Nitellopsis obtusa, Starry Stonewort A Non-Native Submerged Aquatic Lower Plant STARRY STONEWORT (SSW) Nitellopsis obtusa • Scientific name of SSW: Nitellopsis obtusa (Desvaux in Loiseleur) J. Groves (1919) • Common name: Starry Stonewort (SSW) • Synonyms & Other Names: Chara obtusa, C. ulvoides, C. stelligera, Lychnothamnus stelliger, Nitella stelligera, N. stelligera var. ulvoides, N. ulvoides, N. bertolonii, Nitellopsis aculeolata, N. obtusa var. ulvoides, N. obtusa f. ulvoides, N. stelligera, Tolypellopsis obtusa, T. stelligera, T. ulvoides. STARRY STONEWORT (SSW) Nitellopsis obtusa General Characteristics • SSW is a nonindigenous submerged aquatic lower plant. • SSW is a filamentous alga. It has straight branches arranged in whorls of 4 to 6 long branchlets, & are attached at acute angles to stem nodes. • SSW is a summer annual, but can overwinter as a perennial during mild winters. However, SSW in some Michigan inland lakes appears to thrive in the cooler waters of fall, winter, & spring, & becomes dormant or less active during hottest parts of summer lakes (Pullman & Crawford 2010). STARRY STONEWORT (SSW) Nitellopsis obtusa General Characteristics • Most stem & branch cells are around 1 mm in diameter (Hargeby 1990). • Stems can extend up to 80 cm long, or 31.5 inches (Hargeby 1990). • Growth up to 2 meters (6.5 ft) observed at depth of 9 m (29.5 ft) in one Michigan Lake (Pullman and Crawford, 2010). Source: www.seagrant.sunysb.edu. SSW STARRY STONEWORT (SSW) Nitellopsis obtusa General Characteristics The “squeeze test” may be used to distinguish SSW from Chara spp. • In SSW, the protoplasm will pop out of the cell when squeezed. The remaining cell wall becomes limp straw (G. Douglas Pullman, Aquest Corp, personal communication). • In Chara spp., the protoplasm does not separate easily from Source: Online photo. www.startribune.com. the cell wall (Hackett et al. MI Dept. Environ. Quality. Chara sp., a native 2014). lake weed on left; SSW on right. STARRY STONEWORT (SSW) Nitellopsis obtusa General Characteristics • SSW has colorless hair-like filaments called rhizoids that act like roots (SSW does not have roots). The rhizoids attach the plant to an aquatic bottom in early life, but they frequently detach from an aquatic bottom to form a floating mat. • Stoneworts have ability to absorb nutrients through all surfaces, not just the rhizoids (Holeck & Mills, 2007). • SSW can be found at depths of 3-20 feet in lakes or slow moving rivers (Holeck & Mills, 2007). STARRY STONEWORT (SSW) Nitellopsis obtusa General Characteristics • SSW plants can form gyrogonites, which are calcified, spiral-shaped fructifications (Bharathan 1983, 1987). • Another definition for gyrogonites from the online plain text English dictionary is the petrified fruit of Chara hispida, a species of stonewort. STARRY STONEWORT (SSW) Nitellopsis obtusa General Characteristics SEM lateral & apical views of gyrogonites of : • Chara aspera (figs.1-2); • C. hispida (figs. 3-4); • C. globularis (figs. 5-6) Source:www.researchg ate.net STARRY STONEWORT (SSW) Taxonomic Classification • EMPIRE……………………………………………...Eukaryota • KINGDOM)…………………………………………. Protista • PHYLUM………………………………………….... Charophyta • CLASS……………………………………….………Charophyceae • ORDER………………………………………………Charales • FAMILY………………………………………………Characeae • GENUS……………………………………………….Nitellopsis* • SPECIES……………………………………………..obtusa *Other genera in the Characeae family include Chara, Lamprothamnium Lynchnothamnus, Nitella, & Tolypella. Source: Lewis & McCount (2004). STARRY STONEWORT (SSW) Taxonomic Classification Starry stonewort description Stoneworts used to be classified as members of the plant kingdom, but it is now agreed that they belong – along with other green algae – in the kingdom Protista. Put simply, the protistas are simple multi-celled or single celled organisms, descended from some of the earliest life-forms that appeared on Earth. Some of the Chlorophytes, specifically the stoneworts, are thought by scientists to have been the early ancestors of all plants. Stoneworts do indeed resemble plants, are frequently mistaken for them, and are often found as fossils. Source:www.arkive.org/starry-stonewort/nitellopsis obtusa. STARRY STONEWORT (SSW) Nitellopsis obtusa General Life Cycle • SSW plants are dioecious, which means that plants are either male or female. • The best evidence to date indicates that the SSW populations in the United States are all male, though there may be undiscovered females. This means that spread of SSW is probably through human movement of fragments from lake to lake. • (See http://www.maisrc.umn.edu/starry-stonewort. For more information, contact Dr. Daniel Larkin, Asst. Professor & Extension Specialist at [email protected]). • MAISRC stands for Minnesota Aquatic Invasive Species Research Center. STARRY STONEWORT (SSW) Nitellopsis obtusa General Life Cycle • SSW has orange female structures called oogonia that are located at the nodes of upper branchlets. • Male structures also are orange colored, & occur at nodes. Source: Starry Stonewort (Nitellopsis They are called obtusa) Biology & Management by Scott antheridia. Source: www.algaebase.org. Van Egeren, Wisconsin DNR, July 29, Online photo of paired 2015. Photo from a slide presentation SSW oogonia. Collected by given in a public information meeting. Emma Harris, Norfolk, UK. www.dnr.wi.gov/topic/invasives/ 08-04-2014. documents/ssw-info.pdf. STARRY STONEWORT (SSW) Nitellopsis obtusa General Life Cycle The dark red-colored oospores are female gametocytes from which an egg develops. Source:www.wolverinelake.com A decade of starry stonewort in Michigan (Pullman, G. D. & G. C. Crawford, 2010). STARRY STONEWORT (SSW) Nitellopsis obtusa General Life Cycle • In sexual reproduction, plasmogamy (fusion of haploid gametes) is followed by karyogamy (nuclear fusion) to form a diploid zygote (Graham, L. E., & L. W. Wilcox. 1999). • Sexual reproduction in SSW occurs through production & fertilization of oospores. • Mature oospores usually are produced only under eutrophic conditions. • Have a mandatory dormant period before germination (Bharathan 1987; Hackett et al 2014). • SSW spore production may be controlled by light & tends to take place from July to September. STARRY STONEWORT (SSW) Nitellopsis obtusa General Life Cycle • Asexual reproduction is a means by which an individual organism can produce additional copies of itself without unions of cytoplasmic nuclear materials or meiosis. • One way SSW asexual reproduction occurs is by prolific production of vegetative bulbils. • Creamy white bulbils may occur at the base of the main stem just below the substrate water interface, & • On branches of the main stem at nodes. STARRY STONEWORT (SSW) Nitellopsis obtusa General Life Cycle • Bulbils stay viable for several years. • They can be found at any point during the year. • Most abundant in late fall & early spring (Pullman & Crawford 2010; Hackett et al 2014). • Bulbils can sprout in 3-5 days under the right conditions (Bharathan 1987). STARRY STONEWORT (SSW) Nitellopsis obtusa General Life Cycle • Another way SSW asexual reproduction occurs is by possible plant fragmentation. • One release indicates that SSW can easily reproduce from plant fragments (Houseman 2014). STARRY STONEWORT (SSW) Nitellopsis obtusa Life Cycle With Zygotic Meiosis Most chlorophyceans & charophytes (includes Chara spp., & Nitellopsis obtusa) are primarily found in freshwaters. These algae have (1) haploid vegetative phases. (2) the zygote is the only diploid stage. (3) zygotic meiosis occurs. [After L. E. Graham & L. W. Wilcox. 1999.] STARRY STONEWORT (SSW) Nitellopsis obtusa Means of Spread of SSW • SSW can be spread by oocytes. • Oocytes could be easily transported in aquatic plant debris caught in boat trailers. • Oocytes can easily become attached to the fur & feathers of aquatic fauna. Aquatic plants hitching ride on a • An effective way for SSW to boat trailer. Michigan Dept. of spread rapidly among inland lakes (Pullman & Crawford Environmental Quality. MSU 2010). Extension. Online photo msue.anr.msu.edu. STARRY STONEWORT (SSW) Nitellopsis obtusa Means of Spread of SSW • SSW could be spread by plant fragments, but there has been little research in this area. • Believed pathways of SSW dispersal are attachment of fragments, oospores, & bulbils to animals & boats (Hackett et al 2014). • Fragments of SSW can easily be spread between lakes by boats, trailers, waterfowl, & anchors holding sediments (Anonymous 2014; Ford-Steward 2015). • SSW fragments may act as disseminules that could be important in the spread of the plant within a lake & from lake to lake (Pullman & Crawford 2010). STARRY STONEWORT (SSW) Nitellopsis obtusa Means of Spread of SSW • SSW also can be spread by star-shaped bulbils • Bulbils occur mainly at the lower stem nodes near the substrate. • Bulbils reach 4 mm across (about 0.2 in). • Bulbils produce clones of the parent. • Bulbils stay viable for several years (Hackett et al 2014). Source: Online photo at www. uwsp.edu STARRY STONEWORT (SSW) Nitellopsis obtusa Means of Spread of SSW • SSW may be spread in ballast water (Mills et al 1993). • SSW was believed to have been introduced in ship ballast water into the St. Lawrence Seaway (Geis et al 1981; Schloesser et al 1986). STARRY STONEWORT (SSW) Nitellopsis obtusa Distribution Native Range: SSW is native to Eurasia, from the west coast of Europe to Japan (Mills et al 1993; Soulie-Marsche et al 2002). SSW is now in decline in parts of Europe & endangered in the UK (Hackett et al 2014) where