Holly-leaved naiad

Najas marina
Scientific classification
Kingdom:	Plantae
Clade:	Angiosperms
Clade:	Monocots
Order:	Alismatales
Family:	Hydrocharitaceae
Genus:	Najas
Species:	N. marina
Binomial name
Najas marina L.
Synonyms
Ittnera major (All.) C.C.Gmel. Ittnera najas C.C.Gmel. Najas fluviatilis Poir. Najas fucoides Griff. Najas gracilis (Morong) Small Najas laevis Lojac. Najas latifolia A.Braun Najas major All. Najas maritima Pall. Najas microcarpa (A.Braun) Bolle ex Christ Najas monosperma Willd. Najas muricata Thuill. Najas polonica Zalewski Najas tetrasperma Willd.

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.

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 flowers occur in the leaf axils. The plant is dioecious, with male and female flower types occurring on separate individuals.

A long list of varietal and subspecific names have been proposed over the years. At present, only 9 are widely accepted:

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