of asexual reproduction occurring in plants in which a new plant grows from a fragment or cutting of the parent plant or spec ...
by fragmentation and by rhizomes and turions (overwintering), and flowers are rarely seen.Flora of NW Europe
''Hydrilla verticillata''
Blamey, M. & Grey-Wilson, C. (1989). ''Flora of Britain and Northern Europe''. Huxley, A., ed. (1992). ''New RHS Dictionary of Gardening''. Macmillan . They have air spaces to keep them upright. ''Hydrilla'' has a high resistance to
salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...
compared to many other freshwater associated aquatic plants.


Taxonomy and naming

''Hydrilla'' closely resembles some other related aquatic plants, including ''
Egeria densa ''Egeria densa'', the large-flowered waterweed or Brazilian waterweed, is a species of '' Egeria'' native to warm temperate South America in southeastern Brazil, Argentina, Chile and Uruguay. It is considered a problematic invasive species due t ...
'' and ''
Elodea canadensis ''Elodea canadensis'' (American waterweed or Canadian waterweed or pondweed) is a perennial aquatic plant, or submergent macrophyte, native to most of North America.Flora of North America''Elodea canadensis''/ref>Plants of British Columbia''Elod ...
''.
Synonyms A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
include ''H. asiatica'', ''H. japonica'', ''H. lithuanica'', and ''H. ovalifolica''.


Ecology

''Hydrilla verticillata'' is allelopathic to the common hornwort (''
Ceratophyllum demersum ''Ceratophyllum demersum'', commonly known as hornwort, rigid hornwort, coontail, or coon's tail, is a species of ''Ceratophyllum''. It is a submerged, free-floating aquatic plant, with a cosmopolitan distribution, native to all continents except ...
'') and prickly hornwort ('' C. muricatum''), that is, it produces compounds that inhibit growth of the latter two species.


Status as an invasive plant


Introduction

''Hydrilla'' is
naturalized Naturalization (or naturalisation) is the legal act or process by which a non-citizen of a country may acquire citizenship or nationality of that country. It may be done automatically by a statute, i.e., without any effort on the part of the in ...
and invasive in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
following release in the 1950s and 1960s from aquariums into waterways in
Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...
, due to the
aquarium trade Fishkeeping is a popular hobby, practiced by aquarists, concerned with keeping fish in a home aquarium or garden pond. There is also a piscicultural fishkeeping industry, serving as a branch of agriculture. Origins of fishkeeping Fish have ...
. It is now established in Canada and the southeast from
Connecticut Connecticut () is the southernmost state in the New England region of the Northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, New York to the west, and Long Island Sound to the south. Its cap ...
to
Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
, and also in
California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
.Flora of North America
''Hydrilla verticillata''
/ref> By the 1990s control and management were costing millions of dollars each year. Specifically, a Florida west coast aquarium dealer shipped live ''Hydrilla'' from
Sri Lanka Sri Lanka (, ; si, ශ්‍රී ලංකා, Śrī Laṅkā, translit-std=ISO (); ta, இலங்கை, Ilaṅkai, translit-std=ISO ()), formerly known as Ceylon and officially the Democratic Socialist Republic of Sri Lanka, is an ...
under the common name "Indian star-vine." After these plants were considered unsatisfactory, they were dumped into a canal near
Tampa Bay Tampa Bay is a large natural harbor and shallow estuary connected to the Gulf of Mexico on the west-central coast of Florida, comprising Hillsborough Bay, McKay Bay, Old Tampa Bay, Middle Tampa Bay, and Lower Tampa Bay. The largest freshwater in ...
, where they flourished. By 1955, the plants found their way from Tampa to
Miami Miami ( ), officially the City of Miami, known as "the 305", "The Magic City", and "Gateway to the Americas", is a East Coast of the United States, coastal metropolis and the County seat, county seat of Miami-Dade County, Florida, Miami-Dade C ...
as they were transported for cultivation and pet trade sale. It is believed that several undocumented cases of accidental or careless releases followed, as there was extensive spread of the ''Hydrilla'' throughout Florida and the southeastern U.S.


Problems

As an invasive species in Florida, ''Hydrilla'' has become the most serious aquatic weed problem for Florida and most of the U.S. Because it was such a threat as an
invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...
, one of the first cost-effective broadscale herbicide controls developed was
fluridone Fluridone is an organic compound that is used as aquatic herbicide often used to control invasive plants. It is used in the United States to control hydrilla and Eurasian watermilfoil among other species. Fluridone is sold as a solution and as ...
. Unfortunately, this single-use herbicide resulted in fluridone-resistant ''Hydrilla''. “As ''Hydrilla'' spread rapidly to lakes across the southern United States in the past, the expansion of resistant biotypes is likely to pose significant environmental challenges in the future.”, ''Hydrilla'' populations have caused economic, environmental, and ecological damage. ''Hydrilla'' is known to be an aggressive and competitive plant, even out-competing and displacing native species, such as pondweeds and
eelgrass Eelgrass is a common name for several plants and may refer to: * ''Zostera'', marine eelgrass * ''Vallisneria ''Vallisneria'' (named in honor of Antonio Vallisneri) is a genus of freshwater aquatic plant, commonly called eelgrass, tape grass o ...
. Due to its competitive nature, ''Hydrilla'' has created
monoculture In agriculture, monoculture is the practice of growing one crop species in a field at a time. Monoculture is widely used in intensive farming and in organic farming: both a 1,000-hectare/acre cornfield and a 10-ha/acre field of organic kale are ...
s, an area dominated by a singular species, rather than having a balance among many species, like in a normal ecosystem. In Australia, ''Hydrilla'' can become invasive if the nutrient levels are raised in disturbed ecosystems, though is not generally known to be problematic. ''Hydrilla'' can host a
biofilm A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular ...
of the
cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...
Aetokthonos hydrillicola which can produce the brominated
neurotoxin Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature ner ...
aetokthonotoxin which is the causative agent of Avian vacuolar myelinopathy, a fatal brain wasting disease of waterfowl and raptors.


Management

''Hydrilla'' can be controlled by
herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...
s, as well as
grass carp The grass carp (''Ctenopharyngodon idella'') is a species of large herbivorous freshwater fish in the family Cyprinidae, native to the Pacific Far East, with a native range stretching from northern Vietnam to the Amur River on the Sino-Russian ...
, itself an invasive species in North America. Insects used as
biological pest control Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also invo ...
for this plant include weevils of the genus ''
Bagous ''Bagous'' is a genus of snout and bark beetles in the family Curculionidae The Curculionidae are a family of weevils, commonly called snout beetles or true weevils. They are one of the largest animal families, with 6,800 genera and 83,000 spec ...
'' and the Asian hydrilla leaf-mining fly (''Hydrellia pakistanae'').
Tuber Tubers are a type of enlarged structure used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growing ...
s pose a problem as they can lie dormant for a number of years, making it even more difficult to remove from waterways and estuaries. ''Hydrilla'' holds the advantage in that in can spread efficiently through both tubers and turions. In 2011 the inlet of
Cayuga Lake Cayuga Lake (,,) is the longest of central New York's glacial Finger Lakes, and is the second largest in surface area (marginally smaller than Seneca Lake) and second largest in volume. It is just under long. Its average width is , and it is a ...
, one of the
Finger Lakes The Finger Lakes are a group of eleven long, narrow, roughly north–south lakes located south of Lake Ontario in an area called the ''Finger Lakes region'' in New York, in the United States. This region straddles the northern and transitional ...
in New York State, used the chemical herbicide
endothall Endothall (3,6-endoxohexahydrophthalic acid) is used as an herbicide for both Terrestrial plant, terrestrial and Aquatic plant, aquatic plants. It is used as an aquatic herbicide for submerged aquatic plants and algae in lakes, ponds and irrigatio ...
to try to head off a possible future disaster. The first year nearly $100,000 and numerous man-hours were spent trying to eradicate the ''Hydrilla'' infestation. Follow-up treatments were planned for at least five years. The City of
Ithaca Ithaca most commonly refers to: *Homer's Ithaca, an island featured in Homer's ''Odyssey'' *Ithaca (island), an island in Greece, possibly Homer's Ithaca *Ithaca, New York, a city, and home of Cornell University and Ithaca College Ithaca, Ithaka ...
as well as other local officials are willing to pay the price because without quick action the plant could get into the lake and possibly spread to other Finger Lakes in the region. In August 2021 “Hydrilla” was discovered growing in a small boat marina that is connected to the Niagara River in the city of
North Tonawanda North Tonawanda is a city in Niagara County, New York, United States. The population was 31,568 at the 2010 census. It is part of the Buffalo–Niagara Falls Metropolitan Statistical Area. The city is named after Tonawanda Creek, its south bo ...
New York. The New York State Department of Environmental Conservation is involved and working to contain the infestation according to local TV reports. In September 2021 according to local TV reports the Connecticut River Conservancy stated that hydrilla has been overwhelming tributary rivers, coves, inlets and riverbanks along the river for years. Kelsey Wentling, a river steward at the Connecticut River Conservancy stated, "hydrilla can spread through a process known as fragmentation, in which the plants, due to some sort of disruption, break apart and regrow elsewhere. Fragmentation often happens when boats go through a patch of hydrilla. For this reason, it is critical that those using paddle boats, power boats, jet skis, and fishing equipment in the Connecticut River be aware of invasive hydrilla and then take steps to reduce its spread." It has also been reported by local marinas and municipalities that they can no longer access certain boat slips and docks due to the density and severity of the hydrilla. The Connecticut River Conservancy in Sept 2021 requested area boaters to complete a survey to help with the ongoing management of the invasive plant


Phytoremediation

This abundant source of
biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
is a known
bioremediation Bioremediation broadly refers to any process wherein a biological system (typically bacteria, microalgae, fungi, and plants), living or dead, is employed for removing environmental pollutants from air, water, soil, flue gasses, industrial effluent ...
hyperaccumulator A hyperaccumulator is a plant capable of growing in soil or water with very high concentrations of metals, absorbing these metals through their roots, and concentrating extremely high levels of metals in their tissues. The metals are concentrated a ...
of
mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...
,
cadmium Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...
,
chromium Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal. Chromium metal is valued for its high corrosion resistance and hardne ...
and
lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
, and as such can be used in
phytoremediation Phytoremediation technologies use living plants to clean up soil, air and water contaminated with hazardous contaminants. It is defined as "the use of green plants and the associated microorganisms, along with proper soil amendments and agronomi ...
.


Medicinal uses of ''Hydrilla''

''Hydrilla'' is known to have many digestive and health benefits. The plant contains vitamins, minerals, and antioxidants, as well as being useful for fighting indigestion. The plant is also known for its extremely high concentration of calcium, vitamin B-12, iron and magnesium. As such, the plant has become an extremely popular "superfood"


References


External links


Species Profile- Hydrilla (''Hydrilla verticillata'')
National Invasive Species Information Center,
United States National Agricultural Library The United States National Agricultural Library (NAL) is one of the world's largest agricultural research libraries, and serves as a national library of the United States and as the library of the United States Department of Agriculture. Located ...
. Lists general information and resources for Hydrilla. {{Taxonbar, from1=Q2720105, from2=Q164181 Angiosperms of Western Australia Aquatic plants Flora of New South Wales Flora of Queensland Flora of South Australia Flora of the Northern Territory Flora of Victoria (Australia) Hydrocharitaceae genera Invasive plant species in Sri Lanka Monocots of Australia Monotypic Alismatales genera Phytoremediation plants Hydrocharitaceae