Ceratophyllum

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Ceratophyllum
CeratophyllumSubmersum.jpg
Ceratophyllum submersum
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Order: Ceratophyllales
Family: Ceratophyllaceae
Genus: Ceratophyllum
L.
Type species
Ceratophyllum demersum L. [1]
Species

See text

Synonyms [2]
  • Hydroceratophyllon Ség.
  • DichotophyllumMoench
  • RevatophyllumRöhl.
  • FassettiaMavrodiev

Ceratophyllum is a cosmopolitan genus of flowering plants commonly found in ponds, marshes, and quiet streams in tropical and in temperate regions. It is the only extant genus in the family Ceratophyllaceae, [3] itself the only extant family in the order Ceratophyllales. [4] They are usually called coontails or hornworts, although hornwort is also used for unrelated plants of the division Anthocerotophyta.

Contents

Description

Ceratophyllum grows completely submerged, usually, though not always, floating on the surface of the water. The plant stems can reach 1–3 m in length. At intervals along nodes of the stem they produce rings of bright green leaves, which are narrow and often much-branched. The forked leaves are brittle and stiff to the touch in some species, softer in others. Roots are completely absent and are missing even in the embryonic stage, [5] but sometimes they develop modified leaves with a rootlike appearance, which anchor the plant to the bottom. Stomata are not present on any species. [6] The flowers are small and inconspicuous, with the male and female flowers on the same plant. In ponds it forms thick buds (turions) in the autumn, which sink to the bottom and give the impression that the plant has been killed by the frost; but come spring, these will grow back into the long stems, slowly filling up the pond. [7] [8] [9] [10]

Taxonomy

Ceratophyllum was first described by Carl Linnaeus in 1753 with Ceratophyllum demersum as the type species. [1] Ceratophyllum is considered distinctive enough to warrant its own family, Ceratophyllaceae, but was considered a relative of Nymphaeaceae and included in Nymphaeales in the Cronquist system. Recent research has shown that it is not closely related to Nymphaeaceae or any other extant plant family. Some early molecular phylogenies suggested it was the sister group to all other angiosperms, but more recent research suggests that it is the sister group to the eudicots. This notion was supported upon sequencing of the C. demersum genome in 2020. [11] The APG IV system placed the family in its own order, the Ceratophyllales, and gives the following cladogram. [3] [12] [13] [4]

angiosperms

Species

The subgeneric division of the genus Ceratophyllum into its appropriately recognized species, subspecies, and varieties is not settled. More than 30 species have been described and published. A narrow interpretation of this work rejects over 23 of these taxa as variants, accepting only 7 species. This narrow interpretation lumps to the point of failing to give these potential species the taxonomic importance of even being named on a subspecific or varietal level. The genus as narrowly defined in this manner contains the following seven species: [3] [7] [8] [14] [15] [2]

Phylogeny

A 2018 phylogenetic analysis of the above species gives the below cladogram. It finds support for 4 species being monophyletic, while 3 others are paraphyletic. It found C. australe to be a divergent lineage of C. tanaiticum, rendering C. tanaiticum paraphyletic. Nonetheless it still regards C. australe as a seperate species due to significant morphological differences and its geographic isolation from the rest of C. tanaiticum. C. demersum and C. platyacanthum were recovered as paraphyletic with respect to each other, and as such they could possibly be considered one species, although their morphologies and ecologies are distinct. [16]

Ceratophyllum

C. echinatum Ceratophyllum echinatum iNat-9779405 (3x4).jpg

C. demersum Ceratophyllum demersum.jpg

C. platyacanthum

C. australe

C. tanaiticum

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Ceratophyllum demersum, commonly known as hornwort, rigid hornwort, coontail, or coon's tail, is a species of flowering plant in the genus Ceratophyllum. It is a submerged, free-floating aquatic plant, with a cosmopolitan distribution, native to all continents except Antarctica. It is a harmful weed introduced in New Zealand. It is also a popular aquarium plant. Its genome has been sequenced to study angiosperm evolution.

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References

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  2. 1 2 "Ceratophyllum L." Plants of the World Online . Royal Botanic Gardens, Kew . Retrieved 25 July 2023.
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  5. Competition Science Vision nov 2003
  6. Frontiers | Refined Interpretation of the Pistillate Flower in Ceratophyllum Sheds Fresh Light on Gynoecium Evolution in Angiosperms
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  14. Germplasm Resources Information Network: Ceratophyllum
  15. Flora Europaea: Ceratophyllum
  16. Szalontai, Bálint; et al. (24 August 2018). "Molecular phylogenetic analysis of Ceratophyllum L. taxa: a new perspective". Botanical Journal of the Linnean Society. 188 (2): 161–172. doi:10.1093/botlinnean/boy057.