Ruppia cirrhosa

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Ruppia cirrhosa
Ruppia cirrhosa Dungeness.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Alismatales
Family: Ruppiaceae
Genus: Ruppia
Species:
R. cirrhosa
Binomial name
Ruppia cirrhosa
Synonyms
List
    • Buccaferrea cirrhosaPetagna (1787) (basionym)
    • Dzieduszyckia limnobisRehmann
    • Ruppia cirrhosa subsp. occidentalis(S.Watson) Á.Löve & D.Löve
    • Ruppia cirrhosa var. truncatifolia(Miki) H.Hara
    • Ruppia lacustrisMacoun
    • Ruppia maritima var. occidentalis(S.Watson) Graebn.
    • Ruppia maritima var. pedunculataHartm. ex Ledeb.
    • Ruppia maritima var. spiralis(L. ex Dumort.) Moris
    • Ruppia maritima subsp. spiralis(L. ex Dumort.) Asch. & Graebn.
    • Ruppia occidentalisS.Watson
    • Ruppia spiralisJ.K.Fisch., nom. illeg.
    • Ruppia spiralisL. ex Dumort.
    • Ruppia truncatifoliaMiki

Ruppia cirrhosa (syn. Ruppia spiralis), spiral tasselweed, is a species of aquatic plant in the pondweed family, with a cosmopolitan distribution, that grows in brackish to saline waters. It has long, thin leaves that often form a dense layer under the surfaces of coastal ditches, lakes and lagoons. The flowers are tiny and petal-less, and produce pollen that is dispersed by the wind or floating on the water. The name refers to its ability to produce a long, coiled stalk to the fruiting inflorescence, which is not often seen.

Contents

Description

Fruiting spiral tasselweed plant, showing the characteristic long peduncle and the inflated leaf sheath. Spiral Tasselweed Ruppia cirrhosa (6171516651).jpg
Fruiting spiral tasselweed plant, showing the characteristic long peduncle and the inflated leaf sheath.

Spiral tasselweed is a perennial aquatic plant with a monopodial rhizome that each year produces slender, delicate stems up to about 0.6 m long, with many long branches. The leaves are all the same and typically grow entirely submerged, with blades up to about 120 mm long by about 1 mm wide. The tips of the leaves are minutely serrated and quite blunt. The leaf sheaths are up to 25 mm long, open along one side and papery (hyaline) along the other. There is no ligule. [2]

The inflorescences arise singly at the leaf axils, within the distinctively inflated sheaths of the involucral leaves. Each inflorescence contains two flowers close together at the tip of a stalk, or peduncle, which can be up to 300 mm long. Each flower has two stamens, each with two lobes, thus appearing to have four yellow, round anthers. In the middle of this group of four anthers there is cluster of 2-8 carpels, which occur on very short stalks that lengthen as the fruit matures until they get to about 32 mm in length. In spiral tasselweed the peduncle often becomes coiled at this time but, even if not coiled, it is usually at least twice as long as the individual fruit stalks, and sometimes as much as ten times as long. The flowers typically occur on the surface, in which case the pollen is dispersed by water currents, [3] or raised into the air, when they can be wind-pollinated. [4]

Spiral tasselweed flowering on the surface of a ditch. Ruppia spiralis pollen.jpg
Spiral tasselweed flowering on the surface of a ditch.

The fruits are flask-shaped, up to about 3.5 mm long, and brown or grey when mature, with tiny reddish warts on the surface. They are almost symmetrical in outline, unlike the irregularly shaped fruits of beaked tasselweed. [5] [6]

The fruit are slightly asymmetrical, but less so than in R. maritima. Ruppia spiralis fruit.jpg
The fruit are slightly asymmetrical, but less so than in R. maritima.

Identification

The leaf tip is rounded and minutely serrated. Ruppia spiralis leaf tip.jpg
The leaf tip is rounded and minutely serrated.

Great care is needed in identifying the various species of tasselweed. In north-west Europe (including Ireland and Britain) there are only two wild species: spiral tasselweed and beaked tasselweed. Only spiral tasselweed produces a coiled peduncle, but this is rarely seen. The relative lengths of the peduncle and the fruit stalks are more reliable: spiral tasselweed has peduncles up to 4 cm - longer than the fruit stalks, which are up to 3.2 cm, whereas beaked tasselweed has peduncles up to 2.6 cm - shorter than the stalks, which are up to 3.5 cm. [7]

Taxonomy and nomenclature

In 1753 Linnaeus coined the name Ruppia for the genus, but the only species he recognised was Ruppia maritima. [8] It was not until 1827 that Dumortier realised that there were two species, and he named spiral tasselweed Ruppia spiralis. However, Petagna had also named the same plant Buccaferrea cirrhosa in 1787 (although it was not published until 1826). Either way, that pre-dates Dumortier's discovery. The genus Buccaferrea is clearly not needed, so the combination Ruppia cirrhosa was finally published by Loreto Grande in 1918. [9] These overlapping dates leave some uncertainty about which is the correct name to apply, but the general consensus at present is that Ruppia cirrhosa is best. [10] [11] However, a recent (2017) study of herbarium specimens suggests that Petagna's tasselweed might actually have been Ruppia maritima, in which case Dumortier's R. spiralis would be the correct name for the new species. [12]

Ruppia cirrhosa has a complex taxonomy and is sometimes considered an aggregate of numerous taxa. For example, the western Mediterranean plant Ruppia drepanensisTineo could be a subspecies. Some authors have suggested that R. cirrhosa and R. spiralis are actually different species rather than synonyms. [13] The complexity is caused in part because R. cirrhosa occurs as diploid (2n = 20), triploid (2n = 30) or tetraploid (2n = 40) populations. It also hybridises with R. maritima. [14]

The generic name Ruppia was given in honour of the German botanist Heinrich Bernhard Rupp, while the specific name cirrhosa is from the Ancient Greek word κιρρός (kirros), which means tawny.

Distribution and status

Most sources suggest that spiral tasselweed has a cosmopolitan, circumpolar distribution, [10] [15] but there is some debate about this. Generally, it is found only in brackish to saline coastal locations, but North American plants (sometimes referred to as R. occidentalis) grow in freshwater inland lakes. [16] [12]

Its global status has been assessed by the IUCN as LC, or "least concern", which means there is no evidence for a serious decline. [17] However, it is rare in some countries and regions and can have a local conservation status such as VU (vulnerable) in Brittany, extinct in lower Normandy, and NT (near threatened in Britain. [18] [19]

For conservation purposes, spiral tasselweed is generally considered an axiophyte, or indicator of good environmental conditions. [20] There is evidence to suggest that its presence improved the diversity of invertebrates and the nutritional quality of the substrate in coastal lagoons. [21]

Habitat and ecology

A meadow of spiral tasselweed in a lagoon at Minnis Bay, Kent. Ruppia spiralis lagoon.jpg
A meadow of spiral tasselweed in a lagoon at Minnis Bay, Kent.

Although spiral tasselweed often grows on its own, it is occasionally found with other plants such as the eelgrasses Zostera marina and Z. noltii - as at The Fleet, Dorset. [22] Within the British National Vegetation Classification it is probably restricted to the SM2 Ruppia maritima community, although there was much confusion between the two species of tasselweed in the 1980s, and the description of SM2 could usefully be reworked. [23] Most sources seem to suggest that spiral tasselweed is strictly coastal, but not a marine plant. [24] [18]

Individual plants arise from rhizomes buried in the substrate. Ruppia cirrhosa underwater.jpg
Individual plants arise from rhizomes buried in the substrate.

Its Ellenberg values in Britain are L = 7, F = 12, R = 7, N = 4, and S = 4, which reflect its habitat requirements for waterbodies in reasonably sunny places with neutral soils and low fertility, and brackish conditions. [25]

The only insect association recorded in Europe (and probably in Britain, where it has been found on R. maritima, possibly including R. cirrhosa) is with the cercozoan Tetramyxa parasitica , which creates spherical galls in the stems of infested plants. [26] [27]

References

  1. ↑ Short, F.T.; Carruthers, T.J.R.; Waycott, M.; Kendrick, G.A.; Fourqurean, J.W.; Callabine, A.; Kenworthy, W.J.; Dennison, W.C. (2010). "Ruppia cirrhosa". IUCN Red List of Threatened Species . 2010 e.T164280A5808308. doi: 10.2305/IUCN.UK.2010-3.RLTS.T164280A5808308.en . Retrieved 16 June 2024.
  2. ↑ Preston, C.D. (1995). Pondweeds of Great Britain and Ireland. London: Botanical Society of the British Isles. ISBN   0-901158-24-0.
  3. ↑ Verhoeven, J. T. A. (1979-01-01). "The ecology of Ruppia-dominated communities in western Europe. I. Distribution of Ruppia representatives in relation to their autecology". Aquatic Botany. 6: 197–267. Bibcode:1979AqBot...6..197V. doi:10.1016/0304-3770(79)90064-0. ISSN   0304-3770.
  4. ↑ Kitchener, G.D. (2025). Kent Rare Plant Register.
  5. ↑ Sell, Peter; Murrell, Gina (2018). Flora of Great Britain and Ireland, vol. 1. Cambridge: Cambridge University Press. ISBN   978-0-521-55335-3.
  6. ↑ Schou, J.C.; et al. (2023). Aquatic Plants of Northern and Central Europe including Britain and Ireland. Princeton, N.J.: Princeton University Press. ISBN   978-0-691-25101-1.
  7. ↑ Stace, C.A. (2019). New Flora of the British Isles (4th ed.). Middlewood Green: C & M Floristics. ISBN   978-1-5272-2630-2.
  8. ↑ Linné, Carl von; Linné, Carl von; Willdenow, Karl Ludwig; Link, Heinrich Friedrich; Nauck, Gottfried Carl; Schwaegrichen, F. (1797). Caroli a Linné Species plantarum exhibentes plantas rite cognitas, ad genera relatas, cum differentiis specificis, nominibus trivialibus, synonymis selectis, locis natalibus, secundum systema sexuale digestas. Vol. t.1:pt.2 (1797) (Editio quarta, post Reichardianam quinta adjectis vegetabilibus hucusque cognitis, curante Carolo Ludovico Willdenow ed.). Berolini: Impensis G.C. Nauk.
  9. ↑ "Grande, Loreto | International Plant Names Index". www.ipni.org. Retrieved 2025-09-24.
  10. 1 2 "Ruppia cirrhosa (Petagna) Grande". Global Biodiversity Information Forum. Retrieved 24 September 2025.
  11. ↑ "Ruppia cirrhosa (Petagna) Grande | Plants of the World Online | Kew Science". Plants of the World Online. Retrieved 2025-09-24.
  12. 1 2 Ito, Y.; Ohi-Toma, T.; Nepi, C.; Santangelo, A.; Stinca, A.; Tanaka, N.; Murata, J. (2017). "Towards a better understanding of the Ruppia maritima complex (Ruppiaceae): Notes on the correct application and typification of the names R. cirrhosa and R. spiralis". Taxon . 66 (1): 167–171. Bibcode:2017Taxon..66..167I. doi:10.12705/661.11.
  13. ↑ den Hartog, C.; Triest, L. (2020). "A profound view and discourse on the typification and status of three confused taxa: Ruppia maritima, R. spiralis and R. cirrhosa". Botanica Marina. 63 (3): 229–239. Bibcode:2020BoMar..63..229D. doi:10.1515/bot-2019-0045.
  14. ↑ Mannino, Anna M.; Menéndez, M.; Obrador, B.; Sfriso, A.; Triest, L. (2015-07-01). "The genus Ruppia L. (Ruppiaceae) in the Mediterranean region: An overview". Aquatic Botany. 124: 1–9. Bibcode:2015AqBot.124....1M. doi:10.1016/j.aquabot.2015.02.005. hdl:10278/3661481. ISSN   0304-3770.
  15. ↑
  16. ↑ "Ruppia cirrhosa - FNA". floranorthamerica.org. Retrieved 2025-09-25.
  17. ↑ "Spiral Ditchgrass". The IUCN Red List of threatened species. 23 October 2007. Retrieved 25 September 2025.
  18. 1 2 Guillemot, Vincent (2023). Flore du Massif armoricain et ses marges (in French). Mèze: Editions Biotope. ISBN   978-2-36662-301-7.
  19. ↑ "PlantAtlas". plantatlas2020.org. Retrieved 2025-09-25.
  20. ↑ "Axiophytes – Botanical Society of Britain & Ireland" . Retrieved 2025-09-28.
  21. ↑ Munari, Cristina; Casoni, Elia; Cozzula, Cinzia; Pasculli, Alessandra; Pezzi, Marco; Sciuto, Katia; Sfriso, Andrea Augusto; Sfriso, Adriano; Mistri, Michele (2023-06-07). "The Ecological Role of Ruppia cirrhosa (Petagna) Grande in a Choked Lagoon". Water. 15 (12): 2162. Bibcode:2023Water..15.2162M. doi: 10.3390/w15122162 . ISSN   2073-4441.
  22. ↑ Stewart, A.; Pearman, D.A.; Preston, C.D. (1994). Scarce Plants in Britain. Peterborough: Joint Nature Conservation Committee.
  23. ↑ Rodwell, J.S. (2000). British Plant Communities, vol. 5: Maritime communities and vegetation of open habitats. Cambridge: Cambridge University Press. ISBN   0-521-39167-9.
  24. ↑ Preston, C.D.; Pearman, D.A.; Dines, T.D. (2002). New Atlas of the British and Irish Flora. Oxford: Oxford University Press. ISBN   0-19-851067-5.
  25. ↑ Hill, M.O.; Mountford, J.O.; Roy, D.B.; Bunce, R.G.H. (1999). Ellenberg's indicator values for British plants. ECOFACT Volume 2. Technical Annex (PDF). Institute of Terrestrial Ecology. ISBN   1870393481 . Retrieved 27 September 2025.
  26. ↑ "Ruppia cirrhosa – Plant Parasites of Europe". bladmineerders.nl. Retrieved 2025-09-27.
  27. ↑ Redfern, Margaret; Shirley, Peter (2002). "British Plant Galls". Field Studies. 10: 207–531. ISBN   1-85153-214-5.
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