 |
|
|
||||
| NAS - Nonindigenous Aquatic Species |
Translate this page with 
Common Name: brittle naiad
Synonyms and Other Names: Caulinia minor (All.) Coss. & Germ. Minor, Slender, Spiny-leaf, or Bushy Naiad; Brittle Waternymph; Brittle-leaf Naiad, European Naiad
Taxonomy: available through 
Identification: Najas minor is an annual aquatic submersed plant. It is a slender, branching plant with paired (sub-opposite), sometimes appearing whorled, leaves, which usually bunch in the leaf axils. The leaves are typically stiff, curled and pointed, and have spines along the margins that are visible to the naked eye, if not a hand lens. Stems profusely branched near apex distally, 11--120 cm ´ 0.2--1 mm; internodes 0.5--5.8 cm, without prickles abaxially. Leaves usually recurved with age, 0.5--3.4 cm, stiff in age; sheath 1--3 mm wide, apex truncate to auriculate; blade 0.1--1.2 mm wide, margins conspicuously serrulate, teeth 7--15 per side, apex acute, with 1--2 teeth, teeth multicellular; midvein without prickles abaxially. Flowers 1--2 per axil, staminate and pistillate on same plant. Staminate flowers in distal axils, 1.9--2.2 mm; involucre 2-lobed, beaks 0.4--2.1 mm; anther 1-loculed, 0.3 mm. Pistillate flowers in distal to proximal axils, 2.2 mm; styles 1--1.2 mm; stigmas 2-lobed. Seeds slightly recurved, purplish, fusiform, 1.5--3 ´ 0.5--0.7 mm, apex with style situated at center; testa dull, 3 cell layers thick, pitted; aeroleareoles regularly arranged in ca. 15 longitudinal rows, ladderlike, 4-angled, broader than long, end walls not raised. 2n = 24.
Although its growth is usually compact and relatively bushy, the highly branched stems can grow up to 4 ft. (1.2 m) in length and fragment easily. Leaves are about 1 mm wide and 0.5 to 3.5 cm long.
Najas minor, with its mature leaves recurved and with its aeroleareoles broader than long and arranged in longitudinal rows like the rungs of a ladder, is one of the more distinctive species of Najas. Young sterile individuals resemble N. gracillima, however.
Size: to 1.2m
Native Range: Najas minor is native to Europe and western Asia (Merilainen 1968).
Nonindigenous Occurrences:
In North America, it was first collected from Ashtabula County, OH in 1932 (Wentz and Stuckey 1971), and then reported from the tidal Hudson River (Waterford NY) in 1934 (Mills et al. 1997). Sediment records of seeds indicate a more or less simultaneous occurrence (1930's) at the head of Chesapeake Bay (Furnace Bay; Davis 1985).
Great Lakes: 1st Great Lakes sighting 1932 in Ashtabula County, Ohio in the Lake Erie drainage. N. minor was reported from Lake Ontario, NY in 1939; from reservoirs and rivers in PA in 1962; and from numerous locations in IL (Merilainen 1968). Now widespread in IN, IL, MI, NY, OH, and PA.
Other regions: reservoirs and rivers in WV (1947), TN and AL (1943), and FL (1958). Since that time, it has spread throughout much of the eastern United States and can be found from New York south to Florida and west to Arkansas. Ala., Del., Fla., Ga., Ky., La., Mass., Miss., Mo., N.C., Okla., S.C., Tenn., Vt., Va., W.Va.
Ecology: Najas minor prefers calm waters, such as ponds, lakes, reservoirs, and is capable of growing in depth up to 4 meters. The upper salinity limit of it was 0.3 ppt (United States Army Corps of Engineers 1977), but it was found in 'brackish' (probably oligohaline) Brent Marsh (Strong and Kelloff 1994). It is more tolerant of turbidity and eutrophic conditions than some of the native species of Najas and has replaced them in many instances (Wentz and Stuckey 1971).
Although Najas minor can reproduce by fragmentation, the primary means of reproduction appears to be by seed. Its reproductive season starts from August, peaks in Sep, and ends in Oct. During the late summer or early fall, the stems of slender naiad become brittle, and the profusely branched apical portions of the stem break into small fragments. Seeds remain attached in the leaf axils, and the fragments are dispersed by wind and water currents. Populations of Najas within reservoirs can fluctuate dramatically over a period of a few years and have been correlated with years of low rainfall and increased amounts of available light (Peltier and Welch 1970). Longevity here is a bit of a guess since exact time of germination and dieback are not known, but assumed to be about May-October.
Means of Introduction:
The vector of introduction of N. minor to North America is not clear. It does not appear to be widely used as an aquarium and fishpond plant (based on a Web search, Fofonoff, personal observation), but could have been accidentally introduced with more commonly cultivated species. Alternatively, it could have been introduced to the Great Lakes, the Hudson River, or upper Chesapeake Bay by shipping (Mills et al. 1993; Mills et al. 1997).
Minor naiad is easily spread through its many small seeds. These seeds are easily carried by waterfowl, and can easily ‘hitch a ride’ to other water bodies on boats and boat trailers.
Status: It has established from Ontario west to Illinois and southward to Florida. This plant has spread rapidly in the Southeast and Mid-Atlantic states, being reported as far west as Oklahoma and Ontario, Canada in the north.
Impact of Introduction: Najas minor can form dense, monospecific stands in shallow water that inhibit the growth of native species of aquatic macrophytes and hinder swimming, fishing, boating, and other forms of water contact recreation. It often grows with other submersed aquatics such as southern naiad, pondweed, coontail, and watermilfoil.
Remarks: Seven other species of Najas are reported by Haynes (1979) as occurring in the United States. Because several of the species are morphologically similar, identification of the various species can sometimes be difficult. Minor naiad is easily confused with the other Najas species, slender water nymph (N. flexilis), Common water nymph (N. guadalupensis) and Northern naiad (N. gracillima). These species can be differentiated from Minor naiad by looking at the leaf bases and seeds. Furthermore, Minor naiad is usually the only Najas species whose spines on the leaf margins can be seen with the naked eye.
References
Capers, R.S., G.J. Bugbee, R. Selsky and J.C. White. 2005. A guide to Invasive Aquatic Plants in Connecticut. Bulletin No. 997. The Connecticut Agricultural Experiment Station, New Haven, Connecticut.
Crow, G.E., and C.B. Hellquist. 2000. Aquatic and Wetland Plants of Northeastern North America. Vol. 2. Angiosperms: Monocotyledons. University of Wisconsin Press, Madison.
CT DEP. 2006. Nuisance Aquatic Vegetation Management; A Guidebook. http://www.dep.state.ct.us/wst/pestcert/supervisor/aweeds.pdf Invasive Aquatic Plant Program. 2006.
Flora of North America. 2008. www.eFloras.org
Haynes, R. R. 1979. Revision of North and Central American Najas (Najadaceae). Sida 8: 34-56.
http://www.caes.state.ct.us/aquaticplants. The Connecticut Agricultural Experiment Station, New Haven, Connecticut.
Les, D.H., and L.J. Mehrhoff. 1999. Introduction of nonindigenous aquatic vascular plants in southern New England: A historical perspective. Biological Invasions 1:281-300.
Meriläinen, J. 1968. Najas minor All. In North America. Rhodora 70:161-175.
Peltier, W. H. and E. B. Welch. 1970. Factors affecting growth of rooted aquatic plants in a reservoir. Weed Science 18: 7-9.
Wentz, W. A. and R. L. Stuckey. 1971. The changing distribution of the genus Najas (Najadaceae) in Ohio. Ohio Journal of Science 71: 292-302.
Other Resources:
The PLANTS Database, database (version 5.1.1). 2000. National Plant Data Center, NRCS, USDA. Baton Rouge, LA 70874-4490 USA. http://plants.usda.gov
http://el.erdc.usace.army.mil/pmis/plants/html/najas_mi.html
http://www.cropsci.ncsu.edu/aquaticweeds
Author: Ling Cao
Contributing Agencies: 
NOAA - GLERL
Revision Date: 7/11/2008 Citation for this information:
Ling Cao. 2009. Najas minor. USGS Nonindigenous Aquatic Species Database, Gainesville, FL.
<http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=1118> Revision Date: 7/11/2008
| AccessibilityFOIAPrivacyPolicies and Notices | |
  |
|