Biology
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Occurs as either an annual or a short-lived perennial, and flowers in July and August (1). Male plants were only recently discovered in the UK, it was previously thought that the plant could reproduce without cross-fertilisation (1).
Conservation
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Holly-leaved naiad is a UK Biodiversity Action Plan priority species. The Species Action Plan produced to guide the conservation of the species aims to maintain the current populations, and restore the plant to at least five adjoining waterways before the year 2004 (2). All three of the known sites are Sites of Special Scientific Interest (SSSIs), and the Royal Botanic Gardens, Kew are investigating seed-storage techniques suitable for the species (2).
Description
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Holly-leaved naiad is an aquatic plant (1) that has tough narrow leaves on forked, brittle stems. Both the leaves and the stems have spiky projections; these occur particularly towards the tip of the stem (3). The flowers are highly inconspicuous, and the fruit, which lacks a stalk, is fleshy (5).
Habitat
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Prefers clear unpolluted water in fens and reedbeds (2), and shows a preference for sheltered areas (1). It typically grows at depths of between 0.5 and 1.5m (1) often in slightly brackish water (5).
Range
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This species is found in the UK in just three of the Norfolk Broads (2). It is also known from both temperate and tropical areas including Europe, Asia, Australia, Africa, and North and Central America. (1). In Europe the species is classified as Vulnerable (1).
Status
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Classified as Vulnerable in Great Britain, and is fully protected in the UK by Schedule 8 of the Wildlife and Countryside Act 1981 (1).
Threats
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Main threats to the species include nutrient enrichment of water bodies following sewage inputs and agricultural run-off, and boat traffic, which causes pollution and turbulence (2).
Comments
provided by eFloras
With its prickly internodes and prickles along the abaxial surface of the leaves, Najas marina is the easiest of our Najas to recognize. Over its entire range, the species displays considerable morphologic variability (L. Triest et al. 1986), giving cause for ten subspecies to be recognized (L. Triest 1988). In North America, however, variability is relatively minor, so I am recognizing the taxon at the specific level only (R. R. Haynes 1979). The species should be studied over its entire range, utilizing a variety of approaches, to determine adequately what, if any, infraspecific taxa should be recognized.
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- Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
Description
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Stem up to 50-55 cm long, more than 1 mm broad, rather coarse; spiny, the lower internodes up to 10 cm long. Leaves oblong-linear, 1-3.5 x 2-6 mm, prominently spinose-dentate on the margins and the midrib on dorsal side. Sheath short, rounded, entire or with 1-3 inconspicuous spines. Flowers solitary. Male flowers enclosed in spathe, neck cylindrical, edge somewhat lobed; anther 4-thecous. Female flowers without spathe, style with 2-3 stigmas. Fruits ellipsoid, 23-5 x 1-4 mm. Seeds pale yellow-brownish. Areoles irregular in shape and size.
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Description
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Stems branched distally, 6--45 cm ´ 0.5--4 mm; internodes 0.3--11 cm, usually with prickles. Leaves spreading to ascending with age, 0.5--3.9 cm, stiff in age; sheaths 2--4.4 mm wide, apex acute; blade 0.4--4.5 mm wide, margins coarsely serrate, teeth 8--13 per side, apex acute, with 1 tooth, teeth multicellular; midvein with prickles abaxially. Flowers 1 per axil, staminate and pistillate on different plants. Staminate flowers in distal to proximal axils, 1.7--3 mm; involucral beaks 2-lobed, 0.3--0.7 mm; anthers 4-loculed, 1.7--3 mm. Pistillate flowers in distal to proximal axils, 2.5--5.7 mm; styles 1.2--1.7 mm; stigmas 3-lobed. Seeds not recurved, reddish brown, ovoid, 2.2--4.5 ´ 1.2--2.2 mm, apex with style situated at center; testa dull, 10--15 cell layers thick, pitted; areoles irregularly arranged, not in distinctive rows, not ladderlike, 3--4-angled, longer than broad, end walls slightly raised. 2n = 12 (Europe).
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- Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
Distribution
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Ariz., Calif., Fla., Ind., Mich., Minn., Nev., N.Y., N.Dak., Ohio, Pa., S.Dak., Tex., Utah, Wis.; Mexico; West Indies; Central America (El Salvador, Panama); South America; Eurasia.
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- Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
Distribution
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Distribution: Most of Europe, Asia, N. Africa, Australia, N. and S. America.
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Flower/Fruit
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Fl. Per.: March-December.
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Flowering/Fruiting
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Flowering summer--fall.
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Habitat
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Brackish or highly alkaline waters of ponds and lakes; 0--1000m.
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Synonym
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Najas gracilis (Morong) Small
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Najas marina
provided by wikipedia EN
Najas marina is a species of aquatic plant known by the common names spiny water nymph, spiny naiad and holly-leaved naiad. It is an extremely widespread species, reported across Europe, Asia, Africa, Australia, the Americas and many oceanic islands. It can be found in many types of freshwater and brackish aquatic habitat, including bodies of alkaline water.[3][4][5]
Description
Najas marina is an annual producing a slender, branching stem up to 40 or 45 centimeters in maximum length. The evenly spaced leaves are up to 4 centimeters long, 1 to 3 millimeters wide, and edged in tiny sawlike teeth. The leaf has prickles along its midvein. Minute stalkless, green flowers occur in the leaf axils. The plant is dioecious, with male and female flower types occurring on separate individuals.[6][4][5][7][8] In the British Isles it is possible that only female plants occur. It flowers in mid-summer.[9]
Varieties and subspecies
A long list of varietal and subspecific names have been proposed over the years. At present, only nine are widely accepted:[2][10]
Distribution and habitat
Najas marina has a wide, almost circumglobal distribution in temperate and tropical regions. It occurs in mesoeutrophic water over deep peat or mud. It was first recorded in the British Isles in 1883 at Hickling Broad in Norfolk where it had become established. Populations declined in the 1960s because of pollution, but action has been taken to reduce the level of nutrients in the Norfolk Broads and the water quality has improved.[11]
Fossil record
One fossil seed of Najas marina has been extracted from borehole samples of the Middle Miocene fresh water deposits in Nowy Sacz Basin, West Carpathians, Poland.[12]
References
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^ Lansdown, R.V. (2019). "Najas marina". IUCN Red List of Threatened Species. 2019: e.T164322A120204953. doi:10.2305/IUCN.UK.2019-2.RLTS.T164322A120204953.en. Retrieved 22 December 2022.
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^ a b Najas marina L., The Plant List
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^ Stuckey, R. L. 1985. Distributional history of Najas marina (spiny naiad) in North America. Bartonia 51: 2--16.
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^ a b "Najas marina in Flora of North America @ efloras.org". www.efloras.org. Retrieved 2017-01-31.
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^ a b "Najas marina in Flora of China @ efloras.org". www.efloras.org. Retrieved 2017-01-31.
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^ von, Linné, Carl; Lars, Salvius (1753-01-01). "Caroli Linnaei ... Species plantarum". 2. Impensis Laurentii Salvii.
{{cite journal}}: Cite journal requires |journal= (help) -
^ Tzvelev, Nikolai Nikolaievich. 1976. Novosti Sistematiki Vysshikh Rastenii. Moscow & Leningrad 13: 18, Najas major var. polonica
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^ Triest, Ludwig J. 1988. Mém. Acad. Roy. Sci. Outre-Mer, Sci. Nat. Nouv. Sér. 22(1): 54 Najas marina var. ohwii
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^ McClintock, David; Fitter, R.S.R. (1961). The Pocket Guide to Wild Flowers. London: Collins. p. 200.
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^ Kew World Checklist of Selected Plant Families, genus Najas
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^ "Najus marina". Online Atlas of the British and Irish Flora. Retrieved 14 March 2020.
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^ Łańcucka-Środoniowa M.: Macroscopic plant remains from the freshwater Miocene of the Nowy Sącz Basin (West Carpathians, Poland) [Szczątki makroskopowe roślin z miocenu słodkowodnego Kotliny Sądeckiej (Karpaty Zachodnie, Polska)]. Acta Palaeobotanica 1979 20 (1): 3-117.
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Najas marina: Brief Summary
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Najas marina is a species of aquatic plant known by the common names spiny water nymph, spiny naiad and holly-leaved naiad. It is an extremely widespread species, reported across Europe, Asia, Africa, Australia, the Americas and many oceanic islands. It can be found in many types of freshwater and brackish aquatic habitat, including bodies of alkaline water.
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