Holly-leaved naiad  (Najas marina)

Holly-leaved naiad specimen

Facts

Kingdom Plantae
Phylum Anthophyta
Class Liliopsida
Order Najadales
Family Najadaceae
Genus Najas (4)
Size Leaf width (including teeth): 1 - 6 mm (5)
Leaf length: 1.0 - 4.5 cm (5)
Fruit size: 4.0 - 6.0 x 1.5 - 3.0 mm (5)
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Status

Classified as Vulnerable in Great Britain, and is fully protected in the UK by Schedule 8 of the Wildlife and Countryside Act 1981 (1).

Description

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).

Range

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).

Display NBN Map ButtonYou can view distribution information for this species at the National Biodiversity Network Gateway.

Habitat

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).

Biology

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).

Threats

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).

Conservation

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).

UK Biodiversity Action PlanThe UK Biodiversity Action Plan for this species is available at UK BAP.

Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact
arkive@wildscreen.org.uk

Glossary

Annual: lives or grows for just one year.
Brackish: slightly salty water.
Perennial: plants that live for at least three seasons; after an initial period they produce flowers once a year.

References

  1. Wigginton, M. J. (1999) British Red Data Books 1; Vascular Plants. 3rd Edition. JNCC, Peterborough.
  2. UK Biodiversity. Species Action Plan (November 2001):
    http://www.ukbap.org.uk
  3. Clapham, A. R., Tutin, T. G. & Moore, D. M. (1987) Flora of the British Isles. 3rd Ed. Cambridge University Press, Cambridge.
  4. National Biodiversity Network Species Dictionary ( January 2003)
    http://www.nhm.ac.uk/nbn
  5. Stace, C. (1991) New flora of the British Isles. Cambridge University Press, Cambridge.